ER32 Collet Chuck to Suit Hercus 9 Lathes

[Col2310]

See old thread

I ordered an ER32 Collet Chuck to suit my Hercus from Chronos UK at the end of May and after numerous emails, pressing for a delivery date, received the item on 6th. September. Most of the replies from Chronos related to the failure of their supplier (Soba India) to meet the delivery schedules but one reply concerned the rejection of one batch for quality reasons. I should have taken the hint and cancelled the order.

The fitting on the thread was good and tight without any significant movement 'fore or aft' and the fit on the register was good .
I was very pleased at this stage and placed a test bar in a 20mm collet and clocked it 0.07mm TIR...not too good.
I removed the collet and nut and ran the clock on the internal taper with the same result. So removed the chuck and ran the clock on the Hercus spindle register which gave a zero result, so all errors were in the collet chuck.
I emailed Chronos, stating my disappointment with the accuracy, as I had hoped to the maximum TIR would be around 0.01mm.

I had a reply today apologising for the poor accuracy, refunding the purchase price and postage and suggesting that I bin the Collet Chuck. They added that they could not replace the product with an item that would give the accuracy I requested.

Their quick response and immediate refund has to be commended.

I think it is possible to rectify the runout by re-machining the internal taper which should not adversely affect the collet clamping if I removed only a minimum amount.
Any comments on this? or should I scrap it?

I have an air driven Dremel type grinder which I could adapt and mount on thecompound. The grinder has a 6mm collet, supposedly runs at 25000rpm.
If I used this, what type and size of grinding wheel do I need and where do I find one?

[.RC.]

Is it hardened?? If not turn it in situ...

[Big Shed]

That's very disappointing and thanks for posting that. I have been waiting for quite some time for these to come in to stock at Chronos. Few days ago got an email from them to say they had come back in (price had gone up a fair bit though). For one reason or another I haven't placed an order yet, now I don't think I will.

I have their ER25 chuck, which is very accurate, but doing a fair bit of work with 16 and 20mm Delrin rod atm, so I thought I would upgrade to the ER32 (which I should have got in the first place!).

[Bryan]

As I learned from buying drill chucks on ebay: Terms like 'precision' mean nothing. My policy now will be to ask first what the actual tolerances are.

At least I didn't have to wait months for my disappointment.

[nadroj]

Sounds like the collet chuck was the type that threads directly onto the lathe spindle?
In my view, some inaccuracy is very likely with this type, although you could be lucky. Manufacturing tolerances, both on the spindle and the chuck body, conspire against good accuracy. Hercus/Boxford/South Bend spindles have no effective register, unlike say Myford lathes, and rely on the threads to position the chuck. Notice how Hercus chucks with 4 independent jaws are often of the type with a threaded body, but as the jaws can be individually adjusted some inaccuracy doesn't matter. I've never seen a Hercus 3 jaw scroll chuck with a theaded body - they are always fitted to a backplate, which provides for a perfect fit to a given lathe. Like on a typical scroll chuck, inaccuracy in a collet chuck cannot easily be compensated for.
The type of collet chuck that can be mounted to a separate backplate (which Chronos also lists) can be fitted to an individual lathe, which is more likely to give high accuracy.
Either that, or buy say 20 chucks, try for the best fitting one, and return 19. Just kidding, but selective fitting could work, given enough to chose from!
Re: Remachining the taper - There are 2 tapers on an ER collet system. How to adjust so both are in line?

Jordan

[Big Shed]

I just assumed this was their 100mm ER32 chuck which is designed to go on a backplate? That is the one I intend ordering.

Chronos Ltd Lathe Type Collet Holders for ER Collets

But by the sound of it yours is the one that threads straight on to lathe spindle?

Chronos Ltd Soba ER Spring Collets Systems - NEW!!

[Col2310]

RC
It has been heat treated but is machinable. As I will be 'scraping off' a minimum amount I thought grinding would be the best option. Will try turning if I cannot get the grinder working.

Big Shed.
I have bought a lot of items over the last few years, always directly from them and never had a problem. I understand from the many emails that Soba (Shoba) have a major quality problem with this item yet it seems such a simple production engineering problem.
It is this chuck
Chronos Ltd Soba ER Spring Collets Systems - NEW!!

Nadroj
I had seen a similar Collet Chuck (American Sourced and expensive) working on a friends lathe with good concentricty, so thought I would take the risk as I need to machine longish shafts that will pass though the spindle bore.
I will only try to correct the 8 degree taper.

I did consider ordering a few more as Chronos were very prompt in refunding all costs..Just kidding!!

Thank you all for your help and back to my question.

What type of mounted point would do the job?