Vibration

Hi I am quite new to metal turning and I was wondering if anyone had come across the headstock vibrating at a particular small speed range?

I have made sure that all bolts etc are tight on the lathe, the lathe stand to the 6inch concrete floor and the bolts holding the lathe to the stand, that was bought with the lathe.I have isolated this vibration to the spindle as I ran the spindle from a separate motor than the one on the lathe and it still vibrates. This vibration is more like oscillating than vibration and is about 0.070" at its worst. I can reduce this by putting pieces of lead under the lathes feet to dampen the vibration but I am treating the symptoms not the cause. There is a total indicator reading of 0.005" on one part of the spindle where the locknut and adjustment ring is.Could this 0.005" cause this sort of vibration?

I would try to push and pull the chuck in and out to see if there is excessive end float (sounds like it). Your .005" indicator reading is it at the rear of the spindle? up and down? i would try to tighten up the bearings by removing shims until the .005" disappears.

I have run lathes with excessive bearing clearance, on one Southbend , you could lift the chuck by .1" !! But you could do accurate work and absolutely no vibration. It does sound as though you have got some out of balance on the spindle itself, is it bent?

Frank

Got any swarf collecting in the spindle?

Assume you have tried it with no chuck mounted? and gears on the banjo disengaged.

Has it been sitting for a long time without use which may have given the belt a "set"

The back end of the spindle is not finished that well so not ideal to test TIR

Edited By JasonB on 11/08/2014 19:45:30

Hi Alan,
Does this vibration occur even when there is no chuck or face plate fitted to the lathe ? If it only occurs when you have a 4 jaw chuck fitted check that all of the jaws are about the same distance from the centre. Some idea about the size of the lathe and the speed at which the problem occurs might help. I would not have thought the 5 thou run out is the cause of the problem unless it is indicating play in the bearings. The part you are checking may not necessarily be a part that has been machined to be true.

Les.

Alan, make model of the lathe might be helpful also a photo if it's an unknown make. You don't say when the vibration occurs, is it when the machine is just running or under load I.e. Cutting metal ? Sounds like it's when it's just running from what you say regarding the auxiliary motor you used.

Your figure of 0.070" isa large amount of play if that's what you are referring to, you also don't say which direction this is in, end float or up and down?

From your text it seems it is at a low speed? What speed approximately is this ? I'm sure a solution will be found but more info is required to make a better assessment of the problem. Also where are you, there may be a member close by able to assist but you don't have your location on your profile.

Regards John

Its a Warco 250V see top of thread

Sounds like the machine is moving about and giving the "more like oscillating than vibration and is about 0.070" as you would get with an out of balance part in teh 4-jaw or on the faceplate

J

Hello all, I have just got round to checking my e-mails and I would like to thank everyone for responding so quickly.

I live near to Northallerton in North Yorkshire

The lathe is a Warco 250V with the new type motor. This model replaced the 250VF.

I have run the lathe clockwise and counter clockwise and still oscillates at the same speed of 820revs per min without the gears engaged in case it was these causing the problem. When I bought it new, just about 8 or 9 weeks ago, it was delivered with one of the two belts fitted but, this has been changed with a new one which didn't make any difference.

As far as swarf is concerned there hasn't been much as I have only used the lathe twice since I bought for reasons that had nothing to do with the lathe.

I have checked the spindle bearings and there is no play in them either. It was while running the machine and turning something simple out of some mild steel that I realised that there was something wrong as the cutting edge of the tool seamed to be moving although it was tightened up correctly.

While trying to isolate the problem I have run it with the three jaw chuck fitted and without the chuck fitted, and it still oscillates at the same rpm. I have reduced the oscillating down to be just a bit more than normal machine vibration, by using lead dampening pads under the feet and also fitting pieces of 10mm x 200mm x 50mm under the top of the lathe stand, instead of just the washers, that were provided, to try and make the stands tops more rigid. Although it is now a lot better, I am treating the symptoms and not the underlying cause of the oscillation. I haven't tried it with the four jaw chuck as I thought that this wouldn't be as good as the three jaw chuck.

I don't think that part of the part of the lathe I checked and found to be running 0.005" out is the spindle as it looks like it is only turned whereas the rest of the spindle is ground. I checked the runouts of all the Vee pulleys too and they are within 0.001"

Not in desperation, but not far off, I found the high and low points of the part that is 0.005" out and taped some small pieces of lead to it and run the machine to 820 rpm but that didn't change anything. I don't think the spindle is bent but I do think it is the spindle that is causing the problem but what I just don't know. The only other thing I could think of is, could the keyways be causing the out of balance as the key is harder and heavier than the aluminium pulleys. This I think might be a bit of clutching at straws as they say. I believe that if I attached a piece of 10mm steel to cover both of the lathe stand to give the lathe something really rigid to be bolted too could possibly get rid of the problem but as said before this is not curing the cause, just the symptoms.

Some one said to me 2 why don't you just not use the lathe at around the 820 rpm, well yes I could but it is a brand new lathe and it should be right. Unfortunately Warco, as good as they are, don't have a solution either and say they have never had this sort of problem before. By the way there customer after care is very good.

Because lead under the feet reduces the oscillation it could be a slight spindle imbalence is causing the stand to resonate. Touching various stand surfaces will show up any resonances. If it is the problem then damping pads _used in cars to stop panel resonance- will solve the issue when fitted to the right place, almost as good as a lump of wood on the back of the panel.

Lead under the feet would not alter a spindle resonance. Would have suspected the motor controller had it not been said that same effect happened with another drive. Anyway if the machine turns ok at other speeds and produces a good surface finish then it is not the spindle seriously out. Keys don't cause problems at your speeds!

Billy.

Alan:

I have a Warco WM240 lathe, which was bought in 2012, which suffers the same problem.

It was so bad at first that I wished that I had not bought it! I consulted Warco, who are normally very helpful, but received no advice on how to fix the problem of vibration. I was invited to try 'my theory' and report back if I still had problems, however...

I had the impression that the purpose-made lathe stand, bought with the machine, had rather flimsy top plates. This led me to try a stiffening exercise, involving the fitting of 'beams' under the top plates of the stand. These consist of 2"x 1" x 1/8" box-section steel, drilled to suit longer bolts of the same dia. as the supplied fixings, and extending from front to back on the underside of the top plates, inside the two cupboards. This immediately reduced the vibration, but did not cure it. I avoid the range involved, which is around 580 - 600 rpm in the low speed range (it's a variable speed model).

Personally, I believe the problem is related to 'belt whip'. When I have the inclination (and not busy using this otherwise satisfactory piece of kit) I shall run the machine up thro' it's speed range, minus it's end cover (having jury-rigged the cut-out switch, using appropriate care) to observe the drive belt in action. If this proves the theory is right, and adjustment of the drive belt tension does nothing to alleviate the problem, then the only solution may be to fit idler pulleys to settle the belt down! I have no idea, at this time, whether the latter solution would be possible. Either way, fitting idlers may be an unjustifiable 'faff' of a job, given the minor irritation involving the short speed range involved! What do you think?

Meanwhile, I'm happily creating swarf, making a model ....

Regards, Trev.

hi alan,

if warco's customer care is as good as you state then they ought to send someone out to check everything for you!

i suspect that something is seriously amiss and needs attention. there should be no excuses for such problems on a new lathe purchased from warco.

i would consider rejecting the lathe (a legal term) and ask for a full refund or replacement.

cheers,

julian

Hi I read all the threads and have just looked at the Warco website,to read the lathe spec and price £1500 you should not do anything further to the lathe ,you should write a letter (not phone or email)to Warco insisting that the machine is replaced or the money refunded as it is obviously not fit for purpose under the sale of goods act. My suspicion is that the inverter drive could be at fault as how could an out of balance circular shaft vibrate at a certain speed range, vibration within normal speed ranges on a lathe gets worse as the speed increase usually due to an out of balance workpiece in the chuck or face plate , I have a Colchester Triumph 2000 powered by a phase static converter a big machine for the home workshop,when turning as opposed to facing, the finish has traces of vibration marks ,after changing the aluminium framed motor for cast iron framed motor this did improve the finish,I was told that converters work better with iron framed motors, then to find the source I rigged up a drive from a large single phase motor which eliminated the vibration, I live out in the sticks and voltage is a bit low as my lathe is a fairway from the supply which runs down our road, I did have the transformer in the converter rewound to compensate for the voltage drop but there was no improvement, I never bothered to proceed any further as a mains 3phase supply was quoted at 3 to 4 £k and another makers converter was also expensive and I live with the problem as a lot of my work is facing,rather than long shafts, one further thought is is the supply to your to your lathe at the correct voltage,?your problem being within a section of speed range could be electrical and it may be the mains supply or the lathes inverter system, also check the supply voltage in the evening,where I am I have to put my welder up a notch as soon as it gets dark and neighbours are cooking their evening meal.

Hello Trev, This model of mine has the "idler " fitted and according to the instructions it has to rest against the Vee belt to take up any slack in the belt I suppose. I have had a look at the design of the spindle that is with the spare parts list and it looks quite a simple design and can't see where it could be eccentric. From working in a Bearing Manufactures workshop before I retired, I think these spindles would be ground on what is called a centreless grinding machine.

I forget to mention in the last post that Warco will replace my lathe with a new one but the effort to get it off the bench etc ready to send it back is a bit daunting so I have put this offer on hold for the moment.

Hello Trev, This model of mine has the "idler " fitted and according to the instructions it has to rest against the Vee belt to take up any slack in the belt I suppose. I have had a look at the design of the spindle that is with the spare parts list and it looks quite a simple design and can't see where it could be eccentric. From working in a Bearing Manufactures workshop before I retired, I think these spindles would be ground on what is called a centreless grinding machine.