Looking for same chuck.. watching with intrest.

Prob. don't need to remind you ,but you need 12 x 1 not the "usual" unimat 14 x1.

rdgs Jason

Hi Robert,

I had a similar problem in finding a 3-jaw scroll chuck to fit my Perris (now the Cowells) lathe with an obsolete 1/2" x 20 UNF spindle nose. I picked up a cheap 2.5" 3-jaw with an M14x1 thread, bored the hole out and rethreaded it M17(ish) x1, made up a bush with a matching thread, and then bored/threaded the bush to the desired 1/2" x 20 UNF. Full story here. The same technique could be used to bore out and bush a 4-jaw, though it does require access to another lathe with screwcutting facilities.

A backplate would be simpler, at the expense of a little of the chuck to tailstock distance. I was unable to use one, because the bolts attaching it to the 3-jaw might have fouled the internal scroll. That wouldn't be a problem with the solid body of an independent 4-jaw.

Andy

Hi Rob,

I have an HBM 3 jaw chuck on my Chinese lathe and have no problem with it at all. I have used it for a couple of years now and find it one of the most accurate 3 jaw chucks I have used. I have used RDG at times with no problem, either with quality or service.

Regards

Terry

HBM 3 and 4 jaw chucks

Good gear, no problems

Rob Hi,

I agree with Andy and have had to clean and remove burrs on several new chucks in the past and not all "cheap" ones either. You will be able to decide if it is the jaws not sliding or the screws not turning by removing the jaws (mark them first), remove the adjuster and slide the jaw back into the slot. I have found both issues and a simple de-burr with a stone or diamond file has worked for me.

I have found swarf trapped between thread and chuck body as well as between thread and jaw rack (not Chinese either) but unlikely if all 4 jaws are tight. I have also found with one import chuck that the adjustment screws were full form threads (?) and as the slots were a very nice fit the crests were fouling the jaw rack, a quick clean up of the adjuster thread outer diameter with a bit of emery in the lathe fixed that one.

I am not a supporter of grease on chuck threads as it will attract all sorts of swarf and lead to many similar problems when in use. A good clean/de-burr followed by a quick wipe with a trace of good machine oil keeps my chucks fine.

I am thinking of getting one of these independent 4 jaws for my Cowells but will need to re-machine the thread register as mine is the older 14×1.5mm type. Are the jaws reversible? I can't see from the picture on their site.

Best regards

Keith

I'd be surprised if the jaws on an independent chuck weren't reversible, Keith. After all, they have a simple plain thread to engage the adjusting screws.

In contrast, the jaws on 3 (or more) jaw scroll chucks need teeth shaped a bit like this: ((((( so they will engage with the spiral scroll. If you try to reverse them, they won't fit, so a separate set of jaws with teeth the other way round is usually provided with the chuck. Of course, there's an exception to every rule; the jaws on the very cheap and cheerful 3-jaw I modified to fit my Perris (forerunner of the Cowells) are convex on both sides, as a compromise.

Andy.

Rob, Andy

Thanks for the comments, I also agree that the jaws should be reversible but the shape of the jaw outer ends look square to me rather than tapered to grip when reversed. It looks as if the jaws will not completely centre when reversed and the cowells doesn't have a lot of clearance for jaws that stick out beyond the chuck body. OK if I can keep it within the gap but could be a problem if the chuck or my adaptor is a little long.

Terry, all good comments but I can't agree with not checking and removing the burrs if present or indeed breaking corners if they have been left sharp.. Both faults are quite prevalent on some of the cheaper items available these days and apart from causing tightness and possible jamming, they are very good at giving a false impression of a "good fit". Unfortunately, when production times are tight removal of them is often the first thing "forgotten".

I wouldn't advocate removal of metal from any mating faces and always use a touch of engineers blue to identify the "tight" areas, surprising how often I find them to be in the corners of the jaw slides or even on one chuck from burrs left by cutting the idicator rings in the front face.

I am not complaining as I enjoy the very reasonable prices we can get usable tooling for these days with just the simplist of remedial attention.

Best regards

Keith