ML7 : To convert, or not...

[m_c]

I think the big question you need to ask yourself, is what exactly do you intend to make with the lathe?

If you want to knock out multiples of the same part, or items with a lot of profiling, CNC'ing makes sense.
If you only want to make relatively simple parts in single quantities, then CNC can actually take longer.

I've never been a fan of CNC's that still have handles attached. Manual machining with ballscrews is a pain (larger pitch makes accuracy challenging, and they're not selflocking), and CNCing with ACME screws is not ideal.

I still have a manual lathe, and I wouldn't sell it, but then for simple parts I still like being able to take a sketch and just get on with it.
Everything on a manual lathe can be done on a CNC, it's just if I'm going to have to babysit a CNC to ensure tolerances are on spec for a one off part, I'd much rather be spinning the handles than hitting buttons!

Out of curiosity, do you have a DRO on your lathe?
It makes using a lathe far easier.

[Doddy]

I don't have a DRO - and that's half the problem.

With the stuff I have in the shed it would cost me as much to add DROs as to CNC the lathe. It's one of those binary decisions that I need to make.

I don't intend to make many multiples of the same part, no. But, part of the task to CNC it is for the hell of it. One of the appeal is for more complex shapes - tapers (yes, can be done but...) balls (I inherited a ball-turning device with the lathe, but...). Another possibly mis-guided view is that by removing the top slide I can increase the rigidity of the lathe. Also, those silly little hand wheels are not the most ergonomic with my sausage fingers. Then factor in the imperial nature (not a huge issue, but I'm clinging onto this) and a Mach conversion holds some appeal. I'm currently juggling gib-screw forces with the tightness of the part-worn cross slide acme screw to minimise backlash and rigidity.

I also wonder if throwing a micro controller in there could help produce a stand-alone capable machine with fly-by-wire controls and an easy macro option for simple shapes. I don't want to necessarily be tied into F360 to turn down a radius.

It would be my only lathe, I can't afford more space to have a CNC and manual separate option. I have been keeping an eye out for a cheap (hah!) CNC lathe to replace the Myford, and for that keeping it as-is is appealing.

EDIT:

John, can I ask what you've done with the spindle motor?

[JohnHaine]

No manual operation capability though I would like to add some handwheel encoders to give a sort of manual control, but frankly I don't really miss manual. I do have a, XBox controller for jogging which is useful for quick positioning, but not really for cutting. Even if the drivers are not powered up trying to manually turn steppers is not easy and having to disconnect them is a pain.

There is this persistent myth that CNC is only for repetitive work. Once you have calibrated tools and the ability to home the X axis, it's probably quicker to chuck a bit of bar, find its end (I have a "find bar end" macro with a tool touch sensor to do this), select the wizard to use, and let it rip, than do it manually. Mach 3 wizards let you do turning to a diameter, radiusing a shoulder, tapers, balls (internal and external), and threads. Very occasionally there's something where you need to write G code - for example doing odd profiles on gear cutters. There isn't unfortunately a Mach 3 parting wizard but it's very easy to program parting in the MDI. (One day I'll write a macro for it perhaps.) Mach 3 will thread but only syncs on 1 pulse per rev so you have to take light cuts - but so what, the wizard does it all for you anyway.

I haven't controlled the spindle yet - I keep meaning to fit a 3 phase motor and VFD but too many other things to do. So I just start and stop the lathe manually.

Photos will take a while as I'm off on hols and other things for a couple of weeks.

[Doddy]

I'm a little confused now with what I actually have. I fear a Frankenmyford (remember, it was one of the last ML7s off the production line, according to the serial numbers on lathes.co.uk)



The link to the conversion site that John provided at the head of this thread (bottom of https://cncyourmyford.com/modifications-needed/), suggests the extra bolt-hole on the left of the saddle is that of a Super-7 saddle, not the ML7. And the bore for the cross feed screw is 1/2"

[Neale]

If it was a late model ML7, was it actually an ML7R? I have a feeling that at some point the more basic ML7 adopted some bits of the S7, presumably in a vain attempt to keep manufacturing costs down by standardising on parts. In the same way, you cannot trust all threads on a single machine to be from the same family and every bolt needs checking if you need to replace or whatever - might be BSF or metric.

[Doddy]

Agreed with standardisation (sweeping the factory floor for bits) to build up the lathe. No, not a ML7R, and ironically it has the clutch (one significant difference between the 7R and the S7).

[Doddy]

I actually made a 64 slot disc with slot opto sensors. https://photos.app.goo.gl/66KmdtD7TzUziNih7 you have to be able to move the sensors around to get the correct sync

edit: if I was to do it again I might have used a rotary encoder (it would have to be low count with a PP) But its been working for at least 3 - 4 years

https://photos.app.goo.gl/JH1GWVQbhxe6Z6Yo7 This is it simulating an arc that I needed to put on a roller for my belt sander

Clive, if you don't mind I'll cross-reply here to avoid stealing too much(!) of th thin-client thread. This is likely to become something of a conversion thread.

Cheers for the photos - very interesting and useful. I do, and don't like your approach on the saddle - it's a nice design but for my purpose I think it protrudes somewhat into the user space (I've a 13' by 7' shed so have to tip-toe between benches and lathe). But I agree with the two MPGs (I've got one knocking about somewhere) - think that's a necessary solution to keeping a semi-manual mode on the lathe.

The spindle encoder?, I know mach3 needed 1ppr, heard that linuxcnc can use more, effectively. Your experience is that 64ppr is a good number?, it's as good a number as any I support. The quadrature encoding is usually easy enough - easier if you can get a twin-sensor coupler with a pitch smaller than the hole gap space, if you're not worried about symmetry on the A/B signals. That side of things doesn't worry me but good to see that you took the same approach as I'm thinking for the spindle mount.

This, just a placeholder for me to ask more daft questions as I move through the build.