Lubricating DRO linear scale on Mini Mill

Compared with my digital calliper, the DRO slide is fairly stiff and there is stress on the coupling to the table. I've made the coupling fairly rigid but it worries me that it can become loose. (= backlash, eventually)

The units are Shahe style from Arc Eurotrade iirc and I'm wondering if I could use some lubrication on the rails. Or, is it possible to loosen the 'grip' by reducing tension in the screws between the two halves of the slide? Lubrication could gather grot, of course.

I get the impression that several people have used these cheap DROs and I imagine it's a common concern.

I got 7 of them from ebay and they were all fine and smooth

A warped/bent rail?

edit: should be miles nicer than a digital caliper, a definite step up, which is why they are worth getting

Keep them clean with tissue paper, do not lubricateg

Edited By Ady1 on 17/09/2021 23:33:35

Edited By Ady1 on 17/09/2021 23:34:21

What do you call stiff, if its so stiff you think its stressing the connection to the table then something is clearly wrong and I would suspect the mounting of the unit. What did it feel like before it was mounted..? With the reader head fixing released the connecting bracket should be just touching the mounting position there should be no gap or over close which would put pressure on the head when fixed. 

If your mounting is good and the unit is as stiff as you suggest then it's obviously faulty.

Do NOT lubricate the rail it needs to be clean and dry, ARC say in their spec that the units need protection from swarf and coolant etc. I made up guards/covers for mine from 25 x 25 x 1.5 alu angle, simple to do and works well.

Edited By Ron Laden on 18/09/2021 05:23:15

Edited By Ron Laden on 18/09/2021 05:44:32

First thing to do would be take the scale off and see it it runs smoothly which will eliminate how it is fixed.

If still tight then make sure it is clean particularly if you have no protection

If I remember correctly there are two screws for adjustment of a pressure spring , is this a bit tight?

That could be useful information. Thanks, I'll have a look. I didn't make the point that I have three units (XYZ) and they all seem to be the same. I will have a fiddle and see if they will loosen up a bit.

It's not drastically stiff - just more than I would expect and worse than my digital calliper - and it's always worth casting a stone into the ME pond for ideas. I did read a comment somewhere of a version of the DRO slider that has a bracket on it and there were doubts about how strong it is.

The option against lubrication confirms my opinion.

Hi Andrew, make sure the screws that hold the bracket onto the head are not too long so that they rub on the back of the rail, put a washer under the screw heads if need be.

Regards Nick.

HAHA. Been there, done that. They are all well short enough now!!