Bolt Identification

I have a Shapeoko 3 XXL, a few years old (S/N 2248, if that helps). I was installing the pwncnc dust boot and I ran into an issue with the bolts that attach it to the z-axis, at the top. The longer bolts provided with the dust boot are M5x0.5, but they don’t fit. So, I set about figuring out what the existing bolt is. Weirdly enough, it’s not metric at all. None of the metric thread checkers matched at all. But, SAE 24 tpi did fit:

Why on earth is there an SAE bolt on my otherwise entirely metric machine? Is it supposed to be like this? Here is where the bolt came from:

Thanks in advance!


10-24 (I think)
That messed me up too. I thought I was losing my mind.

My guess is the availability of standoffs?


Early machines had #10-24 threaded spacers and bolts for the stops — contact us at and we’ll work out how to get you the correct metric part, or you could order them yourself from

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I just ran to the hardware store and bought some 10-24 bolts of the correct length. Thanks for the help with identification, both of you!


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