FILENAMES:

banjoblock1.jpg  
banjoblock2.jpg  
banjoblock3.jpg  

DESCRIPTION:

These are pictures of a fixture for gear setup on manual 
gear change lathe.

Posted by James Waldby <j-waldby@pat7.com>. 

The following description was provided:

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"Banjo Block" -  Fixture for gear setup on manual gear change lathe
   James Waldby - 3 April 2003

These pictures show a simple fixture for setting up the correct gear
spacing on the banjo of a 7x10 mini-lathe.  This fixture idea probably
will work with any lathe that uses a banjo and requires manual changes
of threading gears.  I didn't invent this fixture; it's based on a 
webpage picture I saw last year but haven't been able to find again.

The "banjo" is a plate with 2 slots and a round hole.  See pictures in
banjoblock1.jpg, showing the banjo on and off the lathe, and the
adjusting nuts.  The slots allow you to move gear mounting bosses back
and forth to get proper engagement for different sizes of gears.

Without such a fixture, setting the intermediate gear requires
reaching in behind the gears with a wrench and then tightening the nut
while attempting to hold the intermediate gear in position.  It's
somewhat faster to use this banjo block and do the adjustments with
the banjo off the lathe.

To use the fixture: Remove the banjo from the lathe, using 5-mm Allen
wrench (to remove final drive gear) and a 14-mm socket.  Install
desired intermediate gears on banjo, then loosen the nut on the
intermediate drive gear's bracket and slide that gear out of the way.
Press the fixture through the round hole of the banjo.  (See
banjoblock2.jpg.)  Place the final drive gear on the fixture.  Slide
the intermediate gear up to engage the final gear.  Tighten the nut on
the intermediate drive gear bracket.  Put the banjo back on the lathe
and rotate to engage the drive gear.  Fasten with 14-mm nut.

Construction: Get a 1.6" long piece of 1" bar.  (Eg, 1" round or
square metal or plastic.  I used a rectangular bit of aluminum scrap.)
For use with the 7x10 mini-lathe, turn 1" down to 0.784 and then turn
0.682" of that down to 0.470".  See banjoblock3.jpg, which shows three
sides of block and a rough sketch with dimensions.  For other lathes,
adapt measurements appropriately.  
- James Waldby