Great video. My father was a gearbox designer and these parameters were often spoken of at out house. He wrote software in Pascal to calculate the various design parameters and working life according to the various DIN/ISO/AGMA/BS standards that all had their own quirks. and incompatibilities. All new designs were metric but he often had to fall back to the other standards when repairs were required for older imported machines. Trip down memory lane, thanks.
That's a great video, thanks. I reverse engineer gears so infrequently that each time I have to re-learn what little I once knew about it, which is time consuming even with the notes I keep on it. Your video is much more concise, and also showed me how to do helicals, which I've never needed to do. I'll be adding a link to it to my notes, and probably checking out some of your other videos too. Thanks again.
Some subjects are best learned from a video rather than falling a sleep reading a machinist book. This is one of those subjects. Great info, thanks for sharing! 👍
Watching your explanation of the helical gear reminded me of a related experience. I worked with a mechanical engineer who specified which direction to feed the tap when tapping holes because he thought that tapping a hole in the "wrong" direction produced a left-hand thread. The machinists just played along with him. Since no incorrect threads were ever produced, the engineer never had any doubts.
I wonder if that would actually be possible with a very large diameter fine thread tap with lots of flutes? (And a lot of force). I expect it would just shred the tap.
@@AndysMachines Sorry, I didn't write my comment very well. The fellow I was referring to would always specify which side of the part to feed the tap into. There was no intention of trying to feed the tap opposite to the normal direction. His intention was to tap the hole from the same side as the fastener was threaded in. He sincerely believed that tapping from the opposite side produced a left-hand thread.
Thanks for the refresher! It’s been more than 30 years I studied this topic, and now that I need it your explanation helped me a lot. Hey I even remembered where my notes were. I need 2 gears in my new (used) lathe and I keep messing something in my calculations. I should’ve started with module and, if not working with diametral pitch. Thanks again.🙏
I used to be given chewed up gears to remake at short notice due to production breakdowns etc. It was like being Sherlock Holmes at times but very satisfying when I sussed out what it was and created a sparkling replacement for the grateful customer.
Excellent! I can now finally identify the change gears on my Chinese made lathe/ milling combination machine. It has some damaged gears and I need to make new ones so I can screw cut some standard metric threads. Obviously I need to know the module so I can buy the involute cutters to do the job. I've got a rotary table with the disks with different holes in them for setting up the number of teeth, god my memory is getting bad these days I can't remember the correct name for them lol anyway thanks for this video it's so helpful.
Each time I was typing a question the answer popped up! 20+ years go I wrote some software that helped me determine screw threads. I was restoring my 1966 Norton 650 SS at the time, and had biscuit tins with indeterminate rusty screws from previous repairs. The result was probabilistic in that, given diameters and very rough tpi/pitch, and correcting for 30 years of rust, a likely thread was proposed. It worked well. I wonder if something similar could be done for gears. The next step would be to determine screw threads and gear splodules optically, using a smartphone app.
It's an amazing compendium about gears identification. Kudos ! I'll save it for future reference. Thanks ! Edit: I'm anxious for part 2, bevel gears ? :o)
Thank you so much! I think it was my comment on your last video that prompted your making this one. I'm so glad. Now I have the information I need to either order an off the shelve gear for one of my old machines, or maybe even make one myself. Thank you!
Yes, it may well have been your question that prompted me to make this, though I've been asked how to identify gears a number of times, both on YT and in real life, so the next time it happens I can point them here!
the last week or so I am literally trying to run all this down for some old transmission gears that are no longer made / in short supply and trying to figure out how to I.D and make my own should it become necessary ! Thank you !!!
BRILLIANT, I've been searching for this exact explanation in simple layman's terms, for ages, came across an American one, but he waffled on for over 8 mins what you explained in 1min. 😊😊 I'm assuming the 25.4 you mention is 1" in mm ?
Excellent learning video Thanks. But "what about the pressure angle" I was thinking. I am bogged down at this step, so I guess from your video I should just go with 20deg unless it looks too fat or too thin. With a small gear I find it hard to judge.
You can use 2 guage pins and a micrometer and a gear chart to find it, but that chart may be extemely hard to find unless you have a gear textbook, and it would only work for even tooth count gears. The best way realistically is to genereate the gear in a cad program, add guage pin cross sections in sketch, and measure the distance in cad and compare to a micrometer measurement
For pressure angle of a spur gear tooth, find the point on the tooth that is radially 5/9 (0.5555) of the distance from the root circle, to the crown of the tooth. Find the centerline of the tooth. This is the tooth's line of symmetry, which passes through the axis of the gear. Measure the angle between the tangent line of the tooth at the aforementioned point and the centerline of the tooth. And _that_ is the pressure angle. *Example 1:* If you find that the point on a tooth that is 5/9 the height of the tooth, has a tangent line angle that is 20° from the centerline of the tooth, then 20° is the pressure angle.
Awesome video! Any chance of you expanding on this and laying down some simple techniques for working out the profile shift factor for non-standard gears?
Bloody hell, you had me at 1:10 And here I thought that TubalCain (that was a schoolteacher) made it easy to understand, you have him beaten hands down
great video! waiting for your next video to find out measuring bevel gears for reverse engineering and also a way to find profile shifting .thanks man.
8:22 Andy: "Okay then, what's this?" me "That's just like the one I'm trying to identify!" (except mine isn't helical) Andy: "Maybe I'll save that for another video." me: "Nooooo!!"
Looking forward to your «another video». Those helical bevel-gears are a nightmare to understand and even more so to replicate. Allmost there, CNCing in nylon, but still not perfect.
Spiral bevel to be exact. I used Gearteq to generate them in solidworks and sent them out for fabrication. They cost a fortune to make on those specialised gleason machines.
Great... What a cliffhanger, exactly at the moment when it got "interesting". Have to wait now for a second part, to identify my strange gear I have in front of me... :)
I didn't go too deeply into the theory in this video (I've covered this in other videos). The reason is that the pitch circle diameter of the gear is equal to the module x the number of teeth. The height the teeth protrude above the pitch circle is (called the addendum) is 1x the module and there is a tooth on each opposite side which makes the outside diameter equal the module x number of teeth +2 x module, which simplifies to module x no. teeth +2.
Now what if they are Stub Tooth gears? Used to cut a lot of those. The Fellows variety. The pitch circle was one DP. And the tooth height was another. The gear pitches expressed by the pitch circle over the tooth height. One example being a 40 tooth 10/12 DP gear. A pitch diameter of 4.000 and an overall diameter of 4.000 + (1/12 x 2).
Experienced eyes would spot the pressure angle or stub teeth etc. Some corrected gears can appear a different pressure angle and when I used to design gears for the motor sport industry, We would often design gears with corrections so that standard tooling can be used for designing strong high pressure angle gears. (Not easy to spot with the nakid eye though)
I think I'm missing something here. I have some old helical gears from a 1970s Triumph gearbox. I measured the OD of one of them (89.85mm.) and it has 33 teeth. That makes the Module = 2.567mm.. I take it that is the width of a tooth around the PCD? I've measured a tooth at the approx. PCD and it is 4.6mm.
The tooth pitch (one tooth+one space) is pi x module, which would be just over 8mm. One tooth width would be half of this, ~4mm, which is a lot closer to your measurement. It can be hard to estimate exactly where the PCD is so you might have measured slightly further down, it's a little above half the tooth depth. 2.567 module sounds like it's probably a 10DP gear (=2.54 module) or if it's likely to be metric then probably 2.5 module.
@@AndysMachines Thanks Andy. The gearbox was derived from the earlier TRs so probably 1960s or even 1950s. I'm guessing we were using imperial measurements back then?
Brilliant , I need to pick your brain. I have a left tooth gear and a right tooth gear both the same size in every way, with a missing gear in the middle but not only is it missing it will be a smaller one in size, How do I determine what tooth and pitch and module tooth gear cog to buy. I own a old jewelers hand crank roller for rolling gold and silver, between the rollers ,but at the top there would of been a T bar handle with the stem of the T bar running through a small tooth cog, So when I turn the T bar the smaller cog would turn, When this small cog turns it also turns the left and right bigger cogs and these raise the roller.
Does the rolling mill have helical gears for adjusting the gap between the rollers, or straight cut spur gears? If they are helical they can't be opposite-handed if there is only one gear in between. A left will only mesh with a right, so the centre drive gear must be the opposite of both the larger driven gears. Perhaps I misundertood, and you just meant they are located on the left and right? If they are spur gears, this can be calculated from the number of teeth, (outer) diameter, and center distance between the gears (measure across both and subtract the diameter of one).
@@AndysMachines If I put it in another way, if I am looking down at the top of the machine (,birds eye view) there are meant to be three gears all in a vertical line so all the centers are in line with each other, The gear on the left is present, the gear on the right is present ,the gear in the middle is missing , so if i was to look down from above at these gears it should look like this OoO but the little center gear in the middle would be more central in line with the left and right , but at the moment it looks like this O O as there is a missing middle smaller gear. Now the left and right gears cannot be moved closer or further as they have center shafts holding them in there position, So the space between them can not be adjusted, So I need to find out what size , pitch and module gear is needed to fit into the center between the other gears, so when turning the middle gear, clock or anti clock it will turn the left and right gear at the same time. IF you could look up jewelers rolling mill on E bay you will see the three gears at the top, the middle one will have a T bar or a round wheel and handle connected to it by a shaft, this is the one that`s missing, on mine
Yes, I know what a rolling mill is. I was confused by your original description of left tooth/right tooth gears, but I think the gears should be straight toothed spur gears? (Teeth not at an angle). Can you provide the measurements above? (no. teeth, OD, center distance). If so I should be able work out what you need.
Great video.
My father was a gearbox designer and these parameters were often spoken of at out house. He wrote software in Pascal to calculate the various design parameters and working life according to the various DIN/ISO/AGMA/BS standards that all had their own quirks. and incompatibilities. All new designs were metric but he often had to fall back to the other standards when repairs were required for older imported machines.
Trip down memory lane, thanks.
That's a great video, thanks. I reverse engineer gears so infrequently that each time I have to re-learn what little I once knew about it, which is time consuming even with the notes I keep on it. Your video is much more concise, and also showed me how to do helicals, which I've never needed to do. I'll be adding a link to it to my notes, and probably checking out some of your other videos too. Thanks again.
Excellent video, please keep them coming, as you are the only person I've found that is putting this in to term even I can understand.
This is a very clear and no nonsense description of gears / gearing - exactly what I have been looking for!
YT is full of over complicated, underinforming rubbish about gears. This is the clearest, most informative video I have seen. Well done!
Can you tell me how to calculate the gear hob machine
This channel is better than school. Gratitude
Some subjects are best learned from a video rather than falling a sleep reading a machinist book. This is one of those subjects. Great info, thanks for sharing! 👍
Simple and useful video. First time I understood the left handed and right handed helical gear. Thanks a lot sir.,
Watching your explanation of the helical gear reminded me of a related experience. I worked with a mechanical engineer who specified which direction to feed the tap when tapping holes because he thought that tapping a hole in the "wrong" direction produced a left-hand thread. The machinists just played along with him. Since no incorrect threads were ever produced, the engineer never had any doubts.
I wonder if that would actually be possible with a very large diameter fine thread tap with lots of flutes? (And a lot of force). I expect it would just shred the tap.
@@AndysMachines Sorry, I didn't write my comment very well. The fellow I was referring to would always specify which side of the part to feed the tap into. There was no intention of trying to feed the tap opposite to the normal direction. His intention was to tap the hole from the same side as the fastener was threaded in. He sincerely believed that tapping from the opposite side produced a left-hand thread.
@@andrewhall2554 If he was making a taper pipe thread then he was right to be careful. :-)
You earned my subscription. Simple and clear explaination. Thank you.
Very clear and well explained. Looking forward to your next episode.
Thanks for the refresher! It’s been more than 30 years I studied this topic, and now that I need it your explanation helped me a lot. Hey I even remembered where my notes were. I need 2 gears in my new (used) lathe and I keep messing something in my calculations. I should’ve started with module and, if not working with diametral pitch. Thanks again.🙏
The best and most wonderful explanation I have ever seen in my life Thank you very much and we want more videos full of knowledge Well done sir
I used to be given chewed up gears to remake at short notice due to production breakdowns etc. It was like being Sherlock Holmes at times but very satisfying when I sussed out what it was and created a sparkling replacement for the grateful customer.
Your video helped me, it's easy to understand
thanks!
excellent description thankyou
You didnt make my nose eyes and ears bleed from brain overheating and I can now actually do it..... thankyou very much
extremely useful! Thank you!
A very clear explanation, thanks Andy
Tanks! I learned a lot about gears with your videos, never learned anything reading books about this topic! Now, a gear is less intimidating!
Excellent explained for gear module. Now you should make another video on bavel gear module formula.🎉🎉
Very good job my friend.... 👍 👍 👍 👍
Thankyou for making this so incredibly easy to understand its helped me a lot
Excellent! I can now finally identify the change gears on my Chinese made lathe/ milling combination machine. It has some damaged gears and I need to make new ones so I can screw cut some standard metric threads. Obviously I need to know the module so I can buy the involute cutters to do the job. I've got a rotary table with the disks with different holes in them for setting up the number of teeth, god my memory is getting bad these days I can't remember the correct name for them lol anyway thanks for this video it's so helpful.
Each time I was typing a question the answer popped up!
20+ years go I wrote some software that helped me determine screw threads. I was restoring my 1966 Norton 650 SS at the time, and had biscuit tins with indeterminate rusty screws from previous repairs. The result was probabilistic in that, given diameters and very rough tpi/pitch, and correcting for 30 years of rust, a likely thread was proposed. It worked well. I wonder if something similar could be done for gears.
The next step would be to determine screw threads and gear splodules optically, using a smartphone app.
It's an amazing compendium about gears identification. Kudos ! I'll save it for future reference. Thanks !
Edit: I'm anxious for part 2, bevel gears ? :o)
Thank you so much! I think it was my comment on your last video that prompted your making this one. I'm so glad. Now I have the information I need to either order an off the shelve gear for one of my old machines, or maybe even make one myself. Thank you!
Yes, it may well have been your question that prompted me to make this, though I've been asked how to identify gears a number of times, both on YT and in real life, so the next time it happens I can point them here!
Very fine explanation of this important technical fact. Great !
Very well explained good job Thanks a lot!
Amazing. Thanks for sharing. This is exactly what I was looking for. I'm just beginning to cut gears on my old Atlas.
Terrific video! Really looking forward to the spiral bevel gear video as that's what I need atm. Thanks for explaining so clearly:)
This really helped me to identify a helical gear! Thank You
Very great explanation💐💐💐
Outstanding, stunningly informative. Many thanks for posting, subscribed 😊
Well done!
A wealth of information.
Thank you so much Sir!
Well done - thanks! I look forward to the follow up video on bevel and whatever that last gear is called!
Great channel.
Just what I'm looking for. Thanks for sharing 🙏
Excellent video, thank you much!
I'll probably never use this knowledge but I really enjoyed it. Thanks
Thank you this is pure gold
Excellennt video, very clear, many thanks!
the last week or so I am literally trying to run all this down for some old transmission gears that are no longer made / in short supply and trying to figure out how to I.D and make my own should it become necessary ! Thank you !!!
This guy is legend👏👏👏 you cleared all my doubts🔥
This was exactly what I needed no more no less. Thank you.
Great video. I learned all that in school many decades ago, and The Algorithm must have known that I'd forgotten how to do it.
Great video, Andy. Don't be teasing me with that spyroid gear! ;)
really nice video 👍
Excellent Sir love from India
Thankyou so much for this!! Your explanations are very good 👍
BRILLIANT, I've been searching for this exact explanation in simple layman's terms, for ages, came across an American one, but he waffled on for over 8 mins what you explained in 1min. 😊😊 I'm assuming the 25.4 you mention is 1" in mm ?
Thanks! Yes, 1" =25.4mm.
You are the best!!! Thanks for the video
Excellent learning video Thanks.
But "what about the pressure angle" I was thinking.
I am bogged down at this step, so I guess from your video I should just go with 20deg unless it looks too fat or too thin. With a small gear I find it hard to judge.
You can use 2 guage pins and a micrometer and a gear chart to find it, but that chart may be extemely hard to find unless you have a gear textbook, and it would only work for even tooth count gears. The best way realistically is to genereate the gear in a cad program, add guage pin cross sections in sketch, and measure the distance in cad and compare to a micrometer measurement
For pressure angle of a spur gear tooth, find the point on the tooth that is radially 5/9 (0.5555) of the distance from the root circle, to the crown of the tooth.
Find the centerline of the tooth. This is the tooth's line of symmetry, which passes through the axis of the gear.
Measure the angle between the tangent line of the tooth at the aforementioned point and the centerline of the tooth. And _that_ is the pressure angle.
*Example 1:* If you find that the point on a tooth that is 5/9 the height of the tooth, has a tangent line angle that is 20° from the centerline of the tooth, then 20° is the pressure angle.
Great info and explanation. Thank you!
Very informative! Thank you for taking the time to share
Great video!!! Thanks for posting! 👍
Awesome video! Any chance of you expanding on this and laying down some simple techniques for working out the profile shift factor for non-standard gears?
Very interesting. Thanks
Bloody hell, you had me at 1:10 And here I thought that TubalCain (that was a schoolteacher) made it easy to understand, you have him beaten hands down
Very useful! Thanks for sharing your knowledge 👍
Damnit I wanted to know the last one lol nice video you do really clean work 👌
Very complete and useful explanations
Thank you
Thank you!! I bought a hand crank slicer and the handle with the gear is missing. I know what to look for now!
great video!
waiting for your next video to find out measuring bevel gears for reverse engineering and also a way to find profile shifting .thanks man.
8:22
Andy: "Okay then, what's this?"
me "That's just like the one I'm trying to identify!" (except mine isn't helical)
Andy: "Maybe I'll save that for another video."
me: "Nooooo!!"
I have a similar trick to figure out which hand is my left from which one is my right: The right hand is the one that has the thumb on the left. easy.
Looking forward to your «another video». Those helical bevel-gears are a nightmare to understand and even more so to replicate. Allmost there, CNCing in nylon, but still not perfect.
Spiral bevel to be exact. I used Gearteq to generate them in solidworks and sent them out for fabrication. They cost a fortune to make on those specialised gleason machines.
Great video you're the mech. God.
Plz make for the bevel and other gears also...
Great... What a cliffhanger, exactly at the moment when it got "interesting".
Have to wait now for a second part, to identify my strange gear I have in front of me... :)
Great information....thanx
Nice
Thanks for sharing 👍
You are awesome 👍🏻👍🏻🎉🎉 .. you got my subscription
These videos of yours should be shown in trade school
Great info mate..thanks👍👍👍👍
I'm still wondering where that formula came from.
Still great video.
I'm already waiting for the next episode
Really clear thanks I enjoyed that. 😀
Very informative, thanks!
can't wait for the another video you mention at the end (I think its name is a bevel gear)
Good job
What a nice job!
thanks i just learnt some thing...i guess the width will be called out for too.
Great video! What animation software are you using and do you like it?
Please keep making videos, they're great!
Why do you need to add 2 to the number of teeth when determine module or DP?
I didn't go too deeply into the theory in this video (I've covered this in other videos). The reason is that the pitch circle diameter of the gear is equal to the module x the number of teeth. The height the teeth protrude above the pitch circle is (called the addendum) is 1x the module and there is a tooth on each opposite side which makes the outside diameter equal the module x number of teeth +2 x module, which simplifies to module x no. teeth +2.
@@AndysMachines seems to me by that logic - the formula would be (OD-2)/N
Informative, Thanks...
Next video please new beast here from the Philippines 🇵🇭🇵🇭🇵🇭🇵🇭
thank you!
Now what if they are Stub Tooth gears? Used to cut a lot of those. The Fellows variety. The pitch circle was one DP. And the tooth height was another. The gear pitches expressed by the pitch circle over the tooth height. One example being a 40 tooth 10/12 DP gear. A pitch diameter of 4.000 and an overall diameter of 4.000 + (1/12 x 2).
Yes, they would be a special case, which would fall into the category of 'all the other types of gear I didn't mention'.
Experienced eyes would spot the pressure angle or stub teeth etc. Some corrected gears can appear a different pressure angle and when I used to design gears for the motor sport industry, We would often design gears with corrections so that standard tooling can be used for designing strong high pressure angle gears. (Not easy to spot with the nakid eye though)
I think I'm missing something here. I have some old helical gears from a 1970s Triumph gearbox. I measured the OD of one of them (89.85mm.) and it has 33 teeth. That makes the Module = 2.567mm.. I take it that is the width of a tooth around the PCD? I've measured a tooth at the approx. PCD and it is 4.6mm.
The tooth pitch (one tooth+one space) is pi x module, which would be just over 8mm. One tooth width would be half of this, ~4mm, which is a lot closer to your measurement. It can be hard to estimate exactly where the PCD is so you might have measured slightly further down, it's a little above half the tooth depth. 2.567 module sounds like it's probably a 10DP gear (=2.54 module) or if it's likely to be metric then probably 2.5 module.
@@AndysMachines Thanks Andy. The gearbox was derived from the earlier TRs so probably 1960s or even 1950s. I'm guessing we were using imperial measurements back then?
I'd guess imperial, but it could be either. 10DP and 2.5 mod are so close to each other though it might not make a difference.
Bravo!
What about bevel helical gear? How to indentify it.
Thanks for explanation
5:18
same applies for a helical gear?
Brilliant thanks for this
I need that 😍
Brilliant , I need to pick your brain.
I have a left tooth gear and a right tooth gear both the same size in every way, with a missing gear in the middle but not only is it missing it will be a smaller one in size,
How do I determine what tooth and pitch and module tooth gear cog to buy.
I own a old jewelers hand crank roller for rolling gold and silver, between the rollers ,but at the top there would of been a T bar handle with the stem of the T bar running through a small tooth cog, So when I turn the T bar the smaller cog would turn,
When this small cog turns it also turns the left and right bigger cogs and these raise the roller.
Does the rolling mill have helical gears for adjusting the gap between the rollers, or straight cut spur gears? If they are helical they can't be opposite-handed if there is only one gear in between. A left will only mesh with a right, so the centre drive gear must be the opposite of both the larger driven gears. Perhaps I misundertood, and you just meant they are located on the left and right? If they are spur gears, this can be calculated from the number of teeth, (outer) diameter, and center distance between the gears (measure across both and subtract the diameter of one).
@@AndysMachines If I put it in another way,
if I am looking down at the top of the machine (,birds eye view) there are meant to be three gears all in a vertical line so all the centers are in line with each other,
The gear on the left is present, the gear on the right is present ,the gear in the middle is missing , so if i was to look down from above at these gears it should look like this OoO but the little center gear in the middle would be more central in line with the left and right , but at the moment it looks like this O O as there is a missing middle smaller gear.
Now the left and right gears cannot be moved closer or further as they have center shafts holding them in there position,
So the space between them can not be adjusted,
So I need to find out what size , pitch and module gear is needed to fit into the center between the other gears,
so when turning the middle gear, clock or anti clock it will turn the left and right gear at the same time.
IF you could look up jewelers rolling mill on E bay you will see the three gears at the top, the middle one will have a T bar or a round wheel and handle connected to it by a shaft, this is the one that`s missing, on mine
Yes, I know what a rolling mill is. I was confused by your original description of left tooth/right tooth gears, but I think the gears should be straight toothed spur gears? (Teeth not at an angle). Can you provide the measurements above? (no. teeth, OD, center distance). If so I should be able work out what you need.
Thank you 🙏
wow this is good
I also have a helical gear. o.d 39.25 helix angle 16 degrees, and 11 teeth. Does the profile shift factor affect the modulus of the gear?
Best regards
Brilliant
I have gears files in STL format in CAd and i don't know what are its parameters? like the module, pitch etc
If you have an .stl you should be able to take measurements from it in the CAD program.