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Ripping plywood, best straight edge

1205 Views 41 Replies 27 Participants Last post by  allpurpose, 
J
Looking for someone who has a method to rip a 8' sheet of plywood. I used my Empire ripping fence and it bowed in the middle. 1/4" off now. Any recommendation of straight edge that can span 96" without bowing. Bora and Kreg both have options. Finding a straight piece of wood seems to be next to impossible. Recommendations? Clamping on each side of 8' seems like it would tend to bow. Any help would be appreciated. I cannot rip this would on my table saw. unlevel surfaces and no helper. Thank for the recommendation.
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DrRobert
MDF is pretty straight.
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Rebelwork
You need to find a solid wood piece about 8”+ wide that straight. I used a 16’ piece of ash for years at the wood shop till someone decided to cut it up..
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sunnybob
Does the supplier not have a wall saw to cut it for you? might cost, but wasting the sheet by curving cuts is costlier
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M
I bought an 8’ level for that very reason (straight edge ) it’s been a dream for saws and routers. I clamp it down with squeeze clamps. I think I paid about $120 for it at HD . Well worth it imo , store it hanging vertical and you never have any problems with it (they don’t like to be leaned). I gave all my other gimmick straight edges away after using level.


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Jar944_2
Track saw? Not the cheapest option but certainly the fastest or easiest.
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woodnthings
3
I had a spare 10 ft length of barn door track on hand and found the Jorgenson F pony clamps OR Irwin squeeze clamps, fit right inside for clamping to the plywood.
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OK, a little pricey these days, but still pretty straight and way easy to clamp down with nothing in the way to get hung up on!
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B
You can rip you sheet in half. Yes that rip may not be perfect, but you can use the straight edge from one half to continue to make your rip cuts on the other half and then use one of the cut-offs to rip the second half.
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Domo
Angle iron. Spend more if you think you'll distort the 1/16" stock.

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F
As suggested in post #8, the factory edge of a sheet of plywood works pretty good.
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S
Jwhitman said:
Looking for someone who has a method to rip a 8' sheet of plywood. I used my Empire ripping fence and it bowed in the middle. 1/4" off now. Any recommendation of straight edge that can span 96" without bowing. Bora and Kreg both have options. Finding a straight piece of wood seems to be next to impossible. Recommendations? Clamping on each side of 8' seems like it would tend to bow. Any help would be appreciated. I cannot rip this would on my table saw. unlevel surfaces and no helper. Thank for the recommendation.
Click to expand...
I looked at home depots site and the guide you used looks rigid enough. If the blade was sharp on the saw you shouldn't have had to put enough pressure on the guide to bend it. The bottom of the saw and perhaps the guide may also need some wax.
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B
If the sheet was flexed while the cut was made that could give you a slight bow. I used some rigid foam sheets underneath when making these cuts. No bend or flex.
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H
Track saws are great for breaking down large sheets. The expensive ones are awesome, but the cheap ones do fine for this purpose (Kreg, Wen, Evolution).
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carlson.douglas.w
Jwhitman said:
Looking for someone who has a method to rip a 8' sheet of plywood. I used my Empire ripping fence and it bowed in the middle. 1/4" off now. Any recommendation of straight edge that can span 96" without bowing. Bora and Kreg both have options. Finding a straight piece of wood seems to be next to impossible. Recommendations? Clamping on each side of 8' seems like it would tend to bow. Any help would be appreciated. I cannot rip this would on my table saw. unlevel surfaces and no helper. Thank for the recommendation.
Click to expand...
Here's a technique that I have used in the past. Get a 4x8 sheet of foam insulation that is a minimum of 1 in thick. and set it on the floor of the garage. Put your sheet of plywood on top of that. Then use a second sheet of plywood for the straight edge and use a circular saw for the cut. The saw will cut into the insulation, just make sure you set the blade so it doesn't hit the floor of the garage. I find that it makes cutting down a full 4x8 sheet when you're only one person a lot easier.
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bwelty5
Jwhitman said:
Looking for someone who has a method to rip a 8' sheet of plywood. I used my Empire ripping fence and it bowed in the middle. 1/4" off now. Any recommendation of straight edge that can span 96" without bowing. Bora and Kreg both have options. Finding a straight piece of wood seems to be next to impossible. Recommendations? Clamping on each side of 8' seems like it would tend to bow. Any help would be appreciated. I cannot rip this would on my table saw. unlevel surfaces and no helper. Thank for the recommendation.
Click to expand...
use 4 inch rip cutoff as your guide from now on?
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highvoltamps
Jwhitman said:
Looking for someone who has a method to rip a 8' sheet of plywood. I used my Empire ripping fence and it bowed in the middle. 1/4" off now. Any recommendation of straight edge that can span 96" without bowing. Bora and Kreg both have options. Finding a straight piece of wood seems to be next to impossible. Recommendations? Clamping on each side of 8' seems like it would tend to bow. Any help would be appreciated. I cannot rip this would on my table saw. unlevel surfaces and no helper. Thank for the recommendation.
Click to expand...
10' piece of unistrut
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D
Jwhitman said:
Looking for someone who has a method to rip a 8' sheet of plywood. I used my Empire ripping fence and it bowed in the middle. 1/4" off now. Any recommendation of straight edge that can span 96" without bowing. Bora and Kreg both have options. Finding a straight piece of wood seems to be next to impossible. Recommendations? Clamping on each side of 8' seems like it would tend to bow. Any help would be appreciated. I cannot rip this would on my table saw. unlevel surfaces and no helper. Thank for the recommendation.
Click to expand...
The problem you are experiencing has to do with the span between your clamping points. I suggest you make your own saw guide using a piece of 1/8” Hardboard 8” wide and a strip of 3/8” plywood.

It doesn’t have to be 96”; make it 54” long.

1) Take a 54” strip of 3/8” plywood with one straight edge.
2) Rip it 2” wide.
3) Glue the plywood to the top of the hardboard along one edge.
4) Glue 120 grit sandpaper to the bottom of the hardboard.
5) Run the circular saw along the edge of the plywood.

You now have a home made track saw 54” long that will not move when placed on top of a piece of plywood. Also, since it is fully secure along its entire length, you will not get any deflection along its length.
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woodnthings
drinehart said:
It doesn’t have to be 96”; make it 54” long.
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You must be kidding?
How do you rip a full length 96" piece with a 54"piece? DUH?

Everyone? likes to recommend using a rip off a plywood with a factory edge, but you need a piece of plywood to get there from here.
Once you do it you can use it and re-use it anytime.
The best way is shown on You Tube,:
Make two pieces, an narrow and a wide. Using the wider one as a base, nail on the narrow with the factory straight edge as the guide, such that it removes 1/2" to 1" off the wide one. Now you have a "no measure" guide to line up on your marks.

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D
drinehart said:
The problem you are experiencing has to do with the span between your clamping points. I suggest you make your own saw guide using a piece of 1/8” Hardboard 8” wide and a strip of 3/8” plywood.

It doesn’t have to be 96”; make it 54” long.

1) Take a 54” strip of 3/8” plywood with one straight edge.
2) Rip it 2” wide.
3) Glue the plywood to the top of the hardboard along one edge.
4) Glue 120 grit sandpaper to the bottom of the hardboard.
5) Run the circular saw along the edge of the plywood.

You now have a home made track saw 54” long that will not move when placed on top of a piece of plywood. Also, since it is fully secure along its entire length, you will not get any deflection along its length.
Click to expand...
Also use it twice for your 96” sheet of plywood.
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S
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What I use:
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Above shows my homemade saw track with the Empire "Pro's Edge" leaning against it for comparison. The picture below gives a better view of the construction. Made with material at hand, it is only 5 feet long but can be made to any length, obviously.
I use the Pro's Edge for longer cuts and have never had it deflect more than 1/16 in the horizontal plane. What I have had happen (too often) is it deflects in the vertical plane and I end up running the shoe of the saw under it, drifting way off course.

I usually cut panels 1/8-1/4 oversize and do final trim up on the table saw.

Another problem I have had is some of these saws do not have their shoe parallel to the blade. The worst offender was a Ridgid 7-1/4 inch saw that was out 1/8 inch, front to back, relative to the blade.

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