Acceptable runout on mill

This topic has 21 replies, 7 voices, and was last updated 24 September 2011 at 09:07 by blowlamp.

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7 September 2011 at 14:37 #74626
nic
Participant
@nic
Hi there,

I have managed to get the runout on my mill down to 4 thou, that’s measuring the top of the cutter in the ER25 chuck,

Do i want it down to less than a thou?

Thanks again.

Nic
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7 September 2011 at 14:37 #5648
nic
Participant
@nic
7 September 2011 at 17:13 #74636
blowlamp
Participant
@blowlamp
You want it as close to zero as possible.

I wouldn’t be very happy with 0.004″ near the chuck.

Martin.
7 September 2011 at 17:25 #74639
Weldsol
Participant
@weldsol
That does sound a lot, have you checked the run out on the sleeve that the chuck sits in ? You may have a bit of foreign matter trapped

Paul
7 September 2011 at 17:32 #74641
Tony Pratt 1
Participant
@tonypratt1
Hi Nic, check the internal spindle taper first, then the chuck itself etc, to find the error.

Tony
7 September 2011 at 18:47 #74644
nic
Participant
@nic
Hi. The chuck itself is brand new and I have measured a selection of centres and other chucks all with the same reading.

So as you say maybe the error is inside the spindle taper.

Tapered hand reamer?

Cheers

Nic
7 September 2011 at 19:05 #74645
Tony Pratt 1
Participant
@tonypratt1
Hi Nic, what do you mean tapered hand reamer?

Tony
7 September 2011 at 19:59 #74649
Steve Garnett
Participant
@stevegarnett62550
Woah!!! Don’t go reaming anything yet!

Even if you’ve got the same runout on several inserts, it doesn’t necessarily implicate the taper. What is far more likely is that you have runout in the bearings it runs in. If the preload on them gets reduced, then when you run the mill unloaded, the end of the shaft is likely to drift, because it’s not fully seated in what should be taper bearings. Normally you adjust the preload from the top of the spindle – the idea is to do up the ring pushing down onto the top bearing (and effectively controlling the pulling up of the lower one) until there is no end play at all, and then just a touch more – it should still run freely.

But until you’ve checked that, you shouldn’t do anything else to the spindle at all. Normally these are precision ground, and they wouldn’t get out of the door with an error that large on them – not even from China.The first thing to do is to put a dial gauge on the bed, apply it to the end of the spindle and just try moving it about without turning it. If you get any movement at all, then you need to sort that out first, as it will indicate that something’s not right with the bearing set-up – and that’s not that unusual, even on new machines, especially after a few hours of running from new – things bed rather better after that.

Anyway, what mill is it?

Edited By Steve Garnett on 07/09/2011 20:04:23
8 September 2011 at 08:16 #74671
nic
Participant
@nic
Hi Steve, thanks for your advice,

I have tightened up that ring at the top end and it makes no difference, to the point where the spindle is quite hard to turn by hand, still the same runout,

With a gauge on the bed as you said, with a tug on the cutter i’m getting about 4 thou of movement!

It is a Raglan milling machine, so somewhere near 50 years old,

It has a tapered roller bearing on the bottom, and have read that it also has one on the top but what i can see is that the spindle passes through a 2inch long rotating cylinder,

Also when i did some test cutting on a piece of Aluminium i was getting a beautiful finish on the top, however on a side cut it looked like someone had attacked it with a chisel, now i know that my gibs aren’t set up properly yet but they are pretty good, would this terrible finish be as a result of the bearings being out of shot,

Thanks,
8 September 2011 at 08:27 #74672
nic
Participant
@nic
However i just put the gauge on the inside of the spindle a tried to move the needle and although it was hard to get a good grip it didn’t move at all.

Thanks

Nic
8 September 2011 at 09:09 #74673
nic
Participant
@nic
Update,

I put the clock on the taper of the chuck while in the spindle, there is just enough there to get the clock on to, anyhow i’m getting about 2 thou run out, and nearly 5 at the top end of the cutter, so that would suggest that the chuck is on an angle?
8 September 2011 at 09:12 #74674
Dusty
Participant
@dusty
Nic

It sounds like someone may have bodged a repair job on your mill and failed to replace the bearing on the top of the spindle. Grab the’ Bull by the horns’ take it appart and have a look at what you have got. If the bearing is missing then it can be replaced, I would replace the one on the bottom of the quill while it is appart, if it were me. I agree with Steve the problem sounds like bearings and his advice not to go anywhere near the quill with a reamer is good, if you find damage to the inside of the taper due to swarf being trapped, then a gentle stone with a fine round stone to remove the burr is the answer keeping it away from the rest of the taper.
8 September 2011 at 09:33 #74675
nic
Participant
@nic
Hi there, as far as replacing bearings go i had this response from another forum,

Bearings are taper roller with a flange on the outer races, and are unavailable unless you want to pay a fortune and add your name to a list for the manufacturers to make a batch! sizes are standard though so you could replace a damaged roller or inner race ( although this is a big engineering taboo, it does work).
8 September 2011 at 10:17 #74676
Steve Garnett
Participant
@stevegarnett62550
Posted by nic on 08/09/2011 08:16:25:

Hi Steve, thanks for your advice,

I have tightened up that ring at the top end and it makes no difference, to the point where the spindle is quite hard to turn by hand, still the same runout,

With a gauge on the bed as you said, with a tug on the cutter i’m getting about 4 thou of movement!

Okay, you’ve convinced me it’s the bearings. It’s the lower bearing that gets most of the strain, although it’s normal to change both as a pair. I’ve just done this on one of the heads of a much larger mill at work, and it really didn’t cost that much (or the boss wouldn’t have countenanced it!).

What you need to do is to ignore the prophets of gloom and despondency on other forums, and disassemble the spindle, and find out what the bearings actually are. Even though I said taper rollers, there are other options they could have used. But despite claims on other forums, taper roller bearings of pretty much any sort are available, and they aren’t that expensive – if you look on the Simply Bearings website, you’ll see what I mean. The other possibility is that it uses deep groove bearings – some mill heads do. But none of these bearings are that expensive, even if you get the higher spec ones of the correct size, especially considering that in a home workshop environment they’re going to last for years without giving trouble.
8 September 2011 at 10:27 #74678
blowlamp
Participant
@blowlamp
Does the spindle rotate smoothly and without any noticeable play when the bearings are adjusted properly?

For a taper-roller bearing to show ~ 0.004″ runout, it would have to worn to the extent that it would sound and feel awful when running.

Provided that the splindle isn’t distorted or badly made, then I would be inclined to give it a quick lick (by hand – not under power), with a Morse No 2 reamer to clean it up and ensure that there is no embedded swarf etc. You’d have to try really hard to remove much material with a Morse taper reamer, so as long as you’re sensible, you won’t impact on the accuracy or take too much off.

Once you’ve done that, you can recheck with a straight bar in a good collet, or ideally, a test bar.

Martin.

Edited By blowlamp on 08/09/2011 10:31:47
8 September 2011 at 10:35 #74679
Steve Garnett
Participant
@stevegarnett62550
Couple of other things:

If you tighten the preload rings a lot, then yes, it will be harder to shake the quill sideways – but the wear will still be there, obviously. On a mill like a Raglan, there’s a good chance that the spindle will be hardened, and the chance of touching it even slightly with a reamer aren’t actually very good! These mills were built back at the time when this was taken seriously.

As for why you get a good end cut but a poor side one – well, that’s down to where the bearings are actually worn. If you take up all the end float with the preload ring, then you’ll probably get an excellent result with things like flycutters for a little while – but all the time you use something like that on worn bearings with all the float taken out in one direction and an interrupted cut, you’ll be bashing those poor bearings even harder on the sides, and you’ll knacker them completely in pretty short order.

One of the reasons for using taper roller bearings in this situation is that the stress forces are vector-coupled – so that an upward force is partially taken sideways, and vice versa. Inherently this is a good solution, because it means that taking up the preload both centres the bearing, and takes out the axial and radial error in one go. So at a guess, I’d say that it’s more likely that you have deep groove bearings on the Raglan, as all the error hasn’t actually gone when you adjust the preload.

Also, if you can post a tool up the taper and it stays there on its own without a drawbar, there’s probably nothing wrong with the taper at all. A four thou error up there would be enough to cause nothing to stay in it very long at all!

But take it to bits, and post pictures – we can tell far more then.

Edited By Steve Garnett on 08/09/2011 10:39:07
8 September 2011 at 11:14 #74681
blowlamp
Participant
@blowlamp
See here http://www.lathes.co.uk/raglanmiller/index.html

A common enough bearing arrangement, except, as you have already said nic, the bearings are flanged and therefore unusual.

Are the bearings noisy?

You could also put some ‘blue’ on a Morse taper and pop it into the spindle to check the fit, before pulling anything apart.

Martin.

Edited By blowlamp on 08/09/2011 11:41:59
8 September 2011 at 12:23 #74683
Ian P
Participant
@ianp
Posted by nic on 08/09/2011 08:16:25:

Hi Steve, thanks for your advice,

I have tightened up that ring at the top end and it makes no difference, to the point where the spindle is quite hard to turn by hand, still the same runout,

With a gauge on the bed as you said, with a tug on the cutter i’m getting about 4 thou of movement!

It has a tapered roller bearing on the bottom, and have read that it also has one on the top but what i can see is that the spindle passes through a 2inch long rotating cylinder,

Also when i did some test cutting on a piece of Aluminium i was getting a beautiful finish on the top, however on a side cut it looked like someone had attacked it with a chisel, now i know that my gibs aren’t set up properly yet but they are pretty good, would this terrible finish be as a result of the bearings being out of shot,

Thanks,

Nic

There are several factors here which do not seem to clarify the problem.

Without doubt, the first thing that you need to establish first is whether the female morse taper of the spindle is running true ie concentric with the spindle. Check the large diameter end with a dial indicator first. If you have a finger type indicator that will also allow you to check further into the bore too.

If you do this with the bearing adjusted tight as you described it will eliminate any confusing readings that you get by tugging or pushing the spindle as depending on where you mount the dial indicator you could see big changes of readings just from flexing of the machine structure.

What is the ‘rotating cylinder’ you mention? not that is sounds responsible for the 0.004″ measurement. Is that value eccentricity we are talking about or is it play (side to side movement) with the spindle not rotating?

I recently discovered that a high quality (Schaublin) MT2 to ER25 adapter I had, exhibited more than 0.001″ run-out, that’s probably 10 time worse than I would have expected so the moral is dont take anything for granted.

Ian P
8 September 2011 at 14:21 #74687
nic
Participant
@nic
Thankyou so much for all your help,

I’m going to do some more investigating with all your advice and get back to you in a couple of days with some more information and hopefully some useful pictures!

Cheers

Nic
24 September 2011 at 07:29 #75347
nic
Participant
@nic
Okay, Update.

Firstly replacing the bearings is’t going to happen, as simplybearings.com want £600 each!

Anyhow now i have the spindle out I have been able to have a good look at the morse taper and there is what looks to be like some very bad corrosion, so i would like to get it re-ground, just the morse taper thats is, assuming the spindle isn’t bent,

Can anyone recommend a company that would take up this small job?

Thanks

Nic
24 September 2011 at 08:51 #75348
Ian P
Participant
@ianp
Posted by nic on 24/09/2011 07:29:31:

Okay, Update.

Firstly replacing the bearings is’t going to happen, as simplybearings.com want £600 each!

Anyhow now i have the spindle out I have been able to have a good look at the morse taper and there is what looks to be like some very bad corrosion, so i would like to get it re-ground, just the morse taper thats is, assuming the spindle isn’t bent,

Can anyone recommend a company that would take up this small job?

Thanks

Nic

I found a company in the midlands (‘Spindle Services’ I think) that gave me a quote for regrinding the taper on my mill (Morse 2). From memory, they had a standard charge of £165 + VAT so its cheaper than your new bearings but not exactly a bargain.

I eventually did it myself using a toolpost grider on the lathe. Actually I used a homemade ‘Dremel’ type tool mounted on the lathe toolpost. It was made from a ‘Foredom’ type handpiece and a 12V motor. The ballrace handpiece accepts collets and mine came from Gloster tooling.

In your case I would mount either the complete mill head, or maybe just the quill assembly in the lathe in such a way that the spindle being ground runs in its own bearings but rotated by the lathe. You could jury rig the quill in a fixed steady (or two ideally) and use a bit of rubber hose as a flexible couplling.

If your top slide does not have sufficient travel to cover MT2 one idea might be to mount the quill at an angle to the lathe bed axis and use the leadscrew for feeding. I would get the correct angle by very careful trial and error. Take very light cuts when grinding and use very slow feed, it pays to let the wheel to metal contact ‘spark-out’ by traversing at the same settings until you are well and truely fed up!
24 September 2011 at 09:07 #75349
blowlamp
Participant
@blowlamp
Nic.

Did you try reaming and blueing the socket as I suggested?

Are the bearings in good condition and what are their dimensions?

To check for a bent spindle you could could pop it between centres in your lathe and check for runout in various significant places, rotating by hand – not under power. This assumes there are centres at each end that would probably have been used when the spindle was originally ground to size.

Martin.
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