Drill Press Repair

My father-in-law has well broken in drill press that he wants me to repair.
He told me it was built in 1918. It says "CANEDY OTTO MFG CO" on the side
of the column. Flat belt driven. Has a counterweight inside the column
with a chain attached to the quill. Has all kinds of open gearing on it.
Has been retro-fitted for an electric motor.
The problem is the gear that engages the rack gear on the quill is stripped.
That means no feedy up or down. The shaft the gear is machined on is in
good shape. It looks looks like they machined the entire shaft and
shouldered up to the gear. Weird.
Two questions:
1) Should I build up the gear with weld and machine it down, or machine the
gear separately & silver solder it on? I have lathe capabilities as well
as a 25" Smith & Mills shaper with a dividing head on the way (generous
payment [gift] for the job.
2) How the hell do I reverse engineer the worn gear? I can count the teeth,
but that's about it. The rack gear on the quill is in decent shape. I'm
sure there is an equation three pages long for it, I'm just ignorant about
gears.
What do y'all think?
--
John L. Weatherly
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Reply to
John L. Weatherly
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I think the angle of the sides of the rack teeth is the pressure angle. Common values are 14-1/2 and 20 degrees.
An old technique for copying gear teeth is to make a crude oversized gear out of thin lead and roll it against the good gear until the center distance is correct. Then grind a shaper bit to fit the gap between lead teeth.
Jim Wilkins
Reply to
Jim Wilkins
Yes. And the number of teeth per inch is the pitch. If you're lucky it'll be a standard spur gear. In which case I'd buy the proper gear from Boston Gear, Union Gear, or Martin. You can verify you've picked the right gear by comparing the center distance between the shaft and rack with the catalog value. The numbers are also in Machinery's Handbook.
Turn down the shaft a bit below the teeth of the old gear, bore the new gear for a shrink fit onto the shaft, and taper-pin it in place. Or some variation based on the actual design of the shaft.
Cute!
Reply to
Ned Simmons
It looks looks like they machined the entire shaft and
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It might be worth taking a closer look. And maybe asking some more specific questions about this part. I would think that even back then they'd have wanted to use a different material for the shaft and for the gear. Take the machine apart, clean up that shaft completely and look at it for a couple of days. Take some pictures and post them. You might find a pin or two that were strategically placed . The head may have been carefully filed to match some other feature, making it hard to see under a lot of grime.
These machines are often called "camelback drill presses". Searching for such a thing may shed a little light on the subject, or give you a clue as to where to go next.
Pete Stanaitis ---------------------
Reply to
spaco
Dress a cutter tool to the root shape of a pair of teeth on an unworn area on the rack. Now count the teeth on the gear and measure the diameter. Layout a circle to that diameter and layout the teeth to match the old gear.
As for how to attach it. I would machine the current gear down the a hub in a standard size. Machine the new gear in that size minus a few thousandths. Attach the new gear by heating it in an oven and pressing it on the hub. Once it cools it will be solid, no key or solder involved.
Reply to
Steve W.
I appreciate all the replies. Here are some photos:
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I had thought about the boring an existing gear idea, but as you can see, the whole depth of the gear is only slightly larger than the shaft diameter. I like the shrink fit idea. Maybe I could make it in three pieces? The good news is there is one good tooth profile left.
Reply to
John L. Weatherly

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