DRO 1/2 Function not accurate

Janderso

Jeff Anderson
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Mar 26, 2018
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Hi gang,
May this post find you and yours healthy and sassy.

I’ve recently discovered the magic of a digital read out. Every function has worked perfectly as far as I have judged.
Last weekend I screwed up. My holes were not centered in my part.
I am using a Starrett edge finder, I carefully zero one edge, up and over to the other side, find the edge, touch the, 1/2 function and the Y axis. I move to the center 0000 and center drill.

In the photos, I am showing you two holes. The one in the center is using the, find the edge, deduct half the edge finder thickness. Zero out then move in half the distance of the width of the part, center drill/spot.

The hole off center is using the DRO 1/2 feature.

I have a DRO Pros, EL402 series. I love it until now.

Any ideas? I have proved this theory at least six times. Same results every time. I am extremely careful.
 

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Head scratcher. I have a TPAC Tools DRO (I believe it's a Ditron or Sino unit) with the 1/2 function and have no issues with it. On mine, I find the first edge and Zero that axis. Move to the opposite side, find the edge and hit the 1/2 function. All it does on mine is divide the number on the display by 2.

For example, touch an edge on the LH side and Zero X. Go to the opposite side and touch off. If it reads 4.5", hitting the 1/2 function changes the X display to 2.25".

Bruce
 
Head scratcher. I have a TPAC Tools DRO (I believe it's a Ditron or Sino unit) with the 1/2 function and have no issues with it. On mine, I find the first edge and Zero that axis. Move to the opposite side, find the edge and hit the 1/2 function. All it does on mine is divide the number on the display by 2.

For example, touch an edge on the LH side and Zero X. Go to the opposite side and touch off. If it reads 4.5", hitting the 1/2 function changes the X display to 2.25".

Bruce
Mine is exactly the same process Bruce.
I even did the same process with two different edge finders assuming one was on the fritz.
 
I'm with Bruce, no clue, that's waaaay off.

I'm assuming maybe just a typo but I assume you have that part mounted in your vise lengthwise parallel to the t-slots. If yes it should be the X axis you are using the 1/2 function for, not Y. Also are your scales plugged into the correct axis? X left & right, Y forward & backward. Sorry for stating the obvious just making sure.

As Bruce said, the 1/2 function just splits the reading in half. I've never encountered an error using the 1/2" function on any of my DROs.
 
I also have a DRO Pros setup on my mill and have not found any problems with the 1/2 function in either X or Y. Something anomalous. Could any of the pickups or slides be loose or flexing?
 
I learned this method from watching YouTube.
I can’t think of how to do it differently.
The interesting thing is, it’s always off on the first measurement side. In other words, the hole is closer to the primary measurement.
It has to be the operator. Everything else works. I have adjusted and checked, re-checked tram and the vise.
 
I also have a DRO Pros setup on my mill and have not found any problems with the 1/2 function in either X or Y. Something anomalous. Could any of the pickups or slides be loose or flexing?
I’ll check, thank you.
 
Hmm, try narrowing it down. Mount a piece of known length, prferefeably a nominal size. Edge find zero, then move to the other end & edge find. Does the DRO read the correct length of the part? If yes....

Zero your handwheel dial. Use the 1/2 function. Then move your spindle to half the distance of the part using your handweel dial. Does the DRO reading match? If not what does the DRO say? I say to possibly use a nominal length part that way it can help you determine if the DRO is just reading some random number or if it's reading an even divison other than 1/2 or whatever.
 
Darkzero, great idea.
I just came in after checking for loose mounts. Couldn’t find anything out of order.
I decided I would try another edge finder surface. I set the quill depth the same on both sides, used the quill DRO.
touched off on both sides using the thickest part of the cone.
I’m on center this time. I cleaned and oiled the edge finder before I did this.
I always oil and check the operation of the tool before use so I wasn’t expecting any change but I did.
I’m on the right track.
Im going to manually check movement via dial indicators and the table dials.
Thanks for the ideas!
 

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Ah, wait just a cotton pickin minute here. What the heck did I find?
A damaged magnetic scale. This is about in the middle of my Y axis table movement.
Ill be contacting DRO Pros next week unless you have another idea?
I was way off on the table movement in the Y axis when I hit this section. Surprisingly the rest of the scale was ok.
My X axis reading is spot on.
 

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