Warping and cracking in glued-up pine

      To find clues for cracked and warped pine panels, a measure of moisture content is needed before the splitting occurs. 1998.

by Professor Gene Wengert

I own a small furniture manufacturing plant that specializes in pine bedroom furniture. For the tops of the case goods we use a 2" x 6" #2 com ponderosa pine that nets at 1-1/2" thick. After the panels are glued we plane them to 1-1/4".

Our problem is warping and cracking along the glue lines. We clean up both edges on a table saw with a power feed attached, then rip it down the center to make two 2-1/2" rippings. The speed on the power feed is on the slowest setting and we're using a 10" 40 tooth blade. We are careful to alternate the growth rings and use adequate pressure using our 'Doucette' clamping system. We apply the glue with a small Black Bros. glue spreader.

We are getting frustrated with our hit and miss attempts to solve this problem. We have measured the moisture content on the warped panels and they are no different than the panels that turn out fine.

When you check the MC of a split panel, is the check made AFTER the panel has split? (Recall, you stated "We have measured the moisture content on the warped panels and they are no different than the panels that turn out fine.")

The reason I ask is that a check made after the split occurs will always show the same MC as an unsplit panel--if the panel was initially too wet and then dried out, causing shrinkage, a check made after splitting and warping is a check made after the panel has dried.

What is needed is a check before anything happens. We also must remember that wood doesn't shrink, swell, or warp except for one reason--change in MC, which is related to changes in relative humidity (not temperature).

Also, keep in mind that a glue joint is always stronger than the wood itself--a broken joint means that the two pieces didn't glue well and the #1 cause of a bad glue joint is that the two pieces didn't mate perfectly, which in turn could be that with wetter pieces, especially the freshly ripped edges, there is some drying out, shrinkage, and un-true edges within 30 minutes after sawing.

Several other questions:

How do you know the MC of the incoming wood--If you check it, how do you do it? How is the wood stored--what is the RH? How long after ripping before the wood is glued?

Professor Gene Wengert is Extension Specialist in Wood Processing at the Department of Forestry, University of Wisconsin-Madison.

Click on Wood Doctor Archives to peruse past answers.

If you would like to obtain a copy of "The Wood Doctor's Rx", visit the Wood Education and Resource Center Web site for more information.

Would you like to add information to this article?
Interested in writing or submitting an article?
Have a question about this article?

Have you reviewed the related Knowledge Base areas below?
  • KnowledgeBase: Cabinetmaking: Commercial Cabinetry

  • KnowledgeBase: Cabinetmaking: Custom Cabinet Construction

  • KnowledgeBase: Cabinetmaking: General

  • KnowledgeBase: Furniture: Furniture Manufacturing

  • KnowledgeBase: Solid Wood Machining: General

  • KnowledgeBase: Woodworking Miscellaneous: Woodworking

  • KnowledgeBase: Knowledge Base

    Would you like to add information to this article? ... Click Here

    If you have a question regarding a Knowledge Base article, your best chance at uncovering an answer is to search the entire Knowledge Base for related articles or to post your question at the appropriate WOODWEB Forum. Before posting your message, be sure to
    review our Forum Guidelines.

    Questions entered in the Knowledge Base Article comment form will not generate responses! A list of WOODWEB Forums can be found at WOODWEB's Site Map.

    When you post your question at the Forum, be sure to include references to the Knowledge Base article that inspired your question. The more information you provide with your question, the better your chances are of receiving responses.

    Return to beginning of article.

    Refer a Friend || Read This Important Information || Site Map || Privacy Policy || Site User Agreement

    Letters, questions or comments? E-Mail us and let us know what you think. Be sure to review our Frequently Asked Questions page.

    Contact us to discuss advertising or to report problems with this site.

    To report a problem, send an e-mail to our Webmaster

    Copyright © 1996-2019 - WOODWEB ® Inc.
    All rights reserved. No part of this publication may be reproduced in any manner without permission of the Editor.
    Review WOODWEB's Copyright Policy.

    The editors, writers, and staff at WOODWEB try to promote safe practices. What is safe for one woodworker under certain conditions may not be safe for others in different circumstances. Readers should undertake the use of materials and methods discussed at WOODWEB after considerate evaluation, and at their own risk.

    WOODWEB, Inc.
    335 Bedell Road
    Montrose, PA 18801

    Contact WOODWEB

  • WOODWEB - the leading resource for professional woodworkers

      Home » Knowledge Base » Knowledge Base Article