Re: [CAD_CAM_EDM_DRO] Re: wrong guy, but have servo question.

Marcus & Eva wrote:

> Hi all:
> What I was actually referring to here, was the consequence of having the
> quill extended, not the presence of the "knuckles for tipping the head
> (although you are quite correct that their presence reduces the stiffness of
> the mill also.)
> As an example of what I mean, try this test:
> Take a 1" dia 2 flute carbide cutter, and take a 0.125" pass in prehardened
> 4140 or P20, with the quill up and clamped. Stick an indicator against the
> quill as you take the cut and watch it bounce around.
> Now drop the quill its full 5" and clamp it lightly, so you can still slide
> it up and down with the handle.
> Try taking the same cut again, and you will soon see what I mean; if you
> don't instantly destroy the cutter, that is.
> I have found very few quill type mills that can pass this test, in fact the
> only one I can remember was a Pedersen mill that had a quill about 6"
> diameter and a massive head that was not tiltable.

Well, SURE! You are making cuts that the Bridgeport Series-I is not really
designed for, and should expect trouble. I would not ever take such a
cut on my machine, no matter what the quill position! I might approach this
on an easy-cutting aluminum, but never in steel! (I only have a 1 HP motor,
so it wouldn't get very far, anyway, before the motor stalled.)

When I upgraded my machine to a J head, I got a bunch of 3/4 and 1"
cutters, and rapidly found out that they really didn't improve metal
removal rate. To use big cutters like that, you need to make very
heavy cuts at high feed rates, and the 1 Hp Bridgport just doesn't have
the power or stiffness to handle it. It works a lot better to spin a smaller
tool faster, and take less feed per tooth, but more teeth/minute. I did some
work hogging out pockets in some really large hot-rolled steel billets,
and used the larger cutters, but it was slow going. If I got too
ambitious, either the work or the head knuckle slipped.

Jon