Something is out of round. How can I tell what?

[dirk martin]

I was turning a large bowl today, and had a significant catch.
I was mounted using a tenon, with the tailstock as support, at the time.
It was a large Ash bowl blank....17" diameter, and 7" deep.

After the catch, the bowl began to wobble, so I shut 'er down right away. I figured it may have moved in the chuck. It's a Oneway Stronghold chuck.

For those of you that don't know, this chuck does not screw onto your spindle directly. You need to mount an adapter on the back of the chuck, to get a female thread on the back of the chuck that accepts the diameter of your lathe spindle. My lathe spindle is 1.25", thus I have the 1.25" adapter mounted to the back of my Stronghold.

In any event, regardless of how many times I remounted my blank, after the nasty catch, it still would wobble when I would turn it on. Mater of fact, even when I unmount the blank of wood, it looks like the chuck is wobbling. For the heck of it, I lightly mounted a can of WD40 in the chuck, just to put something I knew was very round, and turned it on slowly, and indeed the can wobbled.

How do I determine what is bent, or out of round?

Seems like it could be either the lathe spindle, that 1.25" threaded adapter, the chuck itself, or maybe the jaws......I don't know.

I do have a dial calipers.
It's a Grizzly G0694 lathe.
I do also have a Jet mini lathe...I guess I should start by mounting that chuck onto the mini late, and see how it spins over there.

[Kyle Iwamoto]

Take your chuck off, and mount your drive spur. bring your tailstock up real close. they should be aligned. If the spur wobbles..... Must have been a nasty catch. I wouldn't think you could break a Stronghold.
Got anouther chuck? You could also try mounting that.

[dirk martin]

So, if the spur wobbles, then it looks like I bent the lathe spindle?
I don't have another chuck that will fit on that 1.25" spindle.

[Fred Perreault]

If the spindle takes a Morse taper, then jam that in and look for eccentricity. A spindle bearing might be displaced, or the Stronghold has an issue, or the adapter has a problem. Use other chucks, adapters, or round spinny things to eliminate this or that problem. There must be someone nearby (??? miles ???) with another lathe to stick your chuck onto for a test ride, or to borrow their chucks.
Good luck, this is no fun :) :)

[John Keeton]

Dirk, this isn't going to resolve your immediate issue. But, with the broken tool rest on the G0698 and the catch here, both on very large bowls, it sounds like you may want to consider your gouge presentation. We all get catches every now and then, but major events like you have had back to back are unusual and compel one to consider the underlying cause. I hope this event did not cause serious damage and that you get up and running again soon!

[Dennis Ford]

You have received some good advise. Once you get it fixed, I suggest that a blank this large should be mounted to a faceplate. Some experienced turners use a chuck on very large pieces, once you get a lot of experience, you might decide to do the same.

[Fred Belknap]

Dick I would suspect the adapter isn't tight in the chuck. There is two screws that fit in the non threaded holes on the chuck to tighten it down. They need to be fairly tight and tightened down together like a quarter turn on each one at a time. The treaded holes in the chuck is for removing the adapter. When I got my stronghold chuck I put the adapter in and after running it a bit I noticed that I had a noise. The adapter had come loose, I probably didn't get it seated correctly when I first put it in. I took it apart and cleaned it good and put it back together and so far it has been fine. Good luck and keep us posted on what you fined.

[Roger Chandler]

Dirk,

I doubt very seriously that you could have bent the spindle........I may be wrong, there is always a first for everything....but in the year I have had my G0698, I have had several major catches. I have also had a wobble of a blank after a catch and it is a lot of re-adjusting, and then there have been 3 or 4 times I could never get the blank in the same place again, even though I had marked the tenon, and the chuck for re-alignment.

In those cases, you just have to get it the best you can, and re-turn it until it is true again........I know, its a bummer, but sometimes it is what is required.

The adapter issue should be checked out completely to eliminate that cause..........but sometimes a tenon will deform a little, sometimes by only a few degrees, and if you continue to use the same tenon, then the wobble has to be turned out and the blank true to that axis that changed with the catch.

Hope this helps.

[David Reed]

I would disassemble the adapter from the chuck and remove from the headstock. Start with a dial indicator on the threaded shaft emerging from the headstock and rotate by hand to determine any runout. Then do the same with the adapter attached to the shaft and finally remount the chuck. Using this procedure, you can determine which is the culprit and repair or replace.

[Leo Van Der Loo]

Mound a large faceplate on that spindle, that should show you if the spindle is bend.
You say "I guess I should start by mounting that chuck onto the mini late, and see how it spins over there.", do you have another insert for you Stronghold Chuck ??, and if so do you exchange these inserts sometimes ??.
I have a Stronghold chuck, have had it for a dozen years and it has spun some VERY large pieces of wood, that chuck hasn't even ever been apart, and it works as good now as the day I got it new, I am quite sure that lathe would brea before that chuck, but do some proper checking, and not with a tin can :rolleyes: before you question the integrity of the lathe or chuck.
Also learning to turn without catches big or small should be considered, at the least for safety sake :)

[Nate Davey]

I had some out of round problems that ended up being a third party insert from Woodcraft. Probably the first place I would start in looking for a culprit.

[dirk martin]

You have received some good advise. Once you get it fixed, I suggest that a blank this large should be mounted to a faceplate. Some experienced turners use a chuck on very large pieces, once you get a lot of experience, you might decide to do the same.

So, Dennis, the steps would be:
Mount to faceplate, and rough the outside, and get bottom flat.
Flip blank over, and remount the bottom of bowl to faceplate.
Gouge out inside of bowl.
Then, deal with those screw holes on the bottom some way....or I guess I could glue a waste block to the bottom before faceplatting the bottom.

Is that your suggestio?

[dirk martin]

Dirk, this isn't going to resolve your immediate issue. But, with the broken tool rest on the G0698 and the catch here, both on very large bowls, it sounds like you may want to consider your gouge presentation. We all get catches every now and then, but major events like you have had back to back are unusual and compel one to consider the underlying cause. I hope this event did not cause serious damage and that you get up and running again soon!

Of course, John. It's obvios that poor tool presentation will instigate catches.

[dirk martin]

Dick I would suspect the adapter isn't tight in the chuck. There is two screws that fit in the non threaded holes on the chuck to tighten it down. They need to be fairly tight and tightened down together like a quarter turn on each one at a time. The treaded holes in the chuck is for removing the adapter. When I got my stronghold chuck I put the adapter in and after running it a bit I noticed that I had a noise. The adapter had come loose, I probably didn't get it seated correctly when I first put it in. I took it apart and cleaned it good and put it back together and so far it has been fine. Good luck and keep us posted on what you fined.

That's exactly how I mounted the adapter, Fred. Since the nasty catch, I have seated it more than once, and it seems to seat well. I'll double check again, tho. Thanks.

[dirk martin]

Dirk,

In those cases, you just have to get it the best you can, and re-turn it until it is true again........I know, its a bummer, but sometimes it is what is required.

The adapter issue should be checked out completely to eliminate that cause..........but sometimes a tenon will deform a little, sometimes by only a few degrees, and if you continue to use the same tenon, then the wobble has to be turned out and the blank true to that axis that changed with the catch.


Roger, if the wobble is from the chuck or the chuck's adapter being bent, or their threads being bent, then it's impossible to turn a round bowl, correct?
I mean, a wobbly chuck can't create a round bowl, am I right?

[Dennis Ford]

So, Dennis, the steps would be:
Mount to faceplate, and rough the outside, and get bottom flat.
Flip blank over, and remount the bottom of bowl to faceplate.
Gouge out inside of bowl.
Then, deal with those screw holes on the bottom some way....or I guess I could glue a waste block to the bottom before faceplatting the bottom.

Is that your suggestio?

That is pretty close. If you start between centers, should only have to mount faceplate once. When turning the bowl make the bottom past the end of screws so that the screw holes can be removed when the bottom is turned. If your blank is not thick enough for this, then you would need a glue block. Once the bowl is turned inside and outside (and sanded), reverse it (I use a friction chuck) to clean up the bottom. I always reverse bowls and clean up the bottom whether turned on a faceplate or a chuck.

[dirk martin]

I would disassemble the adapter from the chuck and remove from the headstock. Start with a dial indicator on the threaded shaft emerging from the headstock and rotate by hand to determine any runout. Then do the same with the adapter attached to the shaft and finally remount the chuck. Using this procedure, you can determine which is the culprit and repair or replace.

Ok, David, I've been thinking about this.
So I put my dial indicator on the part of the lathe spindle, just behind the threads, and my runout was .002. Then, I screwed the adapter to the spindle, and put the dial indicator on the outside of that adapter...and the runout was 20/1000's. But, before I got alarmed, I got to thinking that putting that dial indicator on the outside hub of the adapter doesn't really mean anything. All that tells me is that they didn't machine the outside of the adapter very well. The inside may still be dead on.....so I can't figure out how the dial indicator can really tell me anything.

[Reed Gray]

Serious catches are good for an adrenaline rush, and not much else, unless you figure out why you had the catch. If it was running true before the catch and not afterwards, most likely it is the tenon on the bowl that is out of whack. With a 17 inch bowl, that is a lot of torque on a short lever (tenon maybe 4 or 5 inch diameter), and the wood will deform. This is kind of like when you take some thing out of your chuck, and then remount it, it never runs true. Testing with the can of WD 40 would not be a good indicator because it is a stamped machine product, not some thing that would be very accurate. I doubt that you bent your spindle. Do check chuck jaws to see if they are screwed down tight as well as some times they work themselves loose.

You don't say how much of a wobble there is. If it is 1/8 inch out, then that is + or - 1/16 inch. Pretty close tolerance for a 17 inch bowl when you think about it. Some times if you rotate the bowl 45, 90, or even 180 degrees, it can help.

robo hippy

[dirk martin]

I think I'm confused on our method, Dennis. I too mount to my faceplate only once, but that then requires mounting on a tenon, when flipped. Here's my steps.
1) Look over blank and determine top and bottom.
2) Mount faceplate to bowl top, and true up outside, bottom, and create tenon on bottom.
3) Take off faceplate, mount chuck, flip blank, and mount tenon to chuck.
4) Gouge interior of bowl, and perform final outside shaping and sanding/finishing.
5) Remove from lathe and cut/sand off tenon.

What are the steps that you are proposing that involves mounting to a faceplate only once, and no use of a tenon?

[dirk martin]

Mound a large faceplate on that spindle, that should show you if the spindle is bend.
QUOTE]

Ok, I'll see what that shows.

[QUOTE] do you have another insert for you Stronghold Chuck ??, and if so do you exchange these inserts sometimes ??.


No, I do not.


Also learning to turn without catches big or small should be considered, at the least for safety sake :)
Ummmmm, ok.

[dirk martin]

I had some out of round problems that ended up being a third party insert from Woodcraft. Probably the first place I would start in looking for a culprit.

I'll get a 1" insert, Nate, and then I can test it on my mini late, too. Heck, while I'm at it, I'll take the chuck into Woodcraft with me, and maybe they can fire it up on one of their lathes, and see how it spins.
Thanks for the info.

[dirk martin]

Serious catches are good for an adrenaline rush, and not much else, unless you figure out why you had the catch. If it was running true before the catch and not afterwards, most likely it is the tenon on the bowl that is out of whack. With a 17 inch bowl, that is a lot of torque on a short lever (tenon maybe 4 or 5 inch diameter), and the wood will deform. This is kind of like when you take some thing out of your chuck, and then remount it, it never runs true. Testing with the can of WD 40 would not be a good indicator because it is a stamped machine product, not some thing that would be very accurate. I doubt that you bent your spindle. Do check chuck jaws to see if they are screwed down tight as well as some times they work themselves loose.

You don't say how much of a wobble there is. If it is 1/8 inch out, then that is + or - 1/16 inch. Pretty close tolerance for a 17 inch bowl when you think about it. Some times if you rotate the bowl 45, 90, or even 180 degrees, it can help.

robo hippy

Reed, I'm seeing this wobble I speak of with no wood mounted inside the chuck jaws. I can see that the jaws of the chuck are not turning true....not much, but it is obvious to the naked eye.

[Dennis Ford]

I think I'm confused on our method, Dennis. I too mount to my faceplate only once, but that then requires mounting on a tenon, when flipped. Here's my steps.
1) Look over blank and determine top and bottom.
2) Mount faceplate to bowl top, and true up outside, bottom, and create tenon on bottom.
3) Take off faceplate, mount chuck, flip blank, and mount tenon to chuck.
4) Gouge interior of bowl, and perform final outside shaping and sanding/finishing.
5) Remove from lathe and cut/sand off tenon.
What are the steps that you are proposing that involves mounting to a faceplate only once, and no use of a tenon?

On your step two;
If you have a flat surface on the side that will become the bottom, mount the faceplate to that and leave it there until bowl is done.
If you don't have that flat surface, mount between centers and turn a flat on the side that will be the bottom (will normally have to chisel off a nub where the tail-stock was). Then mount faceplate and turn bowl.

On your step five;
Reverse the bowl using your preferred method and turn away screw holes (or turn away glue block).

There are many ways to get the job done, nothing wrong with your procedure; I just prefer a faceplate for large items.

[Roger Chandler]

Reed, I'm seeing this wobble I speak of with no wood mounted inside the chuck jaws. I can see that the jaws of the chuck are not turning true....not much, but it is obvious to the naked eye.

Dirk,

It is not likely that you bent the spindle, not impossible though......stranger things have happened. I say this because of the belt driven pulley system your G0698 uses. It wouild likely slip on the pulleys, before it bent a spindle.

If your insert somehow got out of whack with the violence of the catch, then it may have done some kind of damage. The point I tried to make in my earlier post, and the one Reed Gray picked up on is that a tenon can at times deform from true round when a severe catch happens, and it would not likely be visible to the naked eye, but off just enough to produce wobble at any position.

What I do with the blank at this point is remount it the best that I can, and then turn it down once again to bring it true to the new axis of the mount on the tenon. sometimes you loose a good bit of prized wood, but it is a way to save a turning for some good purpose.

If you did damage to the chuck insert, or in the highly unlikely event that you bent a spindle, then a repair is in order, and you should exercise your warranty with Grizzly and have them repair your unit. It will mean some down time, but it is a repairable issue with new parts........that being said, I really at this point do not think it is your spindle, but it is indeed a remote possibility.

[dirk martin]

Dirk,

It is not likely that you bent the spindle, not impossible though......stranger things have happened. I say this because of the belt driven pulley system your G0698 uses. It wouild likely slip on the pulleys, before it bent a spindle.

If your insert somehow got out of whack with the violence of the catch, then it may have done some kind of damage. The point I tried to make in my earlier post, and the one Reed Gray picked up on is that a tenon can at times deform from true round when a severe catch happens, and it would not likely be visible to the naked eye, but off just enough to produce wobble at any position.

What I do with the blank at this point is remount it the best that I can, and then turn it down once again to bring it true to the new axis of the mount on the tenon. sometimes you loose a good bit of prized wood, but it is a way to save a turning for some good purpose.

If you did damage to the chuck insert, or in the highly unlikely event that you bent a spindle, then a repair is in order, and you should exercise your warranty with Grizzly and have them repair your unit. It will mean some down time, but it is a repairable issue with new parts........that being said, I really at this point do not think it is your spindle, but it is indeed a remote possibility.

I agree, Roger...
I can't imagine I bent my spindle.
I haven't been back out to my shop to exercise some of the great suggestions from here, but hope to soon.

[Don Alexander]

hmmmm major catches , very large blanks, broken tool rest , maybe i'm in the minority (wouldn't be the first time likely not the last either), but you might want to consider turning a bunch of small/er blanks and get comfortable with the tools before going for the big blanks if nothing else
would be less likely to break something and alot less nerve wracking too after all turning is fun if you let it be :):)

[dirk martin]

Well, when I put the Morse Taper in the spindle, and bring the tail stock up, it is dead on while spinning, so I'm agreeing with the majority that the spindle didn't bend.

I took the Stronghold chuck and it's insert in to Woodcraft, and it seemed to wobble slightly when we mounted it on one of their lathes.
So, they took it back, replaced it with a Super Nova 2 chuck, which also requires an adapter to fit on my 1.25" spindle.
I remounted the new chuck when I got home, and everything seems to be spinning perfectly.

Thanks for tall the help, gang.

I did like the jaws betters on the Stronghold, because they had ridges in them.
I wonder if I can get similar jaws for the Super Nova.....

[Roger Chandler]

I did like the jaws betters on the Stronghold, because they had ridges in them.
I wonder if I can get similar jaws for the Super Nova.....

Dirk, you can indeed get the jaws with the ridges in them for your superNova2. Get the power grip jaws, they are really good. Last week I got my 3rd supernova and I also got separately some 3" jaws with serrations on them. Craft Supplies USA called them spigot jaws I think, but they are not as big as the power grip jaws, but are designed to hold really well.

Glad to hear you got your issues solved! :cool: