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Rough cutting 4x8 ply sheets

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Forum topic by Betsy posted 02-16-2009 08:40 PM 10026 views 0 times favorited 35 replies Add to Favorites Watch
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Betsy

3338 posts in 3362 days


02-16-2009 08:40 PM

Topic tags/keywords: cutting plywood

Less than a year ago I would have “man” handled a sheet of ply onto a infeed and outfeed table and cut away – no problems. Now with my weight lifting limits that’s not possible – well technically it is, but I’d hurt myself trying. Anyway, I’ve had this nice piece of ply laying straight up against the wall for about 2 years or more now and I’ve finally got a project for it.

I’m thinking about the best way I can cut the ply is to lay the ply on the floor and rough cut it down to more managable sizes. Seems to me the safest way would be to lay it onto some old 2×4’s and use a saber saw.

I’d be interested to know how others rough cut their ply.

Also, I’d be interested in hearing opinions on safely cutting on the floor and tips on doing it properly.

Thanks in advance.

-- "Our past judges our present." JFK - 1962; American Heritage Magazine


35 replies so far

View John Gray's profile

John Gray

2370 posts in 3352 days


#1 posted 02-16-2009 08:45 PM

Thanks Betsy I’d also be interested in a better “lighter” way to cut it up that doesn’t cost an arm and a leg.

-- Only the Shadow knows....................

View shack's profile

shack

114 posts in 3542 days


#2 posted 02-16-2009 08:46 PM

I use 2×4s on the floor and a aluminum straight edge and cut mine . If necessary I cut too size on table saw. make sure your saw blade is adjusted properly so you dont cut any thing like your floor.

-- JohnShackleford,North Carolina

View ChicoWoodnut's profile

ChicoWoodnut

904 posts in 3282 days


#3 posted 02-16-2009 08:53 PM

Ditto,

Wouldn’t use a saber saw though. I’d use my skill saw if I had one (and I do)

Get a much nicer cut that way.

-- Scott - Chico California http://chicowoodnut.home.comcast.net

View Douglas Bordner's profile

Douglas Bordner

4012 posts in 3530 days


#4 posted 02-16-2009 08:57 PM

I’m with John and Scott, 7.25” circular saw and a straight-edge offset by the edge to kerf offset of the saw’s base plate (My Milwaukee is offset the exact width of the short leg of a framing square). The difference is I use a 3 inch thick sheet of styrofoam from some box or other under the sheet goods.

-- "Bordnerizing" perfectly good lumber for over a decade.

View ajosephg's profile

ajosephg

1878 posts in 3027 days


#5 posted 02-16-2009 09:03 PM

I like Doug’s way because you don’t have to contend with the sheet sagging on the 2 by supports, wiggly saw horses, or having the off cut get out of control etc, etc.

Also there is virtually no lifting, only lowering it to the floor after which the weight of the individual cut ups are not a factor.

-- Joe

View SteveKorz's profile

SteveKorz

2134 posts in 3180 days


#6 posted 02-16-2009 09:09 PM

I like to lay a 2×6 or 2×8 on the floor underneath the ply where I’m going to make the cut (so my knees can fit on it as I crawl across the sheet when I cut). I put a 2×4 under each end to support the sheet. Then, I clamp an alluminum level to the sheet and make the cut with a circular saw. I would not use a saber or jigsaw. If you use a panel blade, you’ll get a near perfect cut.

If you want to get a really, really nice cut…. after you cut it with the circular saw, clamp the straightedge on to the sheet to match the base on your router, then take the router along it with a nice 3/8 spiral downcut bit. This will create a very nice, straight, smooth cut with no saw marks- and no jointing necessary.

I have an 8’ jig in my shop similar to Hawk's Jointability. I made mine, though… it looks almost identical. I stick the sheet or board in mine and zip a router along the straightedge with a 3/8 spiral bit in it, and you’ll be surprised how well it works.

I made mine for about $50-60 about 4 years ago. $30 was just to have a big metal shop put the metal in a large break to bend it to the shape I desired, there’s no way you could do it without the break.

Good luck.

Steve

-- As iron sharpens iron, so one man sharpens another. (Proverbs 27:17) †

View Kindlingmaker's profile

Kindlingmaker

2656 posts in 2993 days


#7 posted 02-16-2009 09:12 PM

If the interior wall of your shop is not sheathed another possibility is to clamp it to the wall and saw vertically between clamps using your skill saw with minimum blade. The foam is the best idea if you have foam and a place to store it for the next use.

-- Never board, always knotty, lots of growth rings

View dalec's profile

dalec

613 posts in 3355 days


#8 posted 02-16-2009 09:14 PM

Those 4×8 sheets of plywood are heavy. Have someone help you position the plywood and the supporting pieces on the floor, (be sure to support both sides of the plywood), to avoid binding tearing off the waste side if the plywood is not properly supported. Better yet, have them cut it. :)

Dalec

View HokieMojo's profile

HokieMojo

2103 posts in 3195 days


#9 posted 02-16-2009 09:30 PM

one that I’ve heard of is to use a sheet of 1 or 2 inch foam board under the plywood. You can cut right through the plywood into the foam without much flexing of the material (which may happen depending on the thickness of your plywood or straigtness of your 2×4’s). just an idea.

View Dadoo's profile

Dadoo

1789 posts in 3457 days


#10 posted 02-16-2009 09:32 PM

I posted a jig that works very well for me: http://lumberjocks.com/jocks/Dadoo/blog

I also use a 50” Clamp-N-Tool Guide to get near perfect edges with a circular saw. http://www.amazon.com/Tru-Grip-CT50C-50-Inch-Clamp-N-Tool-Guide/dp/B0000224DM The price is around $30.00!

I’ve also seen a homemade “cart” in one of the woodworking mags a few years ago that looked somewhat like half-moon with wheels on the bottom. You used it like a dolly cart to lift your sheet, roll it to your cutting area, and then by rotating the cart to the floor would raise the sheet flat and level to the bench! It was a pretty cool idea but I can’t find it right now. And when you figure that a sheet of 3/4” MDF weighs around 100 lbs. it makes perfect sense to build one. Maybe one of our LJ’s has seen this and can direct us both to the plan?

-- Bob Vila would be so proud of you!

View lew's profile

lew

11347 posts in 3222 days


#11 posted 02-17-2009 12:00 AM

Betsy,

If you have a “Skill Saw”, instead of the expensive “2 x” material, go the Borg and get some Styrofoam insulation panels- 1” thick- or greater- and lay them down on the floor. Lay the plywood flat on top of them. Now you can crawl around on top of the plywood, layout your lines and cut with the saw. No need to worry about where the 2 x’s are located- the saw will easily pass thru the insulation. Just be careful about the saw blade depth of cut.

Lew

-- Lew- Time traveler. Purveyor of the Universe's finest custom rolling pins.

View Brad_Nailor's profile

Brad_Nailor

2539 posts in 3424 days


#12 posted 02-17-2009 12:05 AM

the best way to cut sheet goods down to manageable sizes is with a cutting guide. I made mine out of a piece of hardboard about 2 feet wide and 4 feet long. Rip a straight piece of 3/4 plywood about 3 inches wide and 4 feet long. Fasten the plywood parallel to one of the edges but inset the piece slightly farther than your kerf distance on your circular saw.glue and shoot it in place with some brads. When its dry just cut off the excess hardboard with your saw, butting the saw shoe against the plywood fence. Now the guide is sized exactly for the kerf of the saw. To cut sheet goods just mark where you want it cut on both sides of the board, line up one side of the guide and clamp it fairly tight. Then move to the other side and line that one up and clamp it tight. Then move back to the original side and adjust it so the edge is right on your mark and clamp tightly. Then (with the board properly supported on horses) make your cut with the shoe of the saw against your fence. I made mine two sided…one side is for my circular saw the other is set up for my router with a compression bit. I use the router/compression bit when I want to crosscut veneer ply without tearout.

-- http://www.facebook.com/pages/DSO-Designs/297237806954248

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sIKE

1271 posts in 3220 days


#13 posted 02-17-2009 12:13 AM

I have a grid that rests on saw horses and breaks down when not in use, that is designed to support a sheet of plygoods. Utilizes a circular saw that is set 1/8” thicker than the sheet I am cutting. The problem is that no matter what you do a full sheet of ply is bulky and the thicker sheets get heavier. They have to be wrestled from the vehicle to the saw horses. If you know the largest piece you need you can have the Borg cut it down a bit over size for you there for free, I think the first couple of cuts are free.

-- //FC - Round Rock, TX - "Experience is what you get just after you need it"

View Betsy's profile

Betsy

3338 posts in 3362 days


#14 posted 02-17-2009 02:32 AM

thanks guys – these are all good ideas.

The reason I’m thinking of using a saber saw instead of a circular saw is that I think I can control it a little better. I’m concerned about the reach needed to cut the width of the ply – can’t do it without sliding my knees onto the ply to reach all the way. I would think that I would have to stop a circular saw but a saber saw I could manage a little easier. Although the saber saw has quite a range of movement – that could pose an issue. I’ve also thought about using the circular saw to cut into the board short way – then going into the cut from the end – so that the pieces would be sized as I went—- not sure if I explained that right – but essentially cutting in pieces so I don’t have to reach.

Brad – I actually have a jig like you describe for my circular saw – that I’ve not used in a very long time.

Dadoo – the folding jig is more than impressive.

I’m not sure guys – I may just need to have a friend come over to help me cut the ply – buy him a pizza dinner—- might be safer all the way around.

thanks for the suggestions.

-- "Our past judges our present." JFK - 1962; American Heritage Magazine

View dalec's profile

dalec

613 posts in 3355 days


#15 posted 02-17-2009 02:45 AM

Betsy, It would be easier cutting a pizza than a full sheet of plywood and tastes better.

Dalec

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