This is a bit of the fine tuning I knew awaited me once I started getting into the chevalet. My original (re-invention of the wheel) blade clamps worked very well, at least I thought they did until I did the “keyhole test” for checking the accuracy of your setup of the blade at exactly 90 degrees to the work. This square setup is essential to success in the boulle or classic cutting methods. The keyhole test is the standard test for accuracy. You cut down into a thickish piece of material, do a circle and cut back out near the entry point. I’f you’re perfectly set up the cutout will slide out either way. If you’re off square in the horizontal, the stem of the keyhole will hang you up in one direction. If you’re off square on the vertical, the circle will hold you up.
Here are my keyholes. #1 was held up by the circle. The stem was fine. In #2 I adjusted the vertical adjuster up about 1/16”+ and the piece came out both ways. The rest are just experiments with how the adjusters affected the keyhole cutout.
So much for the good news. My chevalet is very close to true right out of the chute. There is a serious problem that arises however. The way I originally designed the blade clamp allows the blade to be clamped against the vertical surface of the square bar anywhere on it’s 3/8” face leaving a large opportunity to have a very off square (vertical) blade after removing / re-setting it.
Patrick Edwards helped me out on this one and I re-designed my clamp accordingly. This is the new setup. Now when the blade is fitted into the clamp it is on the same side as the screw and can rest on the screw insuring that it occupies the same spot in the clamp every time. The best way to learn is to make mistakes, discover them and fix them. You live and learn.
I have one more modification that I need to do that I know of. It relates to the hinged side of the veneer clamping jaws. I’ll post it when I get it done. For now, I think tomorrow may be a golf day.
-- Paul M ..............If God wanted us to have fiberglas boats he would have given us fibrerglas trees. http://thecanadianschooloffrenchmarquetry.com/