Wood Movement

[Nicholas Lingg]

Let me take this opportunity to introduce myself and ask a question as well. I'm retired after 34 years in the plastic tooling industry and have been doing wood projects for the last 6 years. They have been mostly "flat board" work (tables chests boxes etc.). I've just recently bought a lathe and have been trying to teach myself to do some turning. So I may be asking questions that have been asked before. So far so good, I actually made something that if you stand far enought away looks like a bowl. I made it from segments of Maple, Walnut, Poplar, Sycamore, and some I don't know woods. Drying times are Walnut at least 20+ years, Maple 10+, all the rest were Kiln dried and have been in my shop for at least 5 years all stored in the same room. My question is this: There is a SMALL mismatch (just enough to catch your fingernail on). What can I do to prevent this? Thanks Nick

 

[MichaelMouse]

More likely from a difference in grain orientation than species response to moisture change. It may interfere with the surface shine, but little else. If it's not finished yet you can certainly sand smooth and seal with shellac inside and out before final finish. Not to say there won't be a touch of difference later on.

 

[odie]

Let me take this opportunity to introduce myself and ask a question as well. I'm retired after 34 years in the plastic tooling industry and have been doing wood projects for the last 6 years. They have been mostly "flat board" work (tables chests boxes etc.). I've just recently bought a lathe and have been trying to teach myself to do some turning. So I may be asking questions that have been asked before. So far so good, I actually made something that if you stand far enought away looks like a bowl. I made it from segments of Maple, Walnut, Poplar, Sycamore, and some I don't know woods. Drying times are Walnut at least 20+ years, Maple 10+, all the rest were Kiln dried and have been in my shop for at least 5 years all stored in the same room. My question is this: There is a SMALL mismatch (just enough to catch your fingernail on). What can I do to prevent this? Thanks Nick

Nicholas.....

I'm having a hard time understanding exactly what you mean.

Do you mean there was a shift of the wood along a lamination after you turned the bowl?

ooc

 

[Richard Baker]

Nick,
Welcome to the forum! Sometimes the moisture in glue will cause a little swelling of the wood at the joint. After the project dries a day or two there may be a slight ridge or mismatch at the joint. As Mouse said, it can be a little worse with cross grain joints. Had one on that egg I just posted. Resanded and refinished. Hope it stays together. Can you show us a picture?

 

[Nicholas Lingg]

Please don't look too closely at the construction of the bowl but the problem is the horizonal joint.

 

[Ed_McDonnell]

I'll let others advise you on the best approach to avoiding / fixing proud joints in segmenting.

I would encourage you to try turning some green wood. As a new turner, you will find it a whole lot easier (and much more enjoyable) than turning dry lumber. Last time I was in NC, there seemed to be plenty of good looking trees. You will still have some wood movement issues (depending on the type of wood), but less troublesome than joint creep (in my opinion anyway).

There are 11 chapters of the AAW in NC. The closest one is about 50 miles away from you. A little far, but maybe worth the drive to meet some other turners and get some hands on help. An hour or two with experienced turners can save you weeks of trying to learn on your own. There may also be some AAW members in your area that might be willing to help you get up the learning curve.

Ed

 

[Richard Baker]

Nick,
Looks like your bowl has a one-piece bottom. Can not tell all the grain direction from the picture, but if the problem is at the joint with the bottom, then Mouse probably ID'd it as a cross grain joint issue. You could re-sand and refinish and hope for the best.

If you do not already have it, consider getting Malcolm's book "The Art of Segmented Woodturning", available from Amazon or from Himself at www.tahoeturner.com. Looking forward to seeing more of your work.

 

[Joe Greiner]

It's hard to see which horizontal joint is the culprit, but uneven clamping pressure during glue-up can produce an uneven glue line. Another suspect could be uneven sanding of the pre-glue surfaces. The final surface can still be filled and re-sanded, as Mouse says.

You've taught yourself pretty well, so far. From here on, take advantage of other teachers. The AAW Home Page has a list of Local Chapters. Members will be eager to help. Also, consult some books on segmented turning, such as by Ray Allen and Malcolm Tibbetts.

Joe

 

[MichaelMouse]

Please don't look too closely at the construction of the bowl but the problem is the horizonal joint.

As in the very bottom? To be expected. The wood contracts and expands within itself, responding to moisture in the atmosphere as indicated in Ch 3 of this fine free publication. http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr113/fplgtr113.htm

When the broader bottom moves 1%, it's a lot more absolute distance than the half inch thick piece above it moving the same 1%.

Lots of people complain about their wet solid wood roughs breaking up because they don't realize this and leave a broad bottom. They would be better off to taper at the outset to take some of the strain off the piece when it's drying.

 

[Joe Greiner]

Type of glue is another "usual suspect." Unless the joint is very thin, most glues should be flexible enough to accommodate some differential shrinkage, if that indeed is the problem.

BTW, what are the dimensions of the piece? If it's really, really miniature, a "solution" might be to trim your fingernails.

Joe

 

[Nicholas Lingg]

Thanks for all the replys. I'm going to give Richard the credit for the solution. If you look at the picture your'll see that it was glued using multiple layers. And after examining the piece more closely not all the joints are raised. Then knowing which one were done last and being in a hurry to get to the lathe I didn't wait long enough on the last glue joints. I also have this tendency of "if a little glue is good a whole lot must be better" Thanks again for all the help I'll just resand and see what happens Nick