Ignoramus28169 wrote:

On 2010-09-02, Pete C. wrote:
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.

Pete, I thought that a dwell would not be accompanied by withdrawing
of the drill. Just dwell, break chips and keep drilling.

If you use that method, you need to do it one of two ways - either with
very short feeds between momentary dwells so you produce small chips
that will feed up the drill flutes without jamming, or very long
aggressive feeds to make continuous chips all the way up the flutes,
break them and then do the same again to force those chips up and out.
Anything in between is likely to jam badly.


Anyway, it is really fun to watch the mill use a peck and drill
cycle. I will try to up the speed.

You can go quite aggressive in most aluminum (except a few gummy
alloys), aluminum is generally very nice to machine.


I crashed yesterday and went to bed early as I was very tired. Had no
time to try anything. I will take pictures of my manual Bridgeport
tonight.

i

I know the feeling, I've had a bunch of different projects going on here
lately. After finishing that island table, I went right to working on a
1954 Ford NAA tractor overhaul, which I am hoping to complete and get
out of the way before coming back with the new mill. In parallel with
those projects I have also been working on a remodeling project at a
friends store, and of course also my "real" job.