Cants pulling away from line bar

      Problems with cants that don't stay properly set up during milling. August 1, 2001

We are having problems with our boards and cants pulling away from the line bar when running them heart-side down and pulling towards the line bar when running sap-side down. The wood pulls away on the in-feed rolls before it is in the machine and in the machine, even with the press rolls down. We can counteract this on the straightedge pieces with the crowd roll, but not on the double live edge pieces. The cants and boards are coming from a 9-foot band saw with a saw running a frost pick to prevent washboard.

The pullout seems to worsen on different species of wood. About a 6 inch pullout on spruce over 20 feet, and only 4 inches on yellow cedar over 20 feet.

We have replaced and aligned all the rolls and bearings on the edger to no avail. Could the frost pick on the 9 foot headrig be causing some sort of fiber tear to cause this pullout?

12 inch 5 saw bull edger,7 inch 3 saw pony edger.

Forum Responses
The first thing to do is to check the thickness of the lumber to make sure that one edge is not thicker than the other--use 0.001" measurement. Measure three spots on each edge.

Next, if you have lumber that is partially quartersawn, you need to change the sawing pattern--use 180 degree rotation from the opening face to the next face. The problem is that there is stress in the tree, so when you edge the lumber, you unbalance the stress. Take a piece that has given you trouble and see if the annual rings are perfectly centered, edge to edge. Also, measure the straightness of a piece, run it through with only one saw in the piece. Then see if the edging strip and the main piece will fit together or if there is a gap. A gap means that you have significant stress in the tree. This test would be best if you were to split an 8" piece into two 4" pieces.

Finally, take a piece that you think will cause problems and cut a skinny strip off of the edge closest to the line bar. Which way does the piece move? Then take the same piece and cut a skinny piece off of the far edge (the opposite edge), away from the line bar. Do you get the same movement both times?

Gene Wengert, forum technical advisor

From the original questioner:
We have done measurements on hundreds of pieces and the variance in sawing from top to bottom from the headrig is very minimal. Maybe .005 inches over 26 inches of width or no real variance at all. Tree quality doesn't appear to be a factor either, as all pieces run away equally. The strangest thing is that the pieces run away from the linebar heart-side down even before they get into the machine. And with sap-side down, they hug the line bar tight from the second you drop it.

To eliminate the lumber surface factors--cup, tension, etc., try running through some pieces that have been planed smooth.

Gene Wengert, forum technical advisor

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: Primary Processing

  • KnowledgeBase: Primary Processing: Sawmilling

  • 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