SuperNova in Expansion Mode

Since we are on the subject of Nova Chucks...

My darling bride bought me a Super Nova Companion Chuck for Christmas amongst many other goodies.

This new chuck performs poorly in expansion mode - I make pleny of boxes and have the need to use the expansion mode twice for each box - in the manner that I make them - and usually have one of the pieces fly off while in expansion mode.

It seems that the jaws contract on their own while the chuck is spinning. I usually expand the jaws enough to fit snugly, but not crack the work piece, so the thing starts with a firm grip on the piece. Then usually within 1 minute of the start of the machine, the jaws begin making a clicking sound - that is my signal to stop, expand and restart. Sort of like lather rinse repeat! There is no end to this cycle of start stop tighten start. This has tried my patience and made my feet ache!

Any suggestions?

Ray Sandusky

Reply to
Ray Sandusky
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Lucky you :)

I use mine regularly with the normal 50mm jaws to make (smallish) bowls, and put quite a bit of strain on the whole shebang when hollowing without too much bother. I've only really had one major mishap and that was due to overtightening the jaws on a recess inside a foot that was too small leading to the " walls" around the recess splitting open.

I've never had the problem you describe though. How deep are you making the recess? One big no-no is to make the recess too deep and to have the inside of the recess being gripped by the flat shoulder behind the dovetail on the jaws, rather than the dovetail itself. This is certainly going to result in the piece falling off. I had this happen to me last night so it's fresh in my mind :)

Reply to
Alun Saunders

As Alun says, first thing to do is to realize that the dovetail is a wedge grip, not an expanding grip. That means the recess is _never_ deeper than the relieved section you see on the jaws unless you relieve the very bottom to allow room beyond the dovetail. It also means a flat-bottomed recess, because the wedging action will seat the faces against the base of the bowl. To help snug up, I use the tailstock with a blunt bumper end. The angle you undercut can be steeper than the angle of the jaws, but should never be broader (less acute), or it won't grip properly. Another thing that happens is if you sand the bottom, you sometimes have dust under the dovetail, and that will interfere with proper grip.

You already know that the dovetail is superior at giving you a precise recenter. I use it for bottom/top turnings all the time myself. You should check out the pin jaws, though. They're very useful.

Reply to
George

I seem to remember the instructions that came with my Super Nova chuck mentioning a "grub screw" that, when tightened, increases the resistance on the jaws opening and closing. Tightening this "grub screw" might help your problem.

Barry

1 > minute of the start of the machine, the jaws begin making a clicking sound - > that is my signal to stop, expand and restart. Sort of like lather rinse > repeat! There is no end to this cycle of start stop tighten start. This has > tried my patience and made my feet ache! >
Reply to
Barry N. Turner

I believe the newer ones are right turn to compress, come to think. The old ones were left to compress, and would be tightened in the expansion mode by starting inertia.

I've lost the grub screw to one of my standard Novas, and other than easy hand operation, don't notice a difference.

Reply to
George

If a 'grub' screw is the equivalent to a 'set screw' the only one on my Super Nova is used to hold the chuck to the insert. There is also a small screw under jaw #1(?) that is to prevent the jaws from being expanded too far.

Reply to
Kevin

Barry

I will have to see if that Grub screw exists on my model. That may be my issue. It seems that the jaws just release on their own, so maybe this grub screw might provide the resistance needed.

I always make sure there is a square sholder to mount the piece on and also try to incorporate a bit ofa dovetail - but that is sometimes difficult when making boxes as the flanges need to be pretty straight to ensure a good fit.

Ray

Reply to
Ray Sandusky

The only two grub screws on my SuperNova are the one to hold the mount adapter in place, and the one to stop the jaws falling out when you extend the jaws fully, as far as I can see, there isn't one that in any way affects the tightness of the jaws and there's no mention of it in the manual either that I can see.

The dovetail is pretty important. You _can_ get a special tool from Teknatool to create the exact angle, but I usually just use a narrowish parting tool at an angle to cut it with no problems.

Reply to
Alun Saunders

Did I dream up this thing about the "grub screw"? Does it really exist? I could have sworn I had read something about a grub screw in the manual that came with my Super Nova chuck. Could I be I'm thinking about my Compac chuck having a grub screw?

Barry

Reply to
Barry N. Turner

Regular Nova. Maybe a compac.

Reply to
George

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