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cutting circles out of glass - tips ?



 
 
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  #11  
Old April 15th 04, 11:53 AM
Moonraker
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"Adrian Brentnall" wrote in message
...
Hi All

Fresh from my success with the big (to me!) stained glass window ...
- the new project requires me to cut a hole out of a piece of 'art'
glass.

The hole needs to be circular - and in the region of 1" to 2.5"
diameter...

I have the Morton hole-cutter attachment - and have become reasonably
good at cutting circular pieces of glass with it - but in this case i
want to end up with the 'negative' of this .

I can make the circular score - no problem. It's geting the piece of
scrap glass out of the middle of the hole without losing/cracking the
main piece that's causing me problems.

Anybody prepared to share their special tips, please ?
(And, no, I don't expect it to be as easy as in the movies! g)

Thanks in advance
Adrian
Suffolk UK


One possibility would be to use a Taurus bandsaw with a sectional blade.
You'd have to drill a small starter hole in your work piece to thread the
blade through, and then you could saw the circle.

Also, you could drill a hole in the work piece that would be big enough to
get a small grinder bit started, and just use your tabletop grinder to grind
out the hole from the inside, increasing the bit diameter as you go.

If you have sandblasting capabilities, you could just mask off everything
BUT the circle you want cut out (on both sides of your work piece) and blast
the hole into the glass,


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  #12  
Old April 15th 04, 12:07 PM
Adrian Brentnall
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Hi Moonraker
Thanks for the comments.

Of the three options I only have a grinder - that might be a plan.

I had considered a sort of composite approach - score a circle, then
use the grinder to make a starter hole in the centre (on secord
thoughts - probably hole first _then_ score circle!).

At least that would give the 'scrap' glass somewhere to go - st the
moment I do quite well with the scoreing and running - but the darned
thing won't come out of the centre.

Eventually I give it one tap too many and the piece of glass that I
want ends up as three pieces of glass. Very frustrating!

I'll have a 'play' with the grinder method.

Thanks
Adrian
Suffolk UK


One possibility would be to use a Taurus bandsaw with a sectional blade.
You'd have to drill a small starter hole in your work piece to thread the
blade through, and then you could saw the circle.

Also, you could drill a hole in the work piece that would be big enough to
get a small grinder bit started, and just use your tabletop grinder to grind
out the hole from the inside, increasing the bit diameter as you go.

If you have sandblasting capabilities, you could just mask off everything
BUT the circle you want cut out (on both sides of your work piece) and blast
the hole into the glass,


  #13  
Old April 15th 04, 05:37 PM
Dennis Brady
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How well the blunt end of your cutter works for tapping depends on how
small that end is. The screw cap on Toyo cutters is enormously too
large to be used for tapping. Some old style glass cutters had a ball
on the handle end. Those are fine for running straight lines but
considerably too large for curves. The old style metal cutters
WITHOUT a ball end are perfect. If you can't get one of those, a
Phillips screwdriver (X end) works beautifully. The object is to have
a tip small enough to be able to strike ONLY on the line to be scored.

As pointed out by Moonraker, you MUST tap on the back of the score.
Although some tappers hold the glass upright while tapping, you'll
have much better success if instead you lay it down flat while
tapping. Tapping will often cause small chips where the glass breaks.
To ensure those chips are only on the scrap side, tap just slightly
(about 1/16") on that side. (another good reason why a small tapping
head is helpful). That way all the chips will be on the side you plan
to trash and the other side will have only small overhangs that can
easily be taken off with a carborundum stone or on a grinder.

If you're having trouble getting the pie pieces to start coming out,
it helps to score another concentric circle about half the size of the
original one. The smaller the pieces inside the circle, the easier
they start popping out. You're right - once the first is out, the
rest fall away.

As to other possible shapes - just about anything. Another demo I
like to do is to debunk the opinion that you can't cut a "V" into a
piece of glass. Take your cutter and score in from an edge, stop,
turn the cutter and score back out leaving a 90 deg corner. If you're
patiently careful, you can tap out that piece. It CAN be done, but
it's NOT something that should be done. The remaining piece WILL
break out from the "V". It's an effective way to demonstrate why saws
shouldn't be used for conventional stained glass. "Any cut that can't
be done by hand, shouldn't have been done at all".
  #14  
Old April 15th 04, 09:42 PM
Randy
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I would think that scratching would be near impossible for a 1 inch hole if
the glass has any thickness to it. Anything thicker than say 3 mm. If
this is the case, you might try Charles suggestion.

A 2.5 inch hole might be easier.

I say this with a limited experience of scratching, and a lot of experience
of working with glass.
The others that have responded have much more experience in this arena.
Please let us know what works best for you.

Randy Hansen
SC Glass Tech
Scam Diego, Comi-fornia

http://f1.pg.photos.yahoo.com/ph/randy2954/my_photos




"Adrian Brentnall" wrote in message
...
Hi Randy


Your safest bet is to core drill the hole. Do not try to scratch it.


Thanks for the advice.....
....unfortunately I don't have a core drill. I'm going to need to be
able to do this to produce a range of specific sizes - might involve
quite a few core drills.

Time is the one commodity that I have plenty of - I'll just have to
try the other techniques that people have suggested - but thanks for
the suggestion anyway....

Regards
Adrian
Suffolk UK




 




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