Informative and practical, another video saved for the brain bank. Thanks for making this, extremely helpful in making sense of all this as an amateur machinist.
Top video Andrew. Have just spent the last few hours getting baffled by other web sites that retreat into complex geometrical and theoretical explanations . No doubt they mean well but your explanation cuts through the BS and gives me a practical method that i can use. Well done.
0:35 thats how you do a youtube video, less than a minute in and all the formulas you need are right there, with he explanation FOLLOWING. Other tutorial channels should be taking notes
Thank you thank you. Thank you. Thank you. Thank you thank you. Thank you. Thank you. Thank you,thank you. Thank you. Thank you. Thank you,thank you. I think you get the point thanks again.
I got several questions: 1.How do you cut tapered gears like in angle grinder gear box ? 2.Could you make a video about tooth profile and gear cutting on the milling machine ? 3.Also how do you make a new gear if old mashing gear is worn? How do you determine module/pitch ,tooth profile ,od etc if gear is worn out and get them to engage properly? (obviously best would be to change both , but we all know we don't live in a fairy world ,in a machine with a lot of gears it would be too expensive to change all until they fit perfectly) 4.How do you cut a worm gear ? Thank you for all the information you provide !
1-they are called bevel gears-high quality ones are generated on a specialty machine 2-We have a 3-part series on gear milling to answer your second question 3-if you know the center distance between the shafts it will help narrow the possible tooth counts/size
Thank you, trawled the net for ages for a simplistic explanation, with examples, without success...until now, but you Americans do like to waffle on.😉🤣 Thanks again.
Gauges are free and easily made with our .DXF Generator found here: evolventdesign.com/pages/spur-gear-generator You can get the output in a very universal file format ".DXF" and then print it to scale. It is a paper gauge, but as long as you can see the outlines it will work. Finer pitches are difficult.
Good question! evolventdesign.com/pages/gear-measurement-over-pins-calculator Here is our calculator that works for both external and internal spur gears. This is how gears are measured. Count the teeth, make some measurements and this calculator can get you very close. As far as rules-of-thumb that is a future video. Thanks for watching!
Thanks for video sir Please guide how to check or calculate spiral bevel gear and pinion module if i don't have a drawing and also how to check angle of spiral means helical gear check with protector but in spiral gear thats not possible please guide. thanks
The standard unit of measure prettt much wordlwide is in kilometer, meter, milimeter. I dont get why we use inches, yards etc. Seems to just make things more complicated
I am building a model IC engine, the plans call for a pair of spur gears, ration 2-1 DP48 60 teeth and 30 teeth. I only have DP 32 cutters, if I cut a 60 teeth and 30 teeth with the DP32 cutter obviously the ratio is still 2-1 but does it make any difference the fact that the gear diameters are slightly larger or would it perhaps throw the timing out? If you have the time any help appreciated thanks
Wow! what a fast reply. I'm very gratefull as I have spent days trying the find a answer on the net. This video is also excellent for us amateur engineers. I have now subscribed.
im trying to model a daihatsu feroza gearbox, and the gears dont seem to be metric or imperial.for 2nd gear countershaft i have a module of 2.6667, and diametral pitch of 9.58. have you ever seen that before?
@@EvolventDesign thanks for the info brother! im guessing aftermarket manufacturers like quaffe would use standard tooling? so i would have to design a gearbox according to standard metrics?
i have a gear with following measurements. But i am confused whether to Pick Metric or Imperial in Designing. because both give different OD. • N = 28 • Face Width = 48.50mm | 1.875in • OD = 262.5mm | 10.334in • Module = 262.5/30 = 8.75 (in Solidworks Design with Mod = 9 - OD = 269.54) • Pitch = 30/10.334 = 2.903 (in Solidworks Design with Diametral Pitch = 3 - OD = 253.54 ) How do I know whether it is Metric or Imperial Gear? Which one to prefer in design? Because I am not getting same size in design as in real.
When given the chance-I prefer Module gear design because the numbers are simpler etc. But the English Pitch System is very much alive with 14.5 degree pressure angle gears. This was standard for so long that it exists and persists today and probably for a long time into the future to maintain equipment and even for select new designs. Boston Gear makes a pretty good company selling Imperial gears - its all they do.
Depends alot on the application. If the gearbox shafts are fixed - NO. It there are banjos that allow for flexible center distances, like found in a lathe or other gearbox applications then YES. But this could alter performance in an unacceptable way.
Hey sorry if you explained this, it’s been a minute since I watched the video, but why do you add 2 to the number of teeth? I posted my calculations in a machinists group and I got a bit of push-back for not measuring the pitch circle. I can’t really explain what the two is for so I’m hoping you could help.
Measuring the pitch circle is ideal - But for most with few tools it is less practical. So usually the well intended “equation guys with clean hands that don’t work in a shop” will say this sort of thing. Both methods work and can be derived from first principles of gear equations that relate OD or pitch circle to tooth count. Measuring the OD with calipers is practical and doable by most people. If you want to measure the pitch diameter or pitch circle go to our MOP calculator and get some pins. But the solution is iterative, because to choose a pin that works you need to know the pitch-see what I mean. Or get some $$$$$ measurement tools. It is easy to spot the different advice you get from a practitioner vs “equation jockeys”
@@EvolventDesign haha well said. Ok I get what you’re saying, but how exactly does the 2 compensate for the fact that you’re not measuring the pitch circle? Obviously if I don’t add 2 to the tooth count, the module will be wrong. Following your guide my result was exactly 1.25 which made me happy, but I’m still curious as to the why.
I can do the math too. But as far as the numbers go, it is in the “Standard” aka AGMA 917 and for coarser pitches it is also standard. Take the definition of pitch diameterPD=T/DP. Then substitute it into the definition of the OD equation OD=PD + 2/DP re-arrange and you get the equation in this video…EXACTLY!
@@EvolventDesign right. So either you know the pitch circle and divide it by teeth to get module, or you only know the OD and you divide by teeth + 2 to get the exact same result? Is that correct?
They are in the AGMA equation definitions: It is in the “Standard” aka AGMA 917 and for coarser pitches it is also standard. Take the definition of pitch diameterPD=T/DP. Then substitute it into the definition of the OD equation OD=PD + 2/DP re-arrange and you get the equation in this video…EXACTLY! In other words if both equations are part of the difinition, rearranging with math yields the equation showing the +2 teeth. Also from practice, the OD is always spelled out as a key reference number on drawings and thus manufacturers cut the OD as close as possible to this diameter. Hence from the definition and the practice - it works. Most seasoned gear manufacturers and engineers will know this relationship.
Very useful video. I bought an old lathe, and needed to figure out the change gears to see if I had a complete set, and if not, the specs for making replacements. Used the formula, and created a gear with Fusion 360, then 3d printed it. Came out perfectly. I wanted to get the tooth count for some of the gears that were currently installed without removing them, so I transposed the formula to T=(Pitch*OD)-2, which worked perfectly. Thanks for a very clear and well done video!
Hi Sir, Do you have a tutorial video on how to know helix, lead, angle etc. of a helical gear from sample, for example someone bring you broken helical gear, how do you get the info from the sample?
Dennis, thanks for watching and joining the conversation. The wrong calculation was purposeful to show that you need to check both Module and Pitch calculations and units. If you don't know whether it is pitch or module to start with, you need to check both.
How do I know what missing gear I need, I own a old jewelers rolling mill, on the very top there would of been a T handle, at the bottom of the T stem there would of been a tooth cog, on the left and right so either side of this tooth cog there is bigger cogs, When turning the cog in the middle this would turn the left and right cogs, when all cogs are turning this would raise the gap between the rollers for what ever metal needed rolling, So my question is , as the cog is missing to the T bar is there a way to determine what size cog and how many teeth and what pitch? i need to buy,
Most likely yes. All of these gears/cogs mesh when they are at a certain center distance of their shafts. Measure them all, then compare their pitch lines which must be tangent to each other. The pitch lines, outer diameters and tooth counts are inter-related.
I have come across 2 scenarios where OD used to calculate gear module/DP can not be relied upon. For example in sliding gears sometimes the OD has to be been trimmed down to allow for the gear to slide over another. Another case take for example a lathe feed box which typically has 8 change gears between two shafts for different threads that requires an exact ratio per gear pair in order to produce a correct thread pitch. Now it is quite impossible to design two shafts sharing a center distance that these 8 gears can mesh with their respective mating gear if we only make them with available modules and DP. So what most manufacturers typically do is use a close enough module or DP a cut a gear that has a substantial accumulated pitch error, and then cut again but on the opposite flank to make the gear symmetrical and then trim the OD so that the gear pairs can now mesh. I think the most fool proof yet simple method to determine module/DP is by measuring the two shafts center distance and counting the number of teeths of 1 of the gears. The rest can then be determined.
Yes, you are right. There are many types of gears that do not work with this method, the ones you mentioned as well as any corrected or altered gear with a profile shift. Also many automototive gears tend to have "Non-Standard" industrial pitches for their specific designs.
Great question. The equation for Diametral Pitch(DP) that also relates to tooth count(N) and a Diameter (Pitch Diameter)(D) is a very simple equation: DP = N/D But when you have an unkown gear the outside diameter (OD) is easiest and most practical to measure. And in that case the equation becomes DP = (N+2)/OD Basically, it is just math combined with the knowledge that the OD of a gear is typically called out as a reference diameter on plans and is machined precisely. This equation makes the reverse engineering of most gears simpler with fewer tools.
Informative and practical, another video saved for the brain bank. Thanks for making this, extremely helpful in making sense of all this as an amateur machinist.
My question answered in under a minute. Not many other things i could say that about... Cheers
Top video Andrew. Have just spent the last few hours getting baffled by other web sites that retreat into complex geometrical and theoretical explanations . No doubt they mean well but your explanation cuts through the BS and gives me a practical method that i can use. Well done.
Glad it was helpful!
Pure Theory is great, sweat and job shop work crunch theorys down to the absolute minimum requirement
My favorite gear channel had a blast at the bash gear School.
Hello Andrew,
Great video. Enjoyable viewing, thank you... I feel sure I will pop back to this video from time to time.
Take care.
Paul,,
This is the video I've been looking for! Thanks for sharing!
oh man this made my weekend. this is bad ass.
That’s great
That was fabulous. All the answers to all my questions cheers
0:35
thats how you do a youtube video, less than a minute in and all the formulas you need are right there, with he explanation FOLLOWING.
Other tutorial channels should be taking notes
Thank you for this video ,it explained things ,its very easy to understand .
Great-that’s the goal
Always enjoy your videos, just wish there were more of them. It was great seeing you at the bash. Gary
Thanks for this kind comments-and for watching
Clear and to the point.
Thanks for watching - gears are everywhere
Absolutely brilliant video.
Thank you thank you. Thank you. Thank you. Thank you thank you.
Thank you. Thank you. Thank you,thank you. Thank you. Thank you. Thank you,thank you. I think you get the point thanks again.
Thank You, another informative video.
You bet
very very good. Easily solution. Thank you
Glad it helped and thanks for watching
Thank u! Great information.
Glad it was helpful!
Awesome! Thank you
I got several questions:
1.How do you cut tapered gears like in angle grinder gear box ?
2.Could you make a video about tooth profile and gear cutting on the milling machine ?
3.Also how do you make a new gear if old mashing gear is worn? How do you determine module/pitch ,tooth profile ,od etc if gear is worn out and get them to engage properly?
(obviously best would be to change both , but we all know we don't live in a fairy world ,in a machine with a lot of gears it would be too expensive to change all until they fit perfectly)
4.How do you cut a worm gear ?
Thank you for all the information you provide !
1-they are called bevel gears-high quality ones are generated on a specialty machine
2-We have a 3-part series on gear milling to answer your second question
3-if you know the center distance between the shafts it will help narrow the possible tooth counts/size
4-worm gears. Yep. That one is on our list. Stay tuned and thanks for watching
Great info Thanks !
Thank You!
You're welcome!
Thank you, trawled the net for ages for a simplistic explanation, with examples, without success...until now, but you Americans do like to waffle on.😉🤣 Thanks again.
Thanks, great video!
Glad you liked it!
We still need to know how to determine the Pressure Angle of the gear without using gauges. Do you have a method for that?
Gauges are free and easily made with our .DXF Generator found here:
evolventdesign.com/pages/spur-gear-generator
You can get the output in a very universal file format ".DXF" and then print it to scale. It is a paper gauge, but as long as you can see the outlines it will work. Finer pitches are difficult.
@@EvolventDesign Thank you.
This is really helpful. What if the gear is an inner ring gear, how does the formula change? Thanks
Good question!
evolventdesign.com/pages/gear-measurement-over-pins-calculator
Here is our calculator that works for both external and internal spur gears. This is how gears are measured. Count the teeth, make some measurements and this calculator can get you very close.
As far as rules-of-thumb that is a future video. Thanks for watching!
Thanks for video sir
Please guide how to check or calculate spiral bevel gear and pinion module if i don't have a drawing and also how to check angle of spiral means helical gear check with protector but in spiral gear thats not possible please guide. thanks
Ok I will try
Nice work Do You Have Any Formulas And Explained on Elica ,,Helicals Deg gears woking it out
The standard unit of measure prettt much wordlwide is in kilometer, meter, milimeter. I dont get why we use inches, yards etc. Seems to just make things more complicated
No sweat, either way works just fine.
I am building a model IC engine, the plans call for a pair of spur gears, ration 2-1 DP48 60 teeth and 30 teeth. I only have DP 32 cutters, if I cut a 60 teeth and 30 teeth with the DP32 cutter obviously the ratio is still 2-1 but does it make any difference the fact that the gear diameters are slightly larger or would it perhaps throw the timing out? If you have the time any help appreciated thanks
Timing Should still work . Your center distance will change, weight will likely increase-might impact performance if heavier
Wow! what a fast reply. I'm very gratefull as I have spent days trying the find a answer on the net. This video is also excellent for us amateur engineers. I have now subscribed.
im trying to model a daihatsu feroza gearbox, and the gears dont seem to be metric or imperial.for 2nd gear countershaft i have a module of 2.6667, and diametral pitch of 9.58. have you ever seen that before?
Automotive and motorcycle gears tend to be non-standard modules. Since they are mass manufactured, they can make a better custom product.
@@EvolventDesign thanks for the info brother! im guessing aftermarket manufacturers like quaffe would use standard tooling? so i would have to design a gearbox according to standard metrics?
The custom gears made by Daihatsu are far superior to standard gears-in other ways. They typically have profile shifts.
only if i could use the dot dash method on counting teeth on a 1 1/4 od gear with 80 teeth
YES, that is a very common problem. Stay tuned, I have a method to count fine pitch teeth.
Here is a method:
ua-cam.com/video/bBHn9kspeug/v-deo.html
i have a gear with following measurements. But i am confused whether to Pick Metric or Imperial in Designing. because both give different OD.
• N = 28
• Face Width = 48.50mm | 1.875in
• OD = 262.5mm | 10.334in
• Module = 262.5/30 = 8.75 (in Solidworks Design with Mod = 9 - OD = 269.54)
• Pitch = 30/10.334 = 2.903 (in Solidworks Design with Diametral Pitch = 3 - OD = 253.54 )
How do I know whether it is Metric or Imperial Gear? Which one to prefer in design? Because I am not getting same size in design as in real.
I prefer metric when designing from scratch. Your gear may be non-standard. What machine does it go to?
Many automotive gears are non-standard
Imperial gears haven't been made since about WW1. It's been all module/metric for a long time. Why use obsolete measuring tools also?
When given the chance-I prefer Module gear design because the numbers are simpler etc. But the English Pitch System is very much alive with 14.5 degree pressure angle gears. This was standard for so long that it exists and persists today and probably for a long time into the future to maintain equipment and even for select new designs.
Boston Gear makes a pretty good company selling Imperial gears - its all they do.
Can you replace a gear with less teeth if you can’t find the same original gear
Depends alot on the application. If the gearbox shafts are fixed - NO. It there are banjos that allow for flexible center distances, like found in a lathe or other gearbox applications then YES. But this could alter performance in an unacceptable way.
Hey sorry if you explained this, it’s been a minute since I watched the video, but why do you add 2 to the number of teeth? I posted my calculations in a machinists group and I got a bit of push-back for not measuring the pitch circle. I can’t really explain what the two is for so I’m hoping you could help.
Measuring the pitch circle is ideal -
But for most with few tools it is less practical. So usually the well intended “equation guys with clean hands that don’t work in a shop” will say this sort of thing. Both methods work and can be derived from first principles of gear equations that relate OD or pitch circle to tooth count. Measuring the OD with calipers is practical and doable by most people. If you want to measure the pitch diameter or pitch circle go to our MOP calculator and get some pins. But the solution is iterative, because to choose a pin that works you need to know the pitch-see what I mean.
Or get some $$$$$ measurement tools. It is easy to spot the different advice you get from a practitioner vs “equation jockeys”
@@EvolventDesign haha well said. Ok I get what you’re saying, but how exactly does the 2 compensate for the fact that you’re not measuring the pitch circle? Obviously if I don’t add 2 to the tooth count, the module will be wrong. Following your guide my result was exactly 1.25 which made me happy, but I’m still curious as to the why.
I can do the math too. But as far as the numbers go, it is in the “Standard” aka AGMA 917 and for coarser pitches it is also standard. Take the definition of pitch diameterPD=T/DP. Then substitute it into the definition of the OD equation
OD=PD + 2/DP re-arrange and you get the equation in this video…EXACTLY!
@@EvolventDesign right. So either you know the pitch circle and divide it by teeth to get module, or you only know the OD and you divide by teeth + 2 to get the exact same result? Is that correct?
@@freestyla101 yep
Why all the formulas dont mention those additional +2 teeth?
They are in the AGMA equation definitions:
It is in the “Standard” aka AGMA 917 and for coarser pitches it is also standard. Take the definition of pitch diameterPD=T/DP. Then substitute it into the definition of the OD equation
OD=PD + 2/DP re-arrange and you get the equation in this video…EXACTLY!
In other words if both equations are part of the difinition, rearranging with math yields the equation showing the +2 teeth. Also from practice, the OD is always spelled out as a key reference number on drawings and thus manufacturers cut the OD as close as possible to this diameter. Hence from the definition and the practice - it works. Most seasoned gear manufacturers and engineers will know this relationship.
I used it for Solidworks and you can't correct it.
Wow 😚
👍💐
Traducir aespañol
Prueba esta configuración
youtube-espanol.googleblog.com/
Gracias por ver
Very useful video. I bought an old lathe, and needed to figure out the change gears to see if I had a complete set, and if not, the specs for making replacements. Used the formula, and created a gear with Fusion 360, then 3d printed it. Came out perfectly. I wanted to get the tooth count for some of the gears that were currently installed without removing them, so I transposed the formula to T=(Pitch*OD)-2, which worked perfectly. Thanks for a very clear and well done video!
Glad it was helpful!
THANK YOU SO MUCH!!!
Have been looking for this for a while and you've explained it simply and well.
Hi Sir, Do you have a tutorial video on how to know helix, lead, angle etc. of a helical gear from sample, for example someone bring you broken helical gear, how do you get the info from the sample?
Not yet. It is most accurately done with a lead checker. There are some other methods- we will put it on the list.
Why did the first calculation come out wrong?
You left that hanging.
Dennis, thanks for watching and joining the conversation.
The wrong calculation was purposeful to show that you need to check both Module and Pitch calculations and units. If you don't know whether it is pitch or module to start with, you need to check both.
You make it look so easy - at some point I want to get to gear making, so this is helpful in making it in terms a layman can understand, lol!
You can do it next time you need to make a gear. Great to hear from you
How do you determine a gear size if you have a rack but no pinion? How do you determine the rack pitch or module? Thanks for your time and sharing!
A rack is a gear with infinite teeth. The easiest way is to measure the number of teeth per inch. Then using this calculator you can find out if it is one of three different pitch measurement systems:
evolventdesign.com/pages/pitch-calculator
For instance use 8 TPI and you get this from our calcuator"
----------------------------------
Inputs
Threads per Inch: 8.000 1/in
Outputs
Module: 1.011 mm
Diametral Pitch: 25.133 1/in
Circular Pitch: 0.125 in
Threads per Inch: 8.000 1/in
© 2022 Evolvent Design, 11-Mar-2023
evolventdesign.com/pages/gear-pitch-calculator
---------------------------------------------------------------------------
So it could be a circular pitch gear if your numbers are VERY GOOD and they are exactly 8.
But if you are off a little, it could be a DP of 25 or a module of 1. Gears and racks are pretty exacting when it comes to pitches.
You could also download our gear identification templates to compare with:
evolventdesign.com/collections/all/products/copy-of-dividing-head-reference-chart-digital-download
Then you can get closer by using this calculator and figuring out a pin and measuring again.
evolventdesign.com/pages/gear-rack-calculator
At this point, determine the pin to use and then measure across the longest span possible to increase the accuracy of your TPI measurement.
It may take an iteration or two, but you can usually figure it out.
How do I know what missing gear I need,
I own a old jewelers rolling mill, on the very top there would of been a T handle,
at the bottom of the T stem there would of been a tooth cog,
on the left and right so either side of this tooth cog there is bigger cogs,
When turning the cog in the middle this would turn the left and right cogs, when all cogs are turning this would raise the gap between the rollers for what ever metal needed rolling,
So my question is , as the cog is missing to the T bar is there a way to determine what size cog and how many teeth and what pitch? i need to buy,
Most likely yes. All of these gears/cogs mesh when they are at a certain center distance of their shafts. Measure them all, then compare their pitch lines which must be tangent to each other. The pitch lines, outer diameters and tooth counts are inter-related.
I cut a lot of 3dp20pa gears
Thanks for watching.
Thanks for valuable information 😊
Really great simple video for figuring this out. I was an electronics engineer, not a gearhead, lol - really really appreciate the help.
Glad you liked it!
Thanks for this great content. My testosterone levels went up just by listening too.
Great to hear!
I have come across 2 scenarios where OD used to calculate gear module/DP can not be relied upon.
For example in sliding gears sometimes the OD has to be been trimmed down to allow for the gear to slide over another.
Another case take for example a lathe feed box which typically has 8 change gears between two shafts for different threads that requires an exact ratio per gear pair in order to produce a correct thread pitch. Now it is quite impossible to design two shafts sharing a center distance that these 8 gears can mesh with their respective mating gear if we only make them with available modules and DP. So what most manufacturers typically do is use a close enough module or DP a cut a gear that has a substantial accumulated pitch error, and then cut again but on the opposite flank to make the gear symmetrical and then trim the OD so that the gear pairs can now mesh.
I think the most fool proof yet simple method to determine module/DP is by measuring the two shafts center distance and counting the number of teeths of 1 of the gears. The rest can then be determined.
Yes, you are right. There are many types of gears that do not work with this method, the ones you mentioned as well as any corrected or altered gear with a profile shift. Also many automototive gears tend to have "Non-Standard" industrial pitches for their specific designs.
Where did you get the chart?
And, thanks for the video!
Awesome video man thanx👌
Glad you liked it!
Thank you, to the point with no waffle. Needed this as I want to start learning how to do this.
Glad it was helpful!
Thanks
thank you
Nice vid!
Thank you for watching
Why add 2 to teeth?
Great question. The equation for Diametral Pitch(DP) that also relates to tooth count(N) and a Diameter (Pitch Diameter)(D) is a very simple equation:
DP = N/D
But when you have an unkown gear the outside diameter (OD) is easiest and most practical to measure. And in that case the equation becomes
DP = (N+2)/OD
Basically, it is just math combined with the knowledge that the OD of a gear is typically called out as a reference diameter on plans and is machined precisely.
This equation makes the reverse engineering of most gears simpler with fewer tools.
Plus
precisely measuring the pitch diameter directly is difficult and usually requires pins or wires to estimate.
@@EvolventDesign thanks!