X2 Mini Mill backlash, and parts supply etc

Jim, look carefully at the lead screw, a good bit of the wear you have may well be on the steel thread, grit gets embedded in the bronze nut. Had this problem with a friends Myford cross slide, it was so warn it looked like a V thread we were able to get, at a better than expected price, a new lead screw, and nut. Ian S C

Thanks for the suggestion Ian - it's a very valid suggestion except that I doubt in this case it would be at all likely as my mill has never really done much work in all honesty. I've had it a long time but only very minor sporadic jobs over the years.

Possible and worth ruling out though obviously!

Hi Jim,
Are you sure the backlash is due to the nut and not the adjustment of the thrust bearings on the end of the leadscrew ? (This is assuming that the design is similar to the X3 mill)

Les.

There's not really anything that I can adjust like that Les. On the X2 the x axis goes through a big bushing before the handle attaches on the other side of the casting. Doesn't seem to be any play in that from what I can tell.

Will double check it all again though since there's still a load somewhere.

Jim

Are the feed nuts 'free' to move in the holes in the castings? There should be grub screws to lock them in place IIRC. By the way only having the screw supported at the handle end and the nut may seem sloppy but is sound practice. The feed nut should be locked in place when as near to the handle bearing as possible to ensure good alignment.

Neil

Hi Jim,
If there are two nuts holding the hand wheel then then it is likely that the end float in the leadscrew can be adjusted. If there is only one nut then adjustment will not be possible other than be means of shim washers.

Les.

Sorry for the delay replying.

Neil, the feed nuts are indeed held snug by the grub screws, but other than that they're suspended by the lead screws and not secure at all. The Y axis uses a single grub, and the X axis uses 2.

Les, yes there are two nuts and a washer on the end of the screw to hold on the handle. When you describe adjusting the end float do you mean by the amount of torque on the inner nut, then locking it with the second one?

I'm not actually able to detect any end float in this respect when the nuts are done up correctly and it's not anything I even have to make an effort to set correctly. It seems a good arrangement and good tolerances in that respect. The backlash is I believe 99% from the lead screw nut, and 1% (all give or take) from tiny amount of slop in the handle/woodruff key.

My boss used to be an engineer, and when I asked him today if he happened to have an M16 1.5 tap (I assume I need that for a nut since it's 15.85mm diameter screw and 1.5mm thread), he said he'd have a look. Then pondered a moment and added "actually, I've a whole big box of taps & dies you can have - I'll never need to use them again". Result!!!

Hi Jim,
There should not need to be any significant tightening torque on the inner nut. It should be tightened until there is no end float in the leadscrew but not so much as to make the thrust bearing tight. the Outer nut is then tightened against it to prevent it from moving. You may have to make further slight adjustments as tightening the nuts together may cause the bearing to become slightly tight. The fact that you cannot detect any end float eliminates this adjustment as a possible cause of the problem.

Les.

.

Jim,

Sorry to labour this point, but did you double check that the screw thread is really 1.5mm pitch, and not 16tpi ?

[see my previous post]

Nicely played, getting the Taps and Dies !

MichaelG.

Sorry Michael I'd missed your previous comment to that effect, and the one following it!!

Not entirely sure if I'm honest. I've only got a cheap thread pitch gauge so it's entirely possible I suppose. I don't have a 16tpi one to compare, but it might be the case that the impending box of goodies includes a tap like that, which I can test against the thread, and see which is the more snug fit.

And if Arc do stock spare ones then it'd be sensible to get one I guess.

.

Jim,

I would suggest that you simply measure, as accurately as you can, the length occupied by a [large] whole number of crests of the thread. This is inherently more accurate than using a pitch-gauge, and it will also average-out any differences caused by wear.

MichaelG.

Jim,
If there are dials on the end of the leadscrews you will be able to see how much one revolution of the handwheel moves the table. If not start with the edge of the machine vice about 60 mm from the spindle. Turn the handweel a few turns to reduce this distance to about 50 mm. Measure this distance with digital calipers and note the reading (Reading 1). Turn the handwheel ten turns in the same direction as you turned it to reduce the distance from 60 to 50mm. Measure the distance again (Reading 2) Subtract reading 2 from reading 1 and divide the result by 10. This will be the pitch of the leadscrew. DO NOT reverse the direction yo turn the handle at any point during this test. If you do then start the test again.

Les.

Remember you are looking for a "Trapezoidal" tap if it is metric or an "ACME" tap if it is imperial. They have a completely different thread form to standard taps.

Russell.

If the thread is very warn, it may appear to be a V shape, rather than an ACME, or similar thread. Ian S C

Sorry for being so slow to update this topic - been mad busy lately so I've not had a chance to act on the most recent replies re' measuring thread etc. Appreciate the input though thanks, and I will be doing these things when I get a moment to!

No joy yet on taps etc as they've failed to materialise alas, but I don't think the right one would have been in there anyway. Since cutting a slot in the existing X- axis nut doesn't seemed to have ended well (not sure why as the Y axis one seems to have helped), I'll have to order a new X nut from somewhere. I think I read on one post that Arc sells these?

Anyway, I'm now the owner of a peugeot 106 bonnet strut so I can copy 's version of the Z-lift conversion. The strut I've got seems way too long for the job but that will presumably be down to how it's mounted. I need to go and study the pictures for what brackets need making basically.

Plus I think my belt conversion has arrived at last. Yay!

Yep - got my belt conversion yesterday and fitted it last night. Very pleased!

This is the version I got: http://www.mbbilici.com/?p=85

I had to modify the metal guard behind the fine feed on the Z axis as one of the bolts on the kit was in the way of this, but apart from that it was an easy install, great fitting parts, and a great end result. Very helpful bloke (in Turkey) that sells the kits too.

Hopefully I will be able to get my 'air spring' fitted imminently too.

One thing that's also apparently is I need a clamping kit for my mill as the litre vice I've got is no use for wide/oddball shapes of course. I tried milling a heatsink for a peltier 'eco fan' I'm making earlier and it jumped out of the vice as it couldn't hold it firmly enough. Could have been painful!

G'day.

I have an X2 mill. The leadscrew is 1.5 mm pitch ( 10 turns = 15.0mm). Backlash is 8 divs of the dial (8 x 0.025mm) about 9 thou. For what I paid for the mill this is quite acceptable. Just keep the gibs tight and if you overshoot then back off a bit and sneak up to the setting. Just for interest, try leaning on the head when flycutting. This shows up the flexibility of the design.

Regards from the land of the kangaroo

* Danny M *

Thanks Danny - more useful info.

Sorry for the slow updates again. I'm no further on with backlash issues, but I now have a nice clamping kit and 3" Toolmakers precision vice, which is a lovely chunk of metal!

Air spring is also fitted and I'm very pleased with that, so thanks for all the assistance chaps.

Please could anyone inform me as to whether or not you can get replacement lead screw nuts for the X2 or SX2.

I'm 99% sure you could get those from ARC they do them for the SX2P which I think uses the same bits, e-mail them and to check.

J