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Ok, so I've got the ball screws ordered. While waiting for my ball screws to arrive, I went ahead and bought a cheap 12" DRO off of e-bay. Perhaps it was the beer that made me click on the buy it now, who knows? Anyways, being stuck inside the house with nothing else to do due to the weather, the DRO was really easy to install on the mill. I was surprised at how easy the casting of the mill was to drill and tap. After playing around with the DRO on the Y axis, I can acually put numbers to how far off the mill was when you change directions. You have to turn the handle nearly 0.02" before you see any movement when you reverse direction on the mill. To me, that seems like a pretty big number. I found a seller on e-bay who had a good deal on the DRO's. His prices were fairly low and he's got a bundled deal where you get 10% off. So anyways, I've ordered a 6" for the Z-axis movement, and a 24" for the X-axis movement. Be aware, that these things are actually a bit longer than the advertised size. The 12" DRO was almost 16.5" long overall. Means you actually get 12" of travel.
The DRO gauge itself is magnetic so I just stuck it to the belt cover until I get the other 2 DRO's in and mount em to a nice little plate. The scales themselves are USB, so perhaps there's a way to integrate them into a better display in the future? Here's a link to the E-bay auction for the scales I bought. Not horribly pricey, and quite a worthwhile upgrade, even if done only one axis at a time.
6" Digital DRO Quill Table Readout Scale for Bridgeport | eBay
Even with my limited experience, installation was pretty easy, I drilled two holes on the bottom casting where I mounted the DRO scale, and then one hole on the back corner of the table, where I used an L-bracket to run an aluminum strip down to the DRO slide. 3 holes in the machine, drilled and tapped in 10-24. I have never tapped cast iron and was a little nervous about breaking a tap off in my machine, but with plenty of WD-40 and taking it easy I had no issues. Worst part was cutting the aluminum strip, the squealing was horrendous.. Note, It's important to keep the scale level so that it doesn't bind up. To do that, I tightened down the screw on the table first to set the height of the slider and finger tightened the scale bar to the side. Then I ran the table all the way to one end of it's travel, gave that end of the scale bar a jiggle and tightened it down snug. Then, I ran the table all the way to the other end of it's travel, gave that end of the scale bar a jiggle, and went ahead and tightened that end down. Then I ran it back the other way yet again, made sure there was no binding along the travel, and tightened down the scale bar for good. That's the entire install process summed up.
I'm still waiting on the ball screws. One shipped a few days ago. The other hasn't been marked as shipped yet. Gotta love the slow boat from China...