On Sat, 30 Jul 2011 17:31:25 -0700, mkoblic wrote:
On Fri, 29 Jul 2011 13:50:15 -0400, "Existential Angst"
wrote:
"The Dougster" dgoncz... wrote ...
A 2- or 4- flute end mill makes a fine trepanning tool on the lathe.

Trepanning of a square blank held on an expaning arbor through a
smallish center hole leaves a square with a round hole, and a disc
with the smallish hole. If what one wants is the disc, trepanning
saves the wear, tear, and irritation of the interrupted cut, and save
turning all those square points into chips.

Assuming the blank is 1/2" thick, idnat why God invented hole saws?

I am struggling to find a good way of cutting out 2.5" disks out of
3/16" steel plate. I have not tried trepanning but it is on the list.

Would a hole saw be useful for this application? How many disks would
one be able to get out of one saw bit?

BTW if I farmed this out to a local shop for plasma cutting it would
cost me $6 per disc. Cutting the same disc with a jeweler's saw costs 1
hour, 2 blades and a sore shoulder.

Do you have a (motorized) scroll saw? I can use the same blades on
mine as on my jeweler's saw. (But not vice versa -- the jeweler's saw
only takes pinless blades, the scroll saw accepts either pinned or
pinless 5" blades.) I've cut lots of wood, paper, and plastic on my
scroll saw, typically with a 15 or 20-tpi blade, and small amounts of
steel with a 40 tpi blade (0.012" x 0.022" cross section). The steel
was 1/20" sheet and I advanced it only about 1 IPM with the saw running
at about 600 strokes per minute, which gave a milled-looking cut surface.
With thicker metal, heavier blade, and higher SPM, you might be able to
race along at 2 IPM!

--
jiw