On Fri, 02 Dec 2011 15:19:47 -0800, Jon Anderson
wrote:

On 12/2/2011 2:12 PM, wrote:

Can you not use a regular worm gear and Acme threaded rod with the
same pitch?


Don't see why not, but I'm looking to either use as much as I can from
my scrap and parts bins, or buy something that'll do the job. If I have
to go buy acme screw stock and a worm wheel and add labor to that, I'm
getting close to the tipping point of just buying a focusing block.
If I could get a post mount focus block for $50, I'd just do that, but
cheapest I've seen one on ebay is around $90.
Spend money and save labor or spend labor and save money. Don't want to
do both... And, I do like the idea of doing something a bit different...


Jon

Greetings Jon,
I have made for myself several worms and wormgears using the tap
method. If you decide to go this route use a high spiral tap if you
have one. These taps stay engaged in the work constantly. I have had
no trouble getting the exact numbers of teeth I wanted. I have used
3/8-16, 5/16-18, M8 x 1.25, and other taps of similar size but
different pitches to cut the wheels. I just hold the tap shank in a
collet. The wormgears (AKA wormwheels) I held with a screw screwed
into a piece of steel stock held in a toolholder on the Aloris
toolpost. Making the gears out of brass is easy and I bet you could
make your first one in less than 1/2 hour.
Eric