"Terry Coombs" wrote in message
...
Bob La Londe wrote:
I had to machine some 3/4 304 stainless round rod last week, and it
performed a little oddly. I first noticed it on the band saw when I
cut the slugs to machine. They would cut with a kind of eye shape on
the end. Then when I cross drilled it I noticed I got beaughtiful
continuous curls about a 1/4 of the way in, then through the middle
it gave me kinda nasty looking munched up looking chips, and as it
approached the other side nice pretty curled continuous chips would
start coming out of the hole again. I drilled them on the KMB1, so
feed was consistant.
It was like the surface 1/8-3/16 was what I was expecting, and then
the middle was something totally different.

When I milled the hex half way through to engage the pins I didn't
notice anything odd, but that was planned to be a pretty light fast
cut.
I have no idea what it means. It was just seemed odd to observe. They
are just cross handles for a core pull pin so the alloy is
really not all that important. Just needed to be stainless.

I've seen that "eye" on a lot of different bar stock , I think it must be
caused by a harmonic vibration of the bandsaw blades . My experience with
304 is that you turn slow with heavy feed , and if you let the cutter
skate at all it'll work harden . Nasty stuff , I'll use 303 instead when I
can .

--
Snag

Interestingly I made the pins with 303. My plan was to just bend an L bend
on them, but I decided I needed to make a bending jig to do that well, and
it was faster to machine the ends and put cross handles on. My local metal
yard (the one I like) only had 304 on hand.

I am aware of stainless work hardening, and took a fairly agressive feed I
thought. I got beaughtiful continuous chips to start each cross drill.
Maybe I should drill more agressively? Maybe even program stuff like that
with a particular familiar stock with three drill operations?