"Roger Shoaf" wrote in message
...

snip

Sure you will get less walk. The surface incontact with the work is only
the small portion of the end face of the tool. Your X any Y gibs are
locked
and your quill gib is snugged, so you have very little room for wiggle.
The feed is linear to your hand and you can feel if you start to over do
it
easier than when you are turning a crank.

Also bu unly taking .010" at a time you will be able to plunge fairly
quickly and you only have to do it 7 or 8 times.

If the mill does flex sideways, you will end up with only a small
deviation
twords the bottom of the slot and it will only be a couple of thou wide
and
deep. This gives you a straight wall of at least 80%.

Right. Forgot you can lock X *and* Y this way. Maybe I won't even have to
use the fine feed this way.

snip


Ok let me see if I can explain. You have done all of your plunges, and
you
now swap your 1/4" end mill for a 3/16" end mill. Since the diameter of
the
new end mill is smaller, You would start from the right side of the slot
and
plunge it to depth or raise the table to bring the mill to depth. Your
cutter should be then centered in the slot and you move the table about
.025
away from you and the cutter should then be .007 from the kiss point.

You now lock the gib, and loosten the side travel gib, and re-snug it so
it
allows you to turn the crank, but with some resistance. Now feed the work
into the cutter. You are going to get a little flex in the end mill but
you
are taking a small bite and all of the flex is going to be away from your
final desired dimention so you still have room to make a clean up cut.
When
you get near the end of your pass, you are going to run out of metal to
cut
as you enter the quarter inch hole. Now you can take a clean up pass back
doing climb milling or extract the cutter and restart from the right side
of
the slot but this timetake about a .003 bite. The bottom of the slot will
be narrower than the top but the end mill will be trying to remove less
material so the flex-away will be a lot less and the side wall should be
really close to square.

Now reset to make your final clean up cut, perhaps upping the speed a
notch
this time you will be climb milling and you should clean up really close
to
what you want to be at.

Now you do the same thing on the other side of the slot.

Got it! The centre line is the reference. Makes sense.

snip.

Your dial is set and locked from when you did the plunge cuts, so you
should
be able to just adjust the crank to accomidate the smaller cutter.

When you get ready to cut the back side of the slot, you need to be
cognisant of the backlash in the feed screw so when you make your first
pass
onthe back side you can sneak up on the firast pass and you will be able
to
keep the slot width from going too wide.

I try to use dial indicators whenever possible. I guess backlash comes into
it even on the near side, depending where one left the wheel to start with.

True - my tolerancies are quite - tolerant. However, the reason I am
beating
this topic to death is to know the right way the next time when the job
is
not so forgiving.

Practice on some scrap to hone the technique, and pretty soon it will
become
second nature.

I learned this technique from a very fussy german mold maker when my task
was to cut the pockets in mold bases 6 inches thick. He started by having
me cut to within .005" of the desired size and then he did the final
sizing
until I had the tecnique down pat, then he let me finish them up to final
size.

Now I understand it. Thanks.

True. At this point it is sometimes difficult to tell which are the
limitations of the machinery and which of the operator. What I got so far
is
a mixture of both.


Practice, and observe the results, and be willing to learn from your
mistakes. Soon the techniques will become second nature, you will get
over
confident has some part you have many hours into and your mistakes will
become fewer and farther in-between.

Also when you by the next machine that has less slop you will really be
appreciative of all of your futzing time. I remember the firs project I
made on a Hardenge lathe Wow!!!

Yes. I might even discover what these quills and tables going up and down
are all about....:-)

--
Michael Koblic
Campbell River, BC