Breaking down sheet goods - Square

[Greg Peterson]

I am making a bass cabinet for a bass player out of 3/4 BB plywood. The old cabinet is simply not worth the time, money and effort to rehab.

What measuring methods or devices do you guys use to ensure perpendicular angles on your layouts.

The several times I have broken down plywood I have not required a high degree of precision. And every time I have struggled trying to get 90 degree angles dead on. Always slightly out of square.

I have clamp guides for both 4 and 8 foot lengths of sheet goods. It's the layout that is problematic.

[Ken Fitzgerald]

Greg....I use the pathagorean theorem......IIRC.....3,4,5 right triangle......measurements....and a straight edge guide.

[Karl Card]

Good question. I was also looking for a good sensable answer also.

[Reagen Ward]

I do it poorly. I clamp a purpose-built straight-edge to the sheet, get out the speedsquare, measure, measure again, measure with a T-square, maybe get out a drafting t-square, and then cut while chanting 'please be square' over and over. Or, I just use the table saw and ask someone to act as outfeed handler.

I'll be watching this thread, as I'm perilously close to investing in a (much too) expensive track saw system like DeWalt or Festool. I don't want a panel saw, and if I'm going to buy something over $100, I want the saw to ride in a track and have a zero clearance plate.

[Jerome Hanby]

I do it poorly. I clamp a purpose-built straight-edge to the sheet, get out the speedsquare, measure, measure again, measure with a T-square, maybe get out a drafting t-square, and then cut while chanting 'please be square' over and over. Or, I just use the table saw and ask someone to act as outfeed handler.

I'll be watching this thread, as I'm perilously close to investing in a (much too) expensive track saw system like DeWalt or Festool. I don't want a panel saw, and if I'm going to buy something over $100, I want the saw to ride in a track and have a zero clearance plate.

I've got both, and the Festool system is definitely easier to use (and that saw is just sweet), but you can get the same functionality out of the PSI Portable Panel Saw system. It works with your circular saw (most brands, some bases might be problematic) and runs about $150 on Amazon. I use mine with my Hitachi circular saw from Lowe's (it lives in the PPS carriage) and does a good job. I still use it when I have long cuts to make (I haven't broken down and bought the long Festool rail yet).

[harry strasil]

http://www.sawmillcreek.org/showthread.php?122725-Super-Square&highlight=square

[David Hostetler]

I measure, measure, measure, measure... Simply put, I measure, and mark just slightly proud of where I want to be, break it down to rough size, mark the side just cut, and move to the table saw for accurate final dimensioning. with some time, and effort you CAN make accurate cuts with a circ saw and a cutting guide, it just takes a bit of work...

You can make a cutting guide with a T-square style end to keep your cuts square. I believe FWW has a video to show you how...

[Andrew Kertesz]

Similar to the Festool method, you need to have two edges parallel to each other. Don't depend on the factory edge. Using a straight edge make one cut along the length or width depending on your cut diagram for maximum yield. Once you have two edges parallel making the rest of the cuts square should be a walk in the park. Your first cut doesn't have to be perfectly straight according to the size of the plywood. The second cut is what matters making sure it is parallel with the first.

[Matt Meiser]

I just work off one edge and use my Festool saw and rail. To square, I bought a big (12"?) speed square which works great, is repeatable, and strong enough not to flex. I just push that against the back side of the rail and the chosen edge.

[Reagen Ward]

I've got both, and the Festool system is definitely easier to use (and that saw is just sweet), but you can get the same functionality out of the PSI Portable Panel Saw system. It works with your circular saw (most brands, some bases might be problematic) and runs about $150 on Amazon. I use mine with my Hitachi circular saw from Lowe's (it lives in the PPS carriage) and does a good job. I still use it when I have long cuts to make (I haven't broken down and bought the long Festool rail yet).

Awesome suggestion! I wasn't aware of that product, but I do like PSI. Thanks!

[glenn bradley]

I use a shop made guide for the saw to get a reference edge. Then I rip to width and use a sled to cut perpendicular ends. I have an oversize sled for large panels as you may encounter.

[Ray Newman]

For more then a few years, I broke down plywood with a PC Trim Saw. I found -- the hard way -- that the quality of the cut also depended upon the quality of the blade. Sometimes the cuts were not square to the face, ragged edges, out of square, etc.
Remedies:
--Purchased a “dedicated” plywood blade.
-- Applied some stick-on sand paper to the shop fabricated jig to prevent the jig from moving ever so slightly.
-- Screw type clamps held the jig firmly in place.

[Bill Miltner]

Can anyone tell what the difference is between the PSI Portable Panel Saw System (PSS-2) $154 and the one on the Penn state website for $99 (plus $17 shipping)?

[Greg Peterson]

Very clever guide Glenn.

Could you provide some particulars and/or pictures on the cross cut sled? It looks interesting.

[Peter Scoma]

My father was given a square from an old glass shop that is about 5ft on its longest edge and 3 feet on its shortest. Its all boxwood with brass fittings. 100 years later its still very accurate.

PJS

[Jamie Buxton]

I built myself a big speed square. It is about 40" x 40". It has plywood arms, for stability, edgebanded with hardwood. The edgebanding allowed me to joint the arms exactly straight. I assembled the square as close to 90 degrees as I could. Then I tested it, tweaked the edge with hand plane, retested, tweaked, etc. The thing is now 90 degrees plus/minus .01" at the end of the arm. That's something like .01 degrees. It took an afternoon to build the square, but now for years I've been able to trust that I'm cutting an exact 90 degree cut.

[glenn bradley]

Very clever guide Glenn.

Could you provide some particulars and/or pictures on the cross cut sled? It looks interesting.

That one is the first of the sled design that I have used several times since for sleds of different capacities and uses. Let's take a trip in the "way-back" machine :D

http://www.sawmillcreek.org/showthread.php?50581-Sled-Purpose-Specific-1

I (http://www.sawmillcreek.org/showthread.php?50581-Sled-Purpose-Specific-1)mportant features that have survived over the years and make your sled easily renewable:

Adjustable fence
Replaceable fence ZCI
Replaceable bed ZCI

[Greg Peterson]

Thanks Glenn. That ZCI is a great idea. How wide of a panel can you cut with your sled?

[Ben Hatcher]

I added a piece of wood to the short end of my 2' carpenter's square that basically turns it into a large speed square. You can check the angle using the 345 method. If your square is too acute, hit the inside corner with a punch to open it up. I think that I saw an article in either Shop Notes or Wood that expanded on this idea. I have found that my 48" drywall square works pretty well for most case work, too.

[Neil Brooks]

I use a 4' Stabila level to verify a factory edge. If needed, I rip a skosh off of the factory edge, and re-verify.

From that known quantity, I use a tape and mark the same distance from top and bottom of the known straight edge, and then clamp a straight edge onto the sheet, and use my circ saw to make the cut.

Results have been VERY good.

In a few months, though, I'll just whip the panel onto my new SS, with 52" rails, and let 'er fly :)

[Stew Hagerty]

I measure, measure, measure, measure... Simply put, I measure, and mark just slightly proud of where I want to be, break it down to rough size, mark the side just cut, and move to the table saw for accurate final dimensioning.

+1 with David. I lay a piece of foam board on the floor, lay it out as close as I can, clamp on my shop-made saw guide, and cut it to a "rough size". Then I move the piece to the TS to cut it to exact size.

[Peter Aeschliman]

The problem with the table saw is that it won't cut square corners. A table saw with huge rip capacity is really good at cutting two parallel sides using the rip fence, but it can't make a perfectly perpendicular cut.

I have 52" rails on my table saw, but I bought an excalibur sliding table so that I can make the squaring cuts. Without a sliding table, I suppose you could do like one of the previous posters and make a huge cross cut sled... not to put anyone down, but a sheet of plywood on your table saw is already difficult to handle. Adding a big cross cut sled with the capacity to handle a 4' cross cut would make it very difficult without a good infeed table.

So I think the circular saw on rigid foam insulation on the floor with a good square and a good straight edge cutting guide is your best (and safest) bet.

[glenn bradley]

Thanks Glenn. That ZCI is a great idea. How wide of a panel can you cut with your sled?

The one in the thread is a bit over 37" between the fences. My "normal" sized on is a bit over 20" which is too small. I wish I would have gone a bit over 24". Its OK as I have the large one but, I could dig it out less often if my primary sled was about 4" bigger. Just food for thought ;-)

[Neil Brooks]

The problem with the table saw is that it won't cut square corners.

Peter, I swear to G-d I tried, but I can't resist.

It cut one in your forehead, didn't it ?

:)

[Tim Morton]

as someone who builds about a dozen subwoofers a year....and maybe a hundred in my life...just how square do you think you need to be to build a bass cab? 5x5 BB is generally square enough out of the shoot to be able to just throw it up on a table saw and make your cuts. If you are off by a 1/32 then you can use a flush bit router.

[Greg Peterson]

Tim - Yeah, it's just a bass cabinet. But the goal is to find a method that generates a repeatable degree of accuracy regardless the project.

Parallel sides isn't really the problem. Square cross cuts are the real bugaboo.

[Peter Aeschliman]

Peter, I swear to G-d I tried, but I can't resist.

It cut one in your forehead, didn't it ?

:)

HA! Alright you got me there!!! ha ha ha

[Glen Butler]

I have just one crosscut sled that is very large and glides very smooth. I use it to crosscut up to 30" wide all the way down to the smallest of pieces. It's the only thing I need. It can be seen here
http://www.sawmillcreek.org/showthread.php?127651-Show-me-your-micro-adjusters-for-Crosscut-Sled

[Pat Barry]

Am I the only one that works off the factory edges and just assumes they are straight, square, and parallel? I expect that they are better than I can do. I guess I never thought to check. LOL on me.

[Jerome Hanby]

Am I the only one that works off the factory edges and just assumes they are straight, square, and parallel? I expect that they are better than I can do. I guess I never thought to check. LOL on me.

I more or less assume that they are straight, but I don't assume right angles. I generally cut to width based on a factory edge,then make two cuts to get me finished length. Actually to be honest, my first cut is usually right off the truck to make two roughly 4'x4' pieces to ease handling...

[glenn bradley]

Am I the only one that works off the factory edges and just assumes they are straight, square, and parallel? I expect that they are better than I can do. I guess I never thought to check. LOL on me.

Apparently not :D


I more or less assume that they are straight,

They are . . . more or less . . . but not to the degree that I think the OP is looking for ;)

[Alan Bienlein]

204012This is what I use to break sheet goods down on. No skill saw and straight edge. Just throw it up on the saw and cut. Using the slider attachment I can get repeatable square cuts and not have to worry about replacing zero clearance inserts cause if you use the proper blade you will get chip free cuts. I've cross cut up to 42" using this setup and pieces up to 8' long.

[Glen Butler]

Am I the only one that works off the factory edges and just assumes they are straight, square, and parallel? I expect that they are better than I can do. I guess I never thought to check. LOL on me.

Remember they are manufacuring this stuff at incredible rates. I doubt they are concerned with the absolute squareness of the sheets. They can easily be off 1/16 in the 4' direction. I have had some very out of square sheets, up to an inch. They are rare, but they happen. Melamine can have very crappy edges. Chunks of particle can easily hold the piece away from the fence, which will affect squareness in the end. Very minor squareness issues compound when using a line bore for shelf pegs. Also try using factory edges when you have a panel that is 5' long and only 14" wide, in which you had to rip it first to conserve material and now need to run the 14" direction against the fence. DUCK!

[Dan Chouinard]

I found a used delta sliding table attachment for $200 on CL. It took time and a new guide bar ($70) but that was the best $270 I have ever spent. Smooth as silk perfectly square panels are a joy to make.

[Curt Harms]

For more then a few years, I broke down plywood with a PC Trim Saw. I found -- the hard way -- that the quality of the cut also depended upon the quality of the blade. Sometimes the cuts were not square to the face, ragged edges, out of square, etc.
Remedies:
--Purchased a “dedicated” plywood blade.
-- Applied some stick-on sand paper to the shop fabricated jig to prevent the jig from moving ever so slightly.
-- Screw type clamps held the jig firmly in place.

+1 on the P-C 314 trim saw hereafter referred to as my "Norm saw":p. Being a worm drive the long axis of the saw parallels the saw guide and tracks really well, stays right against the fence. I used 1/8" hardboard for the base of the guide and it has worked okay. I wanted to limit the loss of cut depth but if I do it again I'll use 1/4" plywood. The key is the fence material. It HAS to have a perfectly straight edge. If it bows, so will every cut you make. I had some leftover aluminum/honeycomb stuff so glued that to the hardboard with RooGlue clear. If the saw base is 3" edge to blade, set the fence 4" from the edge of the guide base. Run the saw along the glued-on edge and you have a zero clearance edge. I've made two passes on plywood, the first a scoring cut then a through cut. Clean edge and no 'step' that I could see or feel.