Mini lathe DRO

[loply]

Hi folks,

After struggling to bore a few holes to a specific depth I decided I needed a carriage DRO and a leadscrew handwheel, and came up with this:






I've seen various similar mods on the internet, though often people make the "screen" of the modified digital calipers the static bit, and make the scale slide back and forth, resulting in the weird scenario that the scale slides off beyond the end of the lathe. I have clamped the scale and attached the "screen" to the carriage.

Various tests with DTIs indicate that it works perfectly in one direction, however, I have 0.05mm of backlash when changing directions. A range of tests with DTI's confirms that the "screen" on the calipers is not moving initially, which I believe is because it's rotating instead...

I heard a rumour that these calipers all have a thread on the rear for attaching things to, which is usually covered up with a conversion chart sticker. Because my linkage operates below the axis of motion of the thing, I think it's rotating it back and forth, so will look into moving the linkage to attach to this thread, if it exists!

Also made this quick-remove chip guard thing, need to make another to protect the DRO too:



Cheers,
Rich

[saw]

Hi, thanks for showing. I think that I have the very same lathe and I have wundering how to moint it. 

[andyf]

Various tests with DTIs indicate that it works perfectly in one direction, however, I have 0.05mm of backlash when changing directions. A range of tests with DTI's confirms that the "screen" on the calipers is not moving initially, which I believe is because it's rotating instead...

Rich, apologies if you already know this, but those calipers usually have a gib strip, with adjusting screws (use a flat-bladed fine screwdriver) accessed through a couple of holes on what is the top side in your pics. Maybe tweaking them a bit would get rid of some of the lost 0.05mm.

Andy

[loply]

Various tests with DTIs indicate that it works perfectly in one direction, however, I have 0.05mm of backlash when changing directions. A range of tests with DTI's confirms that the "screen" on the calipers is not moving initially, which I believe is because it's rotating instead...

Rich, apologies if you already know this, but those calipers usually have a gib strip, with adjusting screws (use a flat-bladed fine screwdriver) accessed through a couple of holes on what is the top side in your pics. Maybe tweaking them a bit would get rid of some of the lost 0.05mm.

Andy

Hi Andy,

I was aware of that, though the idea of tightening it didn't occur to me. I might give that a go. Thanks for the suggestion.

My instinct remains that my linkage is wrong though, I'm "levering" on the reader body thus trying to twist/rotate it, I should've designed it differently in the first place really.

[No1_sonuk]

Thanks for sharing, loply.  I've been trying to think of a way of doing that for a while. 

[loply]

Well I took the sticky label with the useful conversion chart off the back of the caliper, but alas, the alleged threaded hole was not there.

I have two options now to eliminate the backlash/freeplay in the caliper:

1) Stick something to the back of the caliper inline with it's axis of movement using liquid metal or suchlike
2) Try tightening the gib strip
3) Both of the above

Will have a fiddle tonight/tomorrow and let you know how it turns out.

Incidentally though... I used the DTI in anger this weekend and have to say it was a real pleasure to use. Being able to zero it on various points and then "count down" so easily was great. Doing some threading to a shoulder with it and I was able to stop at the same point each time with ease.

Makes me realise how useful a cross slide version will be.