(01-03-2013, 07:31 AM)Mayhem Wrote: OK, so the diameter on these are listed as 0.1000". How much smaller should I drill the hole? Is a #40 drill (0.0980") going to be too tight? Either side is 0.0960" and 0.0995"
This is to reattach the name plates on my mill, so it will be going into cast aluminium on some parts and cast iron on others. I'll mic the drive screws before I start drilling, just to make sure they are 0.1000"
If no one has a 'scientific answer" maybe you could drill a hole of each size is some scrap of a similar material and see how the hammer feels as you drive them in. My not-based-on-anything-scientific thought would be that there would be a difference in the 'correct' size for the dissimilar materials, with the aluminum liking a slightly smaller hole.
And just for completeness, the 2.5mm drill is 0.0994.
Ok, you made me try Google. Looks like you would have been way off with either of them. It calls for a #44 hole.
http://www.smithfast.com/udrivescrew.html
But I still think a couple of trials to see what the hammer tells you would be a good idea.