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I'm making a worktable using pre-laminated melamine on particleboard, and have just finished 'adjusting' the size for the 3rd or so time.

The tabletop came slightly over 4x8 (and not at all square). I wanted it slightly smaller than 4x8 and tried to cut a strip off the side and end using a SKIL saw with the fence attachment.

The cuts are off by over 1/4"

I know some machining, I'm no stranger to working accurately, but for some reason never can cut large stock like this accurately.

Whats the best way to cut this?

Available Tools:

  • decent quality contractors saw, probably not wide enough for this job, with roller stands and an outfeed table
  • circular saw (SKIL saw) with a fence
  • radial arm saw

I'm just wondering how come my work's so inaccurate all the time (which is probably a big kettle of fish) grrr....

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Measure, mark, place fence, measure again before you cut. E.g. stick your circular saw on the piece like you're about to start, mark the blade position, check with a tape measure before pulling the trigger and adjust fence to correct. Check again after adjusting.

With just a circular saw for cuts like that measure distance from edge of blade (remember, blade is not infinitely thin) to edge of guide, draw a line with a square where you want to cut, move over by the blade-to-guide distance you just measured and draw another line. Clamp a long straight board along that line as a fence and ride the guide up the fence with the circular saw, double checking that the blade edge is at your cut line before you start. If you want, use a framing square to double check that your fence is clamped at 90 degrees before cutting.

Also if you have 48" and want 45, measure 45, don't measure 3 and try to cut it off.

If your stock isn't square trim both sides like this, squaring each off the same edge. Always pick one edge as a reference edge and square the other 3 off that. Use a straightedge to check your reference edge first, if you want, and if it's not straight, trim it straight.

You might find this guide useful. Describes a really simple and useful circular saw guide. Nice thing about that one is it shows you exactly where the blade edge is. If you switch blades to one with a different kerf you might want to make another base (narrower) or run the saw over the guide once after changing (wider) for an accurate edge.

Also if you're using a tape measure start from the 1" mark instead of the floppy metal end and remember to subtract 1 when reading. That's not your 1/4" but it can sometimes be 1/32" or so, esp. for cheaper tape measures.

You could use your table saw if it has enough capacity but I think a circular saw is an easier tool to work with for this kind of stuff.

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    Heard but not tried: rather than lifting the plywood onto a table or sawhorses, if you have a flat floor you can just throw down a thick panel of high-density foam insulation , drop the ply on top of it, and cut that way. Just be sure the blade depth won't go thru the foam and into the floor. – keshlam Nov 26 '15 at 6:16
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    Just me personally... I've never been able to cut well with the little fence that comes with circular saws. +1 for using a long saw guide, as linked. One minor tip, cutting melamine from the underside (ie, flip the whole panel) will lead to a better edge on the top surface. – Aloysius Defenestrate Nov 26 '15 at 13:37
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    The guide also acts as a partial zero-clearance fence (on one side), which also helps reduce chipping. Also, FWIW, I've always considered radial armm saws more dangerous than desirable. Circ saw with guide or chop saw between them handle most tasks better and are more portable, the remainder are better served by even a small table saw. The radial arm saw tries to do a few too many things and ends up not being great at any of them. – keshlam Nov 27 '15 at 16:45
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More of a general comment than an answer: if you are going to use large (4x8) pieces for a project such as the melamine laminate,buy and get the piece cut at Home Depot or a store with a panel cutter, save yourself the hassle of cutting it yourself. If you have to cut it yourself, you have to have a straightedge at least as long as the longest dimension you are cutting, no way around that!

  • This is a really bad option at any home store I've ever been to — their panel saws are often out of square in my experience, the blades used are usually dull and provide a very rough edge, and the employees aren't aiming for any kind of precision. – coreyward Nov 29 '15 at 23:57
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    @coreyward: My experience has been great, my Home Depot always does a great job cutting my panels, I usually tell the guy the dimensions and stand there to be sure he cuts on the marks, the cuts always come out to be within 1/8 of an inch of dead nuts. Maybe you should move to RI ;-) – William Hird Nov 30 '15 at 3:13
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Like Jason said a circular saw and a good straight edge. With a good saw and a good quality blade you should be able to split a pencil line if set up right. However things that can throw it off; a dull or incorrect blade can overheat and warp while cutting. Measure from the front and rear of your blade to the table edge to make sure the saw parts have not been bent out of alignment. Also make sure the saw table stays in contact with the straightedge. (Yeah, like what happens when you happen to be standing on the cord, or it gets caught on something.)

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