Re: [ATM] Preparing to trepan for the first time

[<lenses@adelphia.net>]

Hey Chris,
Warm up a 1/4" thick piece of plate glass, put your Bk7 onto it with some wax in between.
Clamp the larger plate glass to your table and your good to go.
This will give you something to clamp to and keep the back of your Bk7 from chipping out.
Hope this helps,
P.S. If you don't want to do this, save the 6.25" for another project and send me your address and I will send you 2pcs 2" diameter Bk-7 blanks you need. What thickness?

Peter Nance, Jr.
lenses@adelphia.net


---- Chris Dalla Piazza <dalchri@hotmail.com> wrote: 
> Dan,
> 
> You know, I had wondered if I could use one of those.  I was afraid it would
> be too aggressive.  Do you still use the carbo at all or do you let the bit
> do all the cutting while using water?
> 
> We are talking about a ~2" hole in a 6.25" disk.
> 
> It appears that the cutter will cut a V-shaped groove into the glass.  Will
> this slow down the process as it gets further into glass, does it not matter
> that much, or am I misunderstanding the application?
> 
> Will the gap left be too much to glue the core back in after it is cut out?
> 
> Just to be sure, you are talking about one of these:
> http://www.grizzly.com/products/g8964 right?
> 
> Is there anything more to centering jig than making sure you drill the pilot
> hole exactly in the center of the disk (which then acts to center the
> cutting from the opposite side)?
> 
> Thank you for that suggestion, it inspires more confidence than my homemade
> cutter!
> 
> 
> 
> -----Original Message-----
> From: Daniel Fundo [mailto:fundo@bellsouth.net] 
> Sent: Tuesday, November 14, 2006 3:58 PM
> To: Chris Dalla Piazza
> Cc: atm@atmlist.net
> Subject: Re: [ATM] Preparing to trepan for the first time
> 
> <<  Should I grind down the bottom of the edge to make it level rather
> than risk throwing the glass because of unbalanced grinding force or
> will it do this itself as the glass is ground quickly enough?  >>
> 
> Chris,  Yes, there will be less of a chance to throw the hole off-center
> if the bottom is flat to the surface your cutting.<<
> 
> <<  Does the glass disk need to be clamped down or should the cutting
> forces be gentle and balanced enough that I am doing something wrong if
> the disk is pushed around?  >>
> 
> Its always a good idea to secure whatever your are drilling, wood,
> metal, or glass.  I don't know what size we are talking about here, but
> you can get circle cutters that will cut up to 10".  A jig made this way
> will be centered under the quill, and will guarentee centering when you
> flip the disk over to cut from the other side.  Just bolt the jig to the
> table before you go at it with the circle cutter. (One thing you learn
> the hard way in building stuff is that the time and material used in
> making a jig MORE than pays for itself in ease and accuracy!!)
> 
> <<  Is it realistic to think I can widen the hole cut if necessary using
> something like a Dremel sandpaper bit?  I am thinking of the phrase "You
> can always cut too much but you can never cut too little."  >>
> 
> Unless you have a source for diamond coated sleeves for the Dremel, the
> answer is "NO"  (If you do, let the rest of us know!!! <G>)  Dremel does
> have several SiC grinding stones, but unless you are just talking a few
> thousandths, the enlarging would take longer than retrepanning.
> 
> <<  Is there a better way to center the trepanning bit than using a
> paper cutout?  >>
> 
> Make a jig as I suggested above.  
> 
> Best of luck
> 
> *****-----
> Dan F.
> Memphis, TN
> 
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