Protractor Head Square Cleanup

I just picked up an excellent vintage Brown & Sharpe No. 4 combination square protractor head and blade for $20. It was in good shape, just needed some cleaning and surface rust removal. Made in Rhode Island, it’s a high-quality, forged and hardened precision measurement tool. Not sure of the vintage.

These are great for transferring angles, measuring and marking at non-square (or square) angles along the length of the blade, and using the bubble level not just to check square, but determine the exact angle of out-of-square surfaces. The blade can flip to both edges on both sides, giving four different graduation sets.

Here’s a photo essay of my cleanup process.

Protractor head & blade

Bubble level

Maker’s mark

Angle screws

Disassembling the head

Soaking in vinegar overnight

The next morning

Ready for cleaning

Emery paper to remove rust and grime

Cleaning the blade with steel wool

Oiled and ready for reassembly

Back together again

Marking an angle

Clean and ready for years of use

I polished up some parts on a buffing wheel for my bench grinder.

Here’s the basic operation of the protractor head, as demonstrated by my filthy hand.

• combination square
• machinist
• protractor
• tool
• Vintage
• woodshop