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.
I assume that you're tapping the holes first, right? If not, that's your
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.
You shouldn't be breaking even the poorest screws just threading them
into a tapped hole without tightening them. Something is seriously wrong
here. Either that or you're trolling :-).
Try McMaster-Carr. They may have sets of screws.
Like by ignoring the question and for some strange reason insisting
that threading a machine screw into a properly tapped hole is the
only valid application for a machine screw. Plastic screws into
properly tapped holes. Threading screws into a hole is not the end
objective. The objective is to keep the pieces together. I can tell
that the bolts aren't strong enough, that's why I ask for better.
If they are better than the apparent crap I get at Lowe's.
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
I suspect that you don't even know what you don't know.
Drill and tap the "bottom" part correctly for a machine screw of your
choice. Drill a hole in the "top" part slightly larger than the body of
said screw. Place the screw through the top part and turn it into the
threaded hole of the bottom part. The top part will now be held tight to
the bottom part by the head of the screw.
I know that. Unfortunately it has nothing to do with the question or
my current situation.
Maybe I should have just asked for better machine screws without any
description, but some people prefer to know what's going on.
When I bought my lifetime guaranteed screw drivers from Lee Valley, I
asked if the guarantee still applied, even if the Phillips drivers
were only used for removal and never for installation.
Is there something wrong with asking for better machine screws in
Considering how badly the picture is being distorted, more is clearly
not better for a troll.
I need better/stronger machine screws. I'm seriously not
understanding why anyone would suggest that machine screw quality
makes no difference, and that all that matters is threading the
screw into a correctly tapped hole. How to use machine screws sounds
like a completely different subject.
And that is something stronger. Besides a stronger machine screw (at
least stronger than junk steel), maybe something different will work
too. I might go with stainless steel. The fitting must be extremely
tight. A correctly tapped hole will not work. I will look into
thread forming fasteners, but I've heard that a machine screw into
aluminum can do that. Unfortunately, as I keep trying to get the
message across, the cheap machine screws I have give way under too
little pressure. I know they aren't going to be strong enough for my
That's another possibility, that he might be tapping the holes in both
parts. If so the starts and ends of the threads may not be aligned, so
that the two parts act like a locknut. If this is the problem, only tap
the hole in the part furthest from the head of the screw. Drill a
clearance hole in the other part.
Okay. It would really help if you could post a picture of the two parts
and the failed screw. Then it would be much less a case of guesswork.
If you don't have any web space, e-mail the picture to me and I'll host
it for you: cdt22 AT cantabgold. DOT net
So you want a little discussion before answering my question?
I usually prefer a concise question, from someone asking for help.
Yeah, I'm pissed at crap machine screws from Lowe's messing up my
project, and I guess it shows. It's definitely not a beautiful day
in the neighborhood here.
Whether it's understood or not, once again. I'm simply asking about
where to buy stronger machine screws than the zinc plated type I get
at Lowe's. And maybe whether stainless steel is the only way to
significantly increase strength from those type of machine screws
that break when you torque them.
Are those machine screws acceptable for anything? I'm surprised
anyone in this metalworking group would appear to be defending them.
Your "guesswork" would go out of orbit.
OK, _I'll_ give it a try. I'll give you some facts and some comments:
Fact: Taking perfectly good machine screws and forcing them into
untapped, undersized holes in aluminum will break them, regardless of
grade or quality.
Comment: So, logically, if a machine screw breaks when you force it
into an untapped, undersized hole in aluminum, it doesn't mean that it's
a bad screw, it means that you aren't applying it correctly.
Fact: Jamming a fastener into a hole where it doesn't belong doesn't
make a 'nice tight joint'. It makes a poorly made, undependable joint.
It's kind of like tying a quadruple granny knot: it's hard to take
apart when you want it apart, but when you _don't_ want it apart it'll fail.
Comment: So, logically, you shouldn't do that.
Fact: The strength of a bolted joint doesn't correlate well with the
fastener torque unless you're using clean, properly dimensioned threads.
Comment: Uh -- you can figure this one out.
Fact: Loctite is your friend.
Comment: So, logically, if you want a properly made, permanently
fastened screw joint, you should get decent screws and put them in with
Loctite red or something stronger. If Loctite red isn't strong enough
for you, see if there's anyone on this group that you haven't alienated
and ask (nicely) for advise on the right stuff to use.
I have never had problems with the fasteners that I get from Home Depot.
I treat them like grade 2 bolts, and everyone is happy. If I need
something stronger I get it from McMaster or Small Parts, and everyone