"Karl Townsend" wrote in message
...
On Fri, 2 Mar 2012 20:13:56 -0700, "Bob La Londe"
wrote:

The HF mini lathe hasn't been used since I got the slightly bigger much
older, and much better HF lathe. I wanted to use it the other day though
because it has gear selectable forward and reverse carriage feed. The I
remembered I stripped those little nylon gears. I am sure I can get a
hold
of HF customer service and get a part number for those gears if its not in
my manual for the machine, but I was wondering if somebody knew of a
source
for metal replacements? I know Little Machine Shop was the threading gear
set in metal, but I didn't see the rest of the gears for the machine.

My next thought was maybe to try and make some metal gears, but I have
never
done that before. Any suggestions on the approach for that? Best alloy
for
reasonable wear?







You'll need a dividing head,

I don't have a dividing head, but I did recently fit my little rotary table
with a lathe chuck, that is reasonable centered and parallel. Is that "good
enough", or do you think a head with dividing plates is a must.

and involute gear cutter for the
diametrical pitch and pressure angle and the approximate number of
teeth in your gear. eBay is a good place to shop.

Involute gear cutter? Is that one of those "wheel" type cutters I often see
in videos on a horizontal mill being used for gear cutting?


With these two tools, its a piece of cake, cut a tooth to depth,
rotate head, cut next tooth.

You might read "Gear and gear cutting" by Ivan Law to get a good grasp
of the subject. You'll need machinery handbook to calculate your
depths and blank and rotation values, etc.

To replace a plastic gear, I'd use AL.

I could certainly cut aluminum. You wouldn't worry about galling in this
application? I don't really think of aluminum usually when I think of an
interacting mechanical part. As a static or linking part sure, but aluminum
to steel with mechanical interaction and friction?

Otherwise, I've made gears out
of 4140 and then hardened. I've had one running in my backhoe for ten
years now.

LOL. On the mini lathe they would outlast the entire rest of the machine.

This is a good basic skill to have. You're sure to be confused at
first, but then it will seem easy. Just like learning to ride a
bicycle.

I have seen some gears cut with a slitting saw, but I wasn't super
comfortable with the process. What do you think? Probably go pretty quick
if I went with aluminum.