Glue Line Failure with Hickory

      Trouble shooting glue line failures when gluing hickory - 1999

Q. I would like some tips on edge gluing hickory. We us a Taylor clamp carrier with approximately 200 psi of pressure on each clamp. The glue we use at this time is Franklin Titebond 50. We are having problems with glue line failure.

A. There a number of possible factors that could be contributing to your glue line failures. Some things to consider when troubleshooting include temperature, joint preparation, pressure consistency, and moisture content.

During the winter months temperature becomes a major concern when working with PVAs (Polyvinyl Acetates). Most standard PVAs have a minimum use temperature of around 40 degrees F. Some can be as high as 50 degrees F and many cross-linking PVAs have minimum use temperatures closer to 60 degrees F. If the wood you are using is stored outside, it may take a while before it rises to the right temperature. Often, the wood on the inside of a stack will take weeks to reach room temperature after being stored outside. It is important that all components of the gluing process are above the minimum use temperature; this includes the wood, glue, ambient temperature and gluing equipment. If this isn't the case, the result is often an effect called "chalking". A chalked glue line has a white chalky appearance and has no strength. At this time of year you should check this first.

Joint preparation and pressure application are equally important factors. By examining your failed glue lines you can tell much about how well a joint is prepared and how well pressure has been applied. Areas of glue thickness in the glue line indicate poor joint preparation. If there are areas where there is no glue it could be a problem of "wetting". To avoid burnishing be sure your blades are sharp and true whether cutting or planing. Also, it's a good idea to use freshly machined stock (within the last 24 hours). Failure at one end of a board or on one side of a joint indicates inconsistent pressure. This is often a result of the clamps being too tight at one end and not tight enough at the other.

Finally, open joints at the ends of panels can be the result of moisture content problems. Especially in the winter months, if the moisture content of your wood exceeds 8-10% you might have problems after the panel is glued up and stored in a heated room where the moisture content of the air is very low. The panels tend to loose the excess moisture out the ends, which results in shrinkage and failed glue joints.

If, after investigating these points, you are still experiencing problems you should contact your adhesive supplier for more technical assistance or send me samples of the failed parts for evaluation. Samples can be sent to Custom-Pak Adhesives, 11047 Lambs Lane, Newark, Ohio 43055. Be sure to include your company name and a short description of your gluing process and equipment.

Jeff Pitcher is Marketing Director for Custom-Pak Adhesives in Newark, Ohio.

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: Adhesives, Gluing and Laminating: Glues and Bonding Agents

  • KnowledgeBase: Adhesives, Gluing and Laminating: Gluing and Clamping Equipment

  • 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 © 1996-2020 - 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