4 jaw Independent for a 7x12

Evening all hope well and safe,

Can any of you kind gentlemen recommend a chuck, my machine is the cl300m. I can buy one £80 from machine mart. I don't know about the quality of what I'm looking at, I would go max a £100. I can see some in £50/80 bracket from chronos to a shocking allly looking cast afair! Obviously I will be giving the latter a very wide berth!

Thanks again.

I recently bought a 125mm vertex taiwanese 4 jaw for £115 if my memory serves me well, in my opinion, well worth the extra 30 quid or so.

Woody,

I had a 100mm independent 4 jaw for my mini lathe from ARC, quality is good and price is £48 currently. It has a 72mm register so should be a straight fit as most mini lathes have a 72mm spindle flange but check yours first. ​​​​​​

ARC part number 040-040-10600

Ron

Edited By Ron Laden on 25/04/2020 05:22:27

Edited By Ron Laden on 25/04/2020 05:25:10

p. s Forgot to say if your lathe came with a 80mm 3 jaw then it will have a 55mm spindle register but you can get a pre machined 55 to 72 back plate I think RDG do them. If your lathe came with a 100mm chuck then you should be fine?

Just noticed ARC list a 80mm to 100mm back plate.

I'd stick with Arc,

Jim

I bought a lathe from machinemart over(?) 25 years ago and later bought some extras including a 4 jaw chuck - possibly a little larger than 100mm - but I would never buy precision stuff from them ever again. Purchase was before the internet and rather a rushed purchase. One that I have since regretted. That said, I don’t know how good, or bad, the chuck is - it still sits with a job, to be completed, ever since I (re)commissioned a decent replacement lathe.

I buy most of my bits from Arceuro these days.  Good reliable service, fair quality and good repartee🙂.

Edited By not done it yet on 25/04/2020 07:44:58

Here is the ARC 4 jaw and backplate just fitted onto my SC3 - it takes up some of the length between centres, but less of an issue on this lathe. The casting is a 7 1/4" Tich wheel - Just trying it for size!!

Did you come to the conclusion that the jaw projection was a bit too much?

I just wanted to see what the capacity is - I only roughly centred it by eye but it ran smoothly enough with plenty of jaw engagement and plenty of clearance over the bed. I need to practice centring things in a 100mm four jaw!

I have access to a larger lathe with backgear at the club workshop, and at my rate of working all of our current troubles will hopefully be out of the way before I need to turn these wheels (actually at my rate of working probably the next two issues to face us as well! )

So unless we are still in lockdown this may not need to be resorted to - but I am confident it could be done should I need to.

The wheel by the way finishes to 4 1/2" over the flange so without measuring it, is probably about 4 3/4" as is.

Edited By Nick Clarke 3 on 25/04/2020 13:55:57

I would try ARC, they probably can supply an adaptor. I bought a SANOU K72 100mm to fit to my 7 X 12 Warco lathe. I was in the enviable position of being able to modify it to fit the spindle flange directly. This was to save a little length which is important with such a small machine. The chuck was originally rear mount with a different register, I modified the register and drilled through the body to take through bolts of 6mm which line up with the original flange holes. I will post photos shortly.

Nick Clarke 3:

Thanks for filling in the background. I suppose that you could rough turn at the club and finish off at home.

My sensitivity to jaw projection is due to having a three jaw with one broken tooth (not my doing); I think the four jaw may be more resistant to this kind of problem, however.

I didn't realise that Tich came in the large size!

I have just got the photo's of the modified 100mm chuck.

So far as jaw projection is concerned rough rule of thumb with three jaws seems to be no further than the first inside step so largest size that can be held is chuck body diameter. Many chucks will have marks on the jaws to indicate exactly how far is OK but its not universal even on quality brands.

Four jaw chuck adjusting systems are much stronger that three jaw ones because the half thread on the back of the jaws engages properly with the thread on the adjuster. Three jaw scrolls are inherently much weaker because the contact between scroll and jaw tooth is pretty much line due to the need for clearance between the tooth and the varying radius of the scroll.

Rough rule of thumb with a four jaw seems to be up to about half way out if you are careful. In practice a four jaw properly sized to the lathe will start hitting the bed once it gets much more than one step outside.

Realistically, for chcks correctly sized to the lathe, its officially the same for both types. Maximum diameter to be held is same as chuck body diameter. As ever some wiggle room.

Clive

ARC say that their 80mm 4 jaw independent will fit directly onto the 80mm flange on the SC1, SC2 and SC3 lathes.

The 100mm chuck needs a backplate, 040-060-10100 finished to fit it's 72mm register, and will set you back another £20.28.

FWIW, based on my experiences with Machine Mart, it is a long time since they saw any of my money, and it may even longer before they do again!

Howard

Edited By Howard Lewis on 25/04/2020 16:05:22

Cheers for the responces guys, I haven't had the 3 jaw off yet but it is 80mm. Register, god knows, it is labelled, batch no:19s, I'm guessing that means 2019 summer? I'd rather not machine a back plate, plus to the fact, chuck stick out more= less rigidity. Ill whip it off and measure up. I would much rather a buy. I will have a look in morn. Again thanks for the replies, much appreciated.

Woody.

Oh yeah, I'm not a fan of machine mart too. The staff are always pretty much useless but nice as pie. It was a buy on credit, I should have looked better, I'll end up paying 700 odd bits for the sucker. But hey ho it happens.

With a 80mm chuck the spindle register will be 55mm so you will need the back plate if you go with a 100mm 4 jaw. If you decide to get it from ARC then the chuck is part number 040-040-10600 £48 and the back plate 040-060-10100 £20.28. So a total of £68 and you won't have any machining to do and don't worry about losing rigidity it will be fine.

Also bear in mind that ARC also stock a 80mm 4 jaw for £44 and you wouldn't need the back plate it will be a straight fit. If all you intend to do is make small parts then the 80mm chucks may be fine.

From my experience with a mini lathe I would go with the 100mm 4 jaw chuck and at a later date you may find you need to go up to 100 for the 3 jaw also but that is your decision. Earlier a 125mm 4 jaw was mentioned but I would avoid that on a 300 watt mini lathe.

Ron

Edited By Ron Laden on 26/04/2020 06:25:20

Woody, you have an unread PM.

I think that the Machine Mart mini lathe is made by Sieg, so Arc should be able to supply parts to fit.

Possibly a red herring.

If you feel the need to modify the register on the new 4 Jaw independent, you could try this. No doubt someone will ,object!

It assumes that the tappings for the retaining studs coincide with the holes in the flange on the Mandrel, and that the register needs to be enlarged..

Clamp a piece of bar in the 3 jaw chuck, and take a light skim, to just clean it up (i.e. the OD will, be truly concentric )

Clamp the 4 jaw to the turned bar, with the jaws toward those of the 3 Jaw..

using a DTI, adjust the jaws to set the body so that it runs true, within whatever limit you see fit to accept.

Machine the register to the size that you require yo be a good fit on the flange.

H T H

Howard