Precisely Cutting a 4×8 with a Circular Saw

This is a trick I saw in Family Handyman I think, some years ago and I finally made use of it. This trick lets you precisely cut a 4×8 with a simple circular saw.

Typically when I get 4×8 stock, I can rough cut it down to maybe 4×4 and that is small enough I can do a precise cut on my table saw. Either that or I just need one cut and I get the lumber store to do it.

For this project, I need to cut roughly a foot off the bottom of each pegboard panel, and I wouldn’t know the exact distance in advance – so I couldn’t use my table saw or the lumber store’s saw.

First, you need a 4×8 panel of 2″ insulation. It was kind of spendy at $35, but it is a tool that will last probably quite a while:

Lay your 4×8 on top of the insulation panel and figure out where you need to cut. BTW, you can put your weight on your knees on the insulation and it supports you fine:

Set the saw’s depth to be roughly 1/2″ deeper than the wood being cut:

Figure out the offset from the edge of the circular saw to the line you need to cut. Mark the guide line, then screw a guide into the waste side of the wood. My first attempt was not quite perfect because I only put 2 screws into either side of the guide and the circular saw’s edge tried to slip under the guide. Once I started using 4 screws it worked perfect.

Make the cut, drawing the circular saw along the guide:

Cut the insulation in 1/2 or into 3rds and create a duct tape hinge. then you can store your new tool w/o too much trouble:

I’m glad I remembered this trick and used it. I had to cut 3 panels of pegboard for my furnace room and I didn’t know the size of each until the prior was mounted so I could see exactly where to cut it to get the holes to align on my slightly sloping floor.

Oct 2014 Update:

Today I found a nice edge clamp for a good price at Harbor Freight:

Clamp this into place rather than screw in a 1×2. It may be a while before I need this, but if I find quality is too poor to recommend I’ll update this again.

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