Once the magic smoke comes out, things don't work any more.
John Kasunich
jmkasunich@fastmail.fm
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Fri, 28 Dec 2007
I've been doing lots of stuff with the Shoptask, but haven't posted in a while. I'm going to cheat and back-date some posts showing what I've been up to.
Cutting keyways on the lathe is a trick that is probably as old as lathes. You mount a cutter so that what will be the top of the keyway points straight forward (or back). Cuts are made by using the lathe carriage as the "ram" of a hand-powered shaper. The cross-slide is used to advance after each stroke.
It's not something you want to do often, or for heavy work, but for the occasional keyway in aluminum it works. However, doing it by hand is a nuisance. A single keyway might need a hundred or more cuts, advancing 0.0005" or less after each one. That gets old fast, and it is also all too easy to accidentally take a heavier cut.
CNC makes it a lot easier. A CNC program can rapid the carriage left to make a cut, then back to clear, rapid right, advance a very small amount, and make another cut, without getting bored or accidently cutting too deep. EMC's dialect of G-code has O-word loops which make it even easier to do highly repetitive work like this.
The first photo below shows it just about to begin a cut. The cutting edge is on the left in the photo (closest to the operator). The end of the cutter facing the chuck has a positive rake, and the cutter is as sharp as I could get it so it could take a fine chip.
Below is the finished part, alone, and installed. This piece replaces the Y-axis handwheel - I don't want a big wheel with a crank handle on it spinning around in the vicinity of my stomach when the machine is running as a CNC. Replacing the handwheel also significantly reduces the inertia that the motor has to accelerate and decelerate.
(posted: 28 Dec 2007 22:15) (permalink)