Laying out a square

[RedOrZed]

OK, this is simple stuff. Totally back to basic.

I want to build a jig, so I can weld up a square frame. I want it actually square, rather than "well, that's not actually circular, so I'll call it square"...

I can mark up my base line, put in my start point (bottom left), call it {0,0}, measure 1m along, call that {0,1}, and then.... get out my engineers square?

measure 1.41m at a 45deg angle from each point, and 1m at 90deg? That should be about right. But I'm wanting to learn something from this exercise about laying out & marking out - I want to get better. When I come to layout something more complex than a square, I wanna have the tools to do it with accuracy.

So can you clever peeps out there teach an ignorant pup? Or point me in the right direction

Cheers!

 

[rtbcomp]

Could you do it with a 3-4-5 triangle? Cut three lengths of wood, steel whatever, one at 3m, 1 at 4m and 1 at 5m. (or whatever units are convenient) Join them together in a triangle and the angle opposite the longest side will be a right angle.

Cut another 3 & 4 metre lengths to form the opposite sides of a rectangle, using the existing 5m length as the hypotenuse for the 2nd triangle.

Measure along the sides for your square.

 

[Drains]

To get an accurate 90 degree square, don't measure the angle. The thing to do is make a 3/4/5 triangle - one side 3 somethings long, one side 4 somethings long, one side 5 somethings long. This will give you an absolutely accurate right angle triangle.

As for other marking out, The Geometry of Sheet Metalwork gives loads of info, though mostly about developing shapes rather than marking out. Great if you need to make ducting and fancy sheet shapes.

For working out general angles and lengths, a triangle calculator can make life easier, as can a good protractor, and some decent trammels.

Edit, Rog beat me

 

[chunkolini]

A simple trick I was told about and would never thought of is to draw out your 'square', then measure the two diagonals, if they aint equal it aint square.
if they is equal it is square. As in square not squareish.
Simples.
Chunko'.

 

[Hitch]

Corner to corner measurements only work out providing the lengths of the 2 sides are equal, cut one of the 4 bits a few mm shorter, and you can get it measuring right, but it wont be square.

Accuracy is the key to marking out. A few simple tools, big square (you can get sets with 3,6,9,12" squares reasonably cheap. Steel rule, scriber...

 

[katluke]

Easiest and quickest way is to make sure all 4 pieces are the same length then tack them together.Then measure diagonally internal corner to internal corner (use a long staff if possible with a nail sticking through to sit snugly in the corner of the diagonal) then tap corners of frame until both diagonals are the same.Then if you want you can go round and check it using a suitably sized jig/square. Ive always just measured internal corner to internal corner and gone with that. 3 4 5 and internal to internal is the way I was shown at college (Joiner) If there is a lot of frames to be squared up you would just make a jig/square to suit them. hth

ps best way is to get site engineer to mark it out/square it up for you

 

[chunkolini]

Good point Mr Hitch.

Chunko'.

 

[RedOrZed]

Thank you all very much

 

[katluke]

Internal corner to internal corner diagonally covers the full size of the frame,or you need to make a triangle/jig/square appropriate to the size of the frame you are building. Here is a link that explains it better than I can http://weldwithavengeance.com/how-to-square-up-a-frame-or-large-object-for-welding/ hth