when the turning out of the nib is too easy

[Charlie Knighton]

i turned these a couple weeks ago, and they have been festering in the back of my mind as they dried......anyway here is what happened.....somehow I did not turn all of the bark inclusion out of the blank and part of it ended in the sidewall of the form.......somehow I adjusted my hollower the first time to do away with the nib.......that's at first btw.......I then needed to take some more thickness away from the bottom sidewall curve......it went downhill then.......the cuts became unbalanced.......should I have lowered the cutting edge or did the walls become unstable with the inclusion????????????? did not have the problem with other vessels the same size, course I did not get the nib the first time on those

 

[hockenbery]

That's a tough one without being there.
The bark inclusion wil definitely make it warp in and asymmetric way.
It does not appear to be a structural issue but there is often a little vibration at the leading edge of the bark inclusion. I usually tape the outside of the vessel to eliminate or reduce the vibration.

That doesn't help much.
Al

 

[Charlie Knighton]

Yes I did Duck tape the outside, only had problem after doing nib, we will see if dremil will clean it up......One of those gotta ya

 

[Dennis J Gooding]

Charley, I hesitate to display my ignorance like this, but what is the nib you refer to?

 

[Charlie Knighton]

The nib is the center point on the inside bottom of hf, unless you have the hollower exactly center level with that point you will have an uneven bottom, the closer you hollow to the exact center the smaller it will be.......It's no fun to try to sand it away.......

 

[Bill Boehme]

Charlie, wood happens.



I think the main reason that things went south is that you violated the cardinal rule that say to never take that last cut. The wood looks like it wasn't completely dry by the looks of the warping or else there was a lot of internal stresses. I'm sure that you already know this, but if there was any warping before you started to refine the inside shape, always make sure that you have enough wall thickness to also refine the outside as well.

I think it's better to sand away the little nub in the center rather than creating a divot by trying to turn it out.

You could always do some creative sanding near the rim to give the appearance of constant wall thickness.

Another option is to send it to Odie. He seems to have recently acquired the power to make warped bowls heal themselves. 😀

Sorry if this isn't much help. 🙄

 

[Charlie Knighton]

yes that last cut I wish I could take back, the wood had some moisture, and it did warp after turning, most all of mine do from this batch of wood I got last summer, I am not concerned because I hope to embellish the form to a degree that it is not material

 

[Pete Blair]

Its a little off topic but I just about always drill with one of these first to minimized the 'nib' issue.

 

[Dennis J Gooding]

The nib is the center point on the inside bottom of hf, unless you have the hollower exactly center level with that point you will have an uneven bottom, the closer you hollow to the exact center the smaller it will be.......It's no fun to try to sand it away.......

I guess I did not recognize the term because they never bother me. Just a quick wipe or two with a 400-grit sanding disk on an extension if necessary works for me. 🙄😛

 

[hockenbery]

There is a joke about the turner who put a dab of red on the tops of the nibs and sold hollow forms with the slogan a tiny volcano in every form.... 🙂
Think I heard it from Trent Bosch when he was teaching a class.

I drill a pilot hole in hollow forms but always leave about a 1/4" of wood in the bottom to turn away. Just like the comfort of being a little conservative rather than boring too deep and ruining the form.

When using the Jamieson system it is fairly easy to adjust the tool rest to hit bottom dead center. I use a scraper tip on a straight bar. Make on light cut to the bottom center.
With the lathe stoped I score the bottom by sliding the scraper from center to left. Look inside with my tiny led and see where the mark is relative to center and adjust the tool rest height. Rotate the vessel and make a score line to check.
Adjust if necessary. Then turn on the lathe and cut the center to depth.
It is better not to create a nub but if I to once I'm on center find the top and push straight in just a little to cut straight down the center on the nub.

 

[john lucas]

I use a Hunter #5 which I think he now calls the Badger. I cut from outside in using it as a bevel rubbing cut. The bottom is clean as a whistle. You can cut from the center out if you start the cut absolutely dead center. When cutting from the outside in it's easy to get the opposite, a dip in the center. What I do was taught to me by Nick Cook. I usually have the bevel rubbing and cutting with the cutter tilted about 45 degrees or maybe even steeper to get a cleaner cut. When I get to the center I rotate the tool so the "flute" points toward 3 oclock. If the cutting tip is vertical going from 12 to 6 it will simply stop cutting as it crosses the center and won't dig a divot. I know the Hunter tool doesn't have a flute so assume the top depressed area is the flute.