Board Length V's Qty x SEL

Discussion in 'Segment PRO Forum' started by Tony Forsyth, Sep 9, 2019.

  1. Tony Forsyth

    Tony Forsyth PRO Member

    Hi All,

    I am getting ready to start cutting my first segments using the summary sheet in Segment Pro and need to question the board lengths. I have the software set to metric (mm) But when I multiply the S.E.L. by the qty of segments (24) the summary board length is shorter than actually required.
    For example the summary shows a board length for row 2 as 728.7 and a S.E.L. of 33.8 with 24 segments required. So 24 x 33.8 = 811.2 which is 82.5 less than what is required. This repeats for all the lower numbered rows but starts to come good the further down the rows I go. :confused:
    Am I missing something.
    Thanks
    Tony
     
  2. Art Bodwell

    Art Bodwell PRO Member

    Tony, when cutting a segment out of a board of a given width, one edge of the board is the edge length, the opposite edge is nothing or close to it. When cutting the next segment, the long segment edge length is on the opposite side of the board. So the total length of two segments is less than multiplying the long segment edge length by the number of total segments. As the board gets narrower, the difference is less, but never equal. If you draw a simple sketch, of a board with a few segments on it, this will become evident. I hope this is clear. If not, let me know.
     
    Tony Forsyth likes this.
  3. Tony Forsyth

    Tony Forsyth PRO Member

    Thanks @Art Bodwell
    As soon as I read your reply the light bulb switched on ;)
    Thanks
    Tony
     
  4. mfisher

    mfisher Super Moderator Staff Member

    Hi Tony:
    The needed board length assumes your are going to economize the board by flipping it for each cut. Refer to the diagram. If you are wanting a grain edge match (that is not flip the board) the needed material would be larger. It looks like that is what you calculated. You would also need to add in the blade kerf width for each cut. The software generally gives a fudge factor of a few inches.

    Woodturner Pro summary gives both the economy board and grain match board length.

    segment cutting.jpg
     
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