How to square a wonky piece of wood?

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Stuart M

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I've probably wasted many hours and many piece of wood trying to make a perfect square (or rectangle) out of a bit of ply or scrap.

I bought this piece of yellow rubbish from Temu for a few quid thinking it would help, but it's pretty worthless, so I'm looking for something similar, but a little more robust.

I've seen a few cheapish right-angle aluminium rulers (attached) which might work for me, but looking for any other recommendations / techniques.

Thanks all

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A square and a gauge are your friends.
Make one edge straight and true - use this as your reference for the rest. From this you can gauge off it to mark a parallel line, and with a square two perpendicular lines.

Cutting accurately to your lines gives you a quadrilateral with square corners.
If you get errors -
-Your gauge line wasn’t parallel - hard to do so unlikely unless you didn’t tighten it down and it drifted.
-Your square isn’t square. Test it off your straight and true edge by marking a line then flipping the square over and marking another line next to the first - and deviation from parallel is a doubling of the error. - get another square or carefully adjust it to be square if you have the skills.
-Your cutting wasn’t accurate - practice helps - as does being able to adjust to the line with plane or sander.

Good check for squareness of the product is to measure the diagonals - if they are even then you’re square
 
What do you want to make the cut with ?
Mitre saw
Table saw
Router
Hand saw and plane ?

The answer differs with the method but a high quality combination square is helpful to most of them.
An aluminium rafter square can also be helpful provided it is a good one with the perpendicular edge milled by machine, not just stamped out. The advantages of the rafter square is it's one piece, robust, no joint to loosen and move. Also that the lipped reference edge is longer than the corresponding edge on a combi square, so any error in pushing the reference edge against your timber isn't magnified upto 3x as it can be on a typical combi with a short cast body and a 300mm rule.
 
Thickness planer first, to get the wide sides parallel. then Jointer with a good fence to joint the edges square.
Or use hand planes and winding sticks for the first face, and check subsequent adjacent face using a square as noted
 
Not quite sure if the OP is asking about dimensioning timber stock so it is square, or if he needs to cut a sheet of board square, The various tools shown would seem to imply the latter.

Marking board for cutting square can be done with a roofing square, as shown in the second photo, but one has to bear in mind, that the inside and outside of these stamped squares are not necessarily true to each other. In other words don't reference an inside to an outside edge, and assume that it will be square. It is often a lot easier to use a plain old T-square to mark your boards.
 
I shall go ahead as if Stuart wants to cut square pieces of ply from bigger pieces of ply, so here goes...This isn't meant to be talking down to anyone, I needed this level of instruction when I made a piped edge velvet cushion for a stool..and two Elastplast..

Stuart, armed with an expanding steel tape, 10ft will do fine, go to a B&Q, Homebase what ever that sells 6mm plywood in pieces smaller than 8 x 4ft.

1. Look for a stack of 4 x 2ft, drag them all out, and start measuring across the diagonals until you find a piece with identical diagonals. ( A willing long suffering? partner will make this easier.)

2. This will be a square piece of ply. Keep hold of it and go to a rack of hardwood profiles/strip wood, and look for square edge rectangular hardwood 25mm x 6mm (ish), straight and unwarped, which is why I suggest hardwood. You'll need about 1.50m. Buy some good PVA glue, I favour Evostick Resin W.

3. When you get home, mark and cut the ply across one diagonal as straight and neatly as you can with a hand saw to form two triangles. (Put a layer of masking tape on the back face to minimise the tear-out.)

4. Now you are going to stick a length of the strip wood along the short edge of both sides of one of the triangles, in effect you are making a giant square so...

5. Pre-glue one side of each piece of strip wood cut to a length a bit longer than the short edge of the triangle and pre-glue one face. Pre-glue a 25mm strip both sides of the short side. This simply means laying on a thin film of PVA leaving a couple of minutes and then wiping off with a lint free cloth and allow to dry. This will allow final construction with less liquid glue, making things less likely to slide about.

6. After spreading a moderate film of glue on one side of each strip, stand the triangle upright on its short side ( A willing long suffering? partner etc... ) on a flat smooth surface and clamp the strips on each side pressing down firmly and evenly along their lengths against the same smooth surface.
A squirt/dribble of superglue at the junction between the pieces will let you relax sooner.
Clamp the ends that you can get at, then add one in the middle once they are holding all safely making sure above all, that the all slices of the wood/ply/wood sandwich are pressed firmly against the smooth flat surface.

7. When dry, unclamp, clean up any extruded glue and add three or four countersunk screws to reinforce the joint. You should have a 4ft long square to draw lines right across sheet materials at 90 degrees to the edge, or a guide against which to run a circular saw.

I do hope this will help.

Doug
 

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