Collet Chucks

Charles, Have a look at this link which should do the job,

However I think you'd be far better off getting rid of that crappy old lathe to me! ( Even though I'd have to change all my MT4 stuff - I didn't know the Mark 3 had a 5MT?)

----------------------------------------------------------------------------------------------------- snipped-for-privacy@boltblue.com John Lloyd - Cymru/Wales

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For some sizes:-

-- Regards,

John Stevenson Nottingham, England.

I've measured the eccentricity on the spindle (at the spigot) of my lathe and it's better then 0.01mm TIR as per spec.

If I cut a new backplate register for a new collet chuck, how true can I get the chuck to run? Should I expect better than 0.02mm TIR on a DTI, say

25mm from the collet? Or even better than that?

This is just standard kit - not top spec toolroom stuff.

Thanks

The backplate will be dead true if you cut it on that lathe have a marking on the spindle and the backplate and align them. You'll end with just the TIR of the collet. And if you spend 10 minutes trying different positions (and mark the best one) you might get better.

Made a collet chuck on my lathe and the runout of the chuck is not measurable (read: less than 1/1000 mm). Only thing having runout are the collets (Fahrion, guaranteed to have less than 6/1000mm)

Nick

Steve

My own experience with an Arc Euro Trade ER32 chuck and a Warco backplate machined on the lathe was .0003" ish (.008mm in your "funny money") about 0.25" in front of the collet. One problem can be how "repeatable" the backplate mounting is on some of the screwed type spindles. I tried to even mine out by marking the backplate and spindle when it was first machined so that I can tighten it exactly the same amount on subsequent fittings. I might just have been lucky but it certainly beats the 0.02mm you mention and I guess without taking too much care mine is repeating to something like 0.015mm.

However, I have to add that a friend who uses an older Myford has trouble repeating within .02mm regularly. My feeling is that his backplate register diameter is oversize and not locating properly on the spindle register. Another instance worth mentioning is where the collet taper in the chuck and the internal backplate register were slightly out as supplied. This was corrected by holding a bit of 20mm bar that had been turned between centres in the lathe in a Collet and mounting it together with chuck between centres to take a "lick" (carbide tooling) off the internal backplate register and rear face of the chuck. He was lucky that his chuck body was not that hard and it worked well for him getting acceptable figures when mounted on a re-machined backplate. I'm not sure that this would work with modern imported collet chucks as the latest ones I've seen (even cheap ones) appear fully hardened and you might therefore have to resort to a toolpost grinder to correct any error if you are unlucky enough to find any.

Of course if you have a lathe with a more accurate spindle mount type then some of these problems won't apply to you.

Best regards

Keith

ARC sell a 95mm and 125mm diameter chucks. In the case of the Myford either of these would fit ok, just a different backplate, so is there any benefit of one size over the other that I may have missed?

Stu G

In general, use the smallest chuck which will safely hold the work you're machining. Ideally, hold your work in a collet chuck for accuracy, security and surface finish. Broadly, the smaller the mass you're spinning, the better the end product is likely to be.

(There must be something there for the 'barrack room lawyers' to get their teeth into :}!) --

Chris Edwards (in deepest Dorset) "....there *must* be an easier way!"

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Thanks Keith.

I have a Sieg C6 which has a "push on" type with 3 studs that engage a locking collar. Sounds like if I make a neat job of cutting a register then I should be able to beat 0.01mm as a repeatable situation.

Just need to cut a decent register on the back plate...

Steve

My shagged old Student has no discernible movement on a dial indicator on the spindle nose, none on the housing of my Burnerd collet chuck when fitted to that and none on a test bar in most of the collets. A couple obviously have a glitch somewhere because I get about half a thou TIR on them but can't see why or where. Even with an old machine it's clearly possible to get almost zero TIR if everything is clean and well maintained.

Sigh.

I have been having trouble with my lathe (Chester Conquest) recently, and measured the runout at 0.08 mm. Bad.

Did a bit of investigating, and found that the main shaft was bent!! 0.30 mm over it's 6" length.

More curious still, I have no idea how it happened - haven't been doing anything heavy since long before the trouble started.

Chester want £59.95 for a new one, but littlemachineshop.com do one for $29.95 - guess who gets my business ...

[snip]

You shop press? :-)

Nick

/snip

snip/

Peter, you may want to check that they will be the same. My Chester Conquest was not manufactured by Sieg but by Bull something or other and there may be slight differences. Chester have sourced from Seig in the past though. Maybe you could negotiate a discount since it has probably always been bent. You could also try Hugh also known as harryuk123 on ebay for the Seig part as he boasts that he can supply spares.

Archie