Ignoramus4117 wrote:

On 2010-09-01, Karl Townsend wrote:
On Wed, 01 Sep 2010 16:25:07 -0500, Ignoramus4117
wrote:

On 2010-09-01, Karl Townsend wrote:
On Wed, 01 Sep 2010 13:33:29 -0500, Ignoramus4117
wrote:

On 2010-09-01, Karl Townsend wrote:
On Wed, 01 Sep 2010 11:48:02 -0500, Ignoramus4117
wrote:

I was making something on the CNC mill last night. It is a little
block that I would clamp to the quill of the mill, so that I would
attach the Loc-Line coolant line to the quill. That way the coolant
would follow the cutting tool as the quill is raised or lowered.

Anyway, as part of that, I had to drill a deep hole (comparatively). I
used a peck drilling cycle and it worked, but took way too long, with
withdrawal of the tool and lowering it down, etc.

So I wanted to double check what is the recommended procedure for deep
drilling aluminum.

My feeling is that at the given RPM of 2400, I should have used a much
more aggressive feed rate than I used.

nobody giving you numbers. I'd go 8 IPM and peck of .125 (1/2 D) if
its a 1/4" drill. But I got dials to quickly change feed and speed, no
doubt an adjust would be in order on part one. Don't consider me the
definitive expert on speeds and feeds - I do it all by feel.

Karl, I mostly do it by feel too. I will get a piece of junk tonight
and will practice somewhat if I have time. Thanks for the suggestion.

i

on second thought, i go a full D in AL, 1/2D in steel per peck. Or .25
for 1/4" drill, etc.

But them, I would have long stringy chips hanging on the drill bit,
beating up loc-lines?

'Xactly the problem.


Karl, what about this routine (with copious coolant): drill a small
increment, then dwell the drill for a small fraction of a second to
break chips, then continue. That would break chips, right? I could
literally stop the Z axis movement to dwell for several times per
second. Would that be enough? Withdrawing to SafeZ every time is very
time consuming.

i

No dwell is required to break the chips. The chips will break the
instant you stop cutting, i.e. when you reverse the feed to retract. The
bit is still spinning and no new metal is being cut to grow the chips,
so they break off from where the cut ended. Any dwell only add time for
the chips to rub more, generate more friction heat, gall the inside of
the hole and potentially jam. The whole idea of a peck drill cycle is to
get down to where you are cutting fast, make a short cut and get the
heck out of the hole fast to evacuate the chips.