laying out a square / triangle

# Thread: laying out a square / triangle

1. WeldingWeb Journeyman
Join Date
Jan 2010
Location
Sv. Filip i Jakov, Croatia
Posts
174

## laying out a square / triangle

I'd like to know what's the procedure to make
a large eg. 600mm long side) square/triangle ?
I'm concerned about making it as square as possible.
I'd like to use the square in woodworking, so am
considering using stainless or aluminium.

Join Date
Mar 2018
Location
East Durham, NY
Posts
255

## Re: laying out a square / triangle

Use the 3 4 5 method to make it square, also for rt angle triangle. Not knowing what you know, do you know the 3 4 5 formula?

3. WeldingWeb Artisan
Join Date
Apr 2010
Posts
2,392

## Re: laying out a square / triangle

vjeko

Here are some pictographs of the Pythagorean Theorem: aka 3-4-5 . . .
For longer runs - any multiple of 3-4-5 works.

Opus

4. WeldingWeb Journeyman
Join Date
Jan 2010
Location
Sv. Filip i Jakov, Croatia
Posts
174

## Re: laying out a square / triangle

OK, thanks, pythagoras theorem is clear, maybe my question was not clear
and my concerns are unfounded (I have concerns because my smaller bought
squares are all out). I was mainly concerned about accurate measurement and
checking before welding - do you just measure as accurately as possible / cut
pieces and use a line perpendicular to an edge as check before welding ?
For the line perpendicular to the edge, I was thinking of using a compass (make one)
and bisecting two tangents.

5. ## Re: laying out a square / triangle

Get it "square" with a square and tack it up. Clamp it tight.Then measure across, corner to corner.
Most problems come from not having the iron the EXACT same length.
8 feet and 8 feet+ 1/64 are miles apart when trying to make a window frame or something

6. ## Re: laying out a square / triangle

Pull an inch.... or a foot. Never trust the hook on a tape.

7. ## Re: laying out a square / triangle

Originally Posted by vjeko
OK, thanks, pythagoras theorem is clear, maybe my question was not clear
and my concerns are unfounded (I have concerns because my smaller bought
squares are all out). I was mainly concerned about accurate measurement and
checking before welding - do you just measure as accurately as possible / cut
pieces and use a line perpendicular to an edge as check before welding ?
For the line perpendicular to the edge, I was thinking of using a compass (make one)
and bisecting two tangents.
Bisecting two radius arcs is a way to find a line perpendicular to another. I have used it often.

I think I would make the triangle from a single piece of stock, what ever you think would work for you. I made some from acrylic and some small ones from thin aluminum.
The check for perfect 90 is to flip the square and have no deviations on the same edge.

Join Date
Mar 2017
Location
Forest Grove OR
Posts
244

## Re: laying out a square / triangle

Without a clamping table/fixture, it will be out of square when you are done welding it anyway. Sometimes you are better off preparing for this by adding a little compensation, or devising methods for re-squaring.

I've used the 345 on vary large layouts, like laying tile in multiple rooms with no square walls where the layout needs to transition into multiple rooms seamlessly. Pick the layout line that has best match of the asymmetry, and then lay a perpendicular that is square to that layout. Any multiple of 3-4-5 works.

I second the advice to pull an inch or foot (not trusting the tape end), it's easier to "see", though harder to hold.

9. Solderer
Join Date
Apr 2018
Location
Norman, ok
Posts
2

## Re: laying out a square / triangle

A method I have used is:
Put the square against it and scribe a perpendicular line
Flip the square along the straight edge (Mirror the inital step)
scribe another perpendicular line from the same point of origin
inspect the scribe marks if they are on top of each other you have a known good square
if not a decision is made whether to bring into square or get another.

This also a good method to determine a known straight edge. Scribe line flip over the scribed line and see if there is a belly.

I have used this method to make fast squares for specific jobs, the largest of which is for building gates and follows the 345 method then checked with the above procedure. It measures 6' x 8' , suitable for 20' gates without using more labor intensive methods as I have in the past.
Hope this helps, and if not clear I can do some photos demonstrating.

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