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  1. #1
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    Default Safest way to cut trapezoid

    Hello, I have a piece of timber in the shape of a trapezoid, as shown attached ( excuse the poor quality sketch, the base line is supposed to be horizontal).

    It has the top and the base parallel, with the sides sloping down and out from the top. It is about 100mm long, and I wish to remove the sloping sides and end up with a rectangular piece as shown.

    Can anyone please recommend a really safe and accurate way of doing this?
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    regards,

    Dengy

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  3. #2
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    Hot-melt glue it to a piece of oversized waste timber making sure at least one edge is perpendicular to the baseline of your workpiece. Pass that thru your tablesaw.

    Acetone to remove hotmelt residue if needed.
    Arron
    Apologies for unnoticed autocomplete errors.

  4. #3
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    Preview - The Incredible L-Fence - Fine Woodworking Article

    This was in FWW the other day. Basically, make an L shaped fence and clamp it to your tablesaw fence at the same height off the saw table as the piece you are cutting, plus a tiny bit. Align the edge of the fence with the left edge of your blade. Put a peice of wood with a flat edge onto the line you want to cut with some double sided tape or something. Push it through the saw.
    The world is a comedy to those that think, a tragedy to those that feel.

  5. #4
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    or put the long side against the back of a chop saw and cut the wing off, then turn it over and cut the other wing off.

  6. #5
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    Thanks _fly_, how about coming up to the beautiful sunny north out of that cold hole and hold the piece for me while I operate the saw. Will have ambos on standby
    regards,

    Dengy

  7. #6
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    Thanks for these suggestions everyone, but I am still not comfortable with doing any of them. I don't like it where you are relying on some glue or some sticky tape to hold a piece down while you pass it through a sawblade - there are a lot of big forces at work here - scary when you think of what might go wrong.

    Looking for something that will physically hold the piece down while cutting. I have a few to do, so a neat jig would be ideal.

    Can use a bandsaw too.
    regards,

    Dengy

  8. #7
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    Quote Originally Posted by _fly_ View Post
    or put the long side against the back of a chop saw and cut the wing off, then turn it over and cut the other wing off.
    Not a problem. I'd happily hold it, your drawing says its 9cm wide.

    If you want to use the clamp that most have to hold it down, go for it.

  9. #8
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    Quote Originally Posted by _fly_ View Post
    Not a problem. I'd happily hold it, your drawing says its 9cm wide.

    If you want to use the clamp that most have to hold it down, go for it.
    I think it is 9mm rather than 9cm.

  10. #9
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    I'd use a table saw sled and secure the work piece with a toggle clamp.

  11. #10
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    Quote Originally Posted by Dengue View Post
    Thanks for these suggestions everyone, but I am still not comfortable with doing any of them. I don't like it where you are relying on some glue or some sticky tape to hold a piece down while you pass it through a sawblade - there are a lot of big forces at work here - scary when you think of what might go wrong.

    Looking for something that will physically hold the piece down while cutting. I have a few to do, so a neat jig would be ideal.

    Can use a bandsaw too.
    Dengue,

    I'm with you - you have to feel confident & most of all be safe when using machines so it pays to think a bit before jumping in.

    As I understand it this trapezoid piece is similar in size to a pen plank @ roughly 12mm sq x 100 mm long? So the cuts you propose to make are both "rip" cuts?

    Have you seen "toggle clamps"? Very handy items that are far safer than using a C clamp etc that can vibrate loose and potentially fall on to an unguarded blade as in the link shown above. ( Yeah - I know they all say it won't or can't happen - but the reality is it is possible and it does happen!)

    Make yourself a temporary sled similar to the table saw sleds used by segmented turners to hold small pieces or the sleds used to make celtic knot pen blanks. This is one pretty good example Adventures in Turning | Tom's woodturning odyssey or more examples Celtic Knot Jigs - A Penturner's Paradise . The "deli slicer" in my second link is the jig you want - however of course design your jig so that the waste is in the saw cut and the "blank" is held secure under the board. OR use a design that combines the placement of the "toggle clamps" in the celtic knot jig shown to replace the hold down board & star nut in the "deli slicer". Toggle Clamps have amazing clamping hold down force & are available in several styles from Carbatec or McJings etc. OR use a hand plane

    Cheers & like you I like to keep all ten fingers
    Last edited by Mobyturns; 9th August 2014 at 09:09 AM. Reason: added the "OR use" lines

  12. #11
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    Yep, it is only 9mm wide at the top, and just over 12 mm at the bottom
    regards,

    Dengy

  13. #12
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    Many thanks for this mobyturns, I like the concept of the slicer, and it has given me an idea for a simpler one to run in the mitre track on a tablesaw or bandsaw: use a block of timber with same height as the workpiece screwed to the base of the jig, parallel to the line of the sawblade but about 100mm in. Then use a flat piece of timber across the workpiece (set on the sawline) and the identical block with a hold down with a screw knob as shown.

    With some small pieces screwed to the base to accurately position the trapezoidal workpiece each time, this will make the first cut nice and quick and safe to do. The 2nd cut can be done on the same jig with another small positioning piece.

    Hope this makes sense
    regards,

    Dengy

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