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How many axes on a lathe DRO?

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That is a beautiful machine Dave, very nice. No air bearings? Whaaa?    Just kidding.


Dave Otto:

--- Quote from: Bearcar1 on March 16, 2021, 12:30:30 AM ---That is a beautiful machine Dave, very nice. No air bearings? Whaaa?    Just kidding.


--- End quote ---



Art K:
I don't have a dro on my lathe but would like to add one. Dave I like the idea of one that is accurate to the tenth couse sometimes I'm trying to hold 5 tenths and that is tough. I really can't think of many reasons to have a third dro. Unless single point threading and have the angle set and are cutting the threads properly using the compound rest. Or are cutting a taper? But even so you're measuring a lot and doing the last few passes with the cross slide. A third would seem redundant. Thats my take and I'm sticking to it.

Ill agree on the higher accuracy scales at least on the cross slide. A one thousandths scale means that the closest your going to get in diameter is +/- 2 thousandths. I highly recommend  spending the money on a good scale for the cross slide as a minimum.

My 2 pennies


I've put a 4-axis 1 micron DRO on my lathe, even though there's no way it will hold that kind of tolerance (nor can it's operator!). In Imperial mode, this means it'll read down to tenths, but the tenths number tends to flicker when the lathe is running, due to vibration; so it was definitely the right choice.

Fitting the scale to the compound slide was a challenge, and in fact I still need to make one minor modification to make it work correctly - the oil wiper cover on the end of the cross slide is about 5 thou above the surface of the compound slide, just high enough that it fouls the bracketry holding the reader & prevents me from swinging it around, unless I take the wiper cover off. It won't take long to fix with an angle grinder, or a file; it just needs the very top lip scuffing off it.

4th axis for me will be the tailstock quill; but I haven't fitted it yet, due to the need to refurbish the tailstock first; the leadscrew nut is worn almost to nothing (in fact, how it's holding up drilling still I have no idea!), and even then it's going to need some crafty bracketry to hold it in a way where the DRO scale reads usefully, but doesn't get twisted, e.g. when a drill bites, there's a noticeable twist on the t/s quill. I'm not 100% sure which part is worn that lets it do that; it's probably the pin that stops it spinning in the t/s barrel.

Anyway - the purpose of the 4th axis was so I could accurately drill holes to depth. My tailstock either doesn't have depth markings, or they're worn off, and more than once I've wanted to drill a hole Xmm deep; or cut a bore to a certain depth, & so on.

One last thing - the DRO I bought was a Chinesium one from a company called Ditron. Nothing but good things to say about them - they shipped it quickly, the price was good (less than 500 for the 4-axis setup), and it all worked perfectly. I do, however, plan to make my own DRO head unit in the future, because I want to be able to link the Y & Z-axis readouts with the compound axis + an angle, e.g. if I've got the compound set over at 45, when I move the compound slide I'd want to see both the Y & Z axes moving. I think this would be ideal for thread cutting, and taper cuts. However, I'm not aware of any DRO head units which will do this..... so currently my 4th axis is in the "laboratory" (er, bedroom) for electrickery experimentation.

PS: Sorry, no photos yet; the lathe is absolutely caked in rust from a job she just did, and looks about 200 years older than she is! I'll take some photos of the installation once I've cleaned her up a bit...


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