Cheap DRO! – part 2

Continued from Part 1

With the X-axis DRO installed, I turned my attention to the Y.

The difficulty here was that there weren’t any pre-existing holes or dovetail slots to take advantage of, so it was an entirely custom installation.

The other complication was that the base of the mill flared out to a wider footprint, so the only surface to mount the DRO’s rail on was at an angle relative to the surface on the sliding table itself.

I started by taking off the handwheel on the left side if the table and moving the table all the way to the right to give me working room.
IMAG0966

I then removed the end cap of the table to give just a little more space.
IMAG0967

There was a flat space just under the lead screw that looked like a promising location to mount the measurement unit’s bracket, so I drilled and tapped a 1/4-20 hole in the center of it (approximately).
IMAG0968
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Just then my daughter woke up from her nap, so I put things on hold until the next day.

Since I knew I would be modifying brackets, I started working on the rail so that I would have precise references to work from.

After cutting the rail to length,
IMAG0970

I drilled and tapped a hole near the back of the mill first. I placed it so that the mounting bracket would sit just under the line where the base began top taper outwards, this way I could use the same line near the front to visually confirm the straightness of the rail.

In order to avoid obstructing the full range of motion along the Y axis, I had to modify a couple of the mounting brackets and attach them to the front of the mill, instead of the side. The modification was essentially to attach two brackets together (using one of the spare brackets from the X-axis), so that I could reach the front of the base and still keep the rail parallel to the table.

Now that I had the rail mounted, I could get a feel for what sort of bracket I would need to fabricate to hold the measuring unit to the sliding table.

I’ll gloss over the details, since they aren’t particularly useful), but suffice it to say that I used a vice, drill, hammer, and welder to create the necessary Frankenbracket.
IMAG0971

Since this bracket is always hidden under the table, the install looks pretty good.
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The display units conveniently had magnets on the back, so while a long term setup will be a little cleaner, I was able to stick the displays on the head of the mill for immediate use.
IMAG0972

With the installation complete, I turned my attention to re-mounting the vice on my table.
Because of the location of the travel locks and the dovetail slot, The X-axis measuring unit sits about a millimeter above the surface of the table.

IMAG0978

I always keep my milling vice installed on the table, so I needed a way to avoid the top of the measuring unit.

I could shim up my vice, but that would introduce instability and inaccuracy.
So I marked the bottom of the vice where it crossed the edge of the table.
IMAG0979

Then I clamped a large aluminum bar to the table, parallel to the Y-axis (front/back),
IMAG0980

and then clamped this bar in the upside-down vice (I had to space the vice from the bar with a 3-2-1 block to clear the clamping bolts).
IMAG0981

Then I milled out a swath 1.5 millimeters deep and 1.5 inches wide, starting from the mark I made and cutting towards the back of the vice(away from the jaws).
IMAG0983

This was sufficient to clear the measuring unit.
IMAG0985

I re-aligned the vice and now I’m back in business (figuratively.. I don’t actually have a machining business…)
IMAG0986

So there you have it. $60 and 4 hours later, I have DRO on all 3 axis of my milling machine.
I’ll let you know at some later point in time if it lives up to expectations.

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