On 2008-02-25, 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.

The latter is more likely.

But -- by "halfway through" to you mean with the screw half-way
into the aluminum? You are asking about machine screws, not self-taping
screw, based on the subject line of your posting, so I have to ask: "Are
you tapping the holes prior to trying to install the screws?" Machine
screws are *not* designed to make their on threads.

If by "halfway through" you mean "when you have about half of
the screws the project requires installed and tightened" then there is
something else seriously wrong, and junk metal is quite likely.

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.

What I would suggest is black oxide finished screws, unless you
need to have light colored screws.

Go to someplace like MSC:

http://www.mscdirect.com

and register there (you have to register before making your first
purchase) and then they will send you a massive catalog ("the Big Book")
which you can use to look up tools and supplies more easily than I find
their web based presence to allow. Then you can phone in a purchase
(remembering the account number you got when you registered) and
typically they will deliver by the next day. (Hopefully you are not in
Canada, because they insist on using UPS for delivery, and UPS insists
on charging a customs brokerage fee on packages to Canada.)

Note that you will find the prices for a box of 100 screws
better than the prices for 10 screws of the same size in Home Depot. I
don't have a convenient Lowes to compare to for prices, but I would
expect them to be similar to Home Depot.

Good Luck,
DoN.

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