Dave Trendymiddlename Starr Posted October 18, 2019 Report Share Posted October 18, 2019 I was making some miter slot runners out of a plastic cutting board today, and I was getting some weirdness in my cuts. Using my calipers to measure the strips of plastic I was cutting, the front of the strip and the back were only off by about 0.05mm in thickness, which I can live with. But for some reason, all the strips get narrower in the middle, by as much as half a millimeter. Which, on miter slot runners, means there's some wiggle to them until both the front and back edges are in the slot, which I'd really like to eliminate. But I'm not sure what would cause a ripped piece to be essentially equal in width at the start and finish, but be narrower in the middle. Any thoughts? Thanks! Quote Link to comment Share on other sites More sharing options...
Ronn W Posted October 18, 2019 Report Share Posted October 18, 2019 Welcome to the forum. I'll start the ball rolling with some questions. Sorry if these seem obvious to you. 1. is your fence straight? 2. Is you blade parallel to the fence? 3. Is the edge of your work piece that is against the fence straight to begin with? I am sure that others will chime in soon. Quote Link to comment Share on other sites More sharing options...
wtnhighlander Posted October 18, 2019 Report Share Posted October 18, 2019 My bet is #3 on Ronn's list. If the factory edge of the cutting board had a curve, it would telegraph through the cut. Attach the plastic to a piece of plywood or other material with a confirmed straight edge, and make the cut with that known straight reference against the fence. Quote Link to comment Share on other sites More sharing options...
Dave Trendymiddlename Starr Posted October 18, 2019 Author Report Share Posted October 18, 2019 Ah, you know, I didn't joint the factory edge of the cutting board first. That's gotta be it. Probably wasn't straight to begin with. Duh. Thanks for the Woodworking 101 reminder! lol palm ---> forehead Quote Link to comment Share on other sites More sharing options...
4square Posted October 18, 2019 Report Share Posted October 18, 2019 Joint one edge before ripping and use a feather board to hold your work firmly against the fence. 1 Quote Link to comment Share on other sites More sharing options...
drzaius Posted October 18, 2019 Report Share Posted October 18, 2019 For a miter slot, .5mm might as well be a centimeter I know if you don't watch for it, it's easy to let the board wander away from the fence a tiny bit in the middle of a cut. I've had this happen before myself. It just requires constant attention and pressure to keep the piece tight to the fence. Of course, as already pointed out, you need to start with a perfectly straight edge Quote Link to comment Share on other sites More sharing options...
Dave H Posted October 18, 2019 Report Share Posted October 18, 2019 Is the plastic sticking to the blade? Is the edge you are cutting getting any melted plastic on the edge and, if so would a faster or slower feed rate get cleaner cuts. I have experienced melted material on the edge of some acrylic glass (Plexiglas ?) anyway I found a faster feed rate eliminated the melting on the edge Quote Link to comment Share on other sites More sharing options...
workswood4food Posted October 20, 2019 Report Share Posted October 20, 2019 Cutting board material works pretty well with a hand plane. You can cut it oversize and nibble it down with a plane. Quote Link to comment Share on other sites More sharing options...
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