Re: cut a holey pear w/ ears? was 4th axis rot (and other tricks)

Alan Wrote:

OK, now I have a real simple *NEWBE* question, I've got the part
designed, and I can generate a "tool path" around the part's outline,
but it occurred to me, this part is .625 thick, and nowhere square
(it's
an eccentric follower, 1" dia on the bottom, .63" dia on top of a
"pear"
shaped part, 1.69 overall). The part has a .75" bore through on the
bottom end, and two ears with a .25" bore through them at the top,
both
top and bottom bores parallel (.JPG on request). <snip>

Alan,
some good questions.

A lot of times generating the code is the easiest part of making the
part. Thinking through the process takes the time. If I understand
the part correctly(.jpg,yes please.), I would do the bore(s) first
while holding the block with flat clamps. Then I could USE the bores
to locate and hold down SECURELY for the outline contouring. (I'd
prob'ly also cut the slot 'tween the ears b4 the outline cuts, while
the pear was square).

<rant mode>
Key word above, securely. Dont be afraid to cut metal! Your sherline
is capable of outlining this part without all the nibbling. Use
oversize roughing passes for sure, and cut to depth in appropriate
steps. Then change the endmill and get your fit and finish.
</end of rant>

Now, re: the pocket ??'s. The control has no idea what/where the
material is. You "could" treat the whole part as an island with 2
holes(the bores) in some arbitrary "pocket" that does not really
exist. If you start with thicker stock,say .75 , you could do all the
profiling and bores at the same time. Then turn it over, and mill the
excess, freeing the desired bit. But, How you gonna hold it? Edge
clamps at the bottom 1/8 "might " work, but might also let loose.
(murphy was a machinist)

Good luck.

Ballendo