Limits and Fits: The ISO System
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- Опубліковано 11 січ 2020
- A few years ago I discovered the magic of the ISO system of limits and fits and now, finally, I got around to making a video about it. I've created lots of unintentional rattle fits in my life, and I found that this system finally made it easy to tolerance precisely fitting parts.
Useful Links:
@tarkka Video on ANSI Fits and Tolerances: • Fits and Tolerances: H...
ISO Limits and Fits Calculator: www.amesweb.info/FitTolerance...
NTN Bearing Fits Primer: www.ntnamericas.com/en/pdf/220...
Patreon: www.patreon.com/hlaps1990
Instagram: tabletop_machine_shop
- Наука та технологія
As an engineer, I've always wanted desk toys / demos of stuff like this. Like a board with a series of holes with different fits and identical pins so I can develop the tactile understanding of what fit feels like what. I wish someone made stuff like that!
Yes
is there no such product?
Oh god I was just going to ask the same thing if these existed! It looks like 2 years later there is still a market for something like this.
@@oliverwan1520It'd be an easy thing to 3d print, I bet
@@comedyreliefguy5112 3D print tolerance is only really comparable to the same printer with the same settings, and typically the same filament material. Layer lines, thermoplastic cooling shrink, etc., all contribute to how bad 3D printing tolerance actually is; and no, other methods outside of FDM printing aren't much better, they might tighten how out of tolerance their parts are but they all have their own set of problems. Using the same printer, settings, and material means that you end up with all of these variables ending up as a near constant, though it also depends on style of print, such as overall size, surface areas, infill, etc., where the tolerances between print A and print B are acceptable, and this is why 3D printing tolerance is only comparable to itself using identical variables. You also need to measure the parts to determine if tolerance is within given spec, or to at least find what the deviation is if two out-of-tolerance parts otherwise fit well.
There's the option to do solid printing with a machining pass for finishing, to bring bad tolerances to widely acceptable tolerances, but you also literally do not see this methodology outside of very niche uses. By the point of doing this, you're better off with just one operation on one machine for less wasted machine time. But by the point of machining something, you're also going to be measuring the tolerances of the parts.
Go-no go gauges exist, but how often are you using parts of the same shapes and diameters? The go-no go board that the original comment is suggesting would evolve to be the size of a room throughout all of the projects it would have encompassed. Unless, again as implied earlier, you're only using the _exact_ same shapes and diameters, which is not often unless you're using off-the-shelf parts. The only area where something like this exists is for bolts and nuts, because they're consistent and various areas of the world have widely agreed on systems, and you rarely deviate from those established systems, unfortunately these go-no go sets for bolts and nuts really only exist for common sizes of machine screws, I have yet to see any for any other thread type, where you just have to use calipers and gauges to determine tolerance and two parts to determine fit.
And this circles around to how tolerances are actually determined, through actual measurement, rather than a gauge that'll quickly tell you if something fits or not. Given the scope of the issue and how easy it is to just measure things with common machine shop tools, the want to have a slip-on go-no go gauge for everything is just pure laziness, and honestly a waste of time and material; go-no go gauges exist for a very specific reason, and that's to rapidly check quickly reproduced parts in the order of tens to thousands, where measurement by tool becomes a waste of time, but these are typically specific to certain parts, not a general purpose pegboard of seeing what fits nicely. Michael also demonstrates how engineers are entirely white collar, because anyone who spends time in a machine shop will quickly learn what proper fits feel like, literally something an apprentice would learn before starting their blue collar career. This is why 3D printers are commonly a white collar toy, because the people using them clearly do not understand their nuances, or why industrially they're only used for rapid prototyping before actual tooling, with better tolerances, are used, and this rapid prototyping is done within the drafting phases so that there is margin for error that feeds into tweaking the design. This is also why machinists will use calipers and measurements to determine tolerance, two parts and feeler gauges to determine fit, and why they'll whip up a custom go-no go gauge if they need to do this process multiple times within the same project or lineage of product. Picking up a tool and doing it properly really isn't that hard, yet inexperienced white collars seem to either be too lazy to do so and/or have a phobia of touching blue collar tools; it's insane how people look for an 'easier' way when the easiest way is the correct way.
A lot of people here clearly have a lot of learning to do, considering the lack of common sense and lack of basic logical thought.
Best explanation of fits & tolerances I've seen in the last fifty years.
Great video as always, couldn't get my 9 year old to sleep last night. Made her watch this and she cried herself to sleep by minute 6.
UA-cam actually makes you specify "Is this video for children?" now. I can see I was wise to check "no" :P
I see your 9 year old doesn't have much "tolerance" for such stuff ;-)
@@tspandya I see what you did there....
😂
Very well explained. Been doing this 30+ years and it was the best I've heard.
Wow thanks!
Me too.
That was a nice compliment you paid that man on his video
...after a very long day of battling the quality operations manager over how we measure, now I don't feel so alone. Thanks.
I know exactly what you mean by working microphone. Thanks so much, don't stop making these
Thanks!
It blew my mind when a machinist showed me how much .004in of clearance in a hole actually felt like. If I ever have fresh grads working with me i will show them this video! My only recommendation would be to speak just a bit slower, it will help people follow you during such instructional content. Awesome work!
Niiice, free views! Just kidding. Thanks for the advice. There were times I found myself running out of breath, so that might be a good indicator for when to slow down :P
For all the european folk... 0.004 inches is 0.01 centimetres or 1 tenth of a milimeter
I've been a machinist (manual and CNC) for 40 years for military and medical clients.
This is an excellent explanation of the machining / inspection process to meet ISO standards.
Good video
Thanks Keith!
Phew! That was like drinking shandy from a fire hose! 😮 Great video, packed full of details, thanks for sharing! ❤
Awesome content. Very concise and perhaps a bit quick for those of us who don’t have a ton of exposure to fits. Thank you for taking the time to put this together.
Thanks Michael! Are there any parts that you feel I glossed over too quickly?
Tabletop Machine Shop Nope! I just went back and rewatched it twice to make sure I caught all the content.
I’d be very interested in a follow up video discussing thread classes and fits. It’s probably quite similar.
Great work!
सर आपने लिमिट, फिट और टालरेंस को बढ़िया उदाहरण के साथ समझाया है. आपके बोलने की गति से सिंक्रोनाइज करने में मेहनत करना पड़ता है.
Very useful!!! You've earned my patreon ;-) love all of your videos, the level you go into and not rambling about is just so valuable
I first came across the tarkka video and thankfully found this one. I found this video to be extremely helpful as it covered some practical examples. Thank you!
You know that a video is right to the point when you have to pause it from time to time to fully understand. Thanks for sharing.
Glad it was helpful!
This is the best GD&T tutorial I have seen I youTube, thank you so much for sharing!
Very good. When I first started designing machines this system was not being used in the US. It took me a while to learn how it worked but never really understood it completely until now.
I really "enjoyed" this video, and will want to review it several times, as an adjunct to the Tarkka video you mentioned. Thanks !!
There is a lot of information packed into this video. Here are some references:
en.wikipedia.org/wiki/IT_Grade
en.wikipedia.org/wiki/Surface_finish
en.wikipedia.org/wiki/Engineering_fit
And thank you for the good sound.
My girlfriend has no tolerance for fits and that is MY limit.
This is the winning comment so far
Is that her at 2:08?
@@TabletopMachineShop ream her out.
So when I hit a bigger number than I’m required I’ll always use a center less grinder
Weld it out and recut
G'day,
I'm learning machining as a hobby to compliment my fast car addiction, and have been looking at reamers as I need to make a shaft out of two interference fit components. You've very nicely summed up the ISO tolerance system, which will now allow me to go find the tooling I need. Also explains nicely about bearing fitment application which will help me as one component needs to hold a couple of bearings. Thankyou very much for the information.
Now to get the 3 non-SI countries to let go of the British units they hold onto...
Thanks for the explanation....
Now it's fitted in my mind in the tolerance of H7g6....
"working mic..." 🤣 wow thanks for showing the drawing at the end ...that was unexpected and much needed for me. I'm a noob at all this machining stuff.
GREAT INFO. Well delivered.
1:04 Giggety!
Really though, this was a really good primer into this system. Tolerances are the bane of my existence, even though I often only do things for myself. This will be very helpful to figure out what I need in the future, or what I am likely able to achieve with the machines available.
I let a lot of giggities go in this one :P. Yeah I've found this helpful. I used to be fairly generous in my estimations on tolerances but this is nice and consistent
If tolerances are the bane of your existence, tolerance stacking is likely to drive you through the roof lol.
@@MFKR696 way ahead of you. On the flip side, I can see the clear starry sky from here!
THIS WAS FANTASTICALLY EXPLAINED THANK YOU VERY MUCH
This is a great tutorial! Actually explained things a college course doesn't...
Excellent refresher, nicely done!! I design injection molded parts/assemblies and rarely use this tolerance system but wish I was more familiar with it. We do measure IT grade for each vendor (molder) and use that for our tolerance calculations. Really enjoyed your video! I’ve subscribed and will be waiting for your next one!
Thanks a lot! I'm glad it was a good refresher!
I just make the parts and if they fit - I call it a “Good” fit.....thats my convention - lol. Very helpful video. Thanks!
Thanks for the really useful video!!
We make aircraft and defense parts using these tolerances. Very well explained.
Wow just watch! I think I'll have to watch this a few more times to catch everything you said holy moly! But well done but I love details I will have to absorb fully understand!
Thanks for a nice video about the ISO system.
This was a great video, thanks very much.
Great video. Very well explained.
Thanks!
This was a great video, from someone with barely any experience in mechanics to understand lots of it
Thanks!
Dude you know your stuff thanks for sharing I’ll look at several more times to learn
This was really useful!
Im going to exam soon, in production technology/construction :-)
Thank you!
Nicely explained. Clear.
super useful video, thanks!
Thank you for this. Your video is now in my references.
Nicely done!!
Very well explained
Awesome explanation!!
AWESOME!!! Thanks for sharing!!!
As a machinist my self who works with tight tolerance parts all day, I can say good job sir!
Glad to hear that, thanks!
Well, i am new to fit and tolerances and so I am stuck at a project of mine. Now I have a 608 bearing with OD of 22 mm, which I want to fit in the housing and I want it to be transition fit. I cant decide as to what should be the size of the housing bore to transition fit the bearing. It will be shaft basis and by your video, I think hole shud have the tolerance of G7? or J5?
Trying to get into more cnc information and came across this. A really helpful video, thanks
Thanks!
what happens when you press fit? Does the entire part that has the hole get larger? Or is it just the hole and a bit of the surrounding material that expands (less and less as the distance to the hole increases)?
Hi, what happens when we do need to zinc-plate one or both shaft and hole? do we need to change the tolerance value? example H7/f7 becomes G7/e7?
Thx for the research!
This is amazing.
Great Video, thanks
Learned a lot of good stuff in here! Cool
Thanks Justin!
That was awesome im new to maching so thanks for the info
Great job. Very informative.
Thanks!
Допуски и посадки за 10 мин вместо 100 часов в колледже
Thanks for video, its very useful
Thank you sharing this knowledge!
Thanks John!
Very good video, beats the week of 400-level lectures I vaguely recall from my engineering degree.
They didn't even teach us this in my degree... They alluded to it in first year with clearances and allowances in drafting and that's it. Sad really..
@@TabletopMachineShop That's weird, what degree is that? I'm a machine shop and CAD teacher in highschool (students age 15-18) and both the general tolerance system (IT tolerances) and the ISO fits and limit system are taught first during mechanics class, and later used in my classes.
When I was doing my mechanical engineering studies this system was also thought very early on, since it's so crucial when designing (and drafting) anything that will be send to someone else for manufacturing.
One of the major mistakes that both my students and many less practical inclined engineers make in making every tolerance to small. Always use the largest tolerance that will work for a given application.
When I was still a machinist, I once worked a week on some parts with tiny tolerances, because the drawing said so (all dimensions to IT2 or something insane like that). When the engineer came to get his parts I asked what they were, and they were door handles. I didn't have to pay for the man hours, but I was still pissed, since it was such a pain to make.
This is amazing! Thanks a lot
Beats the get a bigger hammer system I use 😆
There's always a bigger hammer...
I personally like the "beat to fit, paint to match" system which also goes along with "grinder and paint makes me the welder I ain't "
very clear video! Thanks, its very useful for me :D
This was so helpful, Thanks! For example when pressing a double sealed bearing on an arbor I usually put the arbor in the freezer (making it say minus 17 C or zero F); then I put the bearing in the sun (making it say 65 C or 150 F); now I can run my coefficient of expansion figures with the charts you provided my measurements should be much more controllable or predictable and less risk of stressing a new bearing.
Comment below was helpful too as was your answer:
Mesuri
3 months ago
Great video. Learnt something new today. What about temperature though?
Tabletop Machine Shop
3 months ago
Good question! The ASME standards (and no doubt their ISO counterparts) indicate that parts should always be measured at 20C. You can design your part to be the right size at its operating temperature (using limits and fits for example) and figure out the size at 20C (where it's going to be machined and inspected) based on the coefficient of thermal expansion
What a great video. Thank You!
Thanks Randy!
Funny, I was just last night using homemade tapered reamers to make interference fit holes for water tight fittings in plastic and wondering if there was a system for measuring the tolerances and sizing of holes like this besides just fiddling with it by hand. Amazing video, thanks for sharing.
Thanks! I used to kind of ballpark "ohhhhhh... 0.002" of interference", but it's great having a standard that produces similar fits consistently
Nice explanation of the tolerance system for holes.
The main problem with tolerances is measuring them. But this problem is solved by ISO8015. This standard removes all the variables and ensures the same quality mo matter where the parts are produced. Unfortunately there are not many manufacturers who dare to tackel a part which is according to this standard, because it limits their capabilities.
Can you share links or names of the books you have mentioned in this video ? It would be of great help.
That was surprisingly interesting.
Thanks a lot for this video. I needed a refresher like this to remember what I learned in college since I was working on a different area of mechanics. Keep it up!
Greetings from Lima, Peru.
I really wish this video had existed when I was learning how this worked. I just learned a lot about a topic I thought I understood already.
Thanks!
hats off to you, I used to think I understood fits. My company doesn't adhere to it as accurately as they should. Mainly cost, lack of time and required tools. We tend to use a lot of emery paper. personally I do the best I can with what I have and make very accurate parts I have also in my 6 years there used the cylindrical more than any time before. Company is 21 years old.. shameful. i have made the link between surface finish and tolerance as you can hit size but the pin still wont assemble right. turning vs grinding shafts for bearing fits. 0.003mm turning is hard to achieve but still fits like crap, but hitting 0.001 grinding parts fit very well. To anyone else reading this, no matter what cutter, or tool you use in an assembly flatness, squareness and parallel play as big of a factor as size
Well, hand finishing can be exceptionally accurate, i guess it's just nice when the parts are interchangeable! Yeah I guess if you're aiming for a 3 micron tolerance and your surface finish is in the 0.8 micron range you're looking at 25% of your tolerance zone being the surface finish. Knowing ISO, there's some way of factoring that in, I just havent read that far yet :P.
I'd love to do a video on GD&T with respect to flatness, squareness and parallelism (form and orientation controls) but that is one deep subject and I doubt I could do it justice :P. You make a very good point though; if your parts aren't flat, square, parallel, etc, they can match the print but still won't fit!
Excellent!
Good video. Thanks for sharing
Thanks Steve!
Where can I buy the testing block?
The video sound is pretty good, beyond my imagination
Great stuff. I wish knowing this would improve my turning skills, but probably not!. I will now educate myself further on this matter. Thanks.
Well if it doesn't at least you can say "I'm an IT-20 turner" and lower other people's expectations :P
Thank you, I found that very interesting.
Thanks Craig!
Great video! Thanks for the mention :)
No problem!
Great video! Can I ask for your reference document when choosing fitting tolerances?
Tight is always right!
Good info, thanks for sharing, just subbed.
Cheers
Thanks Rick!
Where can I get recomendations for the tolerances?
Like this 6:17
Thanks!
In the US we call out an outside diameter as plus nothing minus a value, and inside as plus a valley minus nothing. This allows a size for size fit which is actually a light press. In Europe they control with plus, plus and minus minus values making sure that there is some clearance.
What website is shown at 8:37?
Hi, thanks for this video. Very helpful, but there is one thing i'm still confused on. I have a pin which is ground to h6 tolerance. We need it to run smoothly in a hole. This is a shaft basis fit, as the shaft is already made and out of our control. I look in the book for 'close running fit'. Under the shaft basis column it says F8/h7 - well the shaft isnt h7 - its h6! so now what?! How do I translate the F8/h7 fit to work with an s7 shaft? We also have lots of pins that are m6 tolerance, which does not appear anywhere in the ISO 286 table so I am not sure how to handle this either.
Any help would be great. Thanks.
did you figure this out? I am in the same boat. Have a k6 pin and I am trying to design a hole for it so I am shaft-based and want a sliding fitment that would be G7/h6 but my pin is k6.
Literally just came across this on an instalation manual for an industrial gear box with a helical shaft mount. It required an H11 fit
So? H11 is a lot of allowed tolerance around the hole.
Achieving a certain letter is absolutely no problem. The problem is the tolerance (the 11 in your case is way relaxed.. you can carve that with hand tools). Generally 9 is easy, 8 is standard lathe work, drill work, 7 is the same but need more careful touches to creep on dimension, 6 is for the properly tuned lathes/mills/cnc and probably best you can get consistently. 5 is into surface grinding and other fancy process.
great vid
very useful...
tip top my friend!
Nice explanation, I subbed!
tldr: Take H7/h7 all the time ;)
Well... Not all the time, but when you are not sure it's the safest choice :D
Great viedo. Learnt something new today. What about temperature though?
Good question! The ASME standards (and no doubt their ISO counterparts) indicate that parts should always be measured at 20C. You can design your part to be the right size at its operating temperature (using limits and fits for example) and figure out the size at 20C (where it's going to be machined and inspected) based on the coefficient of thermal expansion
I saw the green mat and thought Ave. That's not Ave! I can understand what you are saying! BLISS!!
It's the TMS green mat of keeping everything in frame, not the AVE healing bench :P
@@TabletopMachineShop Ahhhh
Shoot for the middle! That's my motto. I was always tought, make it to print. If you did your job right. It's the engineers fault, if it don't work. These fit tolerances only work, if the engineers know what they're doing. I believe, if you're gonna get an engineering degree. You should have to do a few years in a machine shop.
I found that sometimes a nut and a bolt doest fit because the nut is its lower value of dimension and the bolt in its higher, the solution it is just changing one of them for other and the tolerances will be in an acceptable range.
cant you also vary precisely control the size of the hole by heating or cooling the part x number of degrees for smaller parts, drilling the hole and then viola, perfect hole when the part warms up
Is there a system that determine tolerances and fits for non-circular components? I want to fit square blocks into a square holes with a rubber mallet.
The ISO system also applies for non-Cylindrical shapes. It follows the same principle as for round fits: A Capital Letter (eg. H7) is for an outside dimension and a lowercase Letter (eg. h7) is for inside dimensions.
Any thoughts on applying MMC when calculating limits and fits?
They didn't cover limits and fits in the GD&T course I took, but I'd have to assume they just work like regular tolerances -- perfect form at MMC and then form deviations would be permissible down to LMC
Or maybe you just get the flapper.... hahahahah Thanks for posting, man! I would love to see more from you!
Thanks! I think it's a scientific fact that you can make anything fit into anything with sandpaper, time, and a large hammer :P
thank you so much. keep up the good work!
Great content! Do you do video requests?