I just went to the home improvement shop and found the taps. It's a good thing they were out of single M5 taps (they had only 3-tap sets in stock), because I would have bought it without thinking only to discover it was the wrong size. I stared at the taps for about 20 minutes, and damned if the M5 didn't look too large. I forgot to take the screw to the store with me, but I was almost positive it wasn't that big. So I went over to the screw section and found the same kind of screws. The M4 looked like the right size. I decided I'd better double check, so I came home empty-handed. Googling "tap drill thread metric equivalents M4 M5", I found a PDF file titled "Guide for Specification of Imperial Bolts, Threads and Hole Fits in Advanced LIGO Parts" (http://www.ligo.caltech.edu/docs/T/T030118-01.pdf
). I don't know what Advanced LIGO Parts are, but I downloaded it and found that, sure enough, it contained an imperial/metric equivalent chart. And, as I suspected, the metric equivalent for an 8-32 is apparently M4, not M5. As a lowly newbie who never even used a glue gun before today, I hate to point this out, but it seems the chart Aluke123 included in his (incredibly helpful and informative) post is off by one unit. :-[ Googling again, I see that Aluke123's chart is identical to the one at http://www.engineershandbook.com/Tables/tapdrill.htm
, and you would think the Engineer's Handbook would be definitive, but I'll be damned if the screw that came with my DIY kit is an M5. And the instructions explicitly say to use a 1/8" drill bit, and that equals 3.175 mm, not 4.2 mm. ??? In any event, since I now know my local shop sells the same kind of screw, even if the tap I buy doesn't match the screw that came with the kit, I can buy one that does. I'll let you know how it turns out.