Welder's Square

A simple but effective tool for welders - a small square with a notch milled out of the corner, so it can be used on angles where a fillet weld would normally interfere with the square. This is handy because welding tends to pull joints out of square as the molten joint cools, so it's not enough to simply check for square before welding a corner - you've got to check after welding and make corrections.

• This general-purpose square can be bought for a couple dollars.
• First, I used a milling machine to cut a 1/2"x1/2" chunk out of the outside corner, so fillet welds wouldn't interfere with getting the square flush into corners. You could just as easily use a bandsaw or a hacksaw, but I wanted a neater result.
• I also cut one edge shorter so I could fit it into tighter spaces.
• Lastly, I used a wire wheel to de-burr the cut edges.

There's not much to it, but it's particularly handy. If you want more precision, you could mill the edges true while it's setup in the milling machine. Or, you could make a similar mod on a machinist's square, though they're about 10x as expensive. For my welding projects, the precision of this square is plenty. I created this one at TechShop.