|Neil Greenaway||18/12/2018 10:55:18|
|70 forum posts|
I am not sure how similar the M300 is to the previous L5 series. I have an L5, and remember some years ago having some symptoms similar to those you mention - it turned out that the pre-load on the headstock bearings was not set correctly. In fact the lock nuts (plain OD ring nuts with pin holes on the OD face) had not been locked together and had backed off perhaps through vibration of bad cuts and chattering - hence the situation worsened. I was able to remove the top cover from the headstock (2 caphead screws) and adjust the pre-load and lock the nuts. From memory this solved the issue. Perhaps you have something like this occurring?
1195 forum posts
So a stainless tube of 3.5mm wall thickness.
Depending on its length, I can see it being possible for an opportunity to arise for this job to move in a 3-jaw chuck.
The question seems to be: Is the work moving in the chuck, or is the chuck moving at its mounting point? That is, does the chuck wobble or just the workpiece?
|Sebastian York||18/12/2018 13:09:04|
|14 forum posts|
Thats correct, turn the OD, then for some reason will just start to visibly run out...so goes from spinning perfectly true, to not doing so...when it happens do all the obvious checks, tight jaws, chuck tight on camlocks etc...but thus far have not encountered a solution...I also cannot be sure if its the whole chuck running out, or just the workpiece, but as I cant find anything loose when I check...so I assume its the whole lot shifts...
Today have rebuilt the 3 and 4 jaws, so they are clean, debris free and re lubricated...both work well and close to centre with no issues...but as for balance...how would I check for that?
Like I say I really don't think the spindle is distorted, as it will spin true, and turn a uniform dia...but the vibrations felt through the machine may be what is effecting things.
Start at the bottom and work up as they say. Will order new belts to see if they are setting up bad vibes... run the motor without belts fitted and see how she sounds, and move up to the headstock and see if there are any damaged gears inside...
I'm very much hoping, and thinking now, it is just a case of been sat for many years in my parents garage unused, and is just in need of some tlc. But if the worst is that the bearings are gone least its repairable...my fear now is that more serious damage was caused if it did indeed fall over...but as said, I honestly don't think that is the case...and with a good bedway, the machine should be repairable to a high standard.
The fibre change wheels are in good order. Only one is slightly damaged on just one tooth...and that's only the very corner so will easily clean up. so they are not an issue.
I'm happy to turn this into a project to get right, but if something is worth doing, do it right once...I'm in no hurry to get it right, and like the learning, but don't want to be polishing a turd...as money doesn't allow for that...bottom line I want a machine I know is accurate and dependable.
|Andrew Johnston||18/12/2018 13:25:06|
4699 forum posts
Ho hum, try turning between centres, that will confirm, or otherwise, that the chuck is the problem.
|Rob Rimmer||18/12/2018 13:25:40|
|98 forum posts|
Silly question, and you may already have checked, but your chuck jaws aren't bell-mouthed, are they?
|16 forum posts|
Although work is tight in chuck jaws it can move causing vibration/bad finish and still be tight after moving. Jaws may not be true and gripping along their length.
How much work was out of the chuck when cutting and was it supported ?
I have seen seen the bolts supporting top slide shear causing movement under load whilst top slide felt tight, also clamping on a Dickson style tool post was damaged and the tool moved under load but felt tight to the hand.
|Sebastian York||18/12/2018 14:01:03|
|14 forum posts||Update...|
Ran the machine without a chuck fitted...this is cold admittedly...
The motor sounds fine...there is a nice whir...with a very very faint dull repetitive thud...
Also while the dti reads very little run out at low rpm...and 800rpm it throws about...and the spindle visibly wobbles...can be felt by allowing spindle to run under the fingers...checked by more than 1 person so not imagining...
Edited By Sebastian York on 18/12/2018 14:09:43
|Neil Greenaway||18/12/2018 14:10:49|
|70 forum posts|
If you pre-load the spindle bearings artificially with the tailstock by applying a thrust load with a revolving centre towards the headstock do you experience any movement? I remember this was the case with my spindle and when you force the tapered roller bearings together you can eliminate the "slop". Might be worth a quick check before investing in any purchased parts such as belts etc - although of course belts sitting in one position for a time can take on a "set". If the rubber isn't dozed they may still be OK when warmed up a bit.
|Sebastian York||18/12/2018 19:37:52|
|14 forum posts|
Tonights update on investigations...
Had the top off the headstock. Oilways clear and no visible gumming. Lots of tiny phoshpur bronze looking glittery bits rested in the oilways, but cannot ascertain where they came from...all gear teeth intact and no visible damage to any component. I expected to see small filings as in most gearboxes. May pay to put a magnet in in there somwhere as a collector for any steel that finds its way in...In neutral the bearings can be heard rotating, but no rattle or tight spots...
Loaded the headstock spindle from the front with a revolving centre in the tailstock, and with a calibrated 0.01mm dti mounted on a magnetic base directly on the headstock ( to eliminate the risk of the saddle being a contributing factor) and with the nose of the dti on the smoothest part of the spindle I could find...was able to remove the run out. Even at 2500rpm the needle hovers around 0...so within 0.01mm run out...will assume its more of the surface finish on the spindle than actual runout as when rotating by hand with neutral selected...0 measurable run out with a 0.01 dti.
With the top off exposing the gear train, and the dti engaging the approx centre of the spindle, there is a eccentricity of 0.14mm rise/fall...which I attribute more to the gears that are splined onto the shaft rather than a distortion, as I very much doubt it'd bend in the middle when supported at both ends...
Changewheel end there is an eccentricity run out of just about 0.02mm,
So from what I can fathom the spindle is not rotating true in the headstock...and is spinning at a very slight (0.02mm ish) angle.
So...if the machine has taken a topple at some stage, could this be enough to knock the bearings off centre? Are there any other options that could cause a spindle to either distort or shift the bearing seat to run eccentrically?
On the M300 is the spindle adjustable for eccentricity?
Did however notice that the spindle got very warm, almost to warm to hold for extended period, while the rest of the headstock was at a comfortable temperature.
To much pre-load on the bearings causing the whole lot to get hot quickly? or possibly inadequate lubrication keeping them cool?
dti mounted on the rear of the saddle with the tip bearing on the V and there is no crabbing/movement of the needle over the length of saddle travel.
Still a lot of vibration, so next task is to remove the belts, check the motor for play and ensure all pullys are properly aligned.
|Sebastian York||18/12/2018 19:40:04|
|14 forum posts|
Incidentally anyone with far more experience of these things live anywhere near Exmouth?
|Neil Greenaway||18/12/2018 22:17:23|
|70 forum posts|
Don't suppose you took any photos while you had the cover off and headstock opened?did you notice if there was a pair of preload adjustment ring nuts on the back side of the inner race of the front taper roller bearing? When adjusted correctly you may also have similar adjustment on a pair of deep groove angular contact bearings on the rear end which would also need fine tuning.i am wondering if the preload were slightly out could this cause heat generation.i would doubt if there is bearing eccentricity adjustment.....they normally seat in a machined shouldered bore in the front end with the inner race fitting in on the shaft from tailstock to headstock fitting direction and the various preloads being adjusted. My memory is a bit woolly on the exact details however and trying to put recollections into words! Do you have a manual with assembly general arrangement drawings etc?
One of your concerns as mentioned relates to a potential fall or impact in the past.....I could see features such as the carriage and handwheels being damaged......but the spindle is well in board of the outline so just wondering what spindle or bearing damage likelihood is potentially going to be?
|Neil Greenaway||18/12/2018 22:22:18|
|70 forum posts|
|Another thought.....I think the m390 series had an external oil pump driven inside the changewheel/belt guard. Does the m300 use this forced oil circulation.....if so is it circulating oil as designed or maybe it's just using splash lubrication up to the bearings and causes.|
|Sebastian York||18/12/2018 23:06:17|
|14 forum posts|
No pics taken yet, but as am currently seriously considering a full strip and clean I may make a photo diary...perhaps should have done it with the chucks as they were very dirty inside...with a layer of surface rust...and are now nice and clean...
From my initial inspection there are no pre-load springs or nuts. This is backed up from the exploded parts diagram in the manual...it looks like the races front and rear press in, and preload is adjusted by by a nut at the rear of the spindle.
My concern about it getting hot was if I had introduced too much force onto the front face of the spindle in order to remove the run out...but once the revolving centre was withdrawn the spindle continued to spin true...
Oil delivery is simply by splash...hits the roof of the headstock and is gravity fed down to the bearing races.
Addition of forced oil circulation may be a consideration...along with the magnet and maybe a gauze filter...
Tomorrow I will also tap my parallel bar into the spindle to see how true that happens to be...but at the moment I am feeling that its a combination of lack of use setting the belts, old oil and just being sat, and the spindle having gone very slightly loose, as I cant hear any bad noises...or feel any roughness...only thing is how hot the spindle got...
Incidentally...if I do opt for a full restore...whats the preferred method of paint removal...sandblast with vital areas protected with anti blast tape...or acid dipping?
|Phil P||18/12/2018 23:33:50|
|476 forum posts|
I have an L5A and when I bought it many years ago it was turning strange pitch but uniform patterned lines on the work.
It took a bit of fathoming out as to what was causing it, in the end it turned out to be the main spindle bearing behind the chuck had a faulty cage, and every revolution of the cage caused the strange lines to appear on the work.
Because the bearing cage rotates at a slower speed than the inner race/spindle it took a bit of finding.
At the time a new flanged taper roller bearing from Harrisons stores was £250, so I went to a bearing supplier in Leeds and they supplied one for around £40. I mentioned to them how much Harrisons were charging and was told that they actually supplied Harrisons with bearings. !!!
Once new bearings were fitted and adjusted all was well on my machine.
In an earlier post you mentioned hearing a "very faint dull repetitive thud" I would certainly be looking to see where that was coming from before you do anything else.
|Mike Poole||18/12/2018 23:55:39|
1967 forum posts
I think you need to find the source of the bronze particles and this will probably be where your problems lay.
|Swarf Maker||19/12/2018 01:31:46|
|71 forum posts|
Following up on Mike Poole's and Phil P's responses, one of the more significant possibilities for the erratic behaviour of your spindle is that the cage of one of the spindle bearing is breaking up. The cage may well be a bronze one and the source of your oil contamination. If the cage is allowing the rollers to take up their own positions there will be occasions when they will crowd together and thus allow the spindle to divert off axis. At other times, particularly with a longitudinal load on the spindle, the forces may well cause the rollers to distribute themselves more evenly. Worth serious consideration I feel.
|not done it yet||19/12/2018 08:08:43|
|3028 forum posts|
The three preceeding posts make sense - certainly enough to be checking them out. Anyone ignoring swarf in the lubricating oil in a gearbox needs to find the origin/cause of that swarf.
|Nigel McBurney 1||19/12/2018 09:52:34|
573 forum posts
You mentioned possible restoration and repaint ,do not use a shotblaster to clean any parts on machine tools with the possible exception of sheet metal covers . If you must clean off the paint use a rotary wire brush in an angle grinder.Regarding your spindle problems,the bronze particles in the oil and the severe overheating of the spindle sound serious and a strip down is essential,on a normal lathe the spindle never gets that hot, I read through this thread yesterday and waited to have a good think,the reader who suggested the bearing cages may be breaking up may be close to the truth,I have seen cages break up on old motorcyles,and once saw the table lead screw bearings cages on a large cnc mill break up and and produce oval grooves rather than circular grooveson the workpiece. When the lathe handwheel was broken it may have been a minor shunt with a forklift or a big bang ,ok the hand wheel is away from the spindle,but if the four jaw chuck or a faceplate was fitted at the time that may have also come in contact with some immovable object and given the spindle bearings a big shock,I have also seen machine movers put a lifting strop on the spindle behind the chuck or another favourite is to thread a strop down the spindle bore,put a large spanner into the loop and lift by using the loop at the other end of the stop,both methods putting 2/3 of the lathes weight on the spindle bearings. I would get a handbook,some websites sell handbooks /copies, shop around as some dealers are a bit greedy,assuming Harrisons are still in business,try a phone call.Also when stripped check the straightness of the spindle,if there is a slight error ie bent this may have caused bearing damage in the first place,and it would be a waste of time time fitting new bearings to a damaged shaft.
|Mike Poole||19/12/2018 13:12:53|
1967 forum posts
The castings have probably been smoothed with a filler layer so you may make work for yourself if you go back to bare metal. A rub down and fill of any damaged areas may save some time and effort.
|Sebastian York||19/12/2018 13:38:07|
|14 forum posts|
All measurements taken with a calibrated 0.01mm Oxford dti (is this accurate enough or so I need to dig out the 0.001mm?)
Lathe and bearings cold.
Starting from the front, having supplied artificial preload from the tailstock with a revolving centre:
Dti at 90 degrees to spindle, on very tip of spindle nose, no real measureable run out...needle hovers over 0 line.
Dti at 90 degrees to spindle, on camlock mounting diamete, no real measurable run out...needle hovers over 0 line.
Dti parallel to spindle bore, again, no measureable run out.
Fine needle movement is attributed to surface finish.
Very centre of spindle as previously said has eccentricity of 0.14mm, but this is attributed to the gearing splined onto the shaft...it cannot bend in the middle right?
Having removed the rear bearing cover, and mounting the dti as close to the bearing as is possible, again there is no real measureable run out, needle hovers over the 0 line within 0.01mm. This again is attributed to surface finish.
At the very very end of the spindle there is eccentricity of 0.01-0.015mm. As the spindle looks to only be turned, and not ground finished, I assume this to be just manufacturing tolerances, but would welcome another opinion.
With a no 3 morse taper parallel bar mounted into a 3-5 and then into the spindle bore and tapped into place with a nylon mallet, the tool post runs true to the bar, 0 measureable deflection, needle hovers over the 0 line. Likewise, when measured up close to the spindle 0 run out, when measured at the very tip of the bar, a very small amount of run out, but a few gentle taps with the nylon got it pretty much bang on to 0...
Frustratingly removing the tailstock preload did not allow the spindle to relax, so currently still measuring as I have said...
With all that said, I am 99.99% certain that the spindle is not distorted. Other opinions would again be greatly appreciated.
Nigel has mentioned that some dealers load by stroping around the chuck. Ironically this was exactly how mine was loaded many years ago. Remember distinctly as thought at the time, that cannot be right, or why would they machine a purpose built threaded hole into the bed for a lifting eye...but at the time said nothing...that will not be the case ever again...
Bearing wise, and this is where I think I may have seen issues...
Looking into the rear bearing the needles are hollow, you can actually move the inner race between fingers...and when rotating the spindle you can see the needles rotate, and even move position...ie shift there axis...by inserting a drift into the bore of the needles it is possible to wiggle them left and right very very easily...I don't think thats right. Some of them actually drop just through gravity as they rotate past the TDC position through 45 degrees into 90 degrees rotation...so I am going out on a limb saying that the preload is way off...even though I cannot hear or feel anything wrong when turning the spindle. The heat being generated is possibly down to the front bearing having to have had to work a lot harder to remain concentric, which has led to premature wear.
I am going to endeavour this evening to take some footage of all said above to post for better passage of information...as pictures paint a thousand words.
As for the bronze looking bits in the oil...I cannot see any where they may have come from...but on the exploded diagram I have from a downloaded manual, there are some bushes on some of the gear shafts, which may well be bronze material but hidden from view till stripped out...Looked for evidence of contamination of the rear bearing but cannot see if any of this has made its way into the rear one to cause damage.
The saga continues...
As said, anyone near Exmouth on here that knows more than me?
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