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Tiger
9th May 2006, 05:55 PM
Dear all,

For some time I've been thinking about upgrading the chuck on my lathe. I got a chuck "thrown in" with my lathe when I bought it from Hare and Forbes. It's not great but it does the job. What I need is the ability to turn items with a diameter of less than 40 mm without tailstock support. I have tried various other means including jam chucks etc but the slightest catch puts them off - centre so I want to buy a chuck with the ability to add pin jaws. Obviously this will be a major investment, costing me more than the lathe and I realise this. I have spoken to a couple of people who have bought the pin jaws and they have said they hardly use them. My question is are they worth the money? Do they hold the stock securely enough for you to turn unsupported? What length of stock can you get away with before the pin jaws fail ie 200mm or less?

Skew ChiDAMN!!
9th May 2006, 06:10 PM
For some time I've been thinking about upgrading the chuck on my lathe. I got a chuck "thrown in" with my lathe when I bought it from Hare and Forbes. It's not great but it does the job. What I need is the ability to turn items with a diameter of less than 40 mm without tailstock support. I have tried various other means including jam chucks etc but the slightest catch puts them off - centre so I want to buy a chuck with the ability to add pin jaws. Obviously this will be a major investment, costing me more than the lathe and I realise this. I have spoken to a couple of people who have bought the pin jaws and they have said they hardly use them. My question is are they worth the money? Do they hold the stock securely enough for you to turn unsupported? What length of stock can you get away with before the pin jaws fail ie 200mm or less?

Yes! And no. It depends on what you're doing. I believe Teknatools (the SuperNova people ;) ) have 25mm and, I think 35mm jaws available so they may be better suited to what you're doing.

Pin-jaws are primarily for holding small stock that won't fit a spur-drive. As small stock trends to flex, I usually also use a tailstock. eg. turning lace bobbins from 1cm sq. stock. However, they'll hold shortish lengths unsupported alright; I use mine when drilling pen blanks (with a jacob's chuck), for turning finials, etc. and in expansion mode when cleaning up small rings in the 25-50mm range.

I have used them for turning goblets in the 2" dia. range but I hesitate to say that is safe. Then again, I wouldn't say turning goblets in the normal 45mm jaws is safe either... gimme the power-grips or a faceplate every time! I think that in contraction mode they'd give a firmer grip than the 25/35mm jaws, but in expansion the 25/35mm ones would have the upper hand. As a rule of thumb, I'd say they'll hold an unsupported length equal to 4 times the diameter. So, if ya got a 1"dia piece of wood, you can only turn 4" unsupported, not counting the spigot of course. I'm pretty sure they're rated to 6" unsupported, but that's a bit too much for my taste.

Hmmm... from memory, the 35mm spigot jaws will support 8" in contraction and 10" in expansion. They may be the better option for you... I'm pretty sure the 25mm jaws are nowhere ner that. FWIW, all these jaws (for Teknatool chucks) are in the $35-$55 range.

Errrmm... there've been times when I've simply drilled a 25mm hole into a 12" log and used the pin-jaws in expansion mode to turn the bottom for mounting onto 45mm jaws... but this is another practice I won't recommend. :o:rolleyes:

'Nuff info?

Sprog
9th May 2006, 06:32 PM
Are pin jaws worth it?
If you use them, then yes.
If you do not use them, then no.

I use them, so consider them to be worth the cost.

Here is the pin jaw page from the Nova Accessory Jaws Manual.

Tiger
9th May 2006, 06:34 PM
That's what I like about you Skew, your thoroughness, no one line responses from you. Thanks.

Tiger
9th May 2006, 06:41 PM
Sprog, as a matter of interest and this may help me decide whether to go ahead and get the jaws/chuck, what do you use them on?

Ozartisan
9th May 2006, 08:29 PM
Something to keep in mind with pin jaws is that they fix to the chuck with one screw only on each segment (outer rim).
This means you cannot put as much pressure on them in compression mode as you can in expansion mode.
Having said that - I do use mine occasionally and have used in both modes.
My chucks are Nova BTW.

rsser
9th May 2006, 08:53 PM
Yeah, excellent post Skew.

Tiger, an alternative is to hold your stock in what you have, maybe with tailstock support, then when you're done - and having allowed for this at the start - withdraw the tailstock and part off your piece close to the chuck - one hand on the tool and one reaching over and around to catch the turned piece.

You're angling your tool to make a concave base.

It sounds harder than it is.

Lance Stunning
10th May 2006, 03:38 AM
Sorry, I'm a bit dense, but I can't tell if you want to hold something in expansion or contraction. A cheap solution for contraction is a drill chuck. Is a 1/2" tenon strong enough to hold your pieces? If not, here are two inexpensive options for securing small work:
23340 the drawback is it requires a shallow 3/16" recess to open in and minimum dia. is 1-3/8.
Or:
23341 This is a screw chuck, but you will need a thickness for the screw. I've used this with a tenon, turned a thin piece, and parted the tenon. It's available from Lee Valley tools, 16.95 USD. BTW, this comes as a screw chuck and collet chuck, sorry for making it look like (2) different tools. Lance

Tiger
10th May 2006, 11:29 AM
Thanks for the replies so far. The responses pretty much confirm what my initial suspicions about pin jaws which is they aren't used all that much. The major reason for me wanting some is to finish off the the other end of any slender turning object eg candle-stick, spinning top etc. There are other ways of tackling these eg extra length then part-off. Can anyone think of a situation where you would not be able to make something unless you have pin-jaws? That might help some of us decide if they're worth the money.

CameronPotter
10th May 2006, 11:41 AM
I am looking at them for a number of tasks where I can't part-off as the wood length is already set and there is no other way for me to hold the wood. Furthermore, I think that pin chucks might help you hold some things in situations where the piece can be saved (while it couldn't otherwise).

Cam

Skew ChiDAMN!!
10th May 2006, 02:11 PM
Can anyone think of a situation where you would not be able to make something unless you have pin-jaws?

No... but everything can be made without even a chuck! The real question should be, how much easier do pin jaws make things? A: a lot, when you do need 'em. Not at all, when ya don't. Helpful, ain't it? :D

CameronPotter
10th May 2006, 02:29 PM
Yep. OK then, I suppose you can always glue sacrificial bits on etc, but that is a hassle... As you say, easiness is useful.

rsser
10th May 2006, 02:56 PM
Reread your query.

I don't think pin jaws will be all that reliable at a length of 20cm, esp. in expansion mode in a 40mm diam piece. What they might cope with I can't say. I've done a few tooth pick jars with mine no problem but they're only about 50mm long (though hollowing worked OK on these too.).

A more useful set of jaws would be the Vicmarc shark jaws. My 35mm set will contract to c. 35mm diameter and provide a strong grip. You're still stuck with parting off though or a design that may allow you to reverse the piece and clean up the foot.

Sprog
10th May 2006, 03:49 PM
Sprog, as a matter of interest and this may help me decide whether to go ahead and get the jaws/chuck, what do you use them on?
Anything small, toothpick holders, bottle stoppers, lace bobbins, mushrooms, the list goes on.

Bit like a drill really, when you don't have one you don't miss it but once you have one you find all these holes you need to make :D

Cliff Rogers
10th May 2006, 04:02 PM
What Skew says.

Wood worrier
28th May 2006, 02:32 AM
Pin jaws (as supernova chuck type, not the traditional locking pin type) are excellent for starting off natural edge (half log) bowls, simply bore a 1 inch hole on the bark side, mount and away you go. They give a good solid grip, but be sensible with the speed in the early stages of shaping.

rsser
28th May 2006, 08:35 AM
True.

You can use the smaller set of shark/spigot jaws for this too - inserted into a hole drilled by a 2" forstner bit.