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Strange (to me) chuck jaw design.

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Robin Graham24/01/2020 22:40:23
646 forum posts
147 photos

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

chronos3-jaw.jpg

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.

Michael Gilligan24/01/2020 22:47:15
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14764 forum posts
635 photos

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. enlightened

MichaelG.

David George 124/01/2020 23:22:12
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1054 forum posts
333 photos

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

jimmy b25/01/2020 03:08:00
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569 forum posts
37 photos

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

Gary Wooding25/01/2020 07:52:16
611 forum posts
145 photos

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.

Howard Lewis25/01/2020 14:46:54
2730 forum posts
2 photos

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

Howard

mgnbuk25/01/2020 15:00:50
593 forum posts
24 photos

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

ega25/01/2020 15:44:54
1436 forum posts
115 photos

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

oldvelo25/01/2020 18:53:29
166 forum posts
45 photos
Posted by ega on 25/01/2020 15:44:54:

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".

old mart25/01/2020 22:07:52
1083 forum posts
113 photos

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.

Robin Graham25/01/2020 22:28:57
646 forum posts
147 photos

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.

jimmy b26/01/2020 05:46:43
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569 forum posts
37 photos

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

jimmy b26/01/2020 05:51:15
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569 forum posts
37 photos

soft top jaws.jpgsoft jaws button.jpgdsc00002.jpgdsc00001.jpgbase jaws.jpg

Tony Pratt 126/01/2020 07:37:46
986 forum posts
3 photos
Posted by ega on 25/01/2020 15:44:54:

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

Me.

Tony

Nicholas Wheeler 126/01/2020 10:26:19
301 forum posts
19 photos
Posted by ega on 25/01/2020 15:44:54:

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

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

SillyOldDuffer26/01/2020 11:13:48
5127 forum posts
1073 photos
Posted by Tony Pratt 1 on 26/01/2020 07:37:46:
Posted by ega on 25/01/2020 15:44:54:

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

Me.

Tony

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

Tony Pratt 126/01/2020 11:22:36
986 forum posts
3 photos

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

mgnbuk26/01/2020 15:32:20
593 forum posts
24 photos

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

Dave Halford26/01/2020 18:03:03
557 forum posts
5 photos

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.

old mart27/01/2020 16:33:18
1083 forum posts
113 photos

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.

_igp2550.jpg

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