Re: ATM 48mm thread for Filter Slide?

[Doug Tanaka <dtanaka@seanet.com>]

Jim,

I made a swing filter for my focuser out of 1/8" thick Plexiglas.  I don't 
know about aluminum, but I would think Delrin would work.  I used a hole 
saw to slowly cut a hole smaller than 48mm and then used a curved file to 
slowly widen the hole.  When I got close to size, I started to bevel the 
hole on the side opposite the filter so it had a knife edge.  Going slowly, 
and with a lot of trial fits, I got it to a size where the filter threaded 
on.  It's only one thread, but it goes on very tight - no slop at all - and 
there is no danger of it falling out as long as you don't leave the filter 
in during a drive over bumpy roads to a dark sky site.  No guarantees if 
you try to do it fast and enlarge the hole too fast! ;^)


At 06:10 PM 2/4/2002 -0800, you wrote:

>Any sources or ideas on how to create a 48mm female thread for a filter
>slide?  I wanted to make one out of aluminum or delrin so the self threading
>of plywood idea seems like a long shot.
>
>tnx
>jtm