Shopsmith-Branded Nova G3 Lathe Chuck

[Culprit]

My Shopsmith-branded Nova G3 4 jaw scroll chuck showed up in the mail earlier this week.

I opened it up, installed the spigot jaws according to the directions to true them up, and hit the go-switch. As I watched it go round and round, it didn't look to be spinning true. Next, I chucked up a brad point bit and watched it. There appeared to be a double point on the end of the spinning bit, so I broke out the dial indicator. Here is what I found:

I attached the base of the dial indicator to the way tubes. I rotated the quill through a couple revolutions by hand and recorded the max deflection of the needle, adding the positive and negatives to get the full window.

Bare quill: less than 0.001"

Bare G3 adapter on the quill that the chuck threads onto: 0.0015"

Shaft of a forster bit chucked in the G3 internal jaws: 0.005" - the point of the forster bit appears steady when rotating under power

Shaft of a forster bit chucked in the G3 spigot jaws: 0.016" - the point of the forster bit does not appear steady when rotating under power


I have not been able to find stated or advertised tolerances for the Nova G3 - only advertisements that claim it is a "precision" tool. In my mind, a tool advertised as "precision" and selling for $200 should be better than 16 thousandths of an inch. Did I receive a bad set of spigot jaws, or is this normal?

[beeg]

Try reinstalling the spigot jaws.

[reible]

Hi,

Maybe we ought to say first off that these are woodworking chucks, they are not designed for gripping metal. They are not intended for use as a drilling chuck.

As far as using them for wood turning they should work well for that. I personally have one and am very happy with how it works. I would assume that you read and understood the instructions about the jaw pieces to the chuck keeping the numbers matched, ie 1 to 1, 2 to 2, 3 to 3, and 4 to 4. You also need to be sure they are seating as they are tightened down, if this is unclear please consult the manual that came with your chuck.

Now I have a question for you, when I got my G3 from shopsmith it has nothing to indicate it is anything but a normal Teknatool chuck, it has no rebranding of any sort. So are you saying this has changed?

Ed

[pennview]

There are a few possibilities --
Do the numbers (1,2,3,4) on the jaws match the numbers on the body of the chuck?

There is some slop in the screws that hold the jaws in place. You should bring all of the jaws together before locking down the screws. It may take some trial and error to get the jaws lined up properly.

If neither of these is not the problem, I'd do a dial indicator test of the outside rim of the chuck and see how true that runs. If that's the source of the run out, I'd suspect you have a bad chuck and I'd give Shopsmith a call.

[Culprit]

Thanks for the feedback everyone.

Yes, I know this is a wood-turning chuck. I only chucked up the forster bit because it was a handy piece of round steel of a large enough diameter that the chuck would hold it so I could measure with the dial indicator.

The numbers on the jaws are matched up with the numbers on the chuck.

I re-installed the jaws 4 times, paying attention to the screws seating properly, and following the directions to put equal pressure on each to true things up.

Reible, there is nothing on the chuck to show that it was purchased from Shopsmith. It shipped direct from Teknatool (return address on the package). The only indicator is the packaging - the box says Shopsmith and the barcode sticker says Shopsmith Exclusive Offer (see pics). I guess when I said Shopsmith-branded, I just meant purchased through Shopsmith.com.

The one suggestion I haven't tried yet is to measure the runout of the body of the chuck. I haven't done that yet because nothing indexes off that surface - it could be way out of tolerance or the body of the chuck could even be machined square, and the workpiece could still spin true. That said, I will still take that measurement the next time I'm working in the garage.

Has anyone with a G3 measured the runout of their chuck? Are my numbers close to normal, or are they off?

A few weeks ago someone (Bill Mayo, if I remember correctly) posted about spending time shimming a chuck to get it to run true. Bill, if you're listening, can you shed some light on this and how you did it?

Thanks again for brainstorming with me, and if anyone has measured their chuck, I would love to hear the numbers for comparison before/if I call Nova/Teknatool.

[reible]

Hi,

Thanks for the update.

I will give you one more hint that might help. Even a very small burr can cause things to be off, so use a q-tip on the area where the chuck and jaws meet, with them apart of course. The cotton of the q-tip will find ever a very fine burr.... Old trick that still works 40 years later. You might well want to look inside the jaws as well as a problem there will also show up while testing. Like was a burr on the bit...

The initial numbers you have look like what I remember from some testing I was doing. The jaws you have I've never tested in that way, I have however turned objects being held in them and was happy with the results. I'm not sure at what point one would notice the amount of out of round you are measuring on a work piece.

I could attempt to duplicate what you have set up and give you readings but it would be sometime after the 15th. at the earliest.

Ed

[pennview]

If the body of the chuck is what's causing the problem, you can't fix that on a scroll chuck. Were each jaw adjustable as in an independent four-jaw chuck, you could adjust the jaws independently to correct the problem.

You could also take a reading directly off of the jaws themselves with nothing mounted in them after simply tightened down which would give you some idea where the problem is coming from with respect to each of the jaws.

Unfortunately the instructions with the G3 chuck aren't that informative. If you go to the teknatool web site, you can look at the manuals for the other Nova chucks. I believe the SuperNova chuck talks about a .005 runout maximum. You'll also find better instructions about how to cinch up the screws holding the jaws in place.

If the best I could get out of the chuck is .016 runout, I'd want a replacement. That's really a pretty sloppy chuck, wood chuck or not.

[dusty]

I chucked my 1/2" router chuck into the G3 to take a runout reading. I measured .0018" of runout.

You can decide from that whether your numbers are typical or not.

I was pleased with the reading and in fact pleasantly surprised.

I don't believe you are getting a real good alignment when you tighten down on the forstner. That is why I used the router chuck; it is larger in diameter and the Nova jaws mate with it better.

BTW I did this in the drill press mode if that makes a difference.

[pennview]

I have an older Nova chuck that uses two tommy bars for tightening, not like the newer ones that use a key. I believe mine is one of the originals. With the end of a Shopsmith spindle that I sawed off installed in my Nova and mounted on my Supershop I got .008 run out on this well-used chuck. This is with the standard jaws mounted; I don't have the spigot jaws. I expect I'd get the same results on the Shopsmith because spindle run out is about the same on both machines. In trying to improve on that by fiddling with the four jaws I actually made the run out worse. In the end though, I got it back to where it was and left it there.

When I measured the run out on the outer rim of the chuck I got .003 run out.

[Culprit]

Thanks again everyone. I'll try these suggestions and take some of the suggested measurements this week and let you know what I find.

I think I've heard enough though that I'll be giving Shopsmith a call - or should I call Teknatool directly?