• It's time to cast your vote in the January 2025 Turning Challenge. (click here for details)
  • Conversations are now Direct Messages (click here for details)
  • Congratulations to Alan Weinberg for "Elm Burl Bowl" being selected as Turning of the Week for January 27, 2025 (click here for details)
  • Welcome new registering member. Your username must be your real First and Last name (for example: John Doe). "Screen names" and "handles" are not allowed and your registration will be deleted if you don't use your real name. Also, do not use all caps nor all lower case.

old oliver lathe is not running true when i remount bowl blank to turn the inside.

C

Charles Moser

Joined
Aug 21, 2017
Messages
1
Likes
0
Location
Berkeley Springs, WV
spindle seems to be running true but every time i remount blank & hollow the i/s it is slightly out of round. can anyone comment on what could be the problem? i usually use the wood screw in the nova II chuck & i always make sure it's very tight against the chuck. the way i checked for spindle runout is fix a steel rod to the tool rest, turn the spindle, & check that there is no measurable play. i'm wondering if the chuck or spindle adapter is slightly off but don't know how to check.

thanks.

chuck
 
How much is “slightly” and what diameter of blank are we talking about?

It’s pretty rare, for me at least, to get a non-noticeable turn-around when doing the initial shaping of bowls. It’s usually an 1/8”-ish on a 12-14” piece and I consider that OK. (A smaller bowl should have less wobble.) I pretty sure the issue is that I am changing chucking methods. A woodworm screw is a vastly different method than an externally gripped tenon. I know it should seem like a tenon turned with care should yield the same concentricity as whatever holding method is used to spin the wood when creating it, but that’s not taking into account different forces when you resecure it.

Tenon chucking can compress fibers of the tenon in non-uniform ways that will result in a wobble, for example. Whenever I use a tenon to create a tenon the wobble is reduced a great deal but is oftentimes still perceptible. I think it all comes down to forces of securing the wood being slightly different each time the wood is mounted.
 
Last edited:
Charles Moser said:
spindle seems to be running true but every time i remount blank & hollow the i/s it is slightly out of round. can anyone comment on what could be the problem? i usually use the wood screw in the nova II chuck & i always make sure it's very tight against the chuck. the way i checked for spindle runout is fix a steel rod to the tool rest, turn the spindle, & check that there is no measurable play. i'm wondering if the chuck or spindle adapter is slightly off but don't know how to check.

thanks.

chuck
Click to expand...
Charles......are you speaking of initial rough turning of a twice turned bowl, using the woodworm screw for doing the exterior, and then using your chuck to grip a tenon for doing the interior?

As Owen mentioned, it's not out of the question to have some amount of runout when remounting the bowl to do the interior.....and, the larger the bowl, the more likely the runout will be noticeable. But......if you are consistently getting some runout on the rechucking, then you very well could have some significant runout on spindle, or chuck, or spindle adapter you mentioned.

The further away from the spindle your work is, the more any runout is exaggerated.......and, using a chuck along with a spindle adapter could be significant......besides the fact that each set of threads you use to get there, adds to the possibility of an error.

If I were you, I'd invest in a dial indicator, and magnetic base. That way, you can get some conclusive answers.

-----odie-----
 
There are so many things that can cause a bowl to not run true it's hard to diagnose when we aren't there. For the most part I don't worry about it unless I plan to turn further details on the side that I've already turned or I'm turning really thin and it would show. Reed mentioned in another post that if you hold a pencil up and barely touch a bowl it will almost never draw a line all the way around. Wood moves, the chuck compresses differently, it may not be seated in the jaws perfectly and probably more than i can think of at the moment.
 
You can often get a bowl to run truer in a chuck with some fiddling.
1. Lossen, turn the bowl, tighten
2. Snug the chuck up tight enough to hold the bowl but loose enough to let the ten shift
On low lathe speed tap the rim - when (if) the bowl runs true stop the lathe tighten the chuck.

Always Check to be sure your tenon profile has a smooth surface that matches the jaw profile of your chuck
A poorly shaped or rough turned tenon will cause a bowl not to run true
Tops of the jaws should seat against the bowl

When I turn natural edge bowls I finish turn the outside after the bowl is in the chuck. I also do some hollowing first in case there is tension movement so I am turning the outside after the wood has moved.
These bowls will generally have a thinner wall and being off a little bit is noticeable.
 
Usually the cause is a tenon that is not done right. I do not like the jaws of my Vicmarc chucks to seat 100 % on the lip, I prefer about 70 % or so. They do have to 100% touch all around, each jaw firmly seated. If I get a slight wobble, like AL says, just move it around, that might fix it, taping it, Bill Jones style, might also help. If nothing helps, it takes less than a minute with some slice cuts to true it up. I can cut left handed, so usually I can do a push cut from the headstock side, giving you a nice finish, a better one after the slice cut. Having some softer sap wood and heart wood might be a reason also, the jaws will compress the sap more...
 
It also depends on the wood hardness as mentioned about crushing fibres etc. I have learned to live with small amounts of run-out as part and parcel of the medium I am using. But then I dont turn eggshell stuff either so its not so important for me
 
You must log in or register to reply here.
Back
Top