Strange (to me) chuck jaw design.

I was scouting around for a direct mount D1-4 3-jaw this evening and came across this offering from Chronos:

The only reason for doing it like this I can think of is that maybe they can be reversed, and it's cheaper or more accurate than supplying a separate set of outside jaws. I suppose it would also be possible to mount soft jaws on the 'carriers', but Chronos don't seem to list any. Maybe I'm missing something!

Any comments?

Robin.

Yes, reversible top pieces screwed on

... I think Pratt Burnerd calls them ‘American Style’ or some-such

... Saves having to do matching scrollwork on two sets.

MichaelG.

you can make your own bolt on jaws. we used to make external jaws to suit chuck with a 2 foot diameter hold on a 12 inch chuck. just bolt on bore out to suit job if it needs modifying just weld a bit on a bit of metal and re-bore.

David

I have a similar style chuck (160mm one) from Chester. The jaws do reverse and soft jaws are available.

I converted a set of soft jaws to a master set that takes my own made tops ( I use soft jaws quite a lot!).

Jim

The 3-jaw on my Chester 10x36 lathe is like that. It's so well made and accurate that it certainly wasn't designed to save money. But it is a bit of a palaver to reverse the inserts.

Looks like an ideal chuck to take soft jaws! You have to make your own, of course.

Howard

Pretty standard industrial setup. I bought a HBM 3 jaw of that pattern from RDG Tools for a Harrison 330 at work & the jaws are still a really good fit after several years of industrial use. In practice it doesn't take much longer (if any longer) to swap the top jaws around compared to replacing conventional internal / external jaws.

While Chronos may not list soft jaws, someone like Thame Workholding

will probably have them. Not too dificult to make your own, though. The mounting face patterm is proably to a standard - we were able to interchange top jaws between a Chines made Chester 500mm 3 jaw & a Forkhard 700mm 4 jaw at work.

Nigel B

How many of us remove the spring from the chuck key?

Never had a new fangled chuck key in the 1950's. Old mentor " It's called a chuck key cos if you leave it in the chuck the lathe can chuck it at you".

I believe they are called slot & tenon and if you have a mill, it would be easy to make tops in mild steel or aluminium to bolt on to the master base jaws. Because of the bolt together design, they project further from the face of the chuck than one piece jaws.

Thanks for replies - it seems that this a recognised design, just hadn't seen it before myself.

I am planning on making a set of soft jaws for the anonymous 3-jaw which came with my lathe using the idea of pins to engage with the scroll, as suggested by Martin Connelly in another thread. I had wondered about this sort of thing having seen wood turning systems where there are 'carrier' jaws to which various things can be attached, but hadn't seen it in an engineering context before.

Seems like a good idea.

Robin.

If you get all the sizes of the required jaws, then someone like Rotagrip or Thame Workholding may be able to help.

I have allways manged to find soft jaws for all my chucks. They are usually around £30-£45 a set, I then simply turn these in to "master" jaws and make up bolt on tops

Jim

Me.

Tony

The second key I made for the four jaw chuck feels so wrong without a spring, I'm tempted to fit one.......

Really. Why?

Big employers are hot on best-practice because they've been sued, prosecuted, had expensive machines damaged, paid hefty legal fees, and then been walloped with increased insurance premiums! Once you get beyond near misses and trivial incidents, even small accidents cost tens of thousands. A fatality is likely to cost millions.

Model Engineering has an excellent safety record. But I don't see any advantage in deliberately defeating basic safety features, especially anything like a chuck spring that only slows me down by a few seconds. Real men take up wood-working and start by removing all those inconvenient power-saw guards. Chop, chop!

Dave

SOD,

Of course you are right but after 50 years I will go continue to go spring less, in fact the only key I have used which came with a spring was on my Warco lathe purchased last year, after an incident on a school lathe over 50 years ago I have never been caught out, but it could happen.

Slightly OT, a few months ago I replaced my power saw guard, with a lifetime in metal cutting I still find band / power saws and angle grinders the most frightening [maybe not the right word]

Tony

Big employers are hot on best-practice because they've been sued, prosecuted, had expensive machines damaged, paid hefty legal fees, and then been walloped with increased insurance premiums!

I have been in a great many engineering workshops in the last 43 years & have yet to see a spring on a chuck key in any of them. A spring is no substitute for safe working practice. At the Apprentice training school I did my "First year off the job" training at, the Lord help you if you were lax enough to leave a chuck key in the chuck. Those who did so did not do so a second time !

Nigel B

There's a different version that has lots teeth at 1/16" centers instead of a single slot, not so easy to reverse, but more flexible.

Funny you should mention the other type of top jaws, Dave, these serrated with 1/16" X 90 degree pointed jaws for a 6 1/2" Pratt chuck came through the post this morning. I was lucky and put in the only bid on ebay, and got them for £8.75 including postage. I looked up the Thame code, AJ06 before bidding.