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+-- Thread: Chisel mortiser bits snapping-now what? (/showthread.php?tid=7352520)
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RE: Chisel mortiser bits snapping-now what? - handi - 02-01-2020
The exact exposure of the bit beyond the chisel is important too.
Too little bit, and the setup won’t cut, too much and the bit can snap.
You are correct, the cross section of a mortising Bit is very thin. It has to be, the chips are being forced up between the two parts of the tool. The chisel body tends to support the bit, which is why having too much bit sticking out the end can cause the tip to snap off.
This is why the bits tend to break at the top and not inside the chisel itself.
RE: Chisel mortiser bits snapping-now what? - Admiral - 02-02-2020
(02-01-2020, 10:47 PM)handi Wrote: The exact exposure of the bit beyond the chisel is important too.
Too little bit, and the setup won’t cut, too much and the bit can snap.
You are correct, the cross section of a mortising Bit is very thin. It has to be, the chips are being forced up between the two parts of the tool. The chisel body tends to support the bit, which is why having too much bit sticking out the end can cause the tip to snap off.
This is why the bits tend to break at the top and not inside the chisel itself.
Good and insightful point, as when I first started using one, I got much better results after paying very close attention to the "just right" exposure of the bit. There's a lot going on with a hollow chisel mortiser.
RE: Chisel mortiser bits snapping-now what? - Arlin Eastman - 02-05-2020
For anyone that has the funds these from Grizzly and look like they can handle anything.
https://www.grizzly.com/products/Grizzly-1-Premium-Mortising-Chisel/T10022
RE: Chisel mortiser bits snapping-now what? - Alan S - 02-06-2020
I'd expect a Fisch bit and chisel to come well prepared, but with cheap chisels I've found they work much better after sharpening the auger bit and smoothing the inside of the chisel with a chainsaw file. Those are the most important, but I also sharpen the chisel with an abrasive cone, and polish the outside faces of the chisel while being careful to keep from tapering it. Setting to just the right bit projection matters: a nickle works as a gauge.