Cutting transmission gears on a budget

Hello everyone,

I am interested in cutting a set of spur gears (ie. straight cut gears) for my cars transmission. I've done a lot of research online on the topic of cutting gears, most of the information I come across talks about the use of very large and very heavy shop equipment (ie, 4,000lb, 6ft tall, 220v 3 phase machines). While these machines can be purchased 2nd hand for about $1k~ and converted to run on single phase 110v, I don't have the room for one of these machines.

My question to you guys is, could I get away with a 400lb~ Benchtop Mill/Drill to cut transmission gears? I'm most concerned about deflection while cutting. I don't expect to cut each tooth in one pass, if I have to take it slow while cutting that's OK.

Hello!
Before the crap hits the fan, read this: Machinery Discussion Guidelines

This thread will be locked, and the comments that come before that will not be kind. Don't take it personally. It happens all the time!

What color is the car ?

Please post a pix or 2

digger doug said:

What color is the car ?
Please post a pix or 2

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Dammit Doug... you owe me a coffee and a keyboard.

Thanks Gordon! I'll correct course.

RC car? Probably yes.

Road going car? Probably no.

Definitely,first OP wants to cut gears on a budget,then he wants to cut them on a mill(drill)....indecision is inimical to good governance,or indeed a satisfactory outcome.

TX_to_AZ said:

Hello everyone,

I am interested in cutting a set of spur gears (ie. straight cut gears) for my cars transmission. I've done a lot of research online on the topic of cutting gears, most of the information I come across talks about the use of very large and very heavy shop equipment (ie, 4,000lb, 6ft tall, 220v 3 phase machines). While these machines can be purchased 2nd hand for about $1k~ and converted to run on single phase 110v, I don't have the room for one of these machines.

My question to you guys is, could I get away with a 400lb~ Benchtop Mill/Drill to cut transmission gears? I'm most concerned about deflection while cutting. I don't expect to cut each tooth in one pass, if I have to take it slow while cutting that's OK.

Click to expand...

Yes you can or could cut a gear with a mill drill...
And that method will teach you things you can not imagine.

The thing is thats kinda like cutting an acre of lawn with a pair of scissors. Yes it can be done... but do you wanna?

I am not an expert.... I guess you might say Im a tolerated retired hobby guy. On this web site there are honest to GOD experts that make their livings cutting gears. So my advice aint worth all that much. But then again you didnt pay anything for it...

I have cut several hundred gears over the years. And Im a card carrying novice compared to the guys here!
The mill I bought to cut gears is a Rockwell 21-100
It fits in the area I have and uses the taper 30 tooling I already have. It is small... sometimes too small... It does an okay job. I can always tell when Im making a too heavy cut.... it walks across the shop...

Something like this could do what you want with a minimum of heartache...
if you are in Phoenix gimme a yell.... who knows I might be of some help on your quest for a gear....

And no Im not for hire.

And then if these gears are for a real road going vehicle what about heat treating etc.

JohnEvans said:

And then if these gears are for a real road going vehicle what about heat treating etc.

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If he's making them in a mill-drill then may as well heat treat them with a torch

One question for the OP tho - I hope you aren't thinking that spur gears are better because they have less friction, or some such nonsense ? Because it's not true. You'll be wasting a lot of effort if that's your goal.

Why not?
You need a dividing head (index plate can be made on cnc nowadays) and set of disk cutters.
After cutting, you will have to do lots of hand work - defurring, chamfering, polishing.
Do not heat treat whole stock! Find someone with induction heater (high frequency AC) and ask to heat treat just 1/16" depth of teeth.

kiriba-ru said:

Why not?
You need a dividing head (index plate can be made on cnc nowadays) and set of disk cutters.

After cutting, you will have to do lots of hand work - defurring, chamfering, polishing.
Do not heat treat whole stock! Find someone with induction heater (high frequency AC) and ask to heat treat just 1/16" depth of teeth.

Click to expand...

Pssst....Yes the OP might be able to...just not here.

Please refresh your reading on the "sticky" up top dealing with "discussions".

Gears have been made using a WIDE variety of processes and tools. Early clock makers filled they by hand and made clocks that performed quite well. The big auto makers use very expensive machines that can hold tolerances in the range of millionths of an inch in order to be able to make gears that can take the extreme stresses of road vehicles and last 10, 20, 30 years or more.

You have not even said if "your car" is some kind of model vehicle or a full size, vehicle that you ride in. That would be helpful. Also, it would be very helpful to know just why you want to make these gears. Are you building this transmission from the ground up? Are you trying to change some stock gears for some custom ones for a particular reason, like getting a different ratio?

Frankly, if you think you are going to improve a transmission in a street vehicle that was designed and built by a major auto maker, I think you have a hard row to hoe. Not impossible, but hard. And you will not get the level of precision that a multi-million dollar machine is capable of with a machine that only costs a few hundred dollars. At least not without an extraordinary amount of skill - the type of skill that only comes with decades of gear cutting. But have fun.