Machine screw dimensions online

[Michael Lye <mlye@risd.edu>]

shop-talk supported in part by Fat Chance Garage
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Do any of you have a good suggestion for finding the dimensions for  
common machine screw sizes online? I'm looking for something like a  
table with typical head diameters, clearance and tap hole sizes for  
socket heads, flat heads and so on. Can never seem to find the info  
if I'm away from my shop. And of course I can never remember most  
anything!

MIchael