I would like to be able to jog while a stop or pallet change command
(M00/M01/M60) is active. This has been discussed several times on this list
and the LinuxCNC list but I can't find a resolution other than "it doesn't
work" or use "run from here". Am I missing a simple workaround? 

In case  you are curious, I would like to be able to automatically position
over a hole to be tapped, pause, manually adjust a spring loaded tap guide
in Z, hand tap the hole and then press Cycle Start to continue to the next
hole.

-----Original Message-----
From: Gene Heskett <ghesk...@shentel.net> 
Sent: December 12, 2021 4:50 PM
To: emc-users@lists.sourceforge.net
Subject: Re: [Emc-users] making post square.

On Sun, 12 Dec, 2021 at 4:26 PM, Chris Albertson <albertson.ch...@gmail.com>
wrote:
 

To: enhanced machine controller (emc)
On Sun, Dec 12, 2021 at 12:39 PM Gene Heskett
<ghesk...@shentel.net<mailto:ghesk...@shentel.net>> wrote:

> On Sun, 12 Dec, 2021 at 2:54 PM, Chris Albertson < 
> albertson.ch...@gmail.com<mailto:albertson.ch...@gmail.com>> wrote:
>
>
> To: enhanced machine controller (emc)
> I'm surprised that people don't use kinematics to remove the residual
> alignment errors that can't be mechanically removed.   Of course, you
can't
> remove tool orientation errors this way.   If the z-axis is a few
> milliradians "off" the tool will also be "off" but kinematics can 
> compensate for the X, Y error associated with variable Z movement.
>
> That said, I can't measure this kind of low-level stuff so I don't 
> worry about it.
>
> You should be able to lead the Z- column over at 45 degrees and still 
> hit X, Y point spot on. (it would work only for a spherical tool)
>
>
>
> If it was moveable Chris,  but its not, the column is fixed, but the 
> head can be


No, you never want to do that.


Why not? I needed to drill and rigid tap a motor shaft to pulley joint,
positioning the two holes half in the motor shaft, half in the pulley then
fill the holes with 

4mm metric screws to key the normally screwed on pulley to the shaft. I had 

done similarly to a 1 horse treadmill motor on my 7x12 but Jons pwm-servo
driver can be quite brutal and powdered the grub screws I put in for keys on
the first motor. I used solid screws for the 2nd one, and softened up the
control 

rates, and its now worked for about 6 years. That switch to using the x axis
for rigid tapping bypassed this leaning tower of pizza post, and cut perfect
4mm threads, 

much more precisely than I could do using the leaning z axis.


  My point was that there could be an absurd amount of error and you should
still be able to work with it by telling the kinematics system the column
meets the Y axis at 89.9<http://89.9> degrees.


Its worse than that, if the head is trammed to the table, and you want to
drill all the way thru a tap hat slug with a 7/32 drill, its bending the
drill bit visibly sideways by the time the hole is 3/4" deep in a 1.25" slug
of brass. Way out of tram, but its not.



  I'd think
we are talking arc minutes at most here for a real milling machine.   But
there are home-made CNC machine made with rails mounted to a plywood base.

BTW, even with the 0.1-degree error, you still have good accuracy with
realistic Z-axis moves.

>
> rotated 90 degrees either way and I have several times. That works 
> quite well.
>
-- 

Chris Albertson
Redondo Beach, California

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