[ATM] Re: Source to cut and curve generate refractor blanks.

[fabio@voreas.com]

Even if you manage to align the mirror properly (by ensuring that it is 
circular and the edge is smooth) you still have to contend with the tool 
wondering around a bit when begin drilling from the other side. If you're 
using a drill press, make sure there is no slop or flexure at the chuck or 
else the tool will wobble. Even with these precautions it is possible to end 
up with the halves of the hole mismatched by 1/32in depending on hole 
diameter. If one is going through the trouble of drilling perfect holes, 
going the extra mile and building a jig to keep the tool from wobbling when 
beginning the cut is worth doing it. 

Fabio P.
Redmond, WA (surprisingly sunny; boy do I miss California...) 

Richard Schwartz writes: 

> Bob, 
> 
> I wonder if you have seen any good jigs for accurate alignment of the
> trepan after turning the glass over.   By cutting half way through the
> glass, and then turning the glass over to finish the job, you avoid those
> breakthrough chips on the back side.   But alignment has to be accurate! 
> 
> . . . Richard 
> 
> 
>> [Original Message]
>> From: Bob May <bobmay@nethere.com>
>> To: ATMList Post <atm@atmlist.net>
>> Date: 4/27/2004 1:43:39 PM
>> Subject: Re: [ATM] Source to cut and curve generate refractor blanks. 
>>
>> Trepanning is an easy job once you build the tool.  for small stuff,
> finding
>> a can or tube the right size can be an experience in scrounging of the
> first
>> water.
>> Don't be afraid as the process is somewhat slow (you're grinding the slot
> in
>> the glass with grit rather than some other faster process) and is best
>> motorized if possible although I've seen glass that was hand trepanned of
>> 14" diameter - the guy said that he'd put a drill motor on the next one he
>> does as it took several days as he couldn't keep turning that much at one
>> time.  Consider an inch an hour to be a decent amount of time for the
> first
>> time at this.
>> You can probably find some 4" diameter exhaust pipe at a truck muffler
> shop
>> and a little work on that will make a nice 4" tool for the drill press. 
>>
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