On Feb 25, 1:20 pm, John Doe wrote:
I'm doing an important project. Trying to thread a machine screw
into some aluminum. Halfway through, the machine screw twists apart
just below the head. The heads breaking off is not uncommon here. I
don't put all that much pressure on them, so either I'm Superman or
the machine screws I buy from Lowe's are made out of junk steel.

I guess the upside is that at least the screwheads don't strip first
/

Is stainless steel necessary, or is there an assortment of zinc
plated (or whatever similar type) machine screws/nuts made out of
decent steel someplace on the Internet or at a USA chainstore? I
need sizes like 6, 8, & 10.

Thanks.

I have done many time what you are describing, only using self-
drilling sheet metal screws and an electric drill to drive them. You
and I were both over torquing the screws. Somewhere there is a table
of allowable torque on the screw you are using. If you can find a
toque indicating screwdriver and limit your indicated torque to the
amount allowed for that screw, you will be home free.

The Lowe's screws are undoubtably made in China qand are usually junk.
Try a company like Fastenall for good screws.

Good luck,
Paul