ten years on the job as a mechanical engineer and selecting appropriate GD&T tolerance and feature size numerical values has always been difficult for me...until finding these videos...thanks!
This is excellent, and I very much appreciate your attention to detail in the super-clean whiteboard layout, and even in the manner you point at areas on it. You seem to make it a point to not block the thing you're pointing at, and you come in from different directions based on what point you're trying to get across. One question I have though is while I understand your explanation around the 2:40 mark that the .014 positional tolerance is the industry standard AND that you put the larger tolerance (i.e. the .014) on the threaded holes while using the tighter .007 tol for the clearance holes because that's easier on the machinist, what I DON'T get is where the .007 came from in the first place. I saw in one of your replies that you'd like to know some background on your viewers, so I'll do that here; I'm a 55 yr old design engineer with bachelor's degrees in mechanical eng and electrical eng and about 30 yrs experience. Why am I looking at you videos with that much experience? Well, much of my career has been in the research & development world, where we're only making one or two of something to test a concept or solve a temporary problem. I haven't had to make production-grade drawings for a long, long time. I've also been spoiled by talented and accommodating machinists who just say, "Tell me what numbers you want and I'll nail them dead-nuts." And they always do. Now, however, I'm doing some work for an organization that requires full GD & T on their drawings no matter what. The designs I'm doing for them basically all consist of two plates that mate face-to-face, one of which has two locating pins pressed into it (one round pin and one diamond-shaped) and the other has clearance holes for those two pins. Thanks again for your video.
Hi there TallColdGlass! Thanks for the kind words of positive feedback! As for the .007 positional tolerance at MMC, this is simply half of .014 (I know you're saying to yourself "obviously"). Well the total size of the equivalent traditional tolerance zone would be .005 X .005. square. This is a very achievable positional tolerance at MMC for modern machine tools (both manual & CNC) when they are combined with new, modern tooling. So think about this. You could apply a .014 position tolerance to the clearance hole and then an even larger position tolerance to the threaded feature which will end up requiring an enormous clearance hole diameter. Or you could apply a common sense .014 position tolerance to the threaded feature and a smaller (but very achievable) position tolerance to the clearance hole and then the clearance hole does not have to be this ridiculously large diameter. I do have a few words of caution with your alignment pins. Depending on your application, you may not necessarily want to apply GD&T Position Tolerance at MMC as your design is meant to be alignment assembly and NOT a clearance assembly. If you do plan on applying GD&T position tolerance at MMC, then this link provides a very useful example to follow: insights.faro.com/buildit-software/gd-t-in-precision-engineering-diamond-pins-for-precision-location I would be very willing to offer some advice if you would like to communicate over email. My email is calebsokoll@gmail.com Thanks again for watching and for taking time to comment! Stay safe and healthy!
Hello vinod shirol! Thanks for the compliment! I definitely plan on continuing to generate more videos! I do feel there is a gap when it comes to content that teaches the application of GD&T, not just the theory. Thanks again for watching and have a fun, exciting weekend!
Hello vinod shirol! Thanks for the compliment! I definitely plan on continuing to generate more videos! I do feel there is a gap when it comes to content that teaches the application of GD&T, not just the theory. Thanks again for watching and have a fun, exciting weekend!
Very good explanation and straight to the point. Greatly appreciate that you take the time to do these videos for folks who want to further understand GD&T. One comment: The link for fixed fastener case study is not working.
Hey there Miguel De La Torre! First, thanks for watching and for the uplifting comment, it's very energizing to see people such as yourself find value in the content I work so hard to provide! Second, thank you so much for letting me know about the link. Please let me know if you still have troubles accessing the case study now that I have made the correction. Thank you once more for watching and for participating in the comments section. Have a wonderful week!
Hi there paresh wani! Thank you for watching so many of the videos and for leaving kind words of encouragement in each of the comment sections! I have a new video prepared and will be shooting it this weekend so look out for it soon. (Here's a sneak peak: the next video will cover why we often use a diameter of Ø.014 to control the position of clearance holes as well as how to convert from a traditional "±" location tolerance to a GD&T Position tolerance). Thanks again for watching and have a fun weekend!
Glad you found this helpful Jesse! If you would like to know where this formula is located, just look in Appendix B of any of the last three ASME Y14.5 standards. Thanks for watching and commenting and have a great rest of your day!
Thank you STTPE for the calculations. I was wondering how are these clearance hole dia. are calculated in a technical way. Waiting for more videos like these.
Hi there, thanks again for creating these very informative GD&T videos. I have a question regarding your Step 1 Calculation. Why did you include the max clearance hole length (P) and max thread depth (D) in your calculation? I don't see how they impact the hole location. Maybe I am not seeing something? Thanks in advance for taking the time to explain it, should you reply. Thamer
Hi, Loved the video, but I have the same question as Thamar and Glenn. I assume it has to do with a standard tolerance on the straighness/perpendicularity of the holes?
I can answer that. The Datums he selected include a tertiary datum (C) which is probably the bottom face. This actually means that he is calling out hole perpendicularity to the bottom (or top) face of the plate. You can achieve the same thing if you separately include a perpendicular GD&T Callout. This is especially useful if you have very thick plates and you want to control/refine the hole length to be "straight" and not bowed in/out. If you have a relatively thin plate mate - then this doesn't matter. Anyway - the fact that he is using the third datum (C) - he has to include that in his clearance tolerance calculation because now perpendicularity is part of the envelope. He is also usiing an MMC modifier so he is providing a bonus tolerance.
In this case it seems that the .014 TP on the tapped hole is quite costly. Given that it is only 2/3 the depth that the mating plate is thick, the worst case scenario of the tapped hole being not perpendicular to the mating surface drives exceptionally large clearance hole with a relatively tight positional tolerance on the mating plate. From a machinists point of view, (that's me) given that I would be tapping this hole in the machine that I drill the hole with and not Ray Charles freeballing with a tap handle, the perpendicularity of the tapped hole is relatively easy to control and can be done consistently without even thinking about it. I would say that given a number of parts to produce, the likelihood that the tapped holes would go in crooked by .014 over .500 depth would be quite rare. On the other hand over the same number of parts where the letter O drill chips a cutting edge and walks out of that .007 (.016 at MMC) location is much more likely. Yet a part that is OOT on the true position is only non functional if the tapped hole is crooked AF. The best thing to do would be to use a projected tolerance zone with that same .014 tolerance zone for the tapped hole projected the plate thickness of .75 from the surface into which it is drilled. This would allow for .281 diameter clearance hole and a .014 true position tolerance on the mating part as well. That means I can make more parts that fit together less sloppily at less cost. If I want to keep the hole at .316 then positional tolerance could be .035 greater, split between the two parts, that's .031 TP on both parts. All for the addition of a projected tolerance zone that I can hold all day anyway.
Hi Clayton, thanks for the awesome comment! FYI, I also posted another video that covers exactly how to specify the dimensioning and tolerancing for this same scenario with the addition of utilizing a Projected Tolerance Zone. In that video you will see that I arrive at your same conclusion. The clearance hole size tolerance can indeed be "tighter" which as a result allows the parts to assemble with "less slop". Thank you again for taking the time to add such a detailed, practical, and very useful comment! Have a wonderful day!
Great video. I have a question, first how did you come up with the values for the low cost drill tolerance table and what makes it low cost? I ask because if I use this professionally any manager or boss reviewing my work is going to ask me for an explanation especially if I begin to use these values out of the blue.
Hello PeteGFP! First, thank you for watching and for asking an awesome question! The answer is three parts. First, the tolerance values provided are considered " moderately generous" and so they will yield a low scrap rate when the hole is drilled using a typical CNC canned-cycle drilling operation. Second, the tolerance values themselves are relative to the size of the hole that is being drilled. What I mean is that as the hole sizes become larger, the tolerances you apply also become larger. This keeps the tolerance requirements relatively achievable throughout the range of hole sizes. Third, the tolerances themselves are biased. What I mean is that we are allowing a larger tolerance in the upper tolerance portion than in the lower tolerance portion. This is because we are keeping in mind how drill bits actually perform. When you machine a drilled hole, typically the hole ends up being a bit larger than the actual size of the drill bit due to mechanical variances inherent in the drill bit, chuck, spindle, and how the drill bit locates itself while drilling. So to recap. The tolerances are "moderately generous", they are relative to the size of the hole being drilled, and they are applied in a way which allows for typical drill bit performance. All of these factors combined will yield a relatively low scrap rate and so I would purpose that a low scrap rate can be considered "low cost". I hope this helps and I hope it wasn't too lengthy of an explanation! Thanks again for watching and I look forward to seeing more questions from you! Have a great day and stay safe and healthy!
The link for low cost drills was not working...can you send me pls...do u have metric data for low cost drills... And these low cost drill data got from any standards or calculation??
Hi there! Thanks for letting me the know the link was incorrect. FYI, I updated the video description with the correct link. Also, here is the link for your reference: drive.google.com/file/d/1e-Kv_VZSk1LVeMQduMRHOgiA2Ta_mhuz/view?usp=sharing As for the development of the low-cost drill tolerance values. I have used my experience working in the engineering/design/manufacturing industry to compile this set of values. These are low-cost tolerances specifically for drilling operations using both manual and CNC machining equipment.
@@StraightToThePointEngineering Thanks...Buddy..I need one more details...the data which you are send that the low cost drill was inch drills...can we use the same data for metric drills by converting units...
This is a great way to figure out hole sizes for some fasteners, but this potentially only leaves .021/side of engagement of the head in the case of a SHCS. The Ø.056 allowed by formulated seems like overkill too me. Excellent communication skills and very impressive penmenship, I will be checking out your other videos!
In that case you should reduce T2. His formulas are based on having already set the positional tolerances for both the Tapped holes and the Clearance holes, he is simply calculating a clearance diameter that is certain to mate without interference for the given positional tolerances.
Hello there Armand Matossian! I appreciate the positive feedback! Keep on the lookout as I will be posting some new content soon continuing to focus on practical application of GD&T. Thanks again for the kind words and have a great day!
This is absolutely helpful session, as I had been looking for a good video for long and found one. really this one made it easy to understand clearance hole tolerances. If you got some time to spare, could you please explain why you choose thread depth and clearance hole length into the formula in Step 1???
Why is the calculated hole in this (video 0.281) and in the Projected Tolerance Hole ( next Video is smaller 0.281). Does the Projected Tolerance tighten up the holes so a smaller hole will work. and this video has the larger 0.14 diameter for both holes. ? ? Thank you for your video's.
You don't explain what ther T2*2P/D in step 1 represent. It should be something about the bolt not being perfectly vertical but I can't quite make out what. (it is explained in an answer near the very bottom of the comment section but was not added to an improved version of the video.)
Hi, thank you for creating such a clearly explained video. What would be the "P" value in case of captive fastener's clearance hole? do you still consider the surface where the bolt's head touches on the top plate?
Hi Sahba, yes you want to consider the actual length of the clearance hole from the end face to where the head of your fastener engages. For example, if you have a counterbore hole, then the internal ledge or lip that the fastener head is torqued down to is the face you should use for calculating the total length of the clearance hole. To be absolutely clear, "P" is NOT always simply the thickness of your part or "plate". Thanks for the great question!
Yeah, I was also wondering this. If he ignored the depths (like I would have done) it would have changed Hmin from .3132 to .271. That is a huge difference. The only thing I can think of is it allows for extra clearance in case the holes are not machined perfectly perpendicular to the mating surface.
@@GarranGossage I think you are correct, In another similar video he uses something called a projected tolerance zone applied to the axis of the screw holes, which means the axis of the screw hole must pass through a tolerance zone that sits above the top surface of the plate with the screw holes, this essentially controls the perpendicularity of the hole axis relative to the surface. If using the projected tolerance zone, the clearance hole diameter is .271 as shown in the other video.
Hi Brad, thanks for watching and for the insightful question! In this particular case we are designing each feature and positional tolerance to ensure we do not have any interference during assembly. To be clear, we do not care about the bolt's external threads interfering with the internal threads in the plate (those two features are already guaranteed to fit by purchasing a good quality fastener and specifying the tapped hole quality on the face of our drawing). Instead, we care about the bolt interfering with the clearance hole in the upper plate. Now the bolt can do two things which would create interference. 1. The bolt can move laterally as the threaded hole laterally moves (translates). 2. The bolt can "tilt" as the threaded hole starts to tilt relative to the primary datum. Well, we've already controlled the maximum lateral movement we want to allow by simply specifying the position tolerance of the threaded hole and thus the position of the bolt. However, the position tolerance does not control the total tilt of the bolt as it protrudes upwards past the surface of the bottom plate. The position tolerance only controls the "tilt" of the threaded hole within the bottom plate itself. So, as the bolt is tilted and is protruding upwards further and further away, it could potentially start to interfere with the clearance hole plate's material. To visually explain this, look at this figure I've made available in this link: drive.google.com/file/d/1dfar9k7UyvpNeU1M0ZoTbtmkCJKW7i-h/view?usp=sharing Now, one way to ensure the bolt doesn't interfere with the clearance hole is to use the formula which I've outlined in this video. Yes, it does utilize the Maximum Hole Length and the Minimum Thread Depth within the formula and here's why. Here's our design scenario: Let's say the threaded hole is tilted over as far as it possibly can within the specified tolerance zone. The bolt is going to follow the same tilt because the bolt's axis is going to essentially merge with the threaded hole's axis. So we have a tilted bolt. To understand why we utilize the Maximum Hole Length variable: The thicker the plate with the clearance hole is, the more of the tilted bolt's material merges into the clearance hole plate's material. So we need to account for that maximum distance away from the bottom plate the bolt is going to have to protrude up to in the assembly. We do that by using the Maximum Hole Length. Please understand, I specify Maximum Hole Length rather than Maximum Plate Thickness for a reason. Let's say the hole happened to be a counterbored hole. We would NOT want to use the Maximum Plate Thickness. Instead, we truly want to use the Maximum Hole Length. To understand why we utilize the Minimum Thread Depth variable: the shorter the thread depth is, the sharper the angle of the axis of the threaded hole can tilt within the same tolerance zone. The sharper the angle of the axis of the threaded hole, the sharper the resulting tilt of the bolt. The sharper the tilt of the bolt, the more the bolt can tilt over into the clearance hole plate's material. So we need to account for that maximum tilt of the threaded hole and thus the resulting bolt tilt in our assembly. We do that by using the Minimum Thread Depth. Please understand, I specify Minimum Thread Depth rather than Tapped Hole Depth or Maximum Plate Thickness for a reason. The Minimum Thread Depth is the assembly worst case scenario. Please use the figure I included a link to in order to visualize how the length of the clearance hole combined with the depth of the threaded hole can create more interference due to the geometry of the assembly. Thanks for the question and feel free to reply for clarification. Have a wonderful day!
@@StraightToThePointEngineering I was wondering the same thing as the other people who commented, but your explanation makes it clear. Thanks for your content!
Hi there S To! I worked VERY hard on making sure the graphics on my whiteboard were clean and added value rather than creating confusion so thank you for noticing! Thanks for watching and stay safe and healthy!
From my perspective, the formula shown in the standard is wrong. The correct formula should be H= F+T1+T2*(1+P/D). Could you help me verify if it's correct ? I get it based on Similar triangles theory.
Hi there Cameron! I’ll admit that it is a somewhat contested concept. However let’s go back to the basic fundamentals. MMC can be applied when using Positional Tolerance to control a feature of size. Threads do have a size tolerance associated with them and so threads are indeed a feature of size (you are specifying the thread size tolerance when you specify “Class 1”, “Class 2”, or “Class 3”). What makes threads a little “weird” is due to the actual feature which is being controlled and how that feature is inspected. First, the feature which is being controlled is the axis derived from the “pitch diameter”. So instead of controlling an axis derived from a simple hole surface, you’ve got an axis derived from a “weird” helical theoretical pitch diameter. This is harder to wrap your head around. Second, it is difficult to inspect the material condition of the threads to determine if the theoretical pitch diameter size has deviated away from its MMC condition, especially for an internal thread. Now, just because the helical thread feature is non-traditional and the inspection of the material condition can be difficult does not mean that we cannot invoke the MMC concept. Also, do not mistake inspection of the position of the threaded hole feature with the inspection of the material condition of the threads themselves. The position of the threaded hole can be relatively easily inspected and is done all the time. The inspection of the material condition of the threads is what I am saying is relatively more difficult. However, by specifying the threaded hole Positional Tolerance at MMC, you allow them to invoke the concept of using fixed gauges as well as allowing for additional or “bonus” tolerance if they are so inclined to inspect the material condition of the threads. Which may become necessary if the threaded hole feature might pass inspection if “bonus” tolerance is allowed. So it is in fact legal and logical to invoke MMC on a threaded hole callout. Please give the machinist and inspectors the option to utilize gauges and “bonus” tolerance during a worst-case scenario by specifying MMC. Please don’t steal those options from them by default just because it is a more challenging concept to understand and a more difficult feature to inspect. I hope this helps Cameron. Feel free to reply with additional comments or questions. Thank you for watching and engaging in the comments section! Have a wonderful day!
Hey Karthi, thanks for watching and for commenting! It means a lot to have everyone come down here to the comments section and provide feedback! Enjoy the rest of your evening and thank you again!
Step 3 should NOT be the absolute but to subtract the minimum. If a tool+machine combination with much runout has a tolerance of +0.2 +0.8m (always makes holes too large), you'd design your hole to be smaller to end up right. The point of subtracting is to enture an H-type fit where the smallest possible diameter you end up with is the minimum you allow to have.
Hello and pardon my ignorance. However, why not use the simple formula D - d/2....where D is the smallest hole and d is the biggest pin? Where D values and d values are known (CAD already has the values or find them in std. charts) so you just calculate the position tolerance by the above simple formula and subtract say another 0.1mm (0.004") to be safe? And why would you divide the total margin of error of 0.009" on the holes so unequally? As it bothers the eye as well as the inspection person. Why would you consider the plate thickness at all? Well, in your case where the plate is 0.750" thick where you should be considering it. Thank you.
I know Step 1 formula comes from 14.5M Appendix B.4, but I never understand how the 1+2P/D comes from Any literature proving what that chunk of parenthesis is? I never understood why it has to be 2 times the top clearance hole plate divident by the depth of the thread? that seems to me the ratio only..?
What about if the plate datum b and c have to be flushed to another part. Both parts also have tolerances for flatness or perpendicularity. that will add up to the formula and then you end up with brain damage due to over thinking.
2:50 why have a threaded hole has a looser tolerance zone than a simple hole. I mean the holes are drilled so their position is the same like the clerance holes because same process, and after that there is thread cut into the holes. Or is there another process when you cut thread during drilling in one step, and it is not so precise as normal drilling? Thanks
The hole might be in regular tolerance, but tapping that hole is usually a separate operation and controlling the position of the thread is more difficult as you've stated. The final threaded hole may appreciate a larger position tolerance as a result
It is an international standard for Dimensioning and Tolerancing ASME Y14.5-2009 (this is the version I have but there are newer additions available). It is fairly simple to understand, but he does an excellent job of explaining this information. The visuals are a big key to understanding when starting out.
One can find a copy of ASME Y14.5-2009 online. Go to Appendix B and you will see that this is formula is found in B.5 - Provision for tilting of the axis or center plane when the projected tolerance zone is not used. If you use a projected tolerance, then B.4 will be your equation, for a fixed fastener anyways. I find that I like to actually use ANSI B18.2.8 to determine my clearance holes (3 classes in there) and solve either B.4 for positional tolerance or B.5 for T1 (clearance hole positional tolerance) given a T2 (threaded hole positional tolerance of 0.010"). Goal seek in Excel (ALT +T+G) is very helpful here.
Hi, thanks for so straight forward info! At this point @3:35, ua-cam.com/video/bThrWWcMTvo/v-deo.html, you must be talking about additional assembly features like washers, right? that should be included to account for maximum clearance hole length. I firstly thought that the boss feature you are saying on the top plate is the counterbore and depth of counterbore should be included. But that is not right. Practically it is the max. depth of bolt from its head until the threaded plate's top surface. I wish you might have cleared this in the video. I was reading one of worksheet calculation on same design problem, found your video; now the topic is more clear.
Hello again Good Girl! I can related as GD&T is not an intuitive topic to learn. In the past we arbitrarily assigned rule-of-thumb tolerances that were easy to machine such as ±.005. However, we should NOT arbitrarily assign rule-of-thumb tolerances and simply hope that our parts will assemble, fit, and function based on "that's how tolerances have been applied in the past so it should work for me". We should instead be "designing" our tolerances so that we know with 100% certainty that our parts will assemble, fit, and function within their parent assembly. GD&T is a numbers-based tolerancing system which allows us to calculate our sizes and tolerances so we know with 100% certainty that we can achieve our desired assembly, fit, and function. GD&T can be boiled down to this. You are essentially designing tolerance zones that part features must fall inside of which ensure assembly, fit, and function. Now once you've designed those tolerance zones, you then have to convey the design of those tolerance zones to the machinist and inspector on the face of your drawing/MBD model. I know this answer was a bit long winded but just to recap. Fundamentally, GD&T is a system of tolerancing which allows you to know with 100% certainty that your parts will assemble, fit, and function properly rather than guessing by using outdated rule-of-thumb tolerancing and having to hope that your parts will assemble, fit, and function. Thanks for watching and for taking the time to participate in the comments section. Feel free to place your questions in the comments section. Stay safe and healthy and have a great day!
Straight To The Point hi, thanks for this, I understood what you're saying but what I unfortunately don't understand is how to do a tolerance analysis, I get very confused.
Dayum, I love these videos. He breaks it down so I can understand it pretty quickly.
ten years on the job as a mechanical engineer and selecting appropriate GD&T tolerance and feature size numerical values has always been difficult for me...until finding these videos...thanks!
I would reference a gd&t book and y14.5. I’m not too sure about this math...
your white board penmanship is phenomenal 🤯
This is excellent, and I very much appreciate your attention to detail in the super-clean whiteboard layout, and even in the manner you point at areas on it. You seem to make it a point to not block the thing you're pointing at, and you come in from different directions based on what point you're trying to get across. One question I have though is while I understand your explanation around the 2:40 mark that the .014 positional tolerance is the industry standard AND that you put the larger tolerance (i.e. the .014) on the threaded holes while using the tighter .007 tol for the clearance holes because that's easier on the machinist, what I DON'T get is where the .007 came from in the first place. I saw in one of your replies that you'd like to know some background on your viewers, so I'll do that here; I'm a 55 yr old design engineer with bachelor's degrees in mechanical eng and electrical eng and about 30 yrs experience. Why am I looking at you videos with that much experience? Well, much of my career has been in the research & development world, where we're only making one or two of something to test a concept or solve a temporary problem. I haven't had to make production-grade drawings for a long, long time. I've also been spoiled by talented and accommodating machinists who just say, "Tell me what numbers you want and I'll nail them dead-nuts." And they always do. Now, however, I'm doing some work for an organization that requires full GD & T on their drawings no matter what. The designs I'm doing for them basically all consist of two plates that mate face-to-face, one of which has two locating pins pressed into it (one round pin and one diamond-shaped) and the other has clearance holes for those two pins. Thanks again for your video.
Hi there TallColdGlass! Thanks for the kind words of positive feedback!
As for the .007 positional tolerance at MMC, this is simply half of .014 (I know you're saying to yourself "obviously"). Well the total size of the equivalent traditional tolerance zone would be .005 X .005. square. This is a very achievable positional tolerance at MMC for modern machine tools (both manual & CNC) when they are combined with new, modern tooling. So think about this. You could apply a .014 position tolerance to the clearance hole and then an even larger position tolerance to the threaded feature which will end up requiring an enormous clearance hole diameter. Or you could apply a common sense .014 position tolerance to the threaded feature and a smaller (but very achievable) position tolerance to the clearance hole and then the clearance hole does not have to be this ridiculously large diameter.
I do have a few words of caution with your alignment pins. Depending on your application, you may not necessarily want to apply GD&T Position Tolerance at MMC as your design is meant to be alignment assembly and NOT a clearance assembly. If you do plan on applying GD&T position tolerance at MMC, then this link provides a very useful example to follow: insights.faro.com/buildit-software/gd-t-in-precision-engineering-diamond-pins-for-precision-location
I would be very willing to offer some advice if you would like to communicate over email. My email is calebsokoll@gmail.com
Thanks again for watching and for taking time to comment! Stay safe and healthy!
Not bad. Been working in engineering for 14 years. Used this method to calculate clearance hole of .288 for a 6-32 fastener.
You are jesting for sure. Well, you wouldn't have to worry about interference at the minimum. There won't be much clamping though.
One of the best content up there, Plz do more awesome videos which covers GD&T because there are not much content in UA-cam about this topic
Hello vinod shirol! Thanks for the compliment! I definitely plan on continuing to generate more videos! I do feel there is a gap when it comes to content that teaches the application of GD&T, not just the theory. Thanks again for watching and have a fun, exciting weekend!
Hello vinod shirol! Thanks for the compliment! I definitely plan on continuing to generate more videos! I do feel there is a gap when it comes to content that teaches the application of GD&T, not just the theory. Thanks again for watching and have a fun, exciting weekend!
Very good explanation and straight to the point. Greatly appreciate that you take the time to do these videos for folks who want to further understand GD&T. One comment: The link for fixed fastener case study is not working.
Hey there Miguel De La Torre! First, thanks for watching and for the uplifting comment, it's very energizing to see people such as yourself find value in the content I work so hard to provide! Second, thank you so much for letting me know about the link. Please let me know if you still have troubles accessing the case study now that I have made the correction. Thank you once more for watching and for participating in the comments section. Have a wonderful week!
The Best Explanation, Make More Videos ...Waiting For Ur New Videos❤️
Very well explained!!!!
Waiting for more videos.
Hi there paresh wani! Thank you for watching so many of the videos and for leaving kind words of encouragement in each of the comment sections! I have a new video prepared and will be shooting it this weekend so look out for it soon. (Here's a sneak peak: the next video will cover why we often use a diameter of Ø.014 to control the position of clearance holes as well as how to convert from a traditional "±" location tolerance to a GD&T Position tolerance). Thanks again for watching and have a fun weekend!
An engineer who made his dimensions realistic?! I thought I'd never see the day
this is a great video that i have ever been watched. thank you for your sharing
I would like to say this is immensely helpful
Glad you found this helpful Jesse! If you would like to know where this formula is located, just look in Appendix B of any of the last three ASME Y14.5 standards. Thanks for watching and commenting and have a great rest of your day!
Thank you STTPE for the calculations. I was wondering how are these clearance hole dia. are calculated in a technical way. Waiting for more videos like these.
You didn't explain the equation though. Like why add or why all that stuff in the parentheses.
is this T2 (1+(2P/D)) formula is an experinced value? Where does it derive from? Only part in the formula I could not understand.
I agree, why is it included in the formula?
Clear and precise. Great penmanship too.
Hi there, thanks again for creating these very informative GD&T videos. I have a question regarding your Step 1 Calculation. Why did you include the max clearance hole length (P) and max thread depth (D) in your calculation? I don't see how they impact the hole location. Maybe I am not seeing something? Thanks in advance for taking the time to explain it, should you reply. Thamer
I would love to know this as well.
Hi, Loved the video, but I have the same question as Thamar and Glenn. I assume it has to do with a standard tolerance on the straighness/perpendicularity of the holes?
Great video..
Yes, I also don't understand how this formula comes from.. Appreciate your time to explain more.. Thanks!!!
Yeah, it creates way larger holes than the traditional equation (Hmin = Fmax + T1 + T2)
I can answer that.
The Datums he selected include a tertiary datum (C) which is probably the bottom face. This actually means that he is calling out hole perpendicularity to the bottom (or top) face of the plate. You can achieve the same thing if you separately include a perpendicular GD&T Callout.
This is especially useful if you have very thick plates and you want to control/refine the hole length to be "straight" and not bowed in/out. If you have a relatively thin plate mate - then this doesn't matter.
Anyway - the fact that he is using the third datum (C) - he has to include that in his clearance tolerance calculation because now perpendicularity is part of the envelope. He is also usiing an MMC modifier so he is providing a bonus tolerance.
When you sound "Straight to the point" it's quite interesting and unique and I love your teaching experience.. n skill!
Your Instagram account?
@straighttothepointgdt
In this case it seems that the .014 TP on the tapped hole is quite costly. Given that it is only 2/3 the depth that the mating plate is thick, the worst case scenario of the tapped hole being not perpendicular to the mating surface drives exceptionally large clearance hole with a relatively tight positional tolerance on the mating plate. From a machinists point of view, (that's me) given that I would be tapping this hole in the machine that I drill the hole with and not Ray Charles freeballing with a tap handle, the perpendicularity of the tapped hole is relatively easy to control and can be done consistently without even thinking about it. I would say that given a number of parts to produce, the likelihood that the tapped holes would go in crooked by .014 over .500 depth would be quite rare. On the other hand over the same number of parts where the letter O drill chips a cutting edge and walks out of that .007 (.016 at MMC) location is much more likely. Yet a part that is OOT on the true position is only non functional if the tapped hole is crooked AF. The best thing to do would be to use a projected tolerance zone with that same .014 tolerance zone for the tapped hole projected the plate thickness of .75 from the surface into which it is drilled. This would allow for .281 diameter clearance hole and a .014 true position tolerance on the mating part as well. That means I can make more parts that fit together less sloppily at less cost. If I want to keep the hole at .316 then positional tolerance could be .035 greater, split between the two parts, that's .031 TP on both parts. All for the addition of a projected tolerance zone that I can hold all day anyway.
Hi Clayton, thanks for the awesome comment! FYI, I also posted another video that covers exactly how to specify the dimensioning and tolerancing for this same scenario with the addition of utilizing a Projected Tolerance Zone. In that video you will see that I arrive at your same conclusion. The clearance hole size tolerance can indeed be "tighter" which as a result allows the parts to assemble with "less slop". Thank you again for taking the time to add such a detailed, practical, and very useful comment! Have a wonderful day!
great explanation. appreciate your prep and clear example
Would take me a week to draw up that whiteboard. ;). Nice job!
Great video. I have a question, first how did you come up with the values for the low cost drill tolerance table and what makes it low cost? I ask because if I use this professionally any manager or boss reviewing my work is going to ask me for an explanation especially if I begin to use these values out of the blue.
Hello PeteGFP! First, thank you for watching and for asking an awesome question! The answer is three parts. First, the tolerance values provided are considered " moderately generous" and so they will yield a low scrap rate when the hole is drilled using a typical CNC canned-cycle drilling operation. Second, the tolerance values themselves are relative to the size of the hole that is being drilled. What I mean is that as the hole sizes become larger, the tolerances you apply also become larger. This keeps the tolerance requirements relatively achievable throughout the range of hole sizes. Third, the tolerances themselves are biased. What I mean is that we are allowing a larger tolerance in the upper tolerance portion than in the lower tolerance portion. This is because we are keeping in mind how drill bits actually perform. When you machine a drilled hole, typically the hole ends up being a bit larger than the actual size of the drill bit due to mechanical variances inherent in the drill bit, chuck, spindle, and how the drill bit locates itself while drilling. So to recap. The tolerances are "moderately generous", they are relative to the size of the hole being drilled, and they are applied in a way which allows for typical drill bit performance. All of these factors combined will yield a relatively low scrap rate and so I would purpose that a low scrap rate can be considered "low cost". I hope this helps and I hope it wasn't too lengthy of an explanation! Thanks again for watching and I look forward to seeing more questions from you! Have a great day and stay safe and healthy!
It's not exactly the same as his, but pretty close: www.engineersedge.com/manufacturing/drill-mechanical-tolerances.htm
Why does the thickness of the part effect the size of the clearance holes???
The link for low cost drills was not working...can you send me pls...do u have metric data for low cost drills... And these low cost drill data got from any standards or calculation??
Hi there! Thanks for letting me the know the link was incorrect. FYI, I updated the video description with the correct link. Also, here is the link for your reference: drive.google.com/file/d/1e-Kv_VZSk1LVeMQduMRHOgiA2Ta_mhuz/view?usp=sharing
As for the development of the low-cost drill tolerance values. I have used my experience working in the engineering/design/manufacturing industry to compile this set of values. These are low-cost tolerances specifically for drilling operations using both manual and CNC machining equipment.
@@StraightToThePointEngineering Thanks...Buddy..I need one more details...the data which you are send that the low cost drill was inch drills...can we use the same data for metric drills by converting units...
Videos are awesome and very interesting and engaging. Can you please post a video on Datums.
Very informative! I struggle a lot with this.
This is a great way to figure out hole sizes for some fasteners, but this potentially only leaves .021/side of engagement of the head in the case of a SHCS. The Ø.056 allowed by formulated seems like overkill too me. Excellent communication skills and very impressive penmenship, I will be checking out your other videos!
In that case you should reduce T2. His formulas are based on having already set the positional tolerances for both the Tapped holes and the Clearance holes, he is simply calculating a clearance diameter that is certain to mate without interference for the given positional tolerances.
Hi thank you for video
What is breakthrough clearance space for example 1/2 drill for 1 inch plate?
i mean clear space under plate
These are fantastic.
Hello there Armand Matossian! I appreciate the positive feedback! Keep on the lookout as I will be posting some new content soon continuing to focus on practical application of GD&T. Thanks again for the kind words and have a great day!
This is absolutely helpful session, as I had been looking for a good video for long and found one. really this one made it easy to understand clearance hole tolerances.
If you got some time to spare, could you please explain why you choose thread depth and clearance hole length into the formula in Step 1???
Why is the calculated hole in this (video 0.281) and in the Projected Tolerance Hole ( next Video is smaller 0.281).
Does the Projected Tolerance tighten up the holes so a smaller hole will work. and this video has the larger 0.14 diameter for both holes. ? ? Thank you for your video's.
You don't explain what ther T2*2P/D in step 1 represent. It should be something about the bolt not being perfectly vertical but I can't quite make out what. (it is explained in an answer near the very bottom of the comment section but was not added to an improved version of the video.)
Hi, thank you for creating such a clearly explained video. What would be the "P" value in case of captive fastener's clearance hole? do you still consider the surface where the bolt's head touches on the top plate?
Hi Sahba, yes you want to consider the actual length of the clearance hole from the end face to where the head of your fastener engages. For example, if you have a counterbore hole, then the internal ledge or lip that the fastener head is torqued down to is the face you should use for calculating the total length of the clearance hole. To be absolutely clear, "P" is NOT always simply the thickness of your part or "plate". Thanks for the great question!
Why is the minimum clearance hole diameter a function of hole length and thread depth?
i was wondering the same
Yeah, I was also wondering this. If he ignored the depths (like I would have done) it would have changed Hmin from .3132 to .271. That is a huge difference. The only thing I can think of is it allows for extra clearance in case the holes are not machined perfectly perpendicular to the mating surface.
@@GarranGossage I think you are correct, In another similar video he uses something called a projected tolerance zone applied to the axis of the screw holes, which means the axis of the screw hole must pass through a tolerance zone that sits above the top surface of the plate with the screw holes, this essentially controls the perpendicularity of the hole axis relative to the surface. If using the projected tolerance zone, the clearance hole diameter is .271 as shown in the other video.
Hi Brad, thanks for watching and for the insightful question! In this particular case we are designing each feature and positional tolerance to ensure we do not have any interference during assembly. To be clear, we do not care about the bolt's external threads interfering with the internal threads in the plate (those two features are already guaranteed to fit by purchasing a good quality fastener and specifying the tapped hole quality on the face of our drawing). Instead, we care about the bolt interfering with the clearance hole in the upper plate. Now the bolt can do two things which would create interference. 1. The bolt can move laterally as the threaded hole laterally moves (translates). 2. The bolt can "tilt" as the threaded hole starts to tilt relative to the primary datum. Well, we've already controlled the maximum lateral movement we want to allow by simply specifying the position tolerance of the threaded hole and thus the position of the bolt. However, the position tolerance does not control the total tilt of the bolt as it protrudes upwards past the surface of the bottom plate. The position tolerance only controls the "tilt" of the threaded hole within the bottom plate itself. So, as the bolt is tilted and is protruding upwards further and further away, it could potentially start to interfere with the clearance hole plate's material. To visually explain this, look at this figure I've made available in this link: drive.google.com/file/d/1dfar9k7UyvpNeU1M0ZoTbtmkCJKW7i-h/view?usp=sharing
Now, one way to ensure the bolt doesn't interfere with the clearance hole is to use the formula which I've outlined in this video. Yes, it does utilize the Maximum Hole Length and the Minimum Thread Depth within the formula and here's why.
Here's our design scenario: Let's say the threaded hole is tilted over as far as it possibly can within the specified tolerance zone. The bolt is going to follow the same tilt because the bolt's axis is going to essentially merge with the threaded hole's axis. So we have a tilted bolt.
To understand why we utilize the Maximum Hole Length variable: The thicker the plate with the clearance hole is, the more of the tilted bolt's material merges into the clearance hole plate's material. So we need to account for that maximum distance away from the bottom plate the bolt is going to have to protrude up to in the assembly. We do that by using the Maximum Hole Length. Please understand, I specify Maximum Hole Length rather than Maximum Plate Thickness for a reason. Let's say the hole happened to be a counterbored hole. We would NOT want to use the Maximum Plate Thickness. Instead, we truly want to use the Maximum Hole Length.
To understand why we utilize the Minimum Thread Depth variable: the shorter the thread depth is, the sharper the angle of the axis of the threaded hole can tilt within the same tolerance zone. The sharper the angle of the axis of the threaded hole, the sharper the resulting tilt of the bolt. The sharper the tilt of the bolt, the more the bolt can tilt over into the clearance hole plate's material. So we need to account for that maximum tilt of the threaded hole and thus the resulting bolt tilt in our assembly. We do that by using the Minimum Thread Depth. Please understand, I specify Minimum Thread Depth rather than Tapped Hole Depth or Maximum Plate Thickness for a reason. The Minimum Thread Depth is the assembly worst case scenario.
Please use the figure I included a link to in order to visualize how the length of the clearance hole combined with the depth of the threaded hole can create more interference due to the geometry of the assembly. Thanks for the question and feel free to reply for clarification. Have a wonderful day!
@@StraightToThePointEngineering I was wondering the same thing as the other people who commented, but your explanation makes it clear. Thanks for your content!
Fantastic video, thank you!
Wonderful Lectures ! Thanks.
If you use this method, would you still need to add a projected tolerance to the part with the threaded holes
Beautiful board
Hello Good Girl! I put a lot of work into the board so thanks for noticing!
Notice how the diagrams are all perfect lines used by a ruler on a marker board, never seen such detail for a you tube explanation.
Hi there S To! I worked VERY hard on making sure the graphics on my whiteboard were clean and added value rather than creating confusion so thank you for noticing! Thanks for watching and stay safe and healthy!
From my perspective, the formula shown in the standard is wrong. The correct formula should be H= F+T1+T2*(1+P/D). Could you help me verify if it's correct ? I get it based on Similar triangles theory.
Thank you so much for this.
Nice vedios! But could you explane how come these fomular to calculate, please?
Why do you have an MMC callout on a threaded hole? To my knowledge, there’s no bonus tolerance on a threaded hole.
Hi there Cameron! I’ll admit that it is a somewhat contested concept. However let’s go back to the basic fundamentals. MMC can be applied when using Positional Tolerance to control a feature of size. Threads do have a size tolerance associated with them and so threads are indeed a feature of size (you are specifying the thread size tolerance when you specify “Class 1”, “Class 2”, or “Class 3”). What makes threads a little “weird” is due to the actual feature which is being controlled and how that feature is inspected. First, the feature which is being controlled is the axis derived from the “pitch diameter”. So instead of controlling an axis derived from a simple hole surface, you’ve got an axis derived from a “weird” helical theoretical pitch diameter. This is harder to wrap your head around. Second, it is difficult to inspect the material condition of the threads to determine if the theoretical pitch diameter size has deviated away from its MMC condition, especially for an internal thread. Now, just because the helical thread feature is non-traditional and the inspection of the material condition can be difficult does not mean that we cannot invoke the MMC concept. Also, do not mistake inspection of the position of the threaded hole feature with the inspection of the material condition of the threads themselves. The position of the threaded hole can be relatively easily inspected and is done all the time. The inspection of the material condition of the threads is what I am saying is relatively more difficult. However, by specifying the threaded hole Positional Tolerance at MMC, you allow them to invoke the concept of using fixed gauges as well as allowing for additional or “bonus” tolerance if they are so inclined to inspect the material condition of the threads. Which may become necessary if the threaded hole feature might pass inspection if “bonus” tolerance is allowed. So it is in fact legal and logical to invoke MMC on a threaded hole callout. Please give the machinist and inspectors the option to utilize gauges and “bonus” tolerance during a worst-case scenario by specifying MMC. Please don’t steal those options from them by default just because it is a more challenging concept to understand and a more difficult feature to inspect. I hope this helps Cameron. Feel free to reply with additional comments or questions. Thank you for watching and engaging in the comments section! Have a wonderful day!
Thank you very much 😀, very detailed explanation.
Hey Karthi, thanks for watching and for commenting! It means a lot to have everyone come down here to the comments section and provide feedback! Enjoy the rest of your evening and thank you again!
Hi bro
Enna nanba panringa??
You need to explain the (1+2P/D) you just tossed in there with ZERO explanation.
Yeah definitely would like to see this.
Great Video! Has (1+2P/D) been explained yet? Please provide a link a document or another great video.
Beautiful. Dont piss off your machine shop and QA dept.
Step 3 should NOT be the absolute but to subtract the minimum. If a tool+machine combination with much runout has a tolerance of +0.2 +0.8m (always makes holes too large), you'd design your hole to be smaller to end up right.
The point of subtracting is to enture an H-type fit where the smallest possible diameter you end up with is the minimum you allow to have.
Pourriez-vous faire les memes exercices avec le systeme métrique ( en mm ) s'il vous plait ??
Hello Sir..can you please explain what will be the effect if we interchange hole size tolerance with its position tolerance
Hello and pardon my ignorance. However, why not use the simple formula D - d/2....where D is the smallest hole and d is the biggest pin? Where D values and d values are known (CAD already has the values or find them in std. charts) so you just calculate the position tolerance by the above simple formula and subtract say another 0.1mm (0.004") to be safe? And why would you divide the total margin of error of 0.009" on the holes so unequally? As it bothers the eye as well as the inspection person. Why would you consider the plate thickness at all? Well, in your case where the plate is 0.750" thick where you should be considering it. Thank you.
I know Step 1 formula comes from 14.5M Appendix B.4, but I never understand how the 1+2P/D comes from
Any literature proving what that chunk of parenthesis is?
I never understood why it has to be 2 times the top clearance hole plate divident by the depth of the thread? that seems to me the ratio only..?
What about if the plate datum b and c have to be flushed to another part. Both parts also have tolerances for flatness or perpendicularity. that will add up to the formula and then you end up with brain damage due to over thinking.
2:50 why have a threaded hole has a looser tolerance zone than a simple hole. I mean the holes are drilled so their position is the same like the clerance holes because same process, and after that there is thread cut into the holes. Or is there another process when you cut thread during drilling in one step, and it is not so precise as normal drilling? Thanks
The hole might be in regular tolerance, but tapping that hole is usually a separate operation and controlling the position of the thread is more difficult as you've stated. The final threaded hole may appreciate a larger position tolerance as a result
Thank you so much for this.(ขอบคุณมากกครับTeacher)
When rounding up to the next standard drill bit, you forgot to also add this to the tolerances.
outstanding!
From where do you get all those formulas?
It is an international standard for Dimensioning and Tolerancing ASME Y14.5-2009 (this is the version I have but there are newer additions available). It is fairly simple to understand, but he does an excellent job of explaining this information. The visuals are a big key to understanding when starting out.
Can we use this formula for Metric Thread applications?
How does P get applied ? just learning. Thanks
Why did you not use Projected tolerance zone on the threaded parts?
One can find a copy of ASME Y14.5-2009 online. Go to Appendix B and you will see that this is formula is found in B.5 - Provision for tilting of the axis or center plane when the projected tolerance zone is not used. If you use a projected tolerance, then B.4 will be your equation, for a fixed fastener anyways.
I find that I like to actually use ANSI B18.2.8 to determine my clearance holes (3 classes in there) and solve either B.4 for positional tolerance or B.5 for T1 (clearance hole positional tolerance) given a T2 (threaded hole positional tolerance of 0.010"). Goal seek in Excel (ALT +T+G) is very helpful here.
How did you come up the tolerances for postion?
Well said, thanks
Where is step #3 formula derived from? Thank you.
Step is is common math.
Min. value + lower tolerance = nominal value.
Max. value - upper tolerance = nominal value.
Where to get the lost cost drill tolerance ?
What about the units of dimensions?...is that inches r mm?
Good teacher
Are these measurements in mm
Dimensions in Inches or mm
Hi, thanks for so straight forward info! At this point @3:35, ua-cam.com/video/bThrWWcMTvo/v-deo.html, you must be talking about additional assembly features like washers, right? that should be included to account for maximum clearance hole length. I firstly thought that the boss feature you are saying on the top plate is the counterbore and depth of counterbore should be included. But that is not right. Practically it is the max. depth of bolt from its head until the threaded plate's top surface. I wish you might have cleared this in the video. I was reading one of worksheet calculation on same design problem, found your video; now the topic is more clear.
I can't figure out why I find this so difficult I feel so stupid man
Hello again Good Girl! I can related as GD&T is not an intuitive topic to learn. In the past we arbitrarily assigned rule-of-thumb tolerances that were easy to machine such as ±.005. However, we should NOT arbitrarily assign rule-of-thumb tolerances and simply hope that our parts will assemble, fit, and function based on "that's how tolerances have been applied in the past so it should work for me". We should instead be "designing" our tolerances so that we know with 100% certainty that our parts will assemble, fit, and function within their parent assembly. GD&T is a numbers-based tolerancing system which allows us to calculate our sizes and tolerances so we know with 100% certainty that we can achieve our desired assembly, fit, and function. GD&T can be boiled down to this. You are essentially designing tolerance zones that part features must fall inside of which ensure assembly, fit, and function. Now once you've designed those tolerance zones, you then have to convey the design of those tolerance zones to the machinist and inspector on the face of your drawing/MBD model. I know this answer was a bit long winded but just to recap. Fundamentally, GD&T is a system of tolerancing which allows you to know with 100% certainty that your parts will assemble, fit, and function properly rather than guessing by using outdated rule-of-thumb tolerancing and having to hope that your parts will assemble, fit, and function. Thanks for watching and for taking the time to participate in the comments section. Feel free to place your questions in the comments section. Stay safe and healthy and have a great day!
Straight To The Point hi, thanks for this, I understood what you're saying but what I unfortunately don't understand is how to do a tolerance analysis, I get very confused.
How come all the engineering videos are all in yeee old long gone imperial?
Nyc
9:14
Easy bud
🤣🤣
Hay dios haha esto me ubiera ayudado mucho para hacer mi robot haha no que todo lo tuve que aprender de un libro haha xD
Can u explain in MM unit. Thanks bro