I need to tap a 3/4" BSPT hole in a boss for a project I'm working on. I bought a tap online but tonight when I pulled out my biggest tap wrench I fount its about 2mm too small to take the square on the tap
I need something that will take a 18mm square. Other than buying one new (looks like I'd be up for $100+) I'm going to have to make something up.

Unfortunately I don't have any old 3/4" drive sockets that I could sacrifice otherwise I'd just weld the square from one of those in the middle of a bit of bar and have at it!

Best I could come up with thus far is one of the old style wrenches that are made up of 2 overlapping bars with a vee groove in each bar that when placed together forms the drive square, and the bars get clamped together by a bolt either side of the vees.

Any other suggestions?

Steve


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