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I have a small shop where I work single-handed. I am just starting out on a project that will require a lot of sheet goods to be cut down.
The problem I face is getting true 90 degree cuts when the sheets are too big to square up using the table-saw fence and mitre gauge.
I’m finding that the shop birch I buy almost never has a true corner to it. How do you ol’ wood working hands get it done?
Thanks in advance for any help.
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Hambone,
I have a shop built "panel saw" from plans I got out of a wood working mag. Before that I used a guide clamped to the sheet and the portable circular saw, then cut the largest piece about 1/8" over size, run it and the rest through the table saw at actual. As long as two sides are perfectly parallel, squaring up if necessary, is easily done. Either by using a T-square, rafter square, or by measurement.
When ever possible I use a feather board so the sheet doesn't "cock" when I run it through.
Dano
*I’m no expert with sheet goods, but I’ve had to use it on occasion. I use my power plane to straighten one edge and then use it to square one end. I check the corner with a framing square. I’m more or less a fanatic about having my work square, so I can say without hesitation that it works.
*I forgot one thing, which I have thought of doing, but could not, because until recently I did not own a router with a ½”collet. After getting one edge and end square, you could use a large flush trim bit to square up the other sheets, using the first one as a template. I usually try to give more professional advice, but when it comes to plywood, I’m certainly not well versed, unless your using it for sheathing, then I know far more than I ever wanted to.
*Since I work alone,I have had to devise ways to square ends of sheet goods the easy way.I use the router guided by a straight edge.To check a large piece of sheet stock for squareness it`s hard to beat the check of the diagionals method.If they are the same the corners are square.To check the end of a sheet for accuracy I do this.Measure a diminsion from one end along the long edge and make a tick mark.Using the same diminsion,do the same on the other long edge.Draw a line from one tick to the other.You can now check the diagionals.Make whatever adjustment necesary and make a finish cut on the end,using the straight edge.The longer the diminsion the more accurate the results.I usualy check the diagionals on the sheet plywood to begin with.Most of the time,with cabinet grade material,the results are acceptable.I`m sure that others use different methods.¬¬¬¬¬¬PAT¬¬¬¬¬¬
*Like Rob I am a fanatic when it comes to square...I'm not sure it even makes a noticable difference in the tolerances I try to accomplish (which is absolute squareness) so please understand that I am a bit neurotic. (also note that I have tried several different t-squares, framing squares, tri-squares, etc, etc, they are all in the dumpster)As far as checking the diagonals...it works to a degree, but when your talking about a 32nd or two it's not absolute. You could have, as an extreme example a figure that was 2 ft across at the top, 4 ft across at the bottom( like a piece of pie with the ends cut off), and if it were symetrical, the diagonals would be equal, but there would be no 90° angle to be found.I've tried Major Pat's method and it went something like this:Say I need to cut a 4' x4' square of ply.I measure 48 " down the left & 48 " down the right. one diag. is 68 13/16, the other is a 16th less. So now I know that somewhere the sheet is not square. If I simply move one of the tick marks so that the diagonals are equal, the lengths of the side will be unequal.I think I will have NASA build me some sort of space lazer and start selling "NASA certified True square sheet goods" Now taking orders via the web...PS. FWW to the rescue. FWW #148 pp69-73. Gary Williams' article on shopmade squares just cost NASA a tidy sum. Thank you Gary!Now taking orders....
*I almost never need to square the end of a sheet, because I have devised a method that works for me for 95% of my sheet-good cutting. First I rip the sheet to rough width. Then I cut it to rough length using any of several methods. Then I joint one edge straight and rip the sheet to final width. Last I cut to length using a crosscut sled on the table saw. I have one I use most of the time, for stock less than 25" wide, and another I can use effectively for stock up to 30" wide. For that last 5% of the time when I need to do a final crosscut on ply over 30" wide I use a shopmade circular saw guide and a fine blade on the saw.
*It never occured to me that a new sheet of stock might be pie shaped.Of course in that situation you would be correct. You may want to try the 6-8-10 method. Measure multiples of these numbers.Draw a triangle. 36 on one side, 64 on other side If the third side measures 100,the corner is square(90 deg.)trig. to the rescue.¬¬¬¬¬PAT¬¬¬¬
*how about getting yourself a nice altendorf 10' scoring saw. that would take care of your problem. seriously though, instead of going to all this trouble to square up a piece you should invest a little time and find a trustworthy supplier that has sheet goods with square edges. hell, with the fancy beam and panel saws manufacturers use to cut up sheet goods there is no excuse for an unsquare edge. if i were you i would buy or make a reliable 4' long square, then i would go to my supplier before i bought anything and i would check for squareness. if the panels weren't square then it's the suppliers problem not yours. let them do what they have to to fix the problem. then come back when the problem has been solved, and after your satisfied that it is, load up those sheets and get back to work. hope this helps
*ajIn some of the mills I've visited the cut off saw works production line style & actually cuts the sheets as they pass along a line, so the chances of getting bang on 90* +/- zero is pretty remote. I also find that sheets often arrive with less than perfect edges which is why here sheets are 3/4" larger than their 'specified' sizes & may be cut down to spec by the end user (you & me). Until I did what you suggested in your first line, I set up a square & broke sheets down with a circ saw to manageable sizes & finished them off on either the table saw or planer (= US jointer). I've never regreted buying that saw, (coz apart from cutting sheets it puts a straight edge on solid timber far quicker than I can on the planer), but I do understand economics in a small shop in terms of machinery aquisition & priorities.HamboneIf you have a large number of pieces to cut consider finding a cabinet shop with a slider & contracting the cutting to them. I live in a small town & 2 one person shops do this with me. (I'm not trying to be PC here, one of them is a woman who makes the best damn drawers....but that's another story)Don
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