Ripping Sheet Material
Wednesday 03 September 2008
This handy ripping guide from Alan Holtham will save you lots of time
This handy ripping guide will save you hours of fiddly setting up with straightedges and clamps. The usual tool for breaking down these sheets is a portable circular saw, but normally the widths you will want to cut will be far wider than the standard rip fence will allow.
If you use a conventional straightedge as a guide you will have to make detailed measurements to allow for the offset of the base, always a potential source of error, for me anyhow! This jig allows you to align the edge guide on the line to be cut without having to allow for the offset, obviously a much quicker and easier option.1 To make the jig find two lengths of thin material slightly longer than the longest piece you anticipate cutting. I used 16mm laminated chipboard, but MDF or even solid timber would be fine as long as it is stable. The narrower piece has to be dead straight as this acts as the saw guide, so take your time to get it right. No other edges are important 2 Arrange the narrower piece on top of the wider one so that the resultant step is just wider than the offset of the saw. The exact amount is unimportant 3 Screw the two pieces together, using plenty of screws for rigidity 4 Now using the top piece as the guide, rip down the lower piece... 5 ...to produce a perfectly straight edge with the step equal in size to the width of the saw offset 6 Clean and wax the rubbing surface of the bottom board to help the saw run smoothly 7 In use, you now only have to measure the exact width you need to cut from the sheet and clamp the straightedge guide in place at either end. Allow a suitable margin for the kerf of the sawblade 8 Increase the depth of cut of the saw so that it just protrudes through the sheet and then run it down the jig to produce a dead straight edge to exact width 9 For safety's sake always ensure that the piece being cut off is adequately supported as it becomes free and be careful not to cut through your trestles!