Make a Micro DRO/lathe travel indicator for less than $10
useful is it ?
The readout is seen below measuring carriage travel.
And about to read cross slide travel below.
It's easy to read and has a very small magnetic foot print.
Cutting a very fine 40 TPI thread below - invaluable for resetting and incrementing the depth.
Here is the same short video of it in action as in the original blog.
For cross slide travel it's way ahead of anything else I've seen, for ease of use, and the ability to attach to an area of less than than 15 mm.
Only takes seconds to set up and is dead accurate down to very small increments.
Reading cross slide and carriage travel quickly and accuractely without going to the trouble of setting up a regular dial indicator and magnetic base is a big plus.
It's also ideal for smaller lathes as it's very compact and does not restrict travel in any way.
Being portable it's not subject to long term oil/metal/grit contamination, as can occur with a fixed open scale unit.
A nice little project which is extremely useful.
Further thoughts on construction
I increased the size of the magnetic footprint by milling the alloy base at the opposite end and recessing two magnets into each hole. The stronger the magnetic grip the better.
They were left overs from the job, so I thought I may as well use them and ensure the gauge has support across the full length of the base when reading carriage travel.
So there are now eight magnets in the base. There's no significant weight increase from doing it this way, but it's better mounting them in steel as it more than doubles the magnetic effect.
Recessing the magnets into a steel plate flush with the base helps prevents steel cuttings accumulating.
Think about the size of the area you want the magnets to grip to and mount them to take full advantage of the available bare metal (eg. I could have moved the second row of magnets closer to the probe to get an even stronger grip on the very end of the cross slide dovetail).
Here's a great Pdf document on the various types of rare earth magnets - interesting reading.
I also looked at the left over bits and did a bit more thinking.
As Araldite seems to grip the ABS plastic well, it may be possible to glue a 5 mm section of the tip from one of the discarded ABS wings onto the back of the scale slide to mate with the spring, rather than using a screw.
This would avoid interfering with the scale substrate. The pin could then be placed at any position on the slide and the slot moved accordingly.
This would allow the slot in the base to be closed at both ends, doing away with the need for an end cap.
There are various ways you could compress a spring in the base if you think about it.
Having a flush fitting probe is the main objective to get maximum benefit from the gauge.