How much do I have to spend?
|Iain Downs||04/08/2019 09:43:56|
|617 forum posts|
A while back I bought an Mt3 ER2 collet chuck from eBay which I've not used much until recently.
Whilst turning some 12mm silver steel I noticed a wobble and checked it out.
I found the body of the chuck had a wobble of 0.06mm and that amounted to 0.6mm at around 200mm from the chuck face.
I looked around at alternatives from reputable UK manufacturers and found them to be around 3 times the price.
So I thought I'd have a punt and hope that mine was a Friday afternoon job and bought another one.
This one had a relatively small wobble, though it took the form of a depression around 45 degrees of rotation with the rest being pretty solid.
I measured both chucks again, this time with a 16mm test bar. Chuck number one showed a wobble of 0.36 mm 40mm from the chuck face (110mm from the spindle face) and number two was much better (!) at around 0.15 mm.
I put a test bar in the taper and measured wobble at the same place relative to the spindle face (110mm out). This showed more or less no deviation (under 0.01mm) except for a tick which probably a defect in the test bar (which I regret to say has managed to rust).
I also tried turning the chuck in the spindle and that established that the error was in the chuck not the spindle.
So I expect the advice from the assembled will amount to, 'if you buy cheap, you get sh*t', which seems correct. But what should I expect? ANd what do I need to pay to get a decent quality?
And is it likely that the collets are the problem rather than the chucks?
|Philip Powell||04/08/2019 09:57:53|
|66 forum posts|
Iain. Have you tried removing the collet and measuring the runout on the inside face of the chuck? Within reason it doesn't matter if the outside of the chuck is not true. This should determine if it's the chuck or collets that's causing the problem.
I presume you have a ER32 church not a ER2?
|Iain Downs||04/08/2019 10:20:39|
|617 forum posts|
I think I did and I think it was out. However, I will check that a bit later on.
|5616 forum posts|
Trouble with buying bargains from ebay is there is no correlation between the source and quality. It's like a car-boot sale, anything from a genuine Picasso for 10p to fakes being sold by a fly-boy at top prices. I've done OK on ebay (and similar), but it doesn't surprise me when the odd dud turns up. It's a bit of a gamble. Mostly I've come out on top but I'm always ready to write-off the odd duff purchase.
Your bent chucks may be from a batch of rejects, not just a Friday aberration. All the factory duds collected together and sold on to an ebay vendor ...
The advantages of buying from the UK sellers is being in the trade they have a better chance of selecting reasonable goods in the first place and - if it's wrong - you can usually get a refund without too much fuss. The downside is they are more expensive. Mostly, I buy tools from them. But even these are hobby supplies, not the best available, which also introduces an element of risk. So far I've not had to send anything back, but...
Sellers of professional quality ER collets and chucks tend to be coy about prices but - as an indication - a Roebuck collet chuck can be had for £108 + VAT, with collets £10 to £30 each. Or more. It may not be worth the extra money; certified accuracy is a comfort but you could also be paying for tools rated for use in a 20000rpm CNC machine; completely wasted in a home workshop. I'm afraid new top-end tools are seriously expensive.
|Michael Gilligan||04/08/2019 10:27:40|
15462 forum posts
Typos abound ^^^
[ well, It is Sunday ]
|Old School||04/08/2019 10:45:50|
|323 forum posts|
One thing I have found with ER type collets is the range the have for example 11 to 10mm it is accurate at 11mm and a bit under but nowhere near as accurate at 10.1mm.
I have moved to 5C collets now and use emergency collets for the odd sizes that I need to hold.
|Kiwi Bloke||04/08/2019 11:05:07|
|398 forum posts|
There's been quite a bit of relevant discussion about these things in this forum already. If clocking the chuck taper suggests the chuck is 'out', it's a dud. The collet may also be 'out'. However, it has been pointed out that, even good-quality collets can't be relied upon to be perfectly aligned when the chuck is tightened. Applying a balanced torque (couple) to the nut may help. Collet 'pushers' are available. These are used to apply a temporary, radial force to what the collet's holding, as the nut is tightened. (Tighten a bit, clock it, tweak, tighten, rinse and repeat...)
As I understand it, these chucks were originally designed to hold cutters, not workpieces, so absolute alignment wasn't such a priority, given the short length of (most) cutters.
|Tony Pratt 1||04/08/2019 11:05:14|
|1099 forum posts|
Unfortunately the world is full of crap tooling/washing machines/electrical goods etc. etc. etc., it's the way of our world at the moment.
You get an item but it's not quite right so what do you do, use it or return it???
|Kiwi Bloke||04/08/2019 11:12:01|
|398 forum posts|
'You get an item but it's not quite right so what do you do, use it or return it???' Good question, Tony. I suspect it depends to whom you try to return it. The people who understand that quality matters seem to be dying out - at least in the retail sector.
|Pete Rimmer||04/08/2019 11:45:22|
|684 forum posts|
How hard is the material? Too hard to turn a new taper with carbide? That's what I would be looking to do if it's not getting returned.
Think of it as making yourself a collet chuck except someone else has done the roughing out
|old mart||04/08/2019 13:25:25|
|1521 forum posts|
I have bought two er25 collet holders in R8, the first had a wobble, so I took a chance and bought another which is good. They were both cheap Chinese, but clearly made by different companies. Getting sets of the collets is also a lottery, I ended up buying Vertex and Cutwell collets in 6, 8, 10, 12 and 16mm which are good.
|John Baron||04/08/2019 14:50:03|
274 forum posts
The biggest problem with Chinese ER collets is that they are not properly cleaned and deburred. I've found that there are often tiny burrs left after they have been slit. In some cases large slivers of metal have been left.
I use a Stanley knife blade to clean mine and remove the swarf that has been left. After cleaning properly all the ones that I have used have been in spec. I posted pictures on another forum of the worse ones I had.
Stoning the burrs off is easy on the larger collects, not so on the small ones.
|2494 forum posts|
I bought the majority of my ER32 collets from Arceurotrade and haven't had any with defects like burrs etc. I’ve not checked them for accuracy though.
|Mick B1||04/08/2019 17:59:49|
|1547 forum posts|
I'm glad I read this thread. Looks to me as if collet chucks are not only very limited in range, but also little or no better than a good 3-jaw for concentricity. Apart from repetition bar work that'd be better on a capstan, I can't understand what some people see in 'em.
|Pete Rimmer||04/08/2019 18:44:59|
|684 forum posts|
Good collet chucks and collets are very repeatable. Far better than a 3-jaw.
|Philip Powell||04/08/2019 19:57:58|
|66 forum posts|
As Pete says a decent collet chuck should be very repeatable. In my experience they are very accurate (useally) they will hold work firmly without damaging the surface and with care thin walled components can be held.
|Neil Wyatt||04/08/2019 20:47:31|
17712 forum posts
There are lots of different qualities; to an extent you get what you pay for.
Mine are a mix of secondhand and Arc ones, and I haven't had any with swarf or burrs on.
Expecting concentricity with 8" of overhang in an ER collet seems optimistic even with the most expensive of precision collects, although you ought to be able to get better than 0.6mm.
Edited By Neil Wyatt on 04/08/2019 20:47:41
|Tim Chambers||04/08/2019 20:52:45|
|82 forum posts|
At the risk of teaching granny to suck eggs, you did throughly clean the morse taper in the spindle first?
Its very easy to just bop the chuck into the spindle and tighten the drawbar and forget to check if the taper has any swarf buildup.
Edited By Tim Chambers on 04/08/2019 20:54:51
17835 forum posts
Iain, I wonder if some or all of the error you are getting is from incorrect fitting of the collet. looking at some of your photos it looks like the collet is sitting way to far back into the nut.
The collet should be snapped into the nut and then the two fitted to the chuck, our good friends ARC show how to do it here
|307 forum posts|
Well spotted JasonB !
separately, when I saw ER32 Church I wondered whether it might be another of BrianWood's projects (enjoyed the article, by the way)
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