Lathe Accuracy

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.

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

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

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

got a cl430 never had prob with it.

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

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

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

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Quite ... But it is fairly common for companies to advertise "VAT free" to describe "you, the VAT-paying customer will only pay an amount equal to the nett list price ... we will work out the sums."

Is it really worth making a fuss ?

MichaelG.

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Edit: "fairly common" usage has included this, for Skoda

http://www.rainworthskoda.co.uk/news/0-finance--0-vat--offer-extended#.WExL_bTfWhA

Edited By Michael Gilligan on 10/12/2016 18:44:37

Indeed, and even if you remove it one step on cnc, it's still the guy pushing the buttons whos making the calls and mistakes do happen even in highly automated factories, I should know because I worked for them, customer and general public only sees the preface of the mischief underneath!

Michael W

As they say, it is the nut that holds the cross slide handle that is most critical.

I've seen extraordinarily good work turned out from old far from accurate lathes. I've also seen very good lathes that have never done any serious work at all, aside from turning out test bars.

Roger

I don't agree entirely as I would put it a different way. It's more a case of getting down to the inherent accuracy of the machine when needed and if that isn't acceptable doing something about it. That may mean hand work of some sort. Getting there means taking reliable measurements too. Also usually some thought about the best way to make something.

The taig / peatol I had did turn very round parallel work - until I asked too much if it and then it turned a couple of thou taper over about 4" as the head had warped. Cured by turning it to size in sections. Maybe not everybody's idea of how to cure a problem like that but in that case it was MY best option. It finished up correct to less than a couple of tenths. Ok for a mandrel.

John

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Whilst I agree with John about the nut holding the Handwheels, even an accurate machine will not produce accurate work if it is not properly set up, and aligned. Which is why Myford devote space in their Operator Manuals on levelling.

If the bed is twisted, and/or the gibs slack, on a "good" machine, it will not produce work of the accuracy of which it is really capable. Remember the folk who have improved the performance of fairly mediocre machines by attention to detail.

And, if you want the ultimate in accuracy, it will cost . The sort of machine that we mostly use for hobby work, will probably produce work that meets our requirements. If you want micron accuracy and repeatability, you are not looking for a hobby machine, but a professional toolroom machine, properly set up. and used in a temperature controlled environment.

Did we buy the machine to produce work for what we require, or to pursue theoretical figures?

(My car is claimed to be capable of 100mph+, but because of where it is driven, it rarely reaches 70 mph; so does the claim really matter?)

I have a box of slips, but do not try to work to 100ths of a thou, (1, because I don't need to - and 2, lacking a controlled environment, cannot measure to that level of accuracy anyway)

And how accurate and repeatable are our measuring instruments? Does my 0 -1 " micrometer match the internal mic for accuracy? Letting them both "soak" in the same environment as the slips for 24 hours, with minimal hand contact, may provide a fair indication.

Most of us produce one offs, rather than large volume, so we make one part to fit the corresponding one. For things like piston/bore fits, you can always lap if the fit is that important.

Sorry to rant on, but lets think in practical terms.

Howard

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But, Steven ... This forum is powered by rants ... They are its very life-blood !!

MichaelG.