Occasionally we have customers who are bewildered that we use Chicago screws to adjust our Crucible Type 2 Dividers and Sliding Bevel. Why don’t we use a thumbscrew or wing nut or some other device that doesn’t require a screwdriver?
The answer is simple, but not what they want to hear: Because nothing works as well as a slotted screw and a screwdriver.
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During the development of these tools we tried a variety of thumbscrews and other devices to lock the tools in place. Nothing even came close to using a simple Chicago screw and a driver. With a small twist of the screw, you can lock the setting in so it is almost unmovable.
I say “almost” because I tried an experiment where I locked the screw and then threw the tool across the workshop like a baseball. About half the time the tool held its setting. The other half it moved a bit. So, I don’t recommend throwing tools across the shop.
This week I found a few more thumbscrews worth trying in the tools. I am always looking to improve things. The screw thread is a 10-32, and the threaded section needs to be about 3/8” long.
Here are three thumbscrews worth discussing (a few others were total fails).
The Knurled Head Tumbscrew (above), looked promising because it also offered a slot for a screwdriver. Unfortunately, the head has such a low profile that you cannot tighten it by hand enough to lock the blade. You have to use a screwdriver to get a good lock.
The Raised Knurled-head Thumbscrew was easier to grip, but it still didn’t lock the blade. Plus, there was no way to further tighten the thumbscrew with a screwdriver.
Finally, the Hex-head Thumbscrew looked cool. But you can’t grip it with your fingers. The only way to tighten it is with a box wrench (which worked really well).
If you resist our tools because they require a screwdriver, consider this: Many early bevels, marking gauges and mortise gauges were locked with a screwdriver. Plus, when I use these tools (and I use them every day), I get immense satisfaction locking them down all the way. It reduces any anxiety I have about the tool moving by accident.
This anxiety, I might add, was caused by other tools going out of adjustment and ruining a piece of work.
— Christopher Schwarz