correct,

If you draw 2, different, triangles like that, with their corners on a circle, their hypotenuses intersect in the center of that circle. also the middle of these hypotenuses, of each triangle, would be the center, hence, that is why I was interested in finding  the "half way point" of 2 points, coordinates.


on a mill it would actually be pretty easy.  touch off on a 'reasonable' spot at the edge of a 'circle  (30-60 degree XY axis or so).

Go down/up the X-direction until you find the edge again. From there go in the Y direction til you find the edge yet again. The center (of that circle/hole) will be half way  between where you "touched off" and where you are now.

for a rectangle, similarly you could center the X axis,  and next the Y axis (and find the center of a piece of stock for example). Technically you would have found the center of a concentric circle,  but that's the same thing.



It would be a cool utility,  that you can find all kinds of "spots" on a part with, I'd be interested in 'building' something like that


Ron


On 7/11/21 11:52 PM, John Dammeyer wrote:
Here are your 3 points.  As a math wiz you can see that if you draw a 
perpendicular line from each pair of points they all intersect in the middle.
The third angle is the one I can create graphically and from that the length for the XY of the center but you might be able to explain the math a bit better.
-----Original Message-----
From: R C [mailto:cjv...@gmail.com]
Sent: July-11-21 10:31 PM
To: emc-users@lists.sourceforge.net
Subject: Re: [Emc-users] 'automatically' go halfway between 2 points


On 7/11/21 11:15 PM, John Dammeyer wrote:
Essentially the process involves two touch off operations.  First one side 
until an LED comes on or even better the probe input goes
active.  At that point touch off so the axis is set to 0.
Then you move in the opposite direction until the probe (or LED) goes active.  
Divide that axis value by two and move back to that
position.  Now touch off again to set the axis to 0.  You are now in the middle.

Right,� I can do that with a calculator and some arithmetic, and jog
there manually,� but I am a mathematician,� and we're known to be lazy,�
so I am thinking about a button�� :)


It's probably possible with a fancy G-Code macro.
well,� if one can write a plugin,� it would probably be fairly easy (but
I am a CNC rookie) to do that,� if that plugin can actually move the
tool/spindle


A number of different projects I've done have been set up that way.  Find the 
center of the object which is also where I've set the
center in the CAM software.  Rather than top left or bottom left corner of 
something that has been milled away.

right,� I don't think it is not too difficult to find the center of all
kinds of shapes (geometrically or otherwise), in a math kinda way that is.


But I'm an amateur and probably do things the hard way.  Often...
well,� hobbyist that's trying to learn some stuff here,� I am actually a
mathematician,� I can calculate things,� but I'd be a starving machinist
or CNC person/operator/machinist ...�� this weekend I created 4 proto
types of a stepper motor mount,� aka scrap.
John
Ron


-----Original Message-----
From: R C [ <mailto:cjv...@gmail.com> mailto:cjv...@gmail.com]
Sent: July-11-21 10:00 PM
To:  <mailto:emc-users@lists.sourceforge.net> emc-users@lists.sourceforge.net
Subject: Re: [Emc-users] 'automatically' go halfway between 2 points


On 7/11/21 10:47 PM, John Dammeyer wrote:
I still have my Shumatech DRO on my mill.  I touch one side and zero the axis.  
I then move across and jog until the LED goes on.
Then FCN 1 and the axis letter button.  At that point the axis changes to minus 
halfway between where I just touched off and the
original 0 point.
I move to make the DRO show 0 and then touch off that axis on the AXIS screen.  
Now I have the center point between the two
edges.  Since the LED indicator probe is 0.2" diameter the distance to the 
center doesn't matter.  Only if I am trying to find the
edge
and the Shumatech can be told the diameter of the probe.
Certainly there must be an easy way to do this with LCNC?  The Shumatech 
software has been around for at least 13 years.
Oops,?? I didn't see this last line...?? I think so,??? either some
added functionality in the DRO? (that is where I was looking around),?
or else a plugin.?? it's probably not that hard,? if I knew how to write
a plugin for LCNC


John


-----Original Message-----
From: R C [ <mailto:cjv...@gmail.com> mailto:cjv...@gmail.com]
Sent: July-11-21 9:29 PM
To: linuxcnc-users-list
Subject: [Emc-users] 'automatically' go halfway between 2 points

Hello,


in linuxcnc,? is there an easy/automated way to get halfway between two
points??? (Fort example, you'd touch off somewhere, move to some
coordinate (x, y)? (or even (x, y, z)) and go inbetween right to the the
middle of where you touched off and where the spindle is now?


thanks,


Ron



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