Warco WM18 lead screws upgrade

Hope everyone had a great Christmas day yesterday.

I have a WM18 mill and just wondering if there is an upgrade for the X and Y leadscrews.

Now, to be honest, I am probably being fussy but would love to reduce the back lash without binding the threads with the conventional ACME setup to get an acceptable tollerance

Looking on the internet I have seen people using ball screws.

Just wondering if anyone has done this, not nessessarily to a WM18

Ball screws are a common upgrade when converting a mill to CNC. They are available with anti-backlash nuts.

Paul.

Are they really that bad? Is it the thread fitting between nut and screw, or is there ‘slop’/clearance in the other parts of the mechanism?

I realised how poor my first lathe was, particularly after I changed to an approx 60 year old British built machine.

Backlash is not a problem until it becomes excessive - and while anti-backlash nuts are good, they are an unnecessary luxury on a manual machine IMO.

On my much smaller WM14 the lead-screw nuts are adjustable by virtue of a split in the nut which can be adjusted by tightening a couple of allen headed bolts. These are not evident without disassembly, I don't know if the WM18 is fitted similarly. On mine much of the backlash comes from the handle end and can be adjusted to take up the slack.

John

I am curious re the handle, what is you did to improve things

On the WM14 there is only one handle on the X-axis and I found that by tightening the nyloc nut at the centre of the handle I could remove quite a bit of the backlash from this axis. It might be different with a handle at each end like yours. Similarly with the Y-axis handle some slack can be removed by tightening the nut.

The adjustment on the lead-screw nuts really needs the table removing to get at them. The larger of the two is the X-axis nut. The small holes take M3 allen head bolts to squeeze the slot up

John

Edit: Add image

Edited By Journeyman on 26/12/2019 16:33:49

A backlash eliminator is useful as it will allow climb milling which will usually give a better finish. Ball screws should be backlash free and allow people to use stepper motors without feedback to position reasonably accurately. Even with feedback that is only monitoring shaft rotation then you need to guarantee that the shaft position relates to the slide position. NC machines often had inductosyn feedback which is independent of screw position but now we have various flavours of DRO which could provide accurate feedback if required.

Mike

Couple of points with respect to ball-screws. I looked at fitting these to my WM16 lookalike some time ago.

- I found it would require machining of the table and cross-slide to fit them. That meant either having another mill/suitable proxy or buying spare parts that I could machine on the original mill before fitting. I chose the second path but good old Busy Bee Tools (Canada) let me down. Again.

- I questioned - in several places - whether there was any possibility of the ball-screws back-driving. I received a positive "No" ..... and a positive "Yes". Since I went off the idea (see above) I never did follow up.

Probably easier to fit a DRO then you don't need to worry about backlash compensation when using the handwheel dials.

I have a ballscrew on my Super 7 CNC conversion. If you push the slide without the stepper attached the screw is happily turned by the nut.

.

Out of curiosity, John ... What is the pitch ?

MichaelG.

I have 0.008" backlash (going by the handwheel dials) on both the X and Y and it always bothered me as being too much and something I needed to try and reduce, but having fitted 3 axis DRO,s its now something I dont worry about.

Rather what I suspected at the time .... that the answers I got depended on whether the user's mill was cnc or manual.

A few years ago a friend of mine acquired a scrapped Bridgeport CNC mill. He was busy removing the ball-screws to fit his manual machine to eliminate the back-lash.

I said I didn't think it was a good idea as there would be no self locking of the table. He didn't believe me and could see no problem.

A few weeks later I visited him and lo and lo and behold he is removing the ball-screws and re-instating the original acme screws. He sheepishly agreed that I was right and later confessed he had been machining a cylinder head for a customer when the cutter grabbed and with nothing to prevent the table moving under the cutter power the head was destroyed. He had to buy a new head for the customer at more than £1000!

Lesson learned the hard way!

Well, as Michael was alluding to, I assume, whether it will back-drive does depend on the lead-angle/pitch of the screw ... just like a regular screw thread. Trouble is, when I looked into it there was a pretty limited range available in this respect at sensible, hobbyist prices.

Edit to change "sensible hobbyist" to "sensible, hobbyist"

Edited By Bandersnatch on 27/12/2019 18:24:42

Well for the moment i think i am going to leave it as it is, instead a bit of dismantling, checking, cleaning etc and see how things are after that.

instead of ball screws, if i find the existing ACME nuts needs replacing whats the best material to use?

.

Quite right, Sir

... what a sensible hobbyist you are !!

Perhaps unsurprisingly, the people who supply such things have some advice on the matter:

**LINK**

https://www.linearmotiontips.com/how-to-determine-if-a-screw-will-back-drive/

MichaelG.

Somehow, I doubt you would find the existing nuts are actually ACME.

God knows, something i know nothing about if i was honest

Edited By petro1head on 28/12/2019 06:23:48