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Does this screw centre go inside this set of jaws?

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wcndave

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IMG_20201203_210424__01.jpg


I can't remember where I got this drive centre from, if it came with the sorby Jaws.

If I do mount like this, quite a bit of the screw length is lost.

Does it just go in the chuck without the Jaws, or some other method?

IMG_20201203_211351__01.jpg


IMG_20201203_211402__01.jpg
 

marcros

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I have one and used it with the jaws on I think. I don't use it very often.

Mine came with the vicmarc chuck and standard jaws.
 

wcndave

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I tried with the slot in the Jaws to prevent it coming out, but there was some play in it. Do you put the thick part in the Jaws?
 

Doug B

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If you look at your first photo the bottom of the screw (on the bed bars) locates in the small arc on the inner part of the jaws on mine & holds very positively.
I’m in the shop tomorrow if I remember I’ll take a photo if that helps.
 

NickWelford

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Once gripped in the jaws, you screw the wood tightly up against said jaws to secure it properly. Works well, bus as Robbo says, you may need a plywood disk or similar to shorten it.
 

Yorkieguy

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You remove the jaws, put the worm screw directly into the chuck, drill a hole in the centre of the blank and screw it onto the worm screw. You true up the blank and create either an external or internal dovetail (usually external) to later fit the dovetail jaws back on. While the blanks is still on the worm screw, you then turn, sand and finish the outside of the bowl, leaving the dovetailed foot alone at that stage.

You remove the worm screw, fit the dovetail jaw to the chucks, secure the foot of the bowl to the chuck, hollow out the inside of the bowl, sand and finish it. The last task is to neaten up the dovetail foot, for which you make a 'jam chuck' from MDF, chipboard, ply or whatever is to hand, on which to press the inside rim of the bowl, and bring up the tailstock with a live centre to ensure that the bowl stays in place while you neaten up the dovetail foot. If preferred, masking tape can be used wrapped over the outside of the bowl and jam chuck to secure the bowl in place while the foot is neatened up.

If you want to score any groves in the outside for decoration using a point tool (as I did in the instance), it's best do it before the inside is hollowed out as the bowl will most likely go very slightly oval when hollowed out (only by maybe 1mm or so), in which case if the the grooves are cut at that stage, they will vary from deep to shallow around the perimeter of the bowl. (The bowl was finished with shellac sanding sealer and friction polish).

Occasionally, turners prefer to make an internal dovetail in the base, but caution is needed when turning than bowls as the dovetail of course protrudes into the base. A few pics of a small bowl attached to illustrate the stages. Hope that helps.

David.
 

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wcndave

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Thanks for all the answers chaps. Just to be sure I understand the answers....

Here's a sketch of the chuck with no jaws in, the pink parts are the sliding thingys...
lathe1.png


Then I tried to put the screw in that, like this

lathe2.png


However that didn't feel right

Then i tried in the jaws.
lathe3.png

However there's play and it all rattled around ,as it doesn't meet the jaws and the chuck


If you look at your first photo the bottom of the screw (on the bed bars) locates in the small arc on the inner part of the jaws on mine & holds very positively.
I think you're suggesting this?

lathe 4.png


you can use a wooden disc as a spacer.
Not sure where 😉
 

wcndave

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Hope that helps.
Sorry, you posted this whilst I was posting mine...

So you're method is to use my first idea, no jaws.

lathe1.png
lathe2.png


The space between the check and the workpiece didn't feel quite right here. Maybe this is where the others were referring to a spacer disk?
I can't seat the worm all the way down, as it bottoms out.

BTW: thanks for the great end to end explanation, nice pictures and fantastic end result - my lathe is only up to about 15cm diameter I think, but maybe when I retire in a couple of decades, I'll try things like that. Good job, and thanks again!
 

MichaelB

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Here's a sketch of the chuck with no jaws in, the pink parts are the sliding thingys...
lathe1.png
It looks identical to my Record power screw chuck /SC3 jaws. The instructions say (!) leave the jaws on but ensure the flat part of the screw chuck shaft is gripped by the sliding (pink) bits. So yes the protrusion is reduced. The regular jaws locate in the groove on the screw chuck, which would prevent it coming off if the pink jaws slip (they shouldn't). The work seats against the regular jaws. So once you've turned the spigot/groove, you can reverse it into the jaws which are already in place. (remove screw chuck....!)
 

Yorkieguy

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I've just measured the difference between fitting the worm with the dovetail jaws in place and without. It's actually quite marginal (7mm). With the screw directly into the chuck the length of protruding thread is 23mm, and with the jaws in place is 16mm, which is quite adequate for a small blank. With a bowl blank above 20cms diameter and I'd be thinking about mounting the blank of a faceplate rather than a worm screw. (The groove in the screw fits into the jaws if it's preferred to have the jaws in place with the blank on the lathe).
 

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Dalboy

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The screw fits on the chuck with the jaws in place the slote around the thickest part is where the jaw inner plates fits into it. When fitting bring the jaws in to the slot and then rotate the screw and you will feel it settle into place then tighten the jaws fully. I have the Robert Sorby chuck and that screw comes with it. I can take a photo later if you want.
From your photos you seem to have got it correct
 

Doug B

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Dave your 4th picture in post #9 is how I’ve always used it without problems, as I said previously just make sure the blank is tight up to the jaws.
 

gregmcateer

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I agree with Doug- I think you've got the nova screw there. It can be a little fiddly to get spot on, but it does protrude enough with the jaws in place.
As said above, large blanks want to be on a faceplate or a faceplate ring that is gripped in the jaws. (Search on axminster site you see several examples).
I'll try to get a photo of my chuck screw, if it comes out clear enough
 

wcndave

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ok, so it sounds like the answer is that some put it in the chuck without jaws, and some with.

I felt there was wobble with the pic3 in post 9, and some say try pic4 in post 9.... I will try again for 3, as that seems the most secure. Maybe I just didn't have it quite rotated enough that the flat spots allowed it to close properly.

Thanks all!
 

Richard_C

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I use screw in the various ways described above, normally with Jaws on ready for the next stage. I bring up the tailstock to start with, at least until any out of balance is sorted and usually keep it in place for as long as I can. That way the screw isn't handling any big lateral load without assistance.
 

Dalboy

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The idea of the groove around the screw is so that the inside of the jaws locates in there and prevents it from being forced/pulled out of the chuck it is a safety thing
 

Robbo3

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ok, so it sounds like the answer is that some put it in the chuck without jaws, and some with.
I've not used one for years but you definitely use it with the jaws attached to the carriers - the pink bits in your drawing.
I would say drawing 3 is nearest to being correct but you locate the jaws in the slot, screw on your wood so that the rear of the slot moves forward to touch the rear of the jaw. Tighten the jaws fully onto the screw & check that the wood is sitting on the front face of the jaws. It is this contact with the front face of the jaws that prevents wobble.
If the screw is too long for your work piece, a disc of wood with a centre hole to go over the screw can be placed between the front jaw faces & the work to act as a spacer.
 

Dalboy

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Just to clarify here are some photos of the correct installation of the screw chuck in the Robert Sorby chuck.

It is fitted with the jaws in place and the flats on the screw chuck are rotated so the flats line up with the carriers and stop the screw chuck from rotating and the jaws prevent the screw chuck from being pulled out.

You can see from the second picture how it sits. As can be seen it is the Robert Sorby chuck and the screw thread is also the one supplied with the chuck from new
chuck jaws 2.jpgchuck jaws.jpg
 

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