Milling machine spindle runout

seasons greetings

I have a big Gate turret mill, with an ISO30 spindle. I bought the machine new/old stock probably more than 10 years ago and would think the use ive given it would be considered minimal in my hobby workshop.

A recent job, made me question the runout of the spindle and on inspection measuring the inside of the iso taper im getting a a shocking 0.03 to 0.04 runout. (mm).. ive tried multiple instruments for measuring and get consistent readings.. this obviously compounds out the more variables you introduce after this point, to a 0.10 to 0.11mm at the tool by the time ive introduced a chineesium er collet holder with cheap collet and and an unround drllblank etc

Only other factor worth noting is that although ive not taken things apart, I did look a bit closer and I suspect the auto oiler for the spindle bearings appears to be unconnected and probably never connected

My questions are as follows.

Its probably likely this spindle runout has been present from day1; and maybe the reason I chanced upon the purchase of a to good to be true new old stock machine in the first place.

Does it seems within the realms of possibility that this could be spindle bearings at fault, and perhaps changing them, although probably a difficult job would maybe reduce the runout?.. the voices in my head suspect the spinlde is actually bent? surely not?

I suspect the next move would be to dis-assemble to head and find a way of measuring the spinldle itself before spending money on bearnings?

Any firms in the midlands that recondition milling machine heads?

any inspirational thoughts?

thanks in advance.

I can't offer any advice on your specific issue, I'm not familier with your machine. That being said, If you suspect your spindle is bent or damaged, you could do worse than speak to 'Spindle Services' in Coventry. I managed to bend the spindle on my Boxford X10 lathe, (by lifting it with a strop through the spindle, insert 'idiot emogee' here) then compounded the problem by trying to fix it myself. I nearly ended up breaking the lathe for parts as a replacement part was simply not available. They are, or at least were, a family run business. I spoke to a receptionist who I believe was the daughter of the MD and explained my problem. She promised to get the boss to ring me, which he promptly did. I expained the issue and he gave me a price to repair the spindle, which included replacing missing metal. He even gave me a little discount once he knew I was a private individual and not a company. The spindle was returned in double quick time and once replaced had no discernable runout whatsoever. It wasn't cheap, £300 if I remember correctly, but a lot cheaper than scrapping an otherwise near perfect lathe.

Gavlar, which model of X10 lathe did/do you own, do you still have it?

I have used Rotatecj when still at work, no idea of price and not connected go company.

https://www.rotatech.com/

David

Q: What evidence do you have that the cause is bearings? A:The oiler is disconnected and bearing has been running dry.

Q: What evidence do you have that the cause of runout is a bent spindle? A: None.

First rule of trouble shooting is to eliminate the simple stuff first. Never assume the worst at the outset.

I would reconnect the oiler and make sure there is a copious supply to the bearing and see if that makes any difference.

Then I would consult the machine's manual and make sure the bearings are adjusted properly with correct preload etc as appropriate and see if that makes any difference.

If that doesn't fix it, you either have to live with it or consult the manual again and remove the spindle and bearings for inspection. Bearings should be cleaned in clean solvent and should run flawlessly with catching, roughness or noise when spun by hand. Any notchiness, catching or noise and they are toast.

Checking the spindle for straight is simple but can be tricky for the neophyte. Don't make the mistake someone else on the forum did recently of taking measurments off rough-machined sections of the spinde in between the bearing surfaces. The only relationship that matters on the spindle is between the two bearing mounting surfaces and the tapered hole in the end of the spindle. All the rest in between can flap about where it likes and not matter.

Usual way of checking a spindle for straight is to set it up on two V blocks on the bearing mounting surfaces and rotate it while taking a reading off the taper in the end of the spindle with a good dial indicator. You can also take a prelimary reading off the OD of the spindle nose, but obviously the truth lies in the taper itself. But keeping everything in place while you do this is diffucult. The V blocks usually need to be clamped down so the can't move and some kind of stop in place to stop the spindle moving laterally as it is rotated.

Another way to do it is to carefully mount the spindle in the four jaw chuck int he lathe by one bearing mounting surface set to run dead true. The other bearing surface is supported in the fixed steady and set to run dead true. Then a reading is taken off the taper with a dial indicator as the job is rotated slowly by hand.

If the spindle tests up true, then you know your problem is the bearings. To verify this you could mount the bearings on the spindle and repeat the above tests with the spindle rotating in the bearings.

While you have it all apart it is probably worthwhile to replace the original Chinese bearings in the Gate anyway with good quality precision bearings such as SKF etc. Bearings are cheap, even the good ones, and the quality of some OEM Chinese bearings is highly variable. Some good, some not so good. It's a crap shoot to know which you have.

If the spindle doesn't test up true, it is possible to remachine it in situ by putting it all back together and tilting the head at half the taper angle and recutting the taper with a small lathe boring bar clamped in a toolpost arrangement on the mill table. Not an operation for the faint hearted but it has been done before.

Edited By Hopper on 20/12/2022 23:01:32

Pete, I have a 280 and yes, I still have it. If I can help you with anything, message me so we don't derail this thread.

Cant thankyou all enough for taking the time to respond.

Il reply back with what the outcome is.

Matt, there have been a few threads on this subject recently, one was a 60 degrees V design for checking roundness, I think there was some info there that might help you check your spindle, there was this thread https://www.model-engineer.co.uk/forums/postings.asp?th=183984 where there was some discussion about your problem.

Gavlar, nothing serious I was just going to mention you should have an M16 hole in the first web between the bed way for putting a lifting hook if you need to lift it again.