DRO annoyance

M

Maplehead

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Hi All
I use the EZ-VIEW DRO's on my LMS micro mill. I love DRO's but there is an annoyance I deal with. Every time I advance to a plot point and stop, all is good, but as soon as I tighten my table, on either X or Y, the DRO usually advances .0005 to .001 inches. Is this common?
 
Yes, that can happen. Check to see how much play there is in the various slides, and adjust some of it out if possible, not so tight that the axis has significant friction (drag.) You might also try out some cuts with adjusting it out, and then not adjusting it out, just to see what the actual results are. You can also anticipate the movement and preset for it if it truly happens every time... What really counts is the the actual results you get from your cuts.
 
This is not the fault of the DRO. Your thread should really be "Small lathe/mill annoyance."
 
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Like the others said, its the slop in your machine, not the DRO. As for the .0005" - .001" that's probably better accuracy than what the machine is capable of anyhow. Consider all the things that have to be extremely accurate to actually get better than .001" on your machine. There is some slop in all of the moving parts, or they likely couldn't move on that level of machine. Spindle machined accuracy, bearing preload tolerance, quill to housing clearance, taper accuracy, collet accuracy, less than top quality tooling, spindle alignment to the column, column to the knee or base, base to the table, vibration, rate of feed.... It always surprises me that the results turn out as good as they do, given all the possible variables.
 
Yes that is normal especially for those igaging DROs. 5 tenths (5 ten thousandths) may not even mean anything as that is the lowest resolution of those igaging units like most digital calipers. Accuracy of them is 2 thou per 6" & repeatability is 1 thou.

With those igaging units were talking about numbers that may not even matter in the real world with whatever you make on your mill. Just enjoy you mill & don't worry about chasing those numbers. If curiosity is still poking at you, set up a tenths indicator & see what readings you get.
 
My Bridgeport does that on the Accu Rite dro.
I have found that if I ease down slightly on the axis lock lever prior to the wanted measurement that it takes some of the slack out of the table causing it to lock where it should.
Not saying it will work for you but it's worth a try
Chuck
 
I figured it's more of a mill thing than the actual DRO but I do enjoy reading all the replies as they make me think. Thank you.
Some of the details youguys talk about boggles me as i have no idea where you come up with it. I guess it's all a very long learning experience.
 
Maplehead said:
Is this common?
Click to expand...

Yes.

I have a Kent VM, which is a 9x42 Bridgeport copy, with an old Mitutoyo DRO. It does this almost every time. I play games trying to second-guess which direction and how much. The fact of the matter is that if this amount of movement is important, you need to be checking the dimension by a more precise method. I've known machinists (and shop owners) who covered the tenths position on the display with electrical tape to prevent dithering over an insignificant number.
 
I vaguely recall Mr. Pete/tubalcain saying in one of his tutorials, if you're using digital calipers or other measuring devices that are graduated to ten thousandths or more, put a piece of tape over those digits. They frustrate you more than help you. I can't vouch for the 'help you' comment, but he hit a grand slam on the 'frustrate you' observation.

Regards,
Terry
 
I have a PM-727M mill. When I lock the top gib on the head/z axis I get a MINUS .020 movement on the z DRO. When I lock the 2nd gib on the same gib get a PLUS .010 movement.. (a net of -.01 movement) I've adjusted the slack out as much as I feel isn't causing undue wear. Precision Matthews says it is what it is, I guess like someone else here said, If you know what's gonna happen and compensate for it....
 
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