On Sat, 14 Feb 2015 08:40:19 -0800 (PST), robobass
wrote:


Something is funny there. There should be little or no difference in
the "effort" required by a carbide cutter versus HSS. If anything, the
HSS should require slightly less effort, given equal sharpness.

The only reason to go with carbide when cutting brass is if you're
burning your HSS cutters. This is extremely unlikely.

There is one other potential issue, however: Carbide is stiffer. If
the flexibility of the cutter itself is contributing to the chatter,
carbide could help.

--
Ed Huntress

The tool has 22mm of 4mm length, so I'm thinking deflection is a suspect, and a shorter (and carbide) tool should help. As far as carbide vs. HSSE, so far I've noticed that it plunges with much less strain, but I haven't used it enough for profiling to draw a conclusion.

There are several things that could be going on here, and I don't like
to speculate too much -- especialy from a still photo -- but here are
a couple of thoughts that may help.

First, if there's a difference in plunging with carbide versus HSS,
it's due to geometry or edge sharpness, not the tool material. It's
difficult to make any carbide as sharp as HSS but the carbide may be
sharper to begin with.

Second, 22 mm extension on a 4 mm cutter is indeed an invitation to
deflection and initiating vibration. Carbide is much stiffer.

Third, the machine configuration looks like an invitation to
sympathetic vibrations; changing speeds could help deal with any
oscillations. Have you tried slowing it down? That's why they build
machine tools from cast iron. It doesn't like to vibrate. g

Regarding dubbing, radiusing, or back-chamferring the cutting edge: it
could solve any digging-in, to which brass is very prone; or, by
increasing the cutting force, a radiused or negative-chamferred edge
could make things worse, by increasing tool deflection.

Chatter can be difficult to track down. Good luck.

--
Ed Huntress