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Anayak "Exacto" Vertical Mill Rebuild, Part 24:
The next problem on the list was the knee-elevating crank "gear". While the teeth on the crank itself
were okay, those on the collar on the knee shaft were worn, peened and rounded.
I'd tried to grind some of the teeth back to square just as a stopgap measure, but they were just too
bad to save. And in use, the effort of trying to turn the crank would "cam" the crank away from the
knee collar, meaning you had to keep pushing it inward- hard
- to keep it from slipping off.
So I took a chunk of steel bar out of my scrap pile, and turned up a new collar.
Now, there's a trick to cutting the teeth- or splines, whatever you want to call them. The teeth are triangular-
they form a "pie wedge" that points to the center of the part. With an odd number of teeth, this means you
just have to offset your endmill so that it cuts right along the edge of the centerline.
Then, just divide 360 degrees by the number of teeth you need, and make that number of cuts.
For the typical Bridgeport or other clone, there's nine teeth- 360 ÷ 9 = 40. Meaning you just
turn the indexer or rotaty table 40 degrees between cuts.
For some reason, however, this Spanish-made mill had seven
teeth. 360 ÷ 7 = 51.4285
That's a nice round number, isn't it? :) Fortunately this is not a high accuracy application, so
I simply cut it at 51.5 degrees. After a full turn, I was only off by half a degree in total.
The test piece in aluminum turned out to fit just fine.
So I carefully milled the new steel collar to match.
And it's just
that easy. :)
I marked and drilled the two cross holes, leaving them slightly undersize- and two different
sizes as well- so that I could ream them in place with a No. 4 taper pin reamer,
turned gently and slowly in a hand drill.
I blew out the chips, tapped in a fresh taper pin, and cut off the extra with an air grinder.
And oh, my, what an improvement. The two gears lock together snugly, and hold nicely with only
a token pressure as you crank. This machine has a much heavier knee and table, so it's still
not as light and smooth to move as the Grizzly, but it's a great deal more pleasant
to use now, without having to fight that freakin' crank anymore. :)
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Keep your fingers away from the spinny blades o' death and you should
be all right.