Steve Bedair's
9 x 20 Lathe Site
Longview , Texas
    1 -2003
Hobbing Worm Gears
Gear / Bearing Support

The bearing support uses the the spring loaded locking pin with the ball handle
to "lock" the shaft for attaching and removing the worm gear blank.

        The bearing support in my opinion is the most important part of the hobbing process. The gear blank needs
     to be perfectly centered and set at the proper cutting height to produce an accurate worm gear. You also have
     to make sure that there is no flexing or movement of the gear blank while hobbing.
     Since I plan on building more worm gears I decided to go to the extra effort to build a bearing support that I
     can use over and over without having to spend a ot of time setting up. Here's what I came up with and it works
     beautifully.  I didn't include many measurements since every lathe is a little different.
     Hopefully the pictures will give you some ideas.

Here's all the pieces laid out. I built this entirely from materials I had on hand.
The bearings I used are tapered wheel bearings ( trailer wheel bearings )

    The body of the bearing support is built from a 2"  heavy steel pipe coupling ( 2" ID ). To determine the overall height
    the coupling needed to be I placed the coupling on the top slide of the lathe and used the tail stock live center to scribe
    a line around the coupling. This marked the center line of the gear. I  subtracted .250" from the line to determine the
    actual gear placement height for a 1/2" thick worm gear.  I also had to allow for bearing height and the width of the
    shoulder of the shaft that the gear blank will sit on.
    After the height of the coupling was determined I used the 9x lathe to bore each end of the coupling to accept the
    bearing race. The top bearing race was bored so the the bearing race was flush with the top of the coupling.
    The bottom bearing race was bored deeper to allow for the attaching screw and large washer ( shown later )

        Once the body of the bearing holder was bored for the bearing races , I attached the the body to
        a 1/2" thick steel base. The base is a piece of 4" x 4"  1/2" thick steel plate. I bored a large hole through the
        center of the steel plate to allow the pipe coupling to pass through. I then welded the coupling to the base from
        the bottom.

Bottom view with bearing in place. After the 4 welds were made
I faced the bottom of the mount to achieve a flat surface.

The shaft was turned from 1 7/8" OD stainless steel.
The attaching threads are 3/4"-10 tpi and were turned on
the 9x lathe. The ball handle on the left is a spring loaded
pin that when pushed will "lock up" the shaft to allow the
attaching nut to be tightened or loosened.

The finished shaft. Two slots were milled in the side of the shaft to allow
for a locking pin to fit into. The milling was done on my Grizzly mini mill.

The threads were cut to 3/4"-10 , the shoulder next to the threads
is a precise 1" OD for easy centering the worm blank.
The threads were done on the 9x20.

This shows how the spring loaded locking pin works.
This allows the attaching nut to be tightened and loosened
without the shaft turning.

The bottom of the shaft was drilled and tapped to a 3/8"-16 thread.
The shaft length is approx 1/16" shorter than the bearing.
This allows a large washer and screw ( shown in the next pic )
to tighten the shaft and bearings.

A large steel washer and a beveled 3/8"-16 allen head screw provide
the bearing pre load adjustment. Locktite was applied to the threads
for final assembly. The large washer has just enough clearance to turn
inside the bearing housing.

A thin brass ring works as a cover to protect the top bearing from any cuttings.

I turned a groove to allow a rubber "O" ring. The rubber "O" ring
holds the brass cover in place.

Finished Bearing Support !

Click below for more details

Bearing Support Building Pics Gear Blank Building Pics Worm / Cutter
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 Copyright 2001 / 2003 Steve Bedair