On Apr 22, 5:03*pm, "John L. Weatherly"
wrote:
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.
John L. Weatherly

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