I was reviewing some charts I have on tapping speeds, etc. and noticed that
the creator of the cart included information for tapping ceramics and glass.

I can see tapping macninable ceramic or especially "green" ceramic items,
but glass? I suppose it could be done while the glass is semi-molten, but
how else could you tap a hole in glass?!?

Regards,
Joe Agro, Jr.
(800) 871-5022
01.908.542.0244
Automatic / Pneumatic Drills: http://www.AutoDrill.com
Multiple Spindle Drills: http://www.Multi-Drill.com

V8013-R

"Joe AutoDrill" fired this volley in
news:z78Ni.28281$Ww5.16972@trnddc03:

I was reviewing some charts I have on tapping speeds, etc. and noticed
that the creator of the cart included information for tapping ceramics
and glass.

I can see tapping macninable ceramic or especially "green" ceramic
items, but glass? I suppose it could be done while the glass is
semi-molten, but how else could you tap a hole in glass?!?

It's actually not difficult. The secret is in how _little_ material gets
removed on each revolution. It's easy, for instance, to smoothly contour
a glass edge with an abrasive belt. There's "cutting" going on there,
too. The material is removed in such small amounts per "pass" that it
doesn't break.

There are some special, very-slow-taper, taps for brittle/hard materials
like glass. They progress from minor to major diameter at only a few
thousanths per inch.

Fine threads are a bitch, though. That's more a job for an abrasive
process.

LLoyd

I was reviewing some charts I have on tapping speeds, etc. and noticed
that the creator of the cart included information for tapping ceramics
and glass.

I can see tapping macninable ceramic or especially "green" ceramic
items, but glass? I suppose it could be done while the glass is
semi-molten, but how else could you tap a hole in glass?!?

It's actually not difficult. The secret is in how _little_ material gets
removed on each revolution. It's easy, for instance, to smoothly contour
a glass edge with an abrasive belt. There's "cutting" going on there,
too. The material is removed in such small amounts per "pass" that it
doesn't break.

There are some special, very-slow-taper, taps for brittle/hard materials
like glass. They progress from minor to major diameter at only a few
thousanths per inch.

Fine threads are a bitch, though. That's more a job for an abrasive
process.

LLoyd

Okay... I can understand that concept... Seems to make sense.

It makes me pucture a 24" long 1/4-20 tap, but the concept is at least
clearer now...

I would imagine the taps are silicon carbide, diamond, etc...

Abrasive shaping of glass I've seen. Most do it "wet" rather than dry -
presumably so they don't breathe in glass dust.

Regards,
Joe Agro, Jr.
(800) 871-5022
01.908.542.0244
Automatic / Pneumatic Drills: http://www.AutoDrill.com
Multiple Spindle Drills: http://www.Multi-Drill.com

V8013-R

Joe AutoDrill wrote:

Okay... I can understand that concept... Seems to make sense.

It makes me pucture a 24" long 1/4-20 tap, but the concept is at least
clearer now...

I would imagine the taps are silicon carbide, diamond, etc...

Abrasive shaping of glass I've seen. Most do it "wet" rather than dry -
presumably so they don't breathe in glass dust.
No, the grinding creates hot spots, the thermal stress cracks
the glass. When wet, the grinding area is kept cool, and the
glass doesn't crack.

Jon

"Jon Elson" wrote: (clip) the grinding creates hot spots, the thermal
stress cracks
the glass. (clip)
^^^^^^^^^^^^^^^^^^^
This correct, but generally the piece doesn't crack apart. Little chiops
keep flaking off, so you never wind up with a smooth surface. Often flakes
come off ahead of the cut, spoiling the part you intended to keep. You can
actuaslly see "fire" if you do it dry. DAMHIKT.

Not quite tapping but my local laser profiler will do glass upto about
2mm. I didn't ask what the cutting process was but they said it went
well as long as the part wasn't too intricate. From doing glass blowing
as a hobby I know that the failure issue is down to stress caused by
differing thermal expansion due to uneven heating /cooling or heat
build up fom local operations on the glass.

Joe AutoDrill wrote:

I was reviewing some charts I have on tapping speeds, etc. and noticed that
the creator of the cart included information for tapping ceramics and glass.

I can see tapping macninable ceramic or especially "green" ceramic items,
but glass? I suppose it could be done while the glass is semi-molten, but
how else could you tap a hole in glass?!?

Regards,
Joe Agro, Jr.
(800) 871-5022
01.908.542.0244
Automatic / Pneumatic Drills: http://www.AutoDrill.com
Multiple Spindle Drills: http://www.Multi-Drill.com

V8013-R

On Thu, 04 Oct 2007 18:51:24 GMT, "Leo Lichtman"
wrote:


"Jon Elson" wrote: (clip) the grinding creates hot spots, the thermal
stress cracks
the glass. (clip)
^^^^^^^^^^^^^^^^^^^
This correct, but generally the piece doesn't crack apart. Little chiops
keep flaking off, so you never wind up with a smooth surface. Often flakes
come off ahead of the cut, spoiling the part you intended to keep. You can
actuaslly see "fire" if you do it dry. DAMHIKT.



I want, at some point fairly soon, to make a total internal reflection type
level gauge. I was considering taking very light cuts with lots of coolant on
the surface grinder. I had assumed a silicon carbide wheel would give better
results, but haven't properly researched it yet.



Mark Rand
RTFM