Gear making (was Calling All Machinists)

When I had a watch, clock, and instrument repair shop, cutting gears was a weekly routine. Most were horological, and some involute.

Steve R.

I always made my own cutters for spur gears and pinions. That's what old files are for! :) Material for the cutters that is!

Steve R.

Steve R.

Yes!

Involute cutters sell for nothing (I got some nice ones for £3 GBP a piece at a show) and are a fortune to buy new got quoted £100+ from a couple of places for the same cutters...

Besides which cutting your own gears is good for the soul!

Steve

You might find these old books of interest too:

"Hobs and gear hobbing (c1914)" by John Edgar"

"Examples of machine shop practice (c1910)- Cutting Bevel Gears with a Rotary Cutter " by Howard Parker Fairfield"

[ ... ]

A great deal! Quite an interesting mix of tooling. Looks like the box with the "154" tab has both Woodruff keyseat cutters and T-slot cutters as well as the various conventional milling cutters and slitting saws.

I *did* say above that you can make do with rotary table. It isn't the accuracy which is in question mostly, but loosing track of turns and fractional parts thereof. In the dividing/indexing head, you set a pair of arms on the disc full of circular rows of holes to a specific angle. set the pin on the arm out to the proper row (a table which comes with the head tells you which hole counts you can use, which often means that you don't need to change disks. There are three in the set for a 40:1 dividing head such as my B&S, and changing them is a bit of a pain.

Anyway -- you set the pin in one of the holes, and move the arm pair so one of the arms touches. You mill your first tooth gap to depth (using however many passes make sense to you -- a function of the rigidity of the machine among other things), then you (according to the table) pull the pin, turn the crank N turns, and then continue until the pin is right at the other arm and drop the pin into the hole which is there. Shift the arms so the first arm is again touching the pin, mill your next tooth gap, and repeat the above. When you reach a position where the tooth gap has already beed milled, you are done.

With the rotary table, you have to both count full turns, but have to look up what degree and minute point you need to stop at. It is very easy to lose count and wind up at the wrong position.

If your rotary table has the pin disc and arms (and the table) you might be able to do it just as you do with the dividing head.

Note that the rotary table will be larger in diameter than the indexing/dividing head, so you may have to set up your cuts at a greater distance from the head.

In either process, it is good to go fully around the gear blank making the shallowest of cuts to make sure that it works out even before cutting deep enough to actually make the teeth.

While we are about it -- if you have the long arbor for the right-angle head, *and* the bracket which clamps on the dovetail of the mill's ram, you should be able to take heavier cuts. If you are just using the right angle head and the stub arbor, you may have to be very careful of how deep your cuts are, because too deep a cut may dig in and twist the right angle head on the quill -- probably breaking the cutter.

For practice -- use the rotary table. Just be particularly careful.

The lathe is the most likely thing to benefit from the ability to make gears. The mill should still have replacement gears (and other parts) available. I don't think that the compressor uses any gears at all. :-)

And perhaps list here what you have once you are done?

Enjoy, DoN.

I know a guy that makes gears and all sorts of wild stuff. He does a fair amount of stuff for the commercial marine business and large power this and that is normal. Winches and drive gears.

My wife knows his wife very well.

Mart> >>

Sounds like you've done it a few times.

It's a tedious procedure that demands close attention and you can easily lose count if distracted by a problem. In such cases I make a spreadsheet table of the settings to use as a checklist. It's particularly useful when I have to back up and re-establish position, for instance if the blank shifts or after testing the fit with the mating part.

Once you have the full circle of shallow cuts, and the last coincides with the first, you can use them to confirm the alignment for the next deeper cut.

All the ones I've done required custom cutter shapes. I've roughed the grooves with whatever saw or gear cutter worked best, then alternately ground the bit closer to shape and milled the teeth with it, so that when it's finally right it doesn't have much metal left to remove.

jsw

The arc of holes across the top of the frame is a vernier with 1 degree resolution.

jsw

On Jun 29, 8:35=A0pm, Ignoramus24381

I am a lousy typist. Can not type fast enough so sometimes leave out words. You are correct in that I left out the not.

What I was trying to say is that a cheap Spin index can often be used and it may be easier than using a rotary table. Of course there are other issues with using a spin index. Dan

Thanks Dan... Now I understand much more than I did before you mentioned spin indexes. (or should I say "indices")

i

DoN, thanks, I will post a list when I have it.

i