Swedes have bigger Micrometers.

I recall transferring to a ship that had in line 8 cyl. Cooper-Bessemer diesel engines that had a bosun's chair rigged to lower a man down the bore when needed. A torque wrench was slung overhead with 2 block&tackles. Some 11 feet long, I don't remember the torque range..... Lucky I was an electrician and didn't get involved with it.
 
Most of my working life was as a marine engineer. We used a number of big micrometers, but none quite that big. The largest I recall was on my last ship "Nivosa" ( Shell Australia) A 136,000 t crude oil tanker. The main engine was a Sulzer 8 cylinder in line turbo charged 2 stroke. She burned about 40 t of heavy fuel oil a day. About every 3 - 4 months a piston was removed for measuring, and ring repalcement. At the same time the cylinder bore was measured using an internal micrometer. The nominal dia of a new liner was 760mm, or 29.92 inches about 2 & half feet.. The stroke was 2.2m or about 7 1/4 feet. To measure the liner we would lower an aluminium ladder into the liner one man would climb down using the big mic to measure the liner and calling the numbers up to another to be recoreded. As the bore wore we would fit oversize pistons and rings, then when the liner was eventually replaced we would go back to the standard piston and ring set. A similar outside mic was used to measure the pistons. That was the biggest mic I ever used.
 
40 TPI is 40 TPI, 0.025" per revolution, whatever the diameter, be it a #4 machine screw or something bigger. For my own reasons I have a 3/4" x 40 TPI tap. (and several smaller in that pitch) That would make a hell of a micrometer if I ever had need of one that size. Never used the 3/4" one but it completes the set from my "instrument repair" days.
 
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