DIY Lathe "DRO"

I bought a lathe. I got married. I’m not allowed to buy a DRO.

However, I have some spare calipers…

The lathe is a Smithy Granite 3-in-1. It applies the old adage “Jack of all trades but master of none” but it works well for lightsaber parts. There is an actual gearbox (no fiddling around with gear sets), and while the mill is not that rigid, the build quality is what I would call above average for a machine it it’s price range. They sell a DRO kit, but it is $850.

I recently had to drill a bunch of holes in a section of 3/8" square dowel and decided to clamp a pair of calipers to the cross-slide instead of keeping track of the dials. It worked quite fantastically:

This set the wheels in motion. I found some unused M5 holes floating around on the cross-slide, apron, and on the main casting that would work with some finagling. It took three iterations of prints to get a final product that actually fit perfectly (50% infill…I wasted a lot of filament…:cry:):

The cross-slide uses a pair of 6-inch calipers, while the apron moves a 12-inch pair. The caliper tines are simply clamped by some small 6-32 BHCS, which can be loosened with minimal effort. I might order some thumbscrews just to make it that much easier to free my calipers if needed.

I apologize for the crappy photos. For those who are interested, I made a short video of the movement:

I don’t know if anyone has this lathe on here. Or if anyone has extra calipers. But, I am proud of the modification and it really does work amazingly. I checked the movement accuracy with my dial indicator, and it is staying consistent to the thousandth’s place when moving in both directions. This will help me so much in machining parts.


Ha ha I’m sure it would ha e been a lot simpler if the wife had just said yes.
But well done on coming up with a much cheeper alternative.
Looks fantastic!
I may have to pinch this idea and do it for my dad lathe :+1:

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I don’t suppose you can attach those STLs? I’m thinking this might e a good thing to do for my lathe too. :slight_smile:

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Sure thing!

A couple notes:

  • The STL’s are exported in mm units.
  • The small screw holes for clamping the calipers are sized for clearance/tapping of 6-32 x 3/4" screws.
  • The Central Hub and X-axis support mount to the lathe with M5 screws.
  • The Y-axis support mounts with M4 (I think). I didn’t have an M4 fastener handy, so I just rammed a 8-32 screw in there…:shushing_face:
  • The slots are sized for 0.138" thick caliper tines on the X-axis, and 0.15" thick tines on the Y-axis.

I went ahead and put the Fusion 360 files in the drive folder as well.

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Drive link is nice, although I was hoping to show off the inline STL preview.
Hope you don’t mind if I repost them as attachments:
Y-Axis Support.stl (160.9 KB)
DRO Central Hub.stl (173.7 KB)
X-Axis Support.stl (137.1 KB)


i mentioned this to my father and he said he buys in the DRO set up in kit form when he upgrades his friends machines.
a bit like this one…

a little cheaper than the purpose built kit but essentially does the same job.

i know your a bit of a dab hand so i’m sure you wont find it hard to fit :grin:

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I love spinning stls around. works great on here.