Tail Stock DRO

Whelp I finally did it, and cheap and cheerful to boot! Thanks to some encouragement from my Good Friend Jimmy and him building one for his Optimum Mini, I finally jumped the cliff and built one. I happened to be in HFT the other day and they had the 4" digital calipers on sale for $14.99 so I picked one up. I could have gotten them cheaper but forgot my 25% coupon! I knew they wouldn't be the best quality but as long as they were repeatable it would suit my purpose.

I checked it out with my 1", 2" & 3" mic standards and it was dead on, on all three and repeatable. It also has a little 5 tenths digit and a metric switch. The only real issue I had with it was how cobby it felt opening and closing it. The other thing I wish it had was a incremental mode, but that can be gotten over by just zeroing at the start point. So for $15 it wasn't horrible and fit my cheap and cheerful mode...and as usual I pretty much did this on the fly.

The first thing I did was to remove the battery and the sticky silver label on the back so I could get to the screws to remove the cover. It came off in one piece but the sticky residue was ugly and hard to get off with lighter fluid or brake clean on a rag. Once I got it clean I removed the 4 tiny screws from the back and carefully removed the cover with the electronics. Then pulled out the slider to reveal the spring gib and proceeded to clean everything with denatured alcohol.

It was pretty obvious why it was so cobby from the slide channels in the back housing to the edges of the magnetic scale scale that rode on them...they had all been cut with rock and chisel!

Next was to cut the measuring tangs off the back housing and the magnetic strip blade. Unfortunately I didn't take any pictures of this so I can't share those. I decided on using my Dremel with a thin cut toff wheel and used my small square to scribe some cut guide lines. I took my time and it worked pretty well over all but not necessarily beautiful like Jimmys came out but think the Master used a Fret Saw. Had a little cleanup with a file and stone and it was on to another clean up.

Caliper back plate slides and brass spring gib...already drilled.

In the picture you can see 2 little set screws on the top for tensioning the spring gib, the middle hole is for the locking thumb screw. I spent a little time on this cleaning up best I could and removing the depth blade which was tack welded on. It broke off pretty easily but left a bit of a burr which I removed with the Dremel then used a silicon carbide dressing stone to give a smooth over.

The plate is a piece of 1" x 1/8" CRS that I drilled and countersunk (82º) to match the holes from my Dial Gauge setup, plus I had some 8-32 flat head stainless screws in the drawer. I did have to countersink slightly into the tail stock casting and trim the screw lengths but worked out just fine. I pretty much eyeballed getting the assembly oriented on the edge of the tail stock for clearances and the distance from the edge so I could get a good pull. I also determined that a 1" center to center for the back plate mounting screws was good to go so off I went to drill and tap the back housing and drill and countersink the backing plate.

Back housing and backing plate holes.

You can see I didn't clean up the back of the backing plate as well as I did the top side. The CRS had a warp to it and was afraid if I took off the rest of the scale it would cause me to have to countersink into the back housing, and there are only about 2-3 threads now. Those are 6-32 flat heads because I didn't have any 4-40's but if I had, I probably would have used them instead! I trimmed them to length and used the Dremel to tidy up the inside of the back housing then again with the silicone carbide stone to assure flatness.

The next thing was to cut down the slide to proper length and drill the end for securing to the tail stock shaft. Out of the box it was too long and hit the tail stock handle, but I knew the Mini only has about 2.25" of travel so I eyeballed it on the old dial gauge stop and figured it would be good at about 5.4" overall and still give enough travel for the tail stock shaft and not interfere with the handle or anything else.

For the hole I used .125 from the end and centered on the magnetic slide. I used a tight clearance tolerance drill (#29) for a 6-32 screw. I put it magnetic strip down on a piece of wood and peck drilled it with the drill press from the backside, and ran it in and out a couple of times after I broke through. It worked out perfect as I didn't really want it to be tightened to the quill plate but have minimum tolerance so it could slip only a tiny bit. It seemed like there was some spring back from the plastic cover of the magnetic strip that left it just perfect. I also polished the edges of the rail on some 800 grit, then 1200 grit on the granite to give it a bit better slide in the cobby housing.

Next was to partially assemble it and put the battery back in to make sure I didn't mess anything up. To my surprise...it still worked!

I was originally going to use the Gauge Stop I made for the dial gauge but messed up on my locating the hole for the magnetic strip slider...so off I went to make another leaner version. Basically used the old one as a rough template but kept the new one the same size as the end of the tail stock casting this time but just tall enough to land under the DRO blade. Drilled the shaft hole then drilled and tapped the holes 6-32 for the set screws and blade screw the same as I did previously.

Quill Stop for DRO.

Epilogue

Overall the whole project took about 4 hours just like the dial gauge version and only cost $15, mainly because I still had some of that .188 plate left from the last quill stop and all the rest was out of the bins or stock material I had on hand. I haven't thoroughly run it through the paces yet but so far it works great and is repeatable. I did several tests by setting it to "0" then ran it to stop and various other values, then set to "0" again and ran it back in to stop and every time it gave me the same number only a minus value. It also returns to zero if I don't reset it.

The picture at the top of the page is the first test at zero and this one is after I ran it out to stop and reset to zero, then brought it back to stop. Pretty Good to go for me!

This was great fun and now real happy how compact and easy to set and read compared to the Dial Gauge version...and no pre-loading and counting backward on the dial! My only regret is that I should have done this the first time for only $5 more! I'm thinking now I may put one of these on my drill press because they are so easy, and Cheap n' Cheerful to make!! If you like it, give it a try, you'll be happy you did.