Follow up to some previous inquiries I made recently and more
The tool is a 3/4 x 1/8 x 2" long piece of W-1 water hardening tool
steel. It's bevelled along one of the long sides like a short planer
knife and it must be razor sharp.
Heated with Prestolite acetylene torch, quenched in water, temepred to
light straw at 500º in a toaster oven. [Yes, you can achieve this
temperature in a toaster oven. I got an oven thermometer and checked.
Leaving it in for 20 min gives a light yellow temper. 40 min. gives a
dark straw temper.]
They warped a little after hardening and tempering. Is this just
something you have to live with or are there home shop tricks that
prevent this? It's not that the warp is bad, but it takes a LOT of
grinding / honing to get the blade flat after it's hardened and
tempered. I didn't measure the warp, but my guess is that it's less
than 0.010" longitudinally.
The 6" belt on my belt sander shined up the bottom nicely, but it
certainly doesn't remove metal very fast. The belt was the standard
one that came on this Grizzly sander. Are there belts specifically
intended for metal grinding that will do a faster job?
Is Water hardening tool steel is more prone to warping than oil
Observation - It's a lot easier to put a bevel for sharpening on the
tool steel with a milling machine before it's hard than grinding the
bevel afterwards, even if it has been tempered.
Another observation - you can't "spring" a blade that's been tempered
at 500º back to flat. It breaks first. Boy was that interesting.
The shop isn't really dim, but when that broke, there was a small
flash of light at the break!
Semi-OT - story I heard at college.
When they installed the big (4 or 5 stories tall IIRC) Baldwin testing
machine in Fritz Laboratory at Lehigh Unversity some time in the 50s /
60s they put a piece of steel in it that was at the tolerance of the
machine and stretched it till it broke. One of my professors who
spoke as though he had been there when the test was done said that it
let out a flash of light when it broke and it felt like there was a
small earthquake in South Bethlehem. A few windows in nearby homes
broke according to the professor.
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- posted 18 years ago