John Doe wrote:
Christopher Tidy wrote:


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 [apparently]
the machine screws I buy from Lowe's are made out of junk steel.



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.

I assume that you're tapping the holes first, right? If not,
that's your problem.

Screws should thread into tapped holes very easily. If your tap is
extremely worn, that might be the problem. Or you could be using
the wrong size of tap. Or you might not be cleaning out the swarf
from the hole after tapping.

But I doubt you could break even the cheapest screws by simply
threading them into correctly tapped and cleaned holes.


I need more strength than just enough to thread the machine screw
through a correctly tapped and cleaned hole. If the screw is going
to break so easily, it probably won't hold the pieces together
either. That's my problem.



I agree with Christopher here in that something is very wrong with what
you are doing or the you are seriously failing to provide the whole
picture. I would suggest though that you may want to look at thread
forming fasteners which are often used for ductile materials such as
Aluminium, drill the hole fit the fastener, but you need to work out it
is suitable for your job which sounds like a problem at the moment
..









Best wishes,

Chris