FDM - March 2009

A:First, for those readers not familiar with your problem, the water-based glue used when edge-gluing the panel staves together causes localized swelling at the joints. If the panels are machined too soon after gluing, the swelling will go down after machining, giving a small depression at each joint. So, by waiting three days after gluing, the swelling will go down before machining and everyone is happy, except for the JIT people.

change, be aware that reactive polyurethanes can be difficult to clean up (especially from hands and skin). The uncured adhesive is also a carcinogen, so care in handling is essential. It is also necessary to provide good venting while the adhesive cures. Also, varying wood moisture content will give varying cure times.

Go to www.fdmonline. com to see a full list of Wood Doctor’s Rx question and answers.

All-in-all, I think you would be so much better off using your present

adhesive and waiting three days. JIT is fine but not at the price of quality, as you already appreciate. I am not sure how to convince the JIT powers that this three-day timing is essential until they factor in quality. ●

I think you would be so
much better off using
your present adhesive
and waiting three days,
JIT shouldn’t sacrifice
quality.

One possible choice for you would be a reactive polyurethane adhesive; there are two types and it would seem that the hot melt would not work well in a clamp carrier operation as you have. The other type is available under a variety of labels; some of the names are “Gorilla Glue”, “Excel”, “PL Premium” or “RPA.” They have 100 percent solids so there wouldn’t be any swelling. They’re also quite strong; nearly as strong as the wood itself, so they will be as strong as many glue joints. The price for these adhesives (commercial level) has come down in the past few years, but they’re still pretty expensive (about $4/lb). But it will solve your problem and they also do not require as high a spread rate, so they do glue more panels per pound than water-based adhesive.

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But before you jump into this

Gene Wengert, “The Wood Doctor,” has been training people in efficient use of wood for the past 35 years. He conducts many short courses and has written hundreds of practical articles and books covering all aspects of converting logs into lumber and lumber into finished products. He is presently an extension specialist emeritus at the University of Wisconsin-Madison. Fax your questions to him at 847.390.7100 or e-mail to wooddoc@uwalumni.com.

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