Steve Bedair's
9 x 20 Lathe Site
Longview , Texas
Updated 1-26-03
Hobbing Aluminum Worm Gears
On the Harbor Freight 9 x 20 Metal 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

Bearing Support Building Pics Gear Blank Building Pics Worm / Cutter
Building Pics
a  Gear  & 
9 x 20 Lathe Page 9 x 20 Projects Page Home


Comments /  Questions / Suggestions or Add Your Link

This information is provided for personal use only
 Copyright 2001 / 2003 Steve Bedair