# G4003 change gear specs.



## LEEQ (Mar 29, 2020)

Hi, I'm Lee and I'm a cheapskate. I got a lathe without change gears and I'm not paying what they want for a set. I want to cut my own. I measured up some that are in the drive train and kept coming really close to mod 1.5. I'm thinking that they are indeed mod 1.5 Now as to pressure angle I have no Idea. All of the involute cutters I find in module 1.5 are listed as having a pressure angle of 20 degrees. I think those are going to be the right cutters for me. I would love to hear from anyone who knows all the dirty details on these change gears. Grizzly was no help, and I'm just not certain.


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## Ulma Doctor (Mar 29, 2020)

Hi Leeq,
i possibly have another solution for you...
i went and took a module 1.5 24 tooth gear and adapted it for a 14mm keyway with a 3mm slot.
i can print these gears in PLA plastic in many common tooth counts
if you are game to try one, let me know i can print it.
the only things i will need to know are
tooth count
bore diameter/(with or w/o keyway)
thickness

check out the gear i was able to design quickly....








						3D design 24 tooth modulus 1.5 gear 14mm bore | Tinkercad
					

3D design 24 tooth modulus 1.5 gear 14mm bore created by Ulma_Doctor with Tinkercad




					www.tinkercad.com


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## Lo-Fi (Mar 29, 2020)

If they're metric gears, it's almost a given that they're 20° PA. As a manufacturer, you'd have to go out of your way and have very good reason for doing something oddball.


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## LEEQ (Mar 29, 2020)

I think they are metric. I'm not 100% on that.


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## Ulma Doctor (Mar 29, 2020)

they are metric


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## LEEQ (Mar 29, 2020)

Mike, the 40 tooth in my gear train is 10mm thick with a 16mm bore and a 5mm keyway. I'm pretty sure the change gears match that one . Except the 60 tooth that makes the metric world go 'round. It is going to be 10.07 thick with a 40mm boss on one side that is 8.84mm thick bringing it to 18.91mm thick total. It has a 19mm bore with a 5mm keyway, and the opposite side of the boss from the keyway has a set screw to bear on the shaft. I just pulled the lower 40 tooth gear to get those numbers for the 60 tooth that replaces it for metric set ups. I found a stamp on the back side of it that said 40T m1.5. It would seem I'm on the right track anyway.


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## LEEQ (Mar 29, 2020)

I will want to cut some metal gears for my limited metric needs. If I can't get any solid confirmation I might trouble you for a 40 tooth print up to check against.  I don't think it will come to all that though.


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## Ulma Doctor (Mar 29, 2020)

here you go @LEEQ!
a 60t, 18.91x 19mmx 5mm keyway










						3D design 60t 1.5 mod 19mm , 5mm key from 16U04P_USSR_lathe_change_gears | Tinkercad
					

3D design 60t 1.5 mod 19mm , 5mm key from 16U04P_USSR_lathe_change_gears created by Ulma_Doctor with Tinkercad




					www.tinkercad.com


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## LEEQ (Mar 29, 2020)

Wow, that's perfect. You went right for the fancy one.


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## LEEQ (Mar 29, 2020)

the simple ones are the 10mm thick ones with 16mm bores and 5mm keyways. They are listed as 26,27,35,36,45,50 teeth. You already did the main one. So do I have this right, you can print a plastic copy of that file you made? My 7x12 has hard plastic change gears and they seem to work. I would think that these would work for a bit of threading, if not for big hogging cuts. What do you all think?


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## Ulma Doctor (Mar 29, 2020)

if you would like i can print one to test, it's worth a shot!


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## LEEQ (Mar 30, 2020)

You are to kind. I still haven't repaid your help years back with a fistful of 3phase mill motor and converter wires. The resulting teco vfd and mill are still humming along nicely. For that kindness I owe you for sure.


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## LEEQ (Mar 30, 2020)

I have been pretty deep down the rabbit hole here. I went to good old you tube for help measuring pressure angles. I found nothing useful in the home shop in English. Hindi, yes. English, no. Makes a guy a bit more worried about how far my country has come and what direction we're headed. I eventually found something usable via google. Not a direct method mind you, but thankfully there are only two main suspects for pressure angles. That means probably only running the math twice if the first guess was wrong. What I found was formulae that involved dp. So the first step, divide 25.4mm by module 1.5.  I get a DP of 16.933333.  Now I take the cosign of my first guess of 20degree pressure angle(.9396926) and multiply by Pi, giving me 2.9521314. I divide this by the DP of 16.933333 and get .1743385. I add this to the number measured in inches(.4675) over 3 gear teeth ( as in squeeze them with my calipers). This gives me .6418385 for an answer that should represent the measurement over 4 teeth.  The measurement I took was .6405" over 4 teeth.  That's incredibly close to right. Should that have come out way off I would have done the same math but with the cosign for 14.5degrees. I would say this exercise left me feeling pretty confident of both module and pressure angle. Also a little sore in the noggin. So off to bang good for tools I can justify spending $ on. Hopefully someone else can use the math. I know I'm not the only one to want these answers before spending money.


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## Ulma Doctor (Mar 30, 2020)

LEEQ said:


> You are to kind. I still haven't repaid your help years back with a fistful of 3phase mill motor and converter wires. The resulting teco vfd and mill are still humming along nicely. For that kindness I owe you for sure.


Hi LEEQ,
repayment is not necessary at all.
i'm just happy to have been of service.

it would only take a few hours to print the 60T gear i showed earlier (or any other gear you may desire )
my intention is not to try to rob you of the joy of construction of the 60T gear. 
merely, i was offering another option if you needed something inexpensive and quick.
the offer stands regardless! 

i look forward to seeing the results of your gear making


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## LEEQ (Mar 30, 2020)

For the fancy 60tooth to be of use it would have to have a 45 tooth simple gear for a friend. I can wait though. Either way I'll wind up trying my hand with the involute cutters.  I bet a lot of guys like me would love the option to print them up though. It would take a bit of sting out when ya realize how much the missing gears cost. Higher than a cat's back for sure.


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## JMC_KY (Nov 14, 2020)

I too printed out the 60 tooth but need a 45 to test with 1.5 mm output.  Did anyone post a 45 tooth version?  I am having some issues with trying to use a parametric generator but the mod is limited to 1 or 2, (no 1.5 option).
Thanks in advance.
New to group


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## brino (Nov 16, 2020)

JMC_KY said:


> I too printed out the 60 tooth but need a 45 to test with 1.5 mm output. Did anyone post a 45 tooth version? I am having some issues with trying to use a parametric generator but the mod is limited to 1 or 2, (no 1.5 option).
> Thanks in advance.
> New to group




Hi @JMC_KY,

If I understand this correctly you need the stl file to 3d print a gear, right?

If you can post back with all the specifications I can generate it in Fusion-360 and post it back here.

Here's what the gear-generator pop-up looked like a few years ago......


from this thread:
https://www.hobby-machinist.com/threads/gears-for-my-oldtimer-lathe.82245/post-718697

I'd need all the specs shown in that picture.

Brian


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