NE Bowl advice needed

[Quinn McCarthy]

I am having trouble making my first NE bowl. I have trashed the fir 2 I tried and am in the process of trashing the third. All 3 have been cherry and about 9" in diameter. The problem I am having is when I turn the bowl around and start turning the inside. I keep breaking the tenon on the base of the bowl. I usually try to glue them pack on and it works for a while but they break again and end up being firewood. The one I tried over the weekend was a cherry burl and have ripped the tenon off that one 4 times. The grain is so pretty I really hate to toss this one as well. All 3 have been in the shop for about 9 months and where sealed with wax on the ends. I have the Bill G DVD and am trying to follow that to a tea but I keep getting to the same point. When I enter I am keeping the angle on the gauge in line with the ways. Usually it break when i get past the interupted part and am heading toward the center. Any advice would be greatly appreciated. Also I increased the size of the tenon from 2" to about 2 3/4" hoping that would help but didn't.

Thanks in Advance!

Quinn

[Christopher Hunter]

I think that you are probably "pushing" in too hard while trying to hollow...
I would use a very light touch going in and around the curve,,,
Some good advise I was given is to let the tool do the work and only hold the tool to move the angle of the bevel....
It actually requires very little force to hog out the inside and unless your tenon is too weak then I would say ---TOO MUCH FORCE
--Hope this helps
--Chris

[Bill Grumbine]

Hi Quinn

There are a lot of variables here so it might be tough to narrow down. It could just be the wood. Are all of the pieces from the same tree? Sometimes trees that have been dead on the stump lost all their structural integrity and will break across the grain just as easily as with it.

It could be the sharpness of your tool, or even something as simple as the shape of it. I have seen hundreds upon hundreds of bowl gouges where people are having trouble with bowl ripping catches. Often it is just a matter of tuning up the grind very slightly to make the tool improve tremendously.

It could be the presentation of the tool, the speed of the lathe, the speed at which you move through the cut, etc. Presentation sort of goes along with what I wrote above, but sometimes I will see turners who are having trouble in towards the center of the bowl because they are trying to cut at the same rate as at the outside. As you get closer to the center, you need to ease up on the speed of the cut, the depth of the cut, or both. The wood is moving slower and slower as you approach the center of the bowl.

It could be the shape of the tenon being off just a little bit.

If you could show us some pictures or give us a little more information, that might help diagnose the problem.

Bill

[Quinn McCarthy]

Thanks for the suggestions Bill and Craig.

Both bowls came out of the same piece of wood. The gauge I am using is a Crowm ellsworth gauge. I went right from sharpening to turning.

Here are some picture as Bill suggested.

Thanks

Quinn

[Quinn McCarthy]

Here are 2 more images.

Thanks

Quinn

[Bill Grumbine]

Thanks for the pictures Quinn. The tenons look like they might be the source of your problem. Looking at them it looks like they might be bottoming out on the chuck jaws rather then registering on the tops of the jaws. Additionally, you need to have a square shoulder on the bottom of the bowl itself where it meets the tenon. I will post a picture tomorrow of some roughouts that are in the shop right now to give you a better idea of what I am saying.

The roughness of the cut in the center of the bowl seems to bear this out. If the bowl is not registered firmly against the sides and tops of the chuck jaws, it can vibrate and flex, causing the cuts to be rough no matter what you try to do to smooth them out.

What kind of chuck are you using? If is it a Oneway or Penn State chuck, the tenon needs to be straight with a square shoulder. If it is a Nova, Vicmarc, or other, those two and others use a dovetailed tenon. They still need a shoulder that is flat for the jaw tops to register.

I'll post more tomorrow when I get back into the shop.

Bill

[Quinn McCarthy]

Bill

I have a Oneway Stronghold chuck. I put one of the bowls into the chuck and there is definately daylight between the jaws and the bowl. Can I just belt sand the bottom to get it to seat against the chuck? It there a way to square the bottom of the bowl at this point? Those tenons are in reral tough shape from being glued together so many times.

Quinn

[Kevin McPeek]

It looks like you should be able to put the bowl back between centers to shorten and square the tennon.

A good investment would be Bills two videos. I have to admit that his first one was one of the, if not the, best bowl turning videos I've seen.

[Quinn McCarthy]

I have both of Bill videos. You are right they are really good.

Quinn

[Bill Grumbine]

Quinn, I was able to get a picture detailing what I wrote earlier on.

http://www.enter.net/~ultradad/butternuttenon.jpg

This is a tenon on a butternut bowl that is roughed and just about ready to finish. It was turned using a Talon chuck, so it needs to be straight. There is a square flat shoulder which meets the tenon, and that gives the bowl a lot more stability. If I were using a Nova or Vicmarc chuck, the tenon would need to be dovetailed in shape, but the flat shoulder still needs to be there. In either case, the tenon should not be long enough to bottom out in the chuck before the shoulder seats against the top of the chuck jaws. Practically speaking, that means the tenon usually ends up being right around 3/8" long. Hopefully this will help solve your problem. If not, let us know and perhaps someone else will add their perspective.


Bill

I have a Oneway Stronghold chuck. I put one of the bowls into the chuck and there is definately daylight between the jaws and the bowl. Can I just belt sand the bottom to get it to seat against the chuck? It there a way to square the bottom of the bowl at this point? Those tenons are in reral tough shape from being glued together so many times.

Quinn

Yes, you should be able to remount the bowl. Put it between centers like you do when starting out, and recut the tenon. I have done that lots of times, including times when I ripped the tenon right off the bowl. Below is an example of a bowl I turned where I sheared the tenon right off while coring. I glued it back on, retrued everything, and sold it (and the core) for a whole bunch of money.

http://www.enter.net/~ultradad/spaltedelmburlvase01.jpg



Bill

[Quinn McCarthy]

Thanks Bill for all of your help!

I see what you mean by a square shoulder now. I am going to give it another try and let you know what happened.

Also that is a very gorgeous bowl. Thanks for the pics.

Quinn