A DRO for my Roundbed

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Well-Known Member
HMEM Supporting Member
Aug 19, 2021
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Bristol, UK
I haven't been working on the Gnome engine for the past couple of weeks, I decided to bring my Drummond Roundbed lathe into the 21st Century. Adding a DRO is a fairly straight-forward project for ordinary lathes such as Myfords or similar, but the Roundbed had a clever rotating saddle and a swivelling cross-slide that makes adding a DRO sensor a bit of a challenge. Here's a few photos to show how I did the cross-slide:

The bracket for the encoder has a 1" hole for the post and a small hole for a pin to locate the bracket in the correct plane on the slide

DRO encoder bracket.jpg

This is the bracket fitted to the slide, you can see the locating pin under the centre strip securing screw (the other two holes were to secure the bracket while boring the 1" hole):

DRO slide encoder.jpg

Here's the slide fitted to the saddle with the DRO encoder bracket underneath:

DRO encoder fitted.jpg

And here's how it still works when the slide is swivelled. It does require a bit of space behind the machine:

swivelling encoder.jpg

Here's the work so far, the Y-axis encoder has yet to be fitted, but the most awkward was the X-axis and that's done and working:

21st Century Roundbed.jpg

An added benefit is that the encoder bracket thickness has raised the slide so that the Myford Dividing Head is precisely on centre height:

Dividing head height.jpg

I'll post details of the y-axis encoder fitting - that needs to accomodate the rotatable saddle!

Today I finished the Y-axis installation. I celebrated by practising making some 24tpi screws.

Here's the important bracket to allow the encoder to attach to the saddle while still allowing the saddle to rotate:


And here's how it fits on the lathe - the aluminium brackets were helpfully incuded with the encoders:

Saddle support.jpg

The Y-axis encoder is fitted to the headstock and the tail with a couple of M5 screws into tapped holes drilled for the purpose. I used Milliput in between the encoder bracket and the lathe to make a flat surface for the bracket. This is the head end, the tail looks similar:

DRO to headstock.jpg

One further task was to ensure that the topslide would still rotate enough to be used as a compound slide if necessary. A slight bit of filing to the headtock made sure that was alright:

MAking sure it fits.jpg

That's it for now, the 1922 Roundbed is now a proud 2022 Roundbed.

Thank you! There's a couple small additions - I attached a piece of aluminium T bar to the X-slide to keep it a bit more rigid, and there's a small Teflon traveller on the X sensor to keep it level with the glass scale. I'm sure there'll be further modifications when I get to use the system more extensively....
I think of all the kit I have the DROs were the best purchase. My Warco mill had loads of backlash on the feeds and the DRO from M-DRO solved the problem. I used glass scales on XYZ. On my Myford I used the later magnetic scales on XY and they make lathe usage a dream. I did need to mill a grove in the cross slide but that was not a problem.

I would encourage every modeler to grasp the nettle and convert to a DRO system. Please avoid the very low cost systems as they are very slow to react.

Looks good Mole. I am not as advanced with my Roundbed, although I restored it some years ago it is still treadle powered (who needs to go to a gym??). I look forward to seeing what you are going to do to it next.

Best wishes with your endeavours.


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