I have an issue with a project. I have some 6-32 UNC screws that I need to use. I won't get too far into specifics but this is standardized and I cannot use any other screw. The problem I am having is that I found a specialized nut that I need than only comes in metric. Unfortunately it only comes in M3 and M4, not M3.5 which is a close equivalent to 6-32. Although, after looking into it more, I think the thread pitch between 6-32 UNC and M3.5 is different anyhow. Since M3 is a little smaller, would it be possible to get M3 nuts and use a 6-32 UNC tap on it?
closed as off-topic by isherwood, Daniel Griscom, Tester101 Aug 28 '17 at 14:12
This question appears to be off-topic. The users who voted to close gave this specific reason:
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First, check McMaster-Carr. If anyone will stock a specialty nut, it will be them. (you might also take a swing by Fastenal, but I find them odd to do business with.)
With a tapped hole, the diameter of the hole has a minor and major diameter due to the threads. The major diameter of a hole tapped M3 will be 2.980 millimeters or 0.117 inches, possibly a smidge smaller.
Once you cut a #6-32 thread into a hole, its minor diameter is .114" and its major diameter is .138".
Sounds like it will be fine, assuming your application isn't very high strength. You might want to run the nut through with a drill bit first, such as a #36, .1065", the one recommended for a 6-32 tap.
The tap drill for a m3 is 2.5mm or .0984" the tap for a #6 is .1065" these are fairly close in size but the #6 is larger so there would be some thread depending on the strength needed there may be enough to do the project it would be worth a try since the fasteners are "custom". I would give taping a try to see if there will be enough thread to do the job I don't have any metric taps to measure the depth of the thread for a m3.