Clark CL500m run-out

ok so this might sound like a daft question, but I have recently obtained an old Clark CL500m lathe, I have set it up in my workshop, it is roughly leveled on the ground, and I have been having a bit of a play, the first thing I did was to put a piece of steel in the three jaw chuck and supported it in the tail stock, I did a skim cut, the difference over about 120mm was 0.06mm, so I decided that the tail stock might have been out of line, so I repeated the process, but just with the bar in the three jaw, but this time reducing the amount protruding from the chuck to about 70mm, this time giving me a difference from end to end of about 0.005 ish, I will say ish as my micrometer only measures down to 0.01 and it was about half an increment, so that gives me about 0.01mm over a 100mm length, is this a respectable run out, or is there anything I could do to correct this?

thanks all in advance for your help and guidence

.

What diameter and material was this bar.?

Nick

it was 25mm round steel bar, so not much diflection in it

I would argue a 3 jaw is probably the cause of the runout, you've done pretty well as it is to eliminate that much runout.

Think about it, the jaws are never going to register an absolutely true position on a self centre chuck. The only way to do this is to use a 4 jaw or between centres turning.

Moving the tailstock from left to right will only eliminate any relative bias on that axis. On a self centre fixing, the tailstock can only be used to offer support for an unsupported part, to a decent degree of accuracy, but cannot offer total accuracy.

What makes the conundrum worse is that if you centre drilled the part in the 3 jaw, that will also reflect any corresponding chuck runout when tested on the bar's outer unmachined surface.

Silver steel is a better material than mild to test onto because it's often purchase precision ground.

Michael W

Edited By Michael-w on 14/01/2017 00:42:56

Hi Allan,

That doesn't sound too bad for an old Clark. This has been discussed earlier, see: ***Link***

It is about what I have on my Chinese lathe, I used the methods described by Harold Hall when I set up my lathe. Good luck with your new lathe.

Thor

Hello Allan,

If the lathe is set up properly you should be able to turn accurately. Runout is a problem only when you move the work piece in the chuck. I am not familiar with Harold Hall's methods but I am sure they will be a good guide to set up your lathe. Regards, Michael.

The OP is talking about Taper not runout.

The Myford manual here:- https://www.dropbox.com/s/n2fumms41y3cmyy/MyfordML7Manual.pdf?dl=0

shows and explains how to align (level) the lathe bed.

Nick.

Edited By Nick Hughes on 14/01/2017 09:43:40

I agree Nick, nothing to do with runout.

first all thanks for your reply's, it was the end of a very long week, but Nick and Michael are correct in what I should have actually written was taper as it is being turned.

Allan

thanks for this Nick, I have just started reading but I love the way they recommend the use of asbestos sheets for packing :D

Allan

.

... for the job; it was as-best-'s you could get at the time.

MichaelG.

With the 70mm sticking out I'm assuming that the bar enlarges away from the chuck.

0.005mm ain't much

When it's an error that small try running the same cut several times before you do anything else.

Before even doing this personally I would adjust all of the gibs for slight resistance especially the saddle on this lathe. You can get minor differences based on where the feed starts from / the saddle moving slightly when the cut starts etc. It can even twist slowly as the cut progresses. Various things can happen and depending on the lathe the taper it produces could go either way.

Tailstock - assuming the error on the headstock is that small I would simply adjust it over a turned length of 150mm or via a test bar. It's a very small adjustment to make though. A DTI can help with that so the amount of movement can be seen. A test bar is a good idea really because it allows the relative height of the tailstock to be checked by running a dti across it at several places. That can also give some indication of a bowed bed. Tailstcok centres are usually a tiny bit high. Some might strain the bed to correct it. Personally I would probably re ream the morse socket providing correcting the error doesn't enlarge it too much. But I have only done that on modern bed designs with vertical V guides. That makes suggestions on how to do it difficult.

I had one of these lathes when they 1st started coming over. I oiled the bed up, removed the lead screws and set the gibs up for slight resistance. It produced a nice finish but I was very unhappy when I started mic'ing work on it. The headstock was way out and the tailstock about 1mm too high, quill sloping as well. The headstock could be shimmed up. I eventually sold it to some one who just wanted to shorten bolts. It was an "improved" model over the original Chinese one- hand scraped tailstock and centre distance increased from 18 to 20" by chopping off the taillstock nose. Couldn't turn up to the end of work with a centre in then. Noticing that is when I though it's got to go.

John

-

Take a look at how to dismantle the headstock here: https://m.youtube.com/watch?v=XPpLGtzaErM

It shows the headstock is attached to the bed in the same way as a tailstock, and could, as a last resort, be shimmed laterally if needed.

Of interest if nothing else.

Regards

Richard

thanks both, with a bit of luck this lathe is only going to be a stop gap until a Myford Super7 turns up, but I would still like to get it right before getting rid.

thanks AJohnw there is some good points there for me to look at, I have got a DTI and a test bar here, but until a bit of reaserch last night I didnt know how to get the chuck off as all the other lathes I have used have been a little bigger, and with camlocks to remove the chuck, plus were pre setup as they way well over 2 tones lol.

Allan

Schelsinger limits for a lathe are 0.01mm at spindle nose and 0.03mm at 300mm out.

Given the limitations of measuring runout accurately your lathe sounds pretty much in line with this. Stop worrying and enjoy it

Neil

I though that too Neil but little points can improve numbers like those and the man might be used to better. Nearly if not all dovetail beds have short saddles so good adjustments in that area are more or less essential. Thing give as well and 0.0025mm isn't much at all.

Actually if the one I had wasn't a pigs ear I would probably still have it. I'm glad they have started making them a lot better than they were initially.

Super 7 ? - might be out of the frying pan into the fire.

John

-

Yeah I have to admit, if I had that one I would've dropped it like a hot potato too. What ever they did to that tail stock, and possibly the spindle, they messed it through and through. I can match up both centres perfectly fine.

I got mine circa 2012.. so I presume you got yours much earlier because they've been selling that lathe since the mid eighties I think?

A super seven that hasn't been run into the ground is still a hot piece of kit, no doubt about it.

Another strange quirk of the cl430 is that the 4 jaw sold for the lathe is overkill, it's 7.5" across. It makes it very heavy and awkward to use, a 4" chuck would've sufficed.

Michael W

Edited By Michael-w on 14/01/2017 21:17:13

I wasn't to sure what people classed as acceptable limits, and yes the machines I am use to using are far bigger Colchester machines that are accurate to less than 0.01mm over 1000mm, but as I said they have been set up by people who know what they are doing unlike me

as for the 7, I am getting it of a friend who is just finishing tweaking it, he is an old school machinist, and this lathe came of an old tool maker he knew, in total from new has about 200hours of use, and that is from 1974 so he will make sure its spot on before I get it, then help me to install it when he drops it off, oh and then a few lessons on things like screw cutting while he is at it

I do agree, colchesters are fantastic machines, I'd pick it over any other piece of industrial tooling, but I have used one that was a dog, .2 run out over short lengths. Either the chuck was busted or the spindle bearings had it or possibly the gibs were very loose.

One machine I am very envious of, is the Cromwell lathe s800

Michael W

Edited By Michael-w on 15/01/2017 14:05:48

Edited By Michael-w on 15/01/2017 14:18:51

.

Sorry, Michael ... I'm confused ... Did Colchester really make the Cromwell lathes ?

**LINK**

http://www.lathes.co.uk/cromwell/index.html

MichaelG.

.

I see that you edited whilst I was posting my question.

Edited By Michael Gilligan on 15/01/2017 14:24:58