Lathe Accuracy

[Andrew Moyes 1Participant @andrewmoyes1]

Going back to the original post asking for the manufacturing tolerances of the Myford Connoisseur, on the Yahoo Myford lathe group website, in the files section there is

Myford-7-Series_Inspection-Sheet.pdf

I don't know whether the origin of the information was Myford itself or it is just someone's suggestion but the figures are a pretty good benchmark for a lathe of Myford size. When I checked mine, all but a couple were within tolerance. A little fettling brought them all within the figures quoted.

Andrew M

[Bob JeppParticipant @bobjepp]

Just to throw in my three penneth – during my apprenticeship at Colchester, I spent many hours ( happy ? ) scraping in large Colchester lathes.

The specification for the alignments of the machine were very precise for a relatively low cost industrial machine.

From memory ( 30 years ago ! ), the headstock alignments were specified by clocking a nose bar over the top for horizontal and on the front for skew ( headstock should point up towards the tailstock to allow for the weight of the chuck etc. ). There were many other checks carried out on the spindle to ensure concentricity etc.

The saddle was scraped to turn concave by a few tenths of a thou' and the cross-slide movement checked for straightness on a 'T' bar in the spindle socket.

The tailstock was scraped to get the barrel horizontal and straight with a check made with a precision bar between centres to ensure the tailstock and headstock were level with each other.

After the machines were completed ( before painting ), a turning test was done, skimming the OD of the test piece. This piece was then checked for roundness using a Taylor Hobson Talyrond – maximum allowable out of round was one tenth of a thou'. A circular graph was produced ( rather like a truck tachometer disc ) and was included with the machine accuracy chart.

So, final comments, I started a thread early last year about the quality and accuracy of the Axminster Sieg C0 – the one I bought was unbelievably poor. Axminster were very good and I got my money back without any arguing. I phones Cowells and talked to Colin Childs – we discussed their accuracy policy ( just what the doctor ordered ) and, suffice to say, I am now the proud owner of a sparkling 90ME ( has 'some' swarf on it now ) – fantastic machine !

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Andrew Moyes 1 on 01/02/2015 13:01:47:

Myford-7-Series_Inspection-Sheet.pdf

.

Thanks for the link, Andrew

I will hang a copy on the wall, to remind me not to blame the tool.

MichaelG.

[The Merry MillerParticipant @themerrymiller]

I am having trouble accessing the Myford 7 PDF

Message is " error in downloading the file "

Have tried on Firefox and IE, no joy.

Any clues as to why please?

Len. P.

[Andrew Moyes 1Participant @andrewmoyes1]

Sorry Len, I can't help you with that but if you join the group here

**LINK**

you'll have access to that and much more.

Andrew M

[The Merry MillerParticipant @themerrymiller]

I've just spotted, Andrew, that I can only access it through Yahoo groups as you say.

I don't do Yahoo groups, thanks anyway.

Len. P.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by The Merry Miller on 01/02/2015 16:32:37:

I am having trouble accessing the Myford 7 PDF

Message is " error in downloading the file "

.

How very infuriating !!

I clicked that link this morning, on my iPod Touch, and it opened the document.

… But, of course, I didn't save the file.

Now … I get that same error message, on iPod Touch and on iPad.

I will try some other machines.

MichaelG.

[Neil LickfoldParticipant @neillickfold44316]

Posted by Neil Wyatt on 31/01/2015 09:26:30:

Neil,

I really can't accept that claim. I have a good quality DTI that reads to 0.0005" which is 0.01mm within a spit.

If I turn two concentric diameters on my mini lathe to a good finish, I am unable to see any deflection whatsoever in the DTI on the undisturbed surfaces.

Comparing the very small taig/peatol to a Myford which weighs about fifteen times as much is hardly fair.

I am sure that most 'hobby' lathes are well capable of meeting 0.01mm roundness (which is Schelsinger's limit for finish turning lathes).

Neil

From my experience , when you turn a piece in a chuck, part it off, place it into a Vee block and rotate , then you will see the error. Something turned between centres, especially dead centres, should be round on almost any set up. I have a modified Taig type lathe, and when I turn something in it, measures ok with a mic and looks ok with a dti. Then rechuck the part and get it round, just won't happen. I have a 0.001mm dti that use for checking in a Vee block. It is a lobed shape, not triangular and not very round.The Taig has since been corrected with better accuracy angular contact bearings, but even with those is still no better than 0.003mm, but is a lot better than the original 0.01 to 0.013mm it used to be. A better grade of bearing is available, but am not prepared to pay for them .

Neil L

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Bob Jepp on 01/02/2015 13:05:59:.

So, final comments, I started a thread early last year about the quality and accuracy of the Axminster Sieg C0 – the one I bought was unbelievably poor. Axminster were very good and I got my money back without any arguing. I phones Cowells and talked to Colin Childs – we discussed their accuracy policy ( just what the doctor ordered ) and, suffice to say, I am now the proud owner of a sparkling 90ME ( has 'some' swarf on it now ) – fantastic machine !

.

Bob,

It's good to see that Cowells met your well-informed requirements.

They seem to have developed what was originally quite a modest machine into a little gem.

I posted this link on another thread today; but I think it worth repeating here

… He has some good pages about his Cowells 90CW.

MichaelG.

Edited By Michael Gilligan on 02/02/2015 07:51:04

[Neil WyattModerator @neilwyatt]

Or try this: Schlesinger

Neil

[blowlampParticipant @blowlamp]

Posted by Neil Lickfold on 02/02/2015 05:29:31:

Posted by Neil Wyatt on 31/01/2015 09:26:30:

Neil,

I really can't accept that claim. I have a good quality DTI that reads to 0.0005" which is 0.01mm within a spit.

If I turn two concentric diameters on my mini lathe to a good finish, I am unable to see any deflection whatsoever in the DTI on the undisturbed surfaces.

Comparing the very small taig/peatol to a Myford which weighs about fifteen times as much is hardly fair.

I am sure that most 'hobby' lathes are well capable of meeting 0.01mm roundness (which is Schelsinger's limit for finish turning lathes).

Neil

From my experience , when you turn a piece in a chuck, part it off, place it into a Vee block and rotate , then you will see the error. Something turned between centres, especially dead centres, should be round on almost any set up. I have a modified Taig type lathe, and when I turn something in it, measures ok with a mic and looks ok with a dti. Then rechuck the part and get it round, just won't happen. I have a 0.001mm dti that use for checking in a Vee block. It is a lobed shape, not triangular and not very round.The Taig has since been corrected with better accuracy angular contact bearings, but even with those is still no better than 0.003mm, but is a lot better than the original 0.01 to 0.013mm it used to be. A better grade of bearing is available, but am not prepared to pay for them .

Neil L

You might well find the lobed shape is caused by the 3 jaw chuck you're using, either by clamping pressure from the jaws or uneven wear upon the gripping surfaces, which allows the job to move fractionally. A collet should be used if you want to isolate (as much as possible) the error in the spindle bearings.

Martin.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Neil Wyatt on 02/02/2015 09:29:33:

Or try this: Schlesinger

Neil

.

Sorry Neil, I don't understand the "Or try this" remark.

MichaelG.

[EmgeeParticipant @emgee]

Hi Blowlamp

I think Neil L is referring to the shape of the indicator tip not a turned part, some similar tips can be seen in the Verdict indicator lists, you could say it is 'tear drop' shape.

Emgee

[Neil LickfoldParticipant @neillickfold44316]

You might well find the lobed shape is caused by the 3 jaw chuck you're using, either by clamping pressure from the jaws or uneven wear upon the gripping surfaces, which allows the job to move fractionally. A collet should be used if you want to isolate (as much as possible) the error in the spindle bearings.

Martin.

When I make test pieces, I ruf down the od, then almost part it off, then I finish turn the diameter, and finally part off. That way the stresses in the bar are at the minimum. Some materials are not well suited to make test pieces out of due to the stress in the material stock itself. When looking for small errors it is not quite as easy as it may seem. Anyone who has worked in a metrology lab will know what I am talking about.

Neil L.

[JasonBModerator @jasonb]

Does the fact its almost parted off not reduce rigidity of the part which could affect the finished shape?

[Clive HartlandParticipant @clivehartland94829]

Even if the work is held in a chuck or collet and then supported by a tailstock center there could be a bias due to misalignment of the tailstock ! Is it also said that a ground bar in the same situation as a turned bar is not round. In fact some of the measurements quoted are outside what I would call normal measuring. 0.01 mm is about the limit for our use and well within the tolerances offered by most work. I would not think 0.001 mm due to surface finish and the stated out of round condition is possible and in any case a lot of work carried out is only done to satisfy a personal desire to make something that works. Buy any piece of kit and it can be improved for convenience of use (DRO's perhaps) but to increase accuracy is an expensive task compounded by the cost factor. Linear ball shafts are beyond the need of the amatuer unless he is seeking what i stated before. Work to your best ability, ensure the tooling is new or sharp. Ensure the metal is right for the part being made and follow machining and work holding protocols. Even when a part is made, further work like honing and polishing change the surface and measurement which has to be taken into account, make to fit is all that is required for us but production work means you have tolerances to work to which is totally different.

Clive

[blowlampParticipant @blowlamp]

Posted by Neil Lickfold on 02/02/2015 10:05:48:

You might well find the lobed shape is caused by the 3 jaw chuck you're using, either by clamping pressure from the jaws or uneven wear upon the gripping surfaces, which allows the job to move fractionally. A collet should be used if you want to isolate (as much as possible) the error in the spindle bearings.

Martin.

When I make test pieces, I ruf down the od, then almost part it off, then I finish turn the diameter, and finally part off. That way the stresses in the bar are at the minimum. Some materials are not well suited to make test pieces out of due to the stress in the material stock itself. When looking for small errors it is not quite as easy as it may seem. Anyone who has worked in a metrology lab will know what I am talking about.

Neil L.

Yes, I see what you mean.

My previous post was just to say that there might be other things to look at when out-of-round work is produced, as I'd actually be quite surprised if the bearings themselves were to blame for the 0.003mm error you said you'd got.

Martin.

[Steven HalkerstonParticipant @stevenhalkerston22077]

I know this is an old post but my twopence worth.

I was retired back in 2012 after 35 year in the Electricity Supply Industry, I’m a time served fitter but when aged 30 I went back into further education and became a qualified Engineer, by 1996 I got off the tools and became a project manager amongst many other jobs over the course of my career. Sadly my health got to the point where I was pushed into retirement.

Anyway, I recently built a workshop and bought a Clarke 500. Oh yes, I can hear the laughing and hoots of derision but the first thing I did after fixing it down awry firmly in the workshop was to pretty much strip the machine back and tidy all the rough edges off and yes, there were plenty. I then reassembled the machine and adjusting everything as appropriate. When on the tools the maintenance of all the workshop machinery was down to the fitters and lathe wise we had a cracking Tri Lever Myford that I always loved using, through to large Colchesters and I can’t recall the make now but one machine that you could mount a five to six foot workpiece on.

Anyway, the point is that after playing around with various tooling and adjusting the Clarke up ‘just so’ I have been really surprised at how smoothly it now runs but also the accuracy that can be achieved. A recent project still in progress has given on a 75mm diameter x 100mm long a tolerance of 0.01mm. For my needs and probably around 25 odd years since using a lathe, that will give all I ever need for the jobs I’ll ever do.

There is so much truth though in the statements about user, I certainly have not relied on the handwheel dials apart for roughing. Investing in some decent measuring kit has made a difference as well as the time setting it up. I am also coping with the transition from all imperial to going metric.

All good fun and perhaps never a silk purse, the Clarke has not been the pig’s ear that many told me, after I bought it.

I also paid well under any advertised cost so it so far has left me quite happy.

[MWParticipant @mw27036]

IPosted by Steven Halkerston on 10/12/2016 14:55:23:
I know this is an old post but my twopence worth.

Anyway, the point is that after playing around with various tooling and adjusting the Clarke up 'just so' I have been really surprised at how smoothly it now runs but also the accuracy that can be achieved. A recent project still in progress has given on a 75mm diameter x 100mm long a tolerance of 0.01mm. For my needs and probably around 25 odd years since using a lathe, that will give all I ever need for the jobs I'll ever do.

There is so much truth though in the statements about user, I certainly have not relied on the handwheel dials apart for roughing. Investing in some decent measuring kit has made a difference as well as the time setting it up. I am also coping with the transition from all imperial to going metric.

All good fun and perhaps never a silk purse, the Clarke has not been the pig's ear that many told me, after I bought it.

I also paid well under any advertised cost so it so far has left me quite happy.

No hoots of derision from me, only the gentle hum of agreement if that ever gets heard!

It's certainly not going to give you the works, but what it does give you is a very robust turning and screwcutting machine, I've changed mine a lot but the important thing was it was a sturdy lathe to improve upon and certainly have never found any substantial problems with it's turning capability, did you get it on the VAT free offer machine mart offer in a blue moon perchance?

The lead screw clutch is an example of a "rough edge" I encountered, it was a hex slotted drive bush that's made out of some kind of cast steel or iron, I simply made up a replacement very quickly out of BMS, with a little bit of complexity when it came to milling the hex out with a 3mm end mill! But it wasn't too hard to replace was my point. I certainly didn't howl to the moon when it went wrong, if anything it taught me a lot about the construction of it!

My chuck supplied with the lathe regularly gives me around 0.02 runout on basic stock. I would call that pretty good going for a 3 jaw. No complaints about the spindle, I can barely get the spindle to "blip" or register atall with a baty clock.

I would agree with your other statement that one area you should focus on quality is measurement, definitely makes sense. I've heard plenty of people sneer at it (Clarke cl430/500)and i'm not really making a big fuss of it because I know i'm happy with it and demonstrates a key area where people express judgement on something without ever knowing it.

Michael W

 

 

Edited By Michael Walters on 10/12/2016 16:08:03

[martin perman 1Participant @martinperman1]

Steven & Michael,

I have a CL500, I've tinkered with it and I'm very happy with its accuracy, the biggest job I've done is replace the gib strip adjusters and replace them with longer grub screws and lock nuts to keep the slides adjusted properly.

It does everything I want happily, no micky taking from me.

Martin P

[Steven HalkerstonParticipant @stevenhalkerston22077]

Funnily enough the ‘clutch’ I think the description barely fits what the component is broke on mine after around half a dozen uses. Fair play to Clarke, they had a new item out and in my hands within two days. God knows what it’s cast from but it really is gash an has simply sheared around the smallest diameter. On close inspection it looks as if it may have been partially sheared from New as there were two distinct sections around the shear, one dry the other wet , so it had time to absorb the lube.

I have the luxury of the machine back up working and the broken component as a model to make a new unit. Alternatively I may design a better softer clutch. Banging a male hex into a female hex as I say barely qualifies as a clutch.

Still, it is good to hear others agree that it can be made into a fairly useful jobbing machinine.

I do a lot of serious car modding and within limits this lathe is ideal for my needs. I just need to get tooled up for the milling part now. I am thinking of a collect type Chuck to start with rather than fly a cutter, again in part due to the size of parts I’ll be making.

To be honest I just bought it for the pillar drill to save space.

Thanks.

[martin perman 1Participant @martinperman1]

I've never used my mill because I have a mill drill and a Centec 2A, I bought the lathe off a previous employer for £350 plus tooling because it was never used except for home jobs, it was as good as new, I also bought my Mill drill for £50 off another ex employer, I was told to buy a new mill for light duties and the only person who ever used it was me so I knew its history.

 

Martin P

Edited By martin perman on 10/12/2016 17:10:05

[mick70Participant @mick70]

got a cl430 never had prob with it.

just had to set it up properly when first got it.

[not done it yetParticipant @notdoneityet]

 

Did you get it on the VAT free offer machine mart … ?

Michael,

 

There is no such thing as "VAT free" from Machinemart. It is a fallacy. It is simply a sale period with that particular reduction on the normal retail price as shown normally. The only legit way of buying from a VAT registered company is with VAT added ( or buying VAT exempt items – like books or children's clothing, etc.).

 

 

Edited By not done it yet on 10/12/2016 18:04:48

[Neil WyattModerator @neilwyatt]

Posted by John Stevenson on 30/01/2015 17:52:45:

The accuracy isn't in the machine.

It's in the bloke on the handles.

Going back to the beginning of the thread, i have to agree with John on this!

[Author]

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