$2.50 Shop Made Spring-Loaded Straddle Square

Marking 3 sides of a piece of stock is a error-ridden, clumsy, tedious task. Especially if you have a large number of lines to lay out. Commercial straddle squares capable of marking 3 faces without moving the square are expensive. So, I made one at $77.49 off retail.

Materials: One 2 1/2”, 1/4 20 TPI, hex head bolt. One #57 spring. Cost $2.50 Scrap 3/4” stock.

Construction:
1. Make two identical 3”W x 2”H blocks. My stock happened to be .60” thick Honduran Mahogany.
2. Cut out 1” x your stock thickness slots on each side.
3. Center mark the resulting guide tabs. (See photo 4) It’s important that bolt passes above the guide blocks.
4. Drill through Guide Tab A with a 1/4 bit.
5. Slowly drill tap Guide Tab B, 1/4” 20 TPI. B block is the traveler. I used a Greenlee Combination Drill Tap.
6. Cut two identical guide blocks, 1” x 2 1/2”. Glue in place into place on the A block, spring side.
7. Assemble, use a block to hold the straddle square fully open, carefully trim both ends square with a table saw.

Notes: Accommodates stock 1/8” to 1 1/4”. Works very smoothly and accurately. Sand to suit. A brass insert could be used instead of taping. Finished with Watco Oil. This project begs to have some sharp edges relieved with sanding or a 1/8” round over bit. Adding brass strips to inner faces was suggested in the comments!

Question, how I did cut out the tabs: I used a band saw and touched the cuts up by hand sanding. I checked frequently for square in every direction. Every dimension must be square and parallel to ensure the traveler tab does not bind, runs smooth and straight.

Follow up: This project was worth every minute I spent on it. I am amazed how often I use it. I keep it within reach clipped to a side table by my bench.

-- DJ Peck, Lincoln Nebraska. Lord, keep your arm around my shoulder and your hand over my mouth.