Gear Cutter, What can you get away with

B

Blair

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Hi everyone, new here and is my first Post
I am looking for gear cutters on ebay I need 6 DP 14-1/2 degree PA Cutters #3,#4, and #6. I am having trouble finding the #6 cutter which is located in USA or Canada because China is now shutdown to exports.
So my Question is, Can I get away with cutting a 20 tooth gear with a #5 cutter which is used to cut 21-25 teeth, the #6 cutter is on the High side 17-20 teeth, so would the gear run ok in my change gear train to cut threads?
Also can you use a 20 degree tooth gear with a 14-1/2 degree tooth in a not so perfect world or situation

Thanks for all your opinions and suggestions
Blair
 
if both gears will be cut from the same tool, the point is moot
they will match
 
I likely have a spare cutter, will look. If the gears are cut with the same cutter, they may not mesh properly with each other and others in the gear train, they could run rough or noisy in proper mesh.
 
Good morning, Sir. And welcome aboard. Keep in mind that I am by no means a machinist. I have an electrical background and spent my life keeping the machines running. My knowledge is at a hobby level, not professional. Although I have, and use, a copy of Machinery's Handbook.

With that said, my first suggestion would be to study up on gear cutting, preferably with text instead of videos. Gear cutters "fit" one size correctly, the rest of the span is an "almost right, close enough" fit. If I were facing your particular situation, I would size the gear close to the first number and run some lapping compound for a while instead of oil. But that's me, not professional advice. Further, lapping compound will be "sticky" and you must consider the other gears in the train.

I think the first consideration would be to consider the use for such a gear. Is it a change gear for threading on a lathe, or a transmission gear for an automobile. The lathe gear can be soft, brass or even plastic for a smaller machine. The transmission will have to be tough, will have high torque and carry you away from the ability to quickly repair it. Your call~~~ Would it be practical to print a plastic gear? That opens up a whole 'nuther subject.

The second consideration would be the ability to mesh, specifically the pressure angle. Different pressure angles DO NOT MESH. Period. Consider if you would take a 14 DP gear and try to drive a 16 DP gear? That would be sort of like trying to mesh 14-1/2 and 20 degree teeth. I'm sure that if you had the time and enough lapping compound, and didn't mind sharp edges that they could be made to run together. But there are practical limits.

In both cases, a possible solution could be found using gear cutters from Russia(?). I have several sets that I'm not too sure where they came from. Some from China, some from Eastern Europe, some from Russia. Search eBay, looking long and hard for your particular size(s). And don't necessarily buy the first set you find. Look for price and availability over some time. I took months to find what I wanted. Some for the reasons given, some because I didn't have the money right away. But I got what I wanted eventually, at less than $100 per set of 8. Waiting works wonders~~~

I cut mostly plastics and aluminium so am not too particular about how tough they may be. Your results may (and probably will) vary, depending on material and your patience.

EDIT (or afterthought)
BTW, I do have a 6DP14-1/2* gear cutter but don't know which number it is. I don't use gears that big so never checked. 1 inch mandrel, it came on the mill when I bought it. You're welcome to it if it would help.

Bill Hudson​
 
Last edited:
Bi11Hudson said:
Good morning, Sir. And welcome aboard. Keep in mind that I am by no means a machinist. I have an electrical background and spent my life keeping the machines running. My knowledge is at a hobby level, not professional. Although I have, and use, a copy of Machinery's Handbook.

With that said, my first suggestion would be to study up on gear cutting, preferably with text instead of videos. Gear cutters "fit" one size correctly, the rest of the span is an "almost right, close enough" fit. If I were facing your particular situation, I would size the gear close to the first number and run some lapping compound for a while instead of oil. But that's me, not professional advice. Further, lapping compound will be "sticky" and you must consider the other gears in the train.

I think the first consideration would be to consider the use for such a gear. Is it a change gear for threading on a lathe, or a transmission gear for an automobile. The lathe gear can be soft, brass or even plastic for a smaller machine. The transmission will have to be tough, will have high torque and carry you away from the ability to quickly repair it. Your call~~~ Would it be practical to print a plastic gear? That opens up a whole 'nuther subject.

The second consideration would be the ability to mesh, specifically the pressure angle. Different pressure angles DO NOT MESH. Period. Consider if you would take a 14 DP gear and try to drive a 16 DP gear? That would be sort of like trying to mesh 14-1/2 and 20 degree teeth. I'm sure that if you had the time and enough lapping compound, and didn't mind sharp edges that they could be made to run together. But there are practical limits.

In both cases, a possible solution could be found using gear cutters from Russia(?). I have several sets that I'm not too sure where they came from. Some from China, some from Eastern Europe, some from Russia. Search eBay, looking long and hard for your particular size(s). And don't necessarily buy the first set you find. Look for price and availability over some time. I took months to find what I wanted. Some for the reasons given, some because I didn't have the money right away. But I got what I wanted eventually, at less than $100 per set of 8. Waiting works wonders~~~

I cut mostly plastics and aluminium so am not too particular about how tough they may be. Your results may (and probably will) vary, depending on material and your patience.

EDIT (or afterthought)
BTW, I do have a 6DP14-1/2* gear cutter but don't know which number it is. I don't use gears that big so never checked. 1 inch mandrel, it came on the mill when I bought it. You're welcome to it if it would help.

Bill Hudson​
Click to expand...
When you have a chance check the cutter to see what # it is
About the pressure angle, you compared it to meshing different DP's, but in that case the teeth are different size and pitch so they can't mesh with each other.
I the case of 14-1/2 compared to 20 degree, the 20 has a narrower crown and a wider root, but the pitch of both gears are the same or at least very very close, I would think you should be able to adjust the backlash enough to compensate for it. Another thing I might be able to do if it didn't adjust close enough because the tooth bottoms out, I could turn the OD down to get my clearance tighter for the narrower 20* tooth.

Am I right or am I way off base with this thinking

Thanks Blair
 
Blair said:
Am I right or am I way off base with this thinking
Click to expand...

I'll vote "hold out til you get that $20 correct cutter" . That is one hell of a bargain. I thought heck if he doesn't want it I'll buy it.
But then I checked and I already have one.
 
rgray said:
I'll vote "hold out til you get that $20 correct cutter" . That is one hell of a bargain. I thought heck if he doesn't want it I'll buy it.
But then I checked and I already have one.
Click to expand...
Im going too but I want to understand how it all works and what one can get away with if they have too
the last gear i cut was in vocational school in 1978, got it sitting on a shelf over the living room window
 
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