AJL Electronics

Not that I'd have time either way but generally if someone tells me "I don't know the details of how to build something but I've picked the parts that should be used" then I run a mile.

When using a tap, it is important to keep backing it out to clear the swarf as it cuts and a smear of grease will keep the swarf together. There should be no risk of destroying the insert unless you go at it like a Gorilla!

Yes, no. I give advice based on my own personal engineering experience over five decades. It is up to you what you do with it. All examples of these that I have used take an M3 nicely. If you have one which is larger than normal, then tap M3.5...

I have used many of them, an M3 tap is DESIGNED for metal.

A carbon microphone is a variable resistor, so hopefully that will help you to utilise it. Originally it would have a 50V power supply.

Easy enough to put an M3 tap through them.

The Sumotoy library is rather outdated at this point. @KurtE and myself revamped the Sumotoy library for the Teensy and you should try that. The library is included with Teensyduino. It should be compatible with the Sumotoy library but has...

Finally got the display to work. 100r resistors on MOSI, SCLK and CS cleaned up the ringing nicely.