Converting a non-screwcutting lathe to CNC?

[loply]

Hi folks,

Had my eye out for a while for a Denford Viceroy "plain" (ie non-screwcutting) lathe, because of the lack of screwcutting you can get a real nice quality lathe for cheap on the used market.

Talking around 300kg+ 10x20 lathe for £200ish, saving around £200 over the usual price of a screw cutting version.

I thought this would make an ideal candidate for CNC conversion as it's undervalued due to lack of screw cutting and power feeds, which of course are no use to me! They'd be going in the bin if it had them...

One has come my way and I suddenly thought I better ask the experts before jumping in!

The biggest query I have is how I will mount the bearing blocks to the lathes feet. The lathe has "mounting points" cast in but they were obviously never machined as it never had a leadscrew, and so aren't accurate.

I don't think the bed will fit on my RF45 mill (and don't think I'd like to try!).

My idea is that I would either need to take the bed to a machine shop and have them set it up and mill out two flats for me on the feet, or, that I could try to design bearing blocks that align and attach primarily via the Vee in the bed, thus negating the need for an accurately milled flat on the lathes feet.

Alternatively I thought I could possibly use a hand drill to drill and tap four holes for each bearing block in the lathes feet, and then design some kind of system where I can align the bearing block with the ways by jacking it's four corners in and out of these holes, kind of like how you would level a machine stand. I have concerns about poor rigidity in the screw with this method though.

Just wondering what other people think of this idea and whether or not I'm being daft?

Cheers,
Rich

[MrWild]

A quick change gear box for different threads isn't important with a CNC. All of the feed changes are computer controlled per revolution of the head stock. Machines that don't have a quick change gear box can still cut threads. Different thread pitches are changed by changing entire gears in the back;

[LUCKY13]

Your idea is good, and the problems are as you have already stated. Realyl it probably would not be that bad to get a machine shop to cut your flats.


You might even be able to rig up a spindle on the lathe itself. Something you could slide using the bed ways as the guide to cut the flats. A little router could be used, although it might take awhile to cut but it still would not be bad. You could bring a mount of the carrage to mount the router. I have seen guys use methods like this to rescrape the ways on a lathe. Ofcourse what they where doing was very envolved and took a lot of work but your little job should be pretty easy.



you could even do something like your jacking method you mentioned and then use epoxy under the clearance area to give it stability after yuo have it set. Or put you flats by hand tools, then bolt mounts to them and use hand scraping and a long straight edge to get you possision right.


I think one way or another with a little thought you could get this and get it right without going to extreeme or high cost. I would go for it and figure it out when I got there.


Jess

[loply]

Hi folks,

Well thanks for you advice. I went ahead and bought the lathe.

On close inspection I believe I will mount the bearing blocks primarily via the Vee on the bed. The bed is nice and thick and there's a good gap between the bed and the feet, meaning I can wrap a lot of metal around the top and bottom of the Vee.

I will then use some non-critical 'spacer' bolts to brace the thing against the feet but I think the main work will be acomplished by the Vee.

Hoping to machine both bearing blocks as one part then chop in half to ensure the end result is accurate.

Will post pics as soon as I get started!

[FannBlade]

Will post pics as soon as I get started!

Please do I'm looking forward to see what you come up with.