Simple DRO for my South Bend 16

For the last few months I have been working to restore a 1954 Monarch Model 61 lathe and using my badly worn 1930 South Bend 16” gap bed lathe to make any parts I have needed to make using a lathe. I am about to make three fairly large bronze bushings for the worm and worm drive in the apron of the Monarch, and need a way to monitor the longitudinal position of my boring bar.

I had been using an old Starrett 5” stroke dial indicator to watch the positon of the carriage, but it is easy to miss read, and is not too convenient. I wanted a DRO, but I wanted a DRO that was simple to install and that would not require me to drill holes in the lathe or make any modifications to the lathe. Ideally, I wanted to be able to leave the DRO mounted on the lathe so that I could use it any time I needed it.

I eventually decided to buy a 24” generic (Chinese) DRO from Shars.com. (24" Digital Machine Stainless Steel Scale)
I chose a 24” because I wanted significant travel.

The installation that I came up with involved hanging the DRO on the front V-ways, driving the read head via the bolt hole for the thread dial, and a cheap magnetic indicator stand. I have attached pictures of the installation as well as a drawing of the parts. I did not make drawings of the rod assemble used to drive the read head. The rod is just a piece of 3/8-16 all thread, a piece of ½ inch hex threaded for 3/8-16 on one end and 1/8 NPT on the other, a 1/8 NPT to ¼ compression fitting adapter, and a piece of ¼” drill rod threaded ¼-20 on one end.

A few comments of note:
1) My drawings are mostly sketches for me. They are not complete, and they will most certainly require tweaking for another lathe.

2) No drawings, dimensions, or thread identifications come with the DRO. It is all metric.

3) My lathe has an 8’ bed, and you can see that the DRO has about 5” of unusable travel as configured. With a smaller chuck, the carriage can move further to the left and use up some of that 5”. Eventually I will adjust the length of the ¼” drill rod so that the carriage hits the left DRO bed mount before the DRO read head hits the right DRO bed mount, and the DRO read head cannot hit the left DRO bed mount. This will maximize carriage travel using the DRO.

4) The DRO’s display head lost its magnets and the display head mount lost its steel bar for the magnets in transit. I found the magnets and glued them back in place but had to make a new steel bar for the mount because I did not find it in the package.

5) I checked the DRO against my Starrett 5” stroke dial indicator. The DRO reads well going from positive to negative without any offset. The DRO and dial indicator were in complete agreement from 0 to 1”. At 2” the DRO read .002 more than the dial indicator. At 3”-5” the DRO read .004 more than the dial indicator. I do not know if the difference was error in the DRO, the fact that the indicator point is on a rough casting (carriage side), or if the error is in the old dial indicator. I suspect the error is in the dial indicator mounting.

All in all, I am pretty happy with the DRO and believe it will give me good service.

I've always mounted on the back of the lathe, it's out of the way and easy to attach a bracket to the back of the saddle to drive the read head, mount a long stick of aluminum angle over the top to protect it from swarf.

The cheaper capacitive scales do lose some accuracy over length, if you don't need to hold tight tolerances over longer distances they'll work just fine. I have two lathes equipped with the Igaging DRO Plus scales- but use the Touch-DRO bluetooth processor and tablet for display. Touch-DRO can be compensated for inaccuracies in the scales greatly increasing accuracy. Still, nothing beat glass (or magnetic, better yet) scales- but they're nearly impossible to install on the X-axis on these older lathes because there's not enough clearance.

I used the DRO for the first time today. I was pretty happy with it but I wish the update rate on the readout was about double what it is now.

Hello sir - which model DRO did you get for south bend lathe / and which scale sets? I’m in market and have sale lathe! Kudos Aaron