Bob, I expect that original Lyman 21 came dear and I, myself, would verify the thread pitch with a thread checker, regardless of what you’re told.
My late father left me his machinist tools, including a Starrett pitch gauge, but my eyesight is no longer good enough to see which blade’s set of sawtooth triangles fit a screw’s thread.
The best thing I ever did for my workbench was to order two sets of male/female thread checkers, one SAE and the other metric, from WOODPECKER. Some of the tools they offer are unduly expensive but their “Thread Detective” sets are reasonable for what they do. I’ve used mine repeatedly and they work. http://www.woodpeck.com. They are also a stock item, not a custom run tool.
I haven’t looked around the Web to see if there are cheaper alternatives but there may well be. EDIT: YES, THERE ARE AND MUCH CHEAPER, BUT NOT SURE QUALITY IS THE SAME. My tendency is to buy brand quality — high precision Proto sockets, not stamped Harbor Freight, unless I need one to take the blade off my lawnmower.
Please let us know how you get on with your installation,
Bill
- Bill
WACA # 65205; life member, NRA; member, TGCA; member, TSRA; amateur preservationist
"I have seen wicked men and fools, a great many of both, and I believe they both get paid in the end, but the fools first." -- David Balfour, narrator and protagonist of the novel, Kidnapped, by Robert Louis Stevenson.
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