Mounting a DRO on a SB10, space issues and possible solutions

MontanaLon

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I have decided a DRO is needed for the lathe. It is a SB 10" with legs and no factory chip pan. I am working on a home brew chip pan though but figure I want to get the DRO mounted before I do that since I would just have to take it back off to get the DRO mounted.

The problem I am trying to figure out before I commit to a DRO is how to mount the scale for the cross slide most effectively. The height from the cross slide to the compound is just a little more than an inch and the glass scales are taller than this. I could turn the scale on the side which is only 7/8" of tall. This would have a couple of disadvantages. First the scale and read head would intrude into the space where the tail stock would need to be for some work and also expose it to damage from the tail stock hitting it. Second, it would have the opening to the side where a chip or oil could foul the scale or read head. I have seriously been scratching my head on just this problem for a couple of weeks.

I looked and came up with an idea to mount the scale under the saddle and just run an arm from the moving portion of the cross slide back and down to reach where the read head would be held at the scale. Has anyone ever tried this and been successful? Will it work at all? It would take some engineering to attach the ends of the scale on the bottom of the apron at one end and off the saddle at the back.

I guess I am just looking for confirmation before I commit to the DRO. Any help would be appreciated.
 
I have mounted the X scale on its side on DRO's before with no issue. Whether you mount it on its side or "normal", you will need to drill and tap a hole to put a longer screw in to act as a stop against slamming the tail stock into the scale or the carriage moving back against the tail stock. I have seen so many scales need to be replaced for this exact reason.

I have seen a lot of guys put rubber strips over the scale to protect it from coolant and chips, whether it is on its side or is mounted normally.

I would recommend against mounting the scale underneath the carriage. Ideally, the scale and reader head should be mounted as close to the same plane as the leadscrew and should have the minimal amount of flex points. The more flex points and distance between the reader head and where the bracket is secured to the machine will just cause loss of accuracy.

Jon
 
You might want to look into magnetic scales which are much more compact than glass. They are also almost impervious to fouling from chips, etc. I just ordered a 3 axis 1um resolution kit with LCD graphic readout for $1K delivered, from M-DRO in the UK. They also have much less expensive magnetic, 2 axis DRO packages with standard 5um scales and LED to readouts.You can get even cheaper buying Ditron brand, direct from China on AliExpress.
 
Cross Slide space issues are the reason that I went with a TouchDRO system with iGaging scales. I mounted the cross slide scale on the tailstock side of the cross slide with the pickup nested between the ways. The scale and protective cover eats up about 1.2"" of tailstock travel but this is a minor inconvenience as I would seldom, if ever, need to position the tailstock that close to the headstock (it would be turning a 1" long pice between centers, using the tailstock dead center).

Another issue is that the cover for the cross slide extends slightly above the cross slide so that in certain positions of the compound, the compound crank will hit one of the cover mounting screws. Temporarily removing that screw solves that issue. Also, the scale covers the cross slide gib adjusting screw and needs to be removed to adjust the gib. Again, a minor inconvenience as the gib adjustment is infrequent. The saddle lock is also slightly obstructed by the cover but I can still get in with an Allen wrench. A minor change in the mounting would have prevented that. The 602 has a rather useless cross slide lock if it can be called that, basically tightening one of the gib adjustment screws ,and I never used that. I have another means of locking the cross slide and a better design on the table for that feature.

The iGaging scale also don't have the resolution of the glass scales so reading in diameter mode, the scale changes in .0008" increments. The base glass scale has a 5 micron resolution offering .0004" increments in diameter mode. The 1 micron glass scale will get you down to .0001" in diameter mode.

All in all, I gave up little in the way of functionality for the convenience of a DRO. Here is a detailed write up of my install.
 
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When deciding on my lathe DRO system, several other options were considered for the cross slide. One is to mount the cross slide and pickup to the rear of the lathe. This would involve extending the mounting hardware and prevent the use of the backsplash.

Another idea was to make a 90º bend and run the scale parallel to the ways. This would involve something like a thin stainless steel band similar in concept to that used in some computer hard drives and old floppy drives. The bend would be around a precision ball bearing with an additional bearing or bearings providing close contact.
 
Here's how I did it.

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If I had it to do over again, I'd make it a couple of inches longer to prevent the scale from interfering with the tailstock.
 
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