On the Harbor Freight 9 x 20 Metal Lathe
Hobbing a 180 tooth aluminum worm gear on the 9x lathe
Hobbing a 180 tooth aluminum worm gear on the 9x lathe
Here's some information
on an experimental set of worm gears I built for one of my telescope
mounts. After
visiting Chris
Heapy's web site I decided to give gear hobbing a try!
Please note that my "experimental"
worm gears are no where
close to the quality Chris has achieved but more of a learning experience
for me.
To build a worm
gear using this method requires a mill with either a diving head or a rotary
table and indexing
plates to index or "notch"
the gear blank to the correct number of teeth to be formed. Once
this is done the gear
is placed on the cross slide
of the lathe using a bearing support. A hobbing cutter ( described below
) is then
centered in the lathe chuck
and supported by a tailstock live center. Once it's determined that the
cutter and gear
blank mesh properly the
lathe is ran at a slow rpm while cutting oil is applied to the cutter.
The top slide is slowly
advanced until the teeth
are fully formed. Since I plan on building more than one worm gear
I did go to some
extra effort and build a
heavy duty bearing support just for the 9x lathe. This allows the worm
gear blank to be held
securely & in perfect
alignment while turning cutter form the gear teeth. I've included pictures
along with building
details for anyone interested.
Gear / Bearing support mounted on cross slide of the 9x lathe. The
ball
handle on the left is "pushed in"
to lock up the shaft for attaching or removing the attaching nut on
top. I built the bearing support to fit 1/2"
thick gear blanks. Once the bearing support is attached to the cross
slide no height adjustments are
necessary I also built the bearing support with a 1" OD spindle.
Boring the gear blanks to a 1" ID
makes alignment easy. ( Building details below )
This was an experiment to see just how well threaded bolt stock
could work for worms.
These are 3/4"-10 tpi threaded grade 5 studs 6" long.
For the next project I plan on turning my own 10 tpi worms. ( see below
for update )
Finished 180 tooth worm gear.
Update 1-26-03
Acme Thread
I just finished a set of 200 tooth aluminum gears
using 10 tpi Acme threaded rod. I purchased the
1/2" od x 10 tpi x 3' threaded rod from
MSC industrial supply for $6.00 The Acme thread shown
below makes a very nice worm gear. The Acme threads
are very close to a true worm form. Very good
thread depth. I used the exact same procedures
for hobbing these gears as described in the info below.
If you plan on hobbing any worm gears I would
highly recommend using the Acme threaded rod.
Acme thread on top & a regular bolt thread
on bottom.
Here's the hob I made by grinding slots in the
10 tpi Acme threaded rod.
Finished gear & worm shaft
Finished pair of 200 tooth worm gears !!
Click below for more details
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Copyright 2001 / 2003 Steve
Bedair