Things I’ve learned about trepanning

(some the hard way, pictures at the bottom of the page)

 

 

Procedural Improvements

 

  1. #60 grit is much better than  valve grinding compound
  2. Feed the cutter Lots of grit,  Listen carefully while grinding.  When the noise of the grinder decreases, add grit.  It would appear that frequently adding grit dramatically increases the speed of the cutter.
  3. Create a damn out of Play-dough and fill it full of water
  4. Half way thru the cut, rotate the glass 180 degrees (Don’t flip it, just rotate it)  I find my cutter tends to go thru unevenly,  Rotating the glass helps the cutter to emerge evenly from the back side and reduces chipping.
  5. When the cutter starts breaking thru add a whole BUNCH of grit and KEEP adding grit and water (water leaks out the bottom when the cutter starts breaking thru.)

 

Cutter Improvements

 

  1. Tin Tabs are too thin, they wear out quickly
  2. I tried using ˝” wide two inch long angle brackets.  I had eight of them around the circumference of the cutter.  This didn’t work very good at all.  The 2 inch long “teeth” sang like a tuning fork at about 7Khz and 122db (ouch)  You can see the remains of the brackets in the below picture.  The brackets did come in handing in the next version of cutter.
  3. My most successful cutter has been made from a piece of scrap from a metal roofing project.  I cut a two inch wide 25 inch long piece out with a pair of tin snips.  I then cut the Teeth (aka tuning forks) off flush with the bottom of the cutting disk, loosened the bracket screws and slid the sheet metal between the disk and the brackets.  Next I cut 3 upside down V in to the sheet metal,  The ‘V’s help clear the cutter of debris and feed fresh grit.

 

Some Pictures to help visualize the ideas.

(The Best Cutter so far,  In this pic you can see the old nails used on the original Tin Tab version and  The remains of the noisy angle brackets.  Also notice the V shaped cutout near the top of the cutter.)

 

(The wore out cutter,  This version created  5 blanks at an average of 1.5 hours per blank and 3mm of wear per blank)

 

(Two Blanks and a tool, ready for grinding!)