Installing a DRO Digital Read Out on a Lathe

[henryarnold]

(07-01-2012, 01:40 PM)PixMan Wrote: Henry,

The reader head (not the scale) on the Z axis (longitudinal) got knocked out of position when the carriage pushed the reader head to the end of the scale housing and moved the bracket. It was apparently enough movement to cause the thin cast aluminum "stalk" of the reader head (extending up into the scale housing) to rub against the scale housing seal and wear right though the aluminum casting, seen as the crusty-looking "T"-shaped thing and the now-separated base it used to be attached to.

In looking at the bottom photo, just imagine running that reader head into the end of the scale. It easily moved the bracket at those two long slots, and neither I nor my dad ever "felt" any problem. It took perhaps a year or less to wear right through as you see it.

Sorry about my optical delusion in not realizing that I was looking at just a stack of fender washers there.

I suggest you run the cross-slide all the way in to the stop, then place the scale housing as far back as is practical. The goal is to get the reader head itself far from being struck by the tailstock being slid forward, or anything else for that matter. I sense that's how the one on my dad's lathe was done, but we'll never know. The installation was already done when I got the machine for him.

Pixman,
Thanks for the additional explanation.
My lathe is much smaller than yours. With the scale pushed as far back as it will go, it still can be hit by the tail stock. Your suggestion has prompted me to plan to construct my pickup bracket so that the tailstock will hit the bracket and not the pickup.
Henry

[f350ca]

Henry
Another option is to turn the scale sideways and mount the pickup over the ways. Guess there's a chance of getting cuttings in the seal but hasn't affected mine. On my big lathe they brought a bolt out from the saddle for the tailstock to hit before it contacted the scale.

[PixMan]

It can't quite be seen in the top view photo I'd posted, but there's a long socket head cap screw sticking out just a tiny bit further than the cross slide scale, right about at the middle. That's what the tailstock hits, never the scale housing.

[Bogstandard]

Having got 4 axis readout on my lathe, cross slide X & Y, topslide and tailstock, here are a couple of suggestions.

For locking up your cross slide, now your normal one has been covered up by the read head.

http://www.homemodelenginemachinist.com/...ic=18975.0

Make sure you have a stop, a big bolt, sticking out of the back of your cross slide to stop the tailstock running into your newly installed DRO.

John

[EdK]

(07-03-2012, 03:58 PM)Bogstandard Wrote: Make sure you have a stop, a big bolt, sticking out of the back of your cross slide to stop the tailstock running into your newly installed DRO.

John

John,

That's something I have to add to my cross slide. I just about ran into the reader head the last time I used the lathe.

Ed

[Bogstandard]

This is where mine pokes out from, and as long as it stops the tailstock say 1mm from the read head, then everything should be OK

BTW, it does reduce the reach of the tailstock slightly, but it does stop getting the DRO head mashed up.


John

[henryarnold]

During the last couple of days I was able to resume work on my DRO installation. I've been working on the cross slide mounting first. Because the scale is longer than the length of the cross slide, a mounting plate is needed where the scale screws to the plate and the plate screws to the cross slide. I decided that I also wanted end caps that are integral to the plate so I cut my mounting plate out of 3/4" aluminum. This part could be easily made from 1/4" thick by 3/4" wide aluminum if you don't need the end caps.

I did the rough cutting on my bandsaw in the vertical position. It went surprisingly fast.
   
I first milled an accurate opening for the scale and then milled the back side and the ends to size.
   
Here's the finished mounting plate, the 1" x 1" x 1/16" angle cover, and the scale.
   
I drilled holes for clearance around my gib screws, the threaded holes for the scale mounting, and slotted holes for the screws that mount the plate to the cross slide.
   
Here's a close-up of the scale mounting hole, the slotted mounting hole and the gib screw clearance hole.
   
If you want to simplify your installation, drop the end caps and just cut your plate from flat 1/4" stock.

[henryarnold]

Once I finished making my mounting plate, I did a dry check on my cross slide to make sure everything lined up OK. I also marked where the mounting holes on the cross slide needed to be drilled and tapped.
   
I drilled and tapped the cross slide mounting holes by clamping the cross slide to an angle plate on the mill. The distance between the holes had to be accurate because I did not allow for any movement in the length ways direction. I made both my slots in the up and down direction for adjusting the scale accurately with the movement of the cross slide.
   
Here's the plate screwed to the cross slide. The fit was good and there's 0.100" of up and down movement possible for adjustment which I'll show later.
   
The surface on my carriage where the scale pickup will mount to was cast crooked and at an angle. It would be difficult to shim it in a way that would create a clean mounting of the pickup. I decided to remove the carriage and mill the area square and at right angles to the top of the cross slide. I mounted the carriage on my mill registering off of the dovetail. I milled about 0.050" which was enough to create a square mounting surface. There was plenty of meat to my carriage so the 0.050" won't be missed.
   
Here's a close up of the milled area before I drilled and tapped it for the pickup bracket.
   
I had to do my drilling and tapping of the carriage in a vise because I couldn't come up with a way to mount it on my mill because of it's size.
   

[EdK]

Good progress Henry.

Ed

[henryarnold]

I re-installed my carriage and cross slide with mounting plate. You can see the milled pickup area with two screws. I will make the pickup mounting beefy enough so that the tail stock hits the mount instead of the scale.
   
I used a dial gage to align the plate. I also aligned the scale which has a small amount of up and down play.
   
This photo shows he scale mounted. Next I need to make the bracket that connects the carriage to the pickup.
   
The reason I went to the trouble of making my mounting plate with end plates is that they will support the cover I'm going to make. The cover adds extra protection from oil and swarf getting into the scale.

More photos coming soon.