Some pics of the steps I'm taking to attempt to make
a high accuracy worm and worm gear.
(Inspired by a few articles on the internet and also
keenly following Jeff's progress on his Project 24 thread):
http://www.iceinspace.com.au/forum/s...ad.php?t=39135
This is only part 1. Hopefully, if this works, I will have
a part 2
I started with the spindle.
I made it out of a pipe fitting welded to a piece of ms plate.
After turning down the two housings for the bearings, I then
made a shaft and turned a thread either end.
These parts once assembled are mounted on the tool post
cross travel on the lathe.
This gives you cross travel adjustment for the cut and transverse
travel to centre it on the thread cutter. Height is obviously critical
and some homework was done to make the spindle just the right
height. Some fine adjustment can be done with packers under the
'flange' (below).
The flange for holding the raw worm wheel blanks was turned down from
an old VCR head.
These have the most beautiful aluminium I have ever seen. Probably
what they call aircraft grade.
I cut two steps on the flange for locating centre the two types of
worm wheels I'm ever likely to make:
One for fitting on a 1.5" shaft (my R.A. axis)
One for fitting on a 1.25" shaft (my Dec axis)
To lock the flange down on the spindle I needed to temporarily lock
the spindle from rotating.
This was done with a hole drilled through the side of the spindle
housing and shaft to enable a pop rivet to be slid through for tightening
and undoing the flange. And also for pre-loading the bearings to eliminate
any play (very important).
My first test run will be the aluminium platters from a very old hard disk
drive. These are enormous, but also beautiful high grade aluminium.
The worm thread cutter is obviously also critical for accuracy.
As my lathe can cut almost any metric threads, I decided to try
an M12 thread to start with on the test case blank.
My proper cutter (not shown) is an M12 plug tap mounted on an
extension and held between the chuck and a live centre.
For the test, I will just use a piece of M12 thread also mounted in an
extension.
I have read that the best worm thread is an ACME shaped thread , the
type similar to a vice thread or car jack.
If these test runs go well, I will then try making an ACME shaped thread
in the lathe, starting with M12.
more to follow.
Steve