Each of the guage leaves matches a screw thread. You just hold the screw thread to the stencil till you find the one that fits. It's that simple. This one had fiftytwo imperial and metric threads.
The hex bolts seem to have a Whitworth 55 degree thread with 24 threads to the inch and a size of 3/16" which according to Wikipedia gives them a core diameter of 0.1341". I guess when Whitworth developed his threads in the 1840's people really hated round numbers, but they must've liked Whitworth's threads as they eventually became a standard.
I'd ordered a job lot of thread taps and dies from eBay and there was a 3/16" 24 thread tap amongst the rest. According to the chart on Wikipedia I needed a 3.7mm drill to make the hole for this sized screw, just to keep in confusing a 3.7m drill is apparently called Number Drill 26. As luck would have it nowhere I tried sold 3.7mm drill bits. I opted for a 3.5mm bit and figured the thread tap could probably cut out the extra diameter.
A brief look at a WikiHow post told me how to tap a thread. It also left me wondering why I never learnt this sort of basic stuff in metal work at school, I've never felt the need to make a crappy pen holder from a bent piece acrylic but how to cut a thread seems a really useful (and easy) thing to know.
Working in daylight, unlike when I initially cut them, I secured a bracket in my cheap but adequate unbranded chinese made vice and gave it a squirt with Metal Cutting Lubricant. A week ago I didn't know Metal Cutting Lubricant existed, thanks WikiHow. I then drilled a hole using the 3.5mm drill bit. That done I sprayed the bracket with more lube and put the thread cutting tap into a handle. Never used one before but it's basically a handle with a little vice type arrangement in the middle, one of the handle is threaded counter clockwise which is a bit confusing but means you don't loosen a handle whilstcutting the thread.
The tap is tapered at the start so had no trouble getting it into the 3.5mm hole. Basically you just press and twist the tap clockwise with an occassional counter clockwise twist to break off the shavings. The challenge is keeping it vertical at the start. It's surprisingly easy to be honest. at one point I gave it a little more lube but once the tap was a quarter of the way into the bracket the thread was cut so cleanly that with a flick of the handle it was able to rotate freely.
I then tested it with a bolt. Perfect. At the other end of the bracket I cut a hole for the smaller screw to attach the bracket to the pot and using a larger drill bit countersunk the hole. These didn't need a thread as they were for wood screws which were going straight into the pot. I did the same with the other bracket.
A brief look at a WikiHow post told me how to tap a thread. It also left me wondering why I never learnt this sort of basic stuff in metal work at school, I've never felt the need to make a crappy pen holder from a bent piece acrylic but how to cut a thread seems a really useful (and easy) thing to know.
Working in daylight, unlike when I initially cut them, I secured a bracket in my cheap but adequate unbranded chinese made vice and gave it a squirt with Metal Cutting Lubricant. A week ago I didn't know Metal Cutting Lubricant existed, thanks WikiHow. I then drilled a hole using the 3.5mm drill bit. That done I sprayed the bracket with more lube and put the thread cutting tap into a handle. Never used one before but it's basically a handle with a little vice type arrangement in the middle, one of the handle is threaded counter clockwise which is a bit confusing but means you don't loosen a handle whilstcutting the thread.
The tap is tapered at the start so had no trouble getting it into the 3.5mm hole. Basically you just press and twist the tap clockwise with an occassional counter clockwise twist to break off the shavings. The challenge is keeping it vertical at the start. It's surprisingly easy to be honest. at one point I gave it a little more lube but once the tap was a quarter of the way into the bracket the thread was cut so cleanly that with a flick of the handle it was able to rotate freely.
I then tested it with a bolt. Perfect. At the other end of the bracket I cut a hole for the smaller screw to attach the bracket to the pot and using a larger drill bit countersunk the hole. These didn't need a thread as they were for wood screws which were going straight into the pot. I did the same with the other bracket.
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