Leveling a Lathe

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

I have to agree with Graham , Martin , Harold and many others that the whole matter of lathe bed levelling is simple , obvious and has been described a hundred times over already .

There is however another approach to actually doing the task that is worth a thought :

Most quality lathe beds are machined by accurately skimming and/or grinding the bottoms of the mounting feet first and then inverting the bed onto the feet for machining of the actual shears . The accurately machined bottoms of the feet live for ever as an accurate reference and setting up surface .

On Myford lathes the accuracy of the feet machining is so good that old lathe beds can be re set on them for regrinding with almost perfect conformation to the original alignment .

If therefore a sub bed is prepared with an accurate planar top surface , with or without matched height raising blocks , then the new lathe bed can just be rested carefully on the sub bed , the bolts done up lightly and the lathe should be in its original alignment and ready to use .

I've never had opportunity to try it but I have often thought that a substantial piece of steel channel , accurately skimmed on the broad surface would make a superb sub bed and not only deal with the alignment problem but would improve stiffness of the whole assembly by nearly an order of magnitude .

I've seen this sort of thing actually done on real world machines – substantial concrete base is cast with cast in rag bolts and massive cast in steel bed mounting pads . These mounting pads were then hand finished to dead level . When actual machine was mounted it normally needed no further alignment . All this type of work was part of the traditional millwrights skill . Many large engineering works used to have their own permanent millwrights section . Also machine tool manufacturers always had skilled teams that they would send anywhere to erect their equipment .

Brings to mind the idea of a cast concrete lintel as a sub bed for small machines – weight would be useful to .

Regards ,

Michael Williams .

[KWILParticipant @kwil]

I have one of my Myfords set up exactly as Micheal Williams describes.

I needed a new bench, made a substantial one out of wood, the top is made from 2 1/2" strips glued as a laminate. Beneath the top is a 10" x 3" channel, with plates welded across the end, which are in turn bolted to the horizontal side members of the bench frame. The channel is drilled and studded at the correct pitch for mounting the lathe. steel spacers are set in the wooden top to bring the reference surface level (ie co-planar!) with the top of the wood, the drip tray is then placed on the spacers and the lathe mounting blocks placed next. The lathe can the be set up in the usual way.

A very solid foundation.

[Ian PParticipant @ianp]

Posted by Graham Meek on 22/02/2013 10:12:32:

Like you Martin I do not know how many times it needs explaining on this Forum that it is not so much that the MACHINE TOOL is LEVEL but that the ALIGNMENT is correct.

As I said earllier, this ALIGNMENT will only be exactly the same as when it was manufactured when the machine is LEVELLED to the same degree of ACCURACY.

HOWEVER, there is in life compromises that have to be made, and the purchase of a Precision Level is very low on my list, therefore alternatives have been sought to help the average non-skilled user achieve similar results to using a Level, and these have been been mentioned above.

Page 12 of the Myford Super 7 lathe manual, (publication no S723W) the typically used lathe in these circles states, (in capitals), "ACCURATE WORK CANNOT BE EXPECTED IF THE LATHE IS NOT LEVEL". It also goes on to recommend the accuracy of the level used to be "0.003" per foot or better"

The publication also goes on to deal with "Levelling with a Dial Test indicator", "when a precision level is not available", this is as I have mentioned earlier, there is also a paragraph on "Checking the Levelling", it recommends the diameter, length of the test piece and even the size of the cut to be used.

Now if Myford thought it was important enough to warrant two and half pages of text and drawings then that to me says it all.

As regards the machine tools on Ships etc, these machines do not belong to me, and they are there for one explicit purpose, a Repair, they are therefore open to abuse, if the owner is happy to allow the machine to be twisted periodically that is up to him, it is hardly an example to put forward as an argument against what in essence is "doing the job properly".

The Title of the magazine is Model Engineer, to me engineering any solution is done using fundamental and approved methods of working, not by bodging, or it will do, especially when an engineered solution has already been advised, but the trouble with advice is it is often ignored usually out of shear bloody mindedness

There that's my 2p worth

Gray,

PS College Engineering Supplies do a kit for a precision level at a fraction of those off the shelf, (the usual Discalaimer)

Edited By Graham Meek on 22/02/2013 10:15:17

Graham

Your reply starts off as plain common sense (Alignment not Level that matters) but then you quote what I would call on old wives tale as stated by Myford (Accurate work CANNOT be expected if the lathe is not level)!!! Not surprising is it that Myford's went down the tube. If they meant 'aligned' why didn't they say so.

I have no doubt that the two and a half pages are useful and informative and if followed carefully allow the lathe to be aligned, I have not seen the document but does it clearly differentiate between the importance of level and aligned?

Using a level that meets Myford's specification it seems possible that a bed 2 feet long could have a 5 thou 'twist' from end to end.

You seem quite disparaging as regards lathes on ships, I am sure there are ships engineers who look after their machines and who make and repair high precision parts. As Martin said a lathe would turn out accurate parts stood on its end.

I am quite happy to accept word 'leveling' as a term to describe alignment in respect of lathe but a spirit level is by no means essential for the purpose, it is only one of several and aids and continuous references to the use of a precision 'level' just add to the confusion (and myth!)

Ian

[KWILParticipant @kwil]

Ian,

Twist is measure across the bed, the length of the lathe is irrelevant. In your example, to use your figures the twist is 0.0015" since the bed is 6" front to back

[jason udallParticipant @jasonudall57142]

A couple of things sping to mind.

as has been pointed out many CNC lathes do pretty good work with the ZX plane any thing but level.. ( just wandered round and found all but 1 are at 45 to horizontal and that "odd one" is a "GANG TOOLING" turretless) also from my limited experience .. limited to HARDINGE HARDCREAT machines…. no leveling is done or required ( HARDINGE machine tool's own book of words ).. apart from not to excess because of coolant or hydralic levels.

And these machines seem ok ..

once had a rep come in selling digital high res "dti" .. clocked one of our older mc .. thought his gizmo bust …coudn't find any runnout or squint… ( and that on a '91 machine)…

the only mc ever leveled was a MAZAK and that was to get rid of 0.1um on 300 mm …not bad with out tailstock….

Any way back to "our" machines…My guess is if machine if un clamped the bed will obey Mr Young and bend headstock to tailstock as to level then it is best to keep center of gravity above "feet"..

If you now clamp your lathe so that the feet need to warp the bed ..a subtle warp say… to balance the "sag" of gravity of you lathe bed …might be of benifit but forcing your lathe and its bed to match some notionally flat bench top would mostly make thi9ngs worse…

as to testing…. HOW DOES IT CUT

[Roderick JenkinsParticipant @roderickjenkins93242]

Folks,

One of the joys of the English language is the multiplicity of meanings that can be applied to the same word and the subtlety of expression that results from the context. If I may selectively quote form Chambers' dictionary: " level: …a region with no considerable inequalties…..a condition of equality….". The word level is surely a reasonable one to apply to attaining the condition where the 2 shears of a lathe bed are in the same plane. There is no hint in this that they have to be in the same plane as the surface of the earth – which, as we know, is curved in both the X and Y planes and has to be taken into account when installing large machines.

Using a precision level is just one way of ensuring that the lathe is set up correctly, most appropriately in an industrial context where such things are readily available. Other methods, so eloquently described above, are available to the amateur that may be more lengthy but do not need the purchase of expensive equipment. Myford have, in their usual thorough manner, given us a choice of methods, from which we can choose the one most appropriate to our resources.

So, to answer the OP – the lathe does not have to be level with the ground but the shears do have to be set up so that the lathe turns parallel, a condition usually achieved by ensuring that the shears are not twisted and are level with each other.

Rod

[Brian WoodParticipant @brianwood45127]

I might promote some wrath here, but having introduced the subject of lathes fitted on ships and submarines I feel more is needed to explain the reference.

I was using the example just to question the concept of 'level' and it's importance in setting lathes up correctly. On dry land that is easy to establish, but on floating platforms it is anything but; hence my observation that 'rigid' was what was really needed. That seems to have been accepted by several others as well.

I think Graham was a bit provocative with his comment. Ship's chief engineers are the custodians of their workshops and I feel sure they would be rather upset to think they would allow such equipment to be abused; the risk exists industrially of course and culprits found doing so would be suitably roasted in either regime.

Brian

[Sub MandrelParticipant @submandrel]

I understand Myford tool over Drummond lathes.

What was their procedure for levelling the bed of a Drummond round-bed lathe?

Neil

[Ian PParticipant @ianp]

Posted by Stub Mandrel on 22/02/2013 17:00:28:

I understand Myford tool over Drummond lathes.

What was their procedure for levelling the bed of a Drummond round-bed lathe?

Neil

In Basil Brush's words….

Boom Boom!

[Brian WoodParticipant @brianwood45127]

Hello Graham'

Thanks for clearing that up, I didn't think it would be intentional. Twist from the hull would be a risk.

Sorry to doubt you

Brian

[Brian HallParticipant @brianhall37323]

I certainly didn't intend opening up such a can of worms with my simple question, mind you it has all made very interesting reading even if I don't understand a lot of what has been written.

As for my original question "Would not a normal level be sufficient?", I think the answer to that is a resounding yes and that I should make sure, as far as I am able, to set the lathe up with minimal twist in the bedways – I will do my best.

I have learned a few unexpected things from this topic, not least of which is to remember what I have already read. I refer to Harold Hall's first post with the link to his site. Harold, what you describe on your website is of course in your Lathe book which I have owned for a number of years but forgotten about. You'll be pleased to know that I have started reading it again

I have also finally figured out who Tubal Cain is/was. I have been watching a guy in America (mrpete222 on youtube) who calls himself Tubal Cain but have now realised he is just using it as a pen name as indeed was Tom Walshaw writing for Model Engineer.

I was also pleased to learn about College Engineering Supplies, thank you Graham, a very useful source of materials for the small hobbyist such as myself.

I am collecting the lathe tomorrow so we shall see,

Regards

Brian

[Sub MandrelParticipant @submandrel]

The original Tubal Cain was a biblical descendant of Cain. The general interpretation is that he was the first metal-worker but wikipedia gives a few different interpretations. I think in the US he is strongly associated with freemasonry, more so than in the UK.

Neil

[Roderick JenkinsParticipant @roderickjenkins93242]

**LINK**

A splendid Victorian poem about turning swords into ploughshares

Rod

[Harold Hall 1Participant @haroldhall1]

To expand a little on what Graham quotes from the Myford manual. In the section headed "Checking the Levelling" it starts. A final check—- can be carried out by turning a test piece and then explains how final adjustments are done by raising / lowering the appropriate mounting points.

Logic tells me, that Myford are therefore saying, even if you have used precision levels, or the test bar method, you may still be able to improve on the result.

For me, using a spirit level, or a test bar, are only quick methods of getting very close to the best possible mounting. Without them, the test bar only method will just take a little longer.

Harold

[blowlampParticipant @blowlamp]

The overriding benefit of verifying the flatness of the bed with a precision level is that if the lathe subsequently turns significantly out of parallel, then that is a good indication there is some kind of fundamental fault in the alignment of the machine.

Using only a test bar may allow a nominally parallel part to be produced, but that may be as a result of introducing an unwanted (and unneeded) twist into the machine, which will almost certainly have detrimental knock-on effects with regard to use of the tailstock and fit between saddle and bed.

Martin.

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

(1) A large number of smaller machines as supplied to industry for many years have been aligned and tested by plugging them in and putting them to immediate use on nightshift continuous production . Only testing and investigation done was if , very rarely , dodgy manufactured components started to appear .

(2) Many smaller machines as supplied to Model Engineers are probably as accurate as they are ever going to be if used straight out of the box .

(3) To actual set up larger , more complex and more accurate machines properly requires equipment and understanding not usually available to Model Engineers .

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

If anyone is interested there is commercial equipment and there are specialist companies that will align or check any machine tool and issue a test certificate .

Equipment used varies with the application but laser line of sight and collimator devices are most common .

More traditional methods use levels , white light collimators and ball bars .

There is masses of information about all this on the web .

If anyone actually wants to understand the requirements for setting up machines and also how it can be done then do some research .

Michael Williams .

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

The more I think about it the more there seems to be unsaid regarding machine alignment .

There is a big difference between setting up a machine which is capable of being set up accurately and one which is not capable of being set up accurately .

The most obvious is the difference between setting up a new machine with test certificate and setting up a used machine in completely unknown condition of wear .

Applying the same Model Engineer style setting up procedures to both will result in a reasonably well aligned new machine and a twisted and crooked used machine with a stressed bed .

So perhaps the thing to do in many cases is find out what condition the equipment is in before starting to do anything more complicated about setting it up .

Regards ,

Michael Williams .

[Harold Hall 1Participant @haroldhall1]

As you say Martin, if a significant error exists then it will become apparent, even if only having set the lathe making a test piece. You will then be prompted to go looking for the reason.I do wonder though how often such significant errors occur, unless one has purchased a very old machine that shows signs of considerable use.

We should not give the impression that the spirit level is vital as many cannot justify the expense, I know having first hand experience. Having had a lathe laying mostly idle for many years I eventually purchased a milling machine knowing that one would benefit the workshop appreciably.

However, I did not know that the drill chuck would not hold end mills but as I could not justify the expense of a cutter chuck, I decided to make one. Unfortunately, I needed a steady to do that but as I could not justify the expense I decided to make one, and so it went on. A precision level was certainly way out of the question.

Of course, if one had such a level then one would be foolish not to use it.

Incidentally, the cutter chuck is still being used some 25 years later

Harold

 

Edited By Harold Hall 1 on 23/02/2013 16:52:13

[Keith LongParticipant @keithlong89920]

Just to take Gray's point about the Drummond round bed a bit further – and this is only meant to apply to the Drummond round bed – the easy way to avoid twist in the bed is to NOT tighten up the grub screw that hold the bed into the tail end mounting. The bed tube is machined (originally) to 3 inches od. +/- one tenth of a thou, and is a very good fit in both the headstock and the tail end foot, and is held in place at both ends by a short pointed bolt that locates into a dimple in the side of the bed. Secure it at the head end as that is where you want the alignment but leave the screw just finger tight or even a bit looser at the foot – you won't twist the bed then. The tail foot is simply a support, the tail stock and lead screw are supported and guided from the bed only.That's the way I've mounted mine – and the way I intend to mount the other 3!

Keith

[chris stephensParticipant @chrisstephens63393]

Hi Guys,

My opinion may be biassed 'coz I own a precision level ( it wasn't when I bought it for a few Quid, but that is another story) but I would not recommend removing twist from the bed by anything held between centres. Logically you have to set the lathe up to an equal level of levelness(?) with a precision level, as you can have no idea how well your tail stock has been set true. Tail stocks generally have a system for turning slight tapers and trying to get rid of twist with an off set tail stock is asking for hair pulling problems. Leave test bars for setting the tail stock for parallel turning. If there is a flaw in my logic I have no doubt that one of you chaps will speak up.

As for twist in round beds (Drummonds), can you not still use a precision level by mounting it on the cross slide and by moving it from end to end of the bed?

chriStephens

[Brian HallParticipant @brianhall37323]

I collected the lathe today and have started another thread here with photos and questions.

regards

Brian

[Gordon WParticipant @gordonw]

Back in the days when I was a lad I well remember operators leanig on their lathe , headstock or tailstock, "to get the cut right" . These were big machines, 2foot chucks. I still don't know if they were pulling my leg, but sounded right at the time.

[HopperParticipant @hopper]

Here's an interesting way to check for twist when you bolt down a new lathe.

Sit lathe on its bench with mounting bolts in place but not tightened.

Put a steel bar in the chuck, say a foot to 18" long and 3/4" diameter for a Myford/Drummond etc, and tighten chuck.

Put magnetic base on the bed way with dial indicator registering on the far end of the steel bar in about the position the tool would normaly take.

Tighten down the mounting bolts good and tight.

If the dial indicator does not move, you are good to go.

If the dial indicator shows movement, you need shims under one or more feet of the lathe.

Surprising how much movement you get if you don't shim before tightening.

Edited By Hopper on 24/02/2013 11:05:26

Edited By Hopper on 24/02/2013 11:06:21

[Harold Hall 1Participant @haroldhall1]

It does sound odd Gordon (W)for such a large lathe. But quite recently I was in the process of a lengthy series of tasks on the lathe and came to one which needed a very accurate diameter. I was very near the required diameter and taking a very fine cut with a very sharp HSS tool and power fed.

Having been so long on my feet I was becoming leg weary so instinctively leaned on the top of the Myford belt cover only see that there had been a noticeable change in the cut taken. The change was obviously minute but without doubt there. I must get a seat to sit on!

Harold

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