On Friday 31 March 2017 20:45:01 andy pugh wrote:

> On 1 April 2017 at 01:15, Gene Heskett <[email protected]> wrote:
> >> If you are trying for a full circle then then (in incremental mode)
> >> you want to come back to where you are, so
> >>  G3 X0 Y0 I-2.6625 J0
> >
> > Thank You Andy, that worked well. But why can't I look this up in
> > the docs?
>
> What would the docs say? "In incremental mode, to stay in the same
> place, program a zero length move" ?
>
> You don't actually need the XYZ.
>
> G91 G91.1
> G0 X 1
> G3 I -1
>
> Works fine for a full circle of radius 1.
>
> To spiral down
>
> G91 G91.1
> G0 X 1
> G3 Z -10 P10 I -1

Humm, odd thought, for incremental mode, can I use the magnitudes and 
signs of I & J to rotate this cut around the 0,0 assumed anchor point? 

I'm thinking in terms of something like:
 
G3 Z-#<_depth> I[#<_rad>*SIN[#<_angle>]] J[#<_rad>*COS[#<_angle>]] p20

followed by a last cut at depth:
G3 I[#<_rad>*SIN[#<_angle>]] J[#<_rad>*COS[#<_angle>]]

to clean up the bottom of the counterbore?

Sitting around today, 44F out so shop is cold, and the next thing I need 
to do is make an EDM electrode assembly on TLM to remove a busted 
5mmx.80 tap, it hit the bottom of the hole & broke off flush. So that 
and a sink stopper to plug the center hole so I can keep a half inch 
of distilled water above it while I burn the center of the tap away.

Fun? Not. But I've at least another 15 days till the rest of the 
bearings ship. I can either rotate the pattern and drill 3 more holes
beside these, but drill even deeper, with a better drill bit.

But I learn from doing, and one of the things I should have done was 
use one of those spot drills you usually use in a tailstock chuck to 
start a well centered hole. My long bit tended to walk as it started 
cutting and then drilled a slightly slanted hole. Not the best effort.

I can do that a lot faster than burning out the broken tap, if I can 
find a decently hard drill in my 20 lbs of drill bits thats also the 
right size. 4.15 to 4.20mm's for the tap drill.

In fact thats what I'll do next, look for a better drill bit than the
one I was using (and resharpening frequently, but this code has a tool
length checker in it, if not on zero at contact, break and touch off z).

Thanks Andy.

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>

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