Improving an XJ9525 milling machine.

Inspired by the recent articles on improving an X2 milling machine, I wondered if anyone has tried to improve an XJ9525 milling machine.

Mine is disappointing, with backlash on the motions and lack of stiffness in the spindle.

I have searched the Workshop magazine index, without success.

Not familiar with your machine, but, having done a bit of research on the 'net, it looks very similar to my XJ12-300. I got over the backlash problem by fitting a 3-axis DRO system. I've fitted a belt drive to replace the (noisy) gear drive - a well worthwhile modification, in my opinion. Also a rev counter and I've replaced the spindle bearings with better quality ones. I'm in the process of fitting a pair of 12v LED mini boards to illuminate the work area (see the thread elsewhere on this forum). Just waiting for parts to arrive from the UK. You never know, I might actually get around to making something soon!  You can see a few pictures in my album.

John

Edited By John Hinkley on 26/03/2013 23:01:59

Hi John,

Thank you for your comment. I looked up your machine on the net; I see it has a rack and pinion for the vertical axis; mine has a lead-screw and judging by the enormous back lash, I think it may be about to fail. (This motion is a real pain to adjust - very heavy and un-assisted.) It is on the urgent list for disassembly! I had the X-axis lead-screw nut fail long ago and had to turn a new one. After just a few hours of use the brass motor pinion stripped. I really regret having spent over 800 quid on this machine because of its poor design and construction. I wonder if I would be better advised to get rid of it and start again - or whether it would be worth trying to improve it. That will cost quite a lot, I expect, but it might make a good project in itself.

There is some play in the spindle and I wonder if this is in the sliding part rather than the rotary bearings; I suspect that would be very difficult to improve?

Do you have a gearbox? Your belt drive appears to be direct on the spindle?

Does DRO mean Digital ReadOut? If so I guess this cannot reduce chatter caused by backlash in the leadscrew nuts? I wonder if it would be worth (and possible) replacing the leadscrews with zero-backlash types?

Regards,

Norman

Hello Norman!

See here, please ***LINK***. The BF20 miiling machine is mainly the same machine you have. I have one and comparing the schematic drawings and pictures I see no differences except in the shape of the motor.

Best regards
Dias Costa

Norman,

I've sent you a PM as your response came through on my email account. Didn't realised I'd bookmarked this thread! (Whatever that means.)

Regards,

John

Norman,

My emailed got bounced back, so I'll reproduce it here:

Norman,

Well, I'm certainly no expert, by any manner of means, but from how you describe your machine, it sounds like a bit of a basket case, if you don't mind me saying! Did you buy it new? I got my mill from Amadeal about a year ago for the princely sum of £416. I think they've gone up a little, but not that much. Got some extras with it, too - a half-decent vice and a collet set. The latter was a non-standard design, since replaced with a "proper" ER25 set from CTC Tools in Hong Kong. (I find their stuff really good value, even taking into account shipping costs.) My mill spindle is fixed, in as much as it does have the facility to go up and down in the head, much like a drill press spindle would do. I get the impression that it's just one more thing to go wrong and introduce play when worn. Maybe this is what's happening in your case? No doubt there are ways around all your problems and hopefully someone will point you in the right direction. I suppose, in your position, if I could afford it, I'd pass it on to a new owner and invest the money in a new one. At least, then, you'd have a year's guarantee with it!

DRO is indeed digital readout. I got mine from Arc Eurotrade. It's the cheap end of the market, but the accuracy far out-performs my machining ability! The belt drive is cobbled together from a design on the web and my own ideas. Originally, I bought the conversion kit from The Little Machine Shop in the USA, thinking it would just be a straight forward fitting job. I should have known better! Turns out that although the spindle is 30mm in diameter (a fact I found out when I changed the bearings) it reduces to 28mm where the pulley fits. Not only that, but the pitch of the securing bolts for the base plate were different, too. Not much, but enough to make it necessary to make a new one. So, all in all, I'd have been better off making it from scratch. To be fair, there was a warning on the web site to check the spindle etc to ensure the kit would fit, so I suppose it was my fault it didn't. You live and learn.

All in all, from your description of your proposed mods, I think that I'd be inclined to use the money elsewhere on a new mill. Easy for me to say - it's not my money!

Anyway, best of luck, whichever way you choose to go about it.

Regards,

John Hinkley

Thank you Dias and John,

I did buy the mill new from SPG Hinckley for 830 pounds. It included a power drive on the Y axis and a 50 pound collet set and a free clamping set. The power drive had a digital readout which showed rate or distance but the distance was of limited use becauise A) it was the wrong side of the backlash and B) it continued counting up when the table movemnet was reversed.

I followed Dias's link and the ballscrew modification would be a superb mod but very expensive for all 3 axes.

My son bought a mill from Wabeco and this came with ballscrews and he has fitted his own CNC; I am very envious but I wonder if I have sufficient knowledge.

I shall consider options carefully and maybe try to see if some simple mods might improve things and perhaps make it more honestly saleable!

Best wishes,

Norman

I have just removed the motor and gearbox and found that the 2 screws that hold a steel block, which mates with the leadscrew nut, were loose allowing the block to tip and also allowing the nut to separate from the block; this was what was causing the backlash. The bronze leadscrew nut has a 20mm diameter boss which mates with the steel block but it is not attached to it. I have drilled the steel block and tapped the bronze boss so that they will be firmly held together. The steel block was counterbored to take the cap-screw heads below the surface. It is possible to re-assemble by entering the leadscrew into the machine and fitting the steel block through the central slot, before screwing the steel block to the slider. I used threadlock to prevent the 2 offending screws loosening again. The pictures show the 2 offending screws in the horizontal slot above the large circular boss and the mated steel block and bronze nut with the new holes and one 4mm cap-head screw.

Hi Norman,

You are not alone with your mill as I am fellow XJ9525 sufferer since December 2010! My motor drive gear stripped yesterday and I found your post this morning while searching for spares/remedies/ideas so decided to sign up and reply. Can I ask where you obtained a replacement gear please?

I too have regretted spending the money and in hindsight should have returned the machine swallowing the losses on shipping and spent my money elsewhere but I do think there is a usable machine in there with some work. I have been repairing and tolerating most of the problems as I use the machine with a view to completely stripping and rebuilding it from the ground up, now the gear has gone now might be that time as I was just about to invest in a cheap DRO system for all three axes.

Have you made any progress with the machine?

Mike

Update to my previous post: After a fruitless time trying to obtain parts from the company this milling machine was purchased from I approached Amadeal as their XJ25 mill is pretty much the same machine. What a difference in service, all the parts I needed in stock and arrived a day later! I took the opportunity to order a new plastic gear for the gearbox as a spare and upon inspection the low gear had not been meshing correctly due to casting flash in the housing.

As this meant a complete strip down of the head I decided to replace all the bearings with SKF as the main drive bearings were rough and the spindle runout has been diabolical from new. The best runout I managed was 0.002" with the original Chinese bearings and that was never in the same spot but the SKF bearings are showing a consistent 0.0002", quite a difference.

I think a belt drive conversion will be on the cards as a future project once the machine is back together.

Mike

The BF20 looks very very similar to my Warco WM16 am I right? Maybe the ballscrews would fit it. I will have to do some investigation.

Mark P

Hi Mike,

My apologies, I did not get pinged for your 1st message - or missed it somehow.

I got the replacement gear from SPG Tools who supplied the mill. Simon had to order the part from China and it took a while to arrive. I am glad you managed to get a replacement. I was expecting the replacement gear to strip again but so far it has not, though maybe my usage has dropped a bit. Interesting that you have managed to reduce the runout. I should follow your lead.

Norman

Mark P,

You might be right about the BF20 and Warco WM16, unfortunately I have no hands on experience with either to give a definitive answer, sorry.

Hi Norman,

No need to apologise it might be because I am a Newbie here and to do with anti-spam permissions. I was hoping for an improvement with the spindle bearings but wasn't quite expecting that much. I spent quite some time working on the spindle when I first bought the machine and decided to live with the runout in the end until time permitted a good strip and rebuild. Marking the high spot on the runout produced an interesting result as each revolution the high spot indexed to a new position! The spindle bearings are easy to replace and adjust, the two SKF 32006X/Q I purchased were about £25 for the pair.

When you replaced the motor gears, did you look at the plastic 2 speed gear inside the head? Mine has only been meshing the teeth around 50% in the low range and started to chew the plastic teeth as the mating gears are steel. Casting flash was partly to blame but with that out of the way the selector fork still does not allow full meshing. I can see a way round the problem with a little machining and modifying the selector detent but a two speed belt drive would overcome this problem as the gears would not be needed.

Mike

Hi Mike,

I have not been using the mill for many months, having switched to playing with Arduino microprocessors for a bit. I must admit I have forgotten exactly what I did. I had also lost enthusiasm for this machine having seen the difference between it and my son's Wabeko machine. But I must get back to it in the new year; you have certainly encouraged me with the improvement you obtained by replacing the bearings. The backlash in the X and Y motions are still a problem for me though. Going down-hill is dangerous! As said above, I have already had to remake a lead-screw nut, which failed after a few months. I wonder if there is a way to reduce the backlash but I suspect it would mean replacing the original rather nasty nuts. Although I managed to make one on the lathe, I expect the tolerance achieved left much to be desired. Ballscrews would be too expensive for me and in any case they have their own problems unless you fit Numerical Control as well!

Did you buy from SPG?

I shall be on other duties for a few days now.

Norman

Hi Norman,

Have a look at this link if you have not seen it for a cheap alternative to Ballscrews and if you are playing with Arduino processors this link may renew your interest in the mill!

I'll keep you updated with the work I do and take plenty of photos too.

Mike

Thanks Mike. I look forward to your progress. I had a quick look at your links - fascinating. I will return to them IDC. Currently in Barcelona for a break.