How I cut the Glass Mirror Blanks
After picking up a truckload of two foot square
¾ inch thick glass from Dave Bross in Gainesville (Dave's Website) it was time to figure out how
to cut mirror blanks. Here is what I ended up building.
My really ugly Trepanning Machine
The drive assembly is from a boat winch. I
removed the reel with a hacksaw and welded a 3/8” socket adapter to the output
shaft. The shaft turns at 30 RPM and runs a home made cutter which looks like
this:
The Cutting Wheel
The cutter is made from a piece of ¾ inch thick,
8-inch diameter Teflon cutting board material (it was handy). To the perimeter
of this was nailed a series of Roofing “tin tabs” for holding down tar paper.
The Tin Tabs were further secured with an 8” Circle Clamp. The Tin tabs are a
little thin, but flexed nicely for the curvature of the disk. My next tool will
use a piece of 2” galvanized sheet metal instead of the tin tabs. In the center
of this cutter I installed a 3/8” carriage bolt and nut. The motor is attached
to the cutting wheel by a 9/16” - 3/8” drive socket. The business end looks
like this:
Where the Glass meets the cutter :)
A nice 8" Blank!
I've got a few kinks to work out with the machine,
But all in all not bad for my first attempt. I look forward to cutting a few
more and gaining some experience, which is half the fun :)
UPDATE: Using a two inch wide strip of 18 Gage
Galvanized roofing material and some Good old 60 grit carbarundum, I have had
much better success. I also learned
that it is very helpful to rotate the glass 180 degrees about half way thru the
cut. Rotating the glass helps avoid the problem I ran into of the cutter not
cutting thru evenly which resulted in part of the cut emerging from the back
side of the glass before the rest, this in turn resulted in severe chipping of
the back side of the blank. Since I’ve
started rotating the glass, chipping during breakthrough has been almost
entirely overcome.
Let me
know what you think, My email address is: James Lerch