Source of Cast iron for lapping plates *LINK*
Phil Smith
>The source of cast iron that we used for the lapping plates in message posted by Bill below was from Metal Express. They sell a broad range of metals in small quantities. Everything from cast iron to bronze and a few tool steel. They will also custom cut to length.
We ordered a total of 6 pieces of cast iron 1.25 in X 2.25 in X 12 in. Cast iron gray cl40. We had a local machine shop split the pieces in half and surface grind the plates on both sides. We wound up with a total 12 plates which are all the same thickness, approx. 5/8 in X 2.25 in X 12 in for a cost of about $20/plate.
I wanted 8 plates to make sure I had enough to cover all of the grits we would need based on our experience with sharpening with sand paper. That is clearly not necessary. 15 micron diamond will take out grinding marks from a 36 grit grinding wheel. Likely we will only need 3 grits to get good working edge.
Tonight I ground the hollow out of a chisel (CPM 3V)that had been ground on a 36 grit 8 in grinding wheel with about 50 to 75 strokes on 15 micron lapping plate. Will test cleaning in sonic cleaning bath tomorrow.
Phil Smith
Bill Tindall
Metal Express