Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

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Default Where to buy machine screw assortment?

Bruce L. Bergman wrote:

On Tue, 26 Feb 2008 06:02:23 GMT, John Doe


Would you agree that a harder/stronger higher grade bolt takes
more torque to break?


Absolutely the higher grade screws will be stronger than the
ungraded "mystery metal" screws at the local hardware store


Too much torque is still too much torque.


I will keep that in mind.















-- Bruce --


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John Doe wrote:
Christopher Tidy wrote:


So you are attempting to drive a machine screw into an untapped
hole?



I was asking for specific locations to buy stronger/better screws,
but the information about grades and stuff is probably at least as
useful.


That's not the answer to the question I asked above. Please read it
again. If you answer the question I asked, it will make it much easier
for everyone to help you, and will make the answers we give more
relevant to your problem.

We're not here to criticise you unfairly; we're just trying to
understand the problem better.

Best wishes,

Chris

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Default Where to buy machine screw assortment?

Jon Elson wrote:

I rip a little piece of a paper towel off and twist it into a thin
cone and poke it into the hole and twirl it to get the chips out.


I keep a basket full of recycled used paper towel portions (from
non-chemical/biological uses). They can be used for cleaning bolts
too. Fold the paper towel into several layers, hold it on the bolt
with your fingers, and use a cordless drill to slowly spin it off of
the bolt. To get rid of plastic chips on plastic screws, just move
them around against the carpet.

Have fun.







(Professional shops use compressed air, but my family would
object to this late at night.)

Jon


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A few notes about machine screws and where to buy them:





Don't buy ANYTHING that has a "slot-head".

Put a decent chamfer on the clearance bolt-holes. Some screws, in
fact most screws, have a root radius, which is why you place a washer
under the head.

Try a proper supplier, like Fastenal or somebody's "Nut & Bolt"
Company locally, or any mill supply house. Ask for "Grade 8" in
whatever style you need. Be prepared to spend more money than at
Lowes, but depending on what and where and how many you buy, the best
Holo-chrome's might not be a lot more bucks. Personally, I find that
Allen-head bolts are less likely to break than cap screws. Not sure
you can buy "machine screws" in Grade 8, but purchased from a good
supplier they will be at least Grade 5.

Twice (at least) in previous replies you mentioned using stainless
bolts rather than the zinc-plated machine screws used at present. You
should note they S/S are NOT stronger that good steel bolts. In
fact, may be quite a bit softer if they are not also Grade 8 or
better. "Stainless" is a quality of the material, and not directly
related to strength or holding/breaking capacity.







I was taught to use Grade 5 or better bolts in the automotive world.

Since I'm using more and more ACQ treated lumber, the need for
non-corroding hardware has led me to stainless research. McMaster has
half a dozen stainless alloys and their differences astounded me.
From their comparison chart + delving into the individuals:

17-4 PH Stainless Steel, 140,000 psi
Combines the high-strength of alloy with corrosion resistance of
stainless steel.
18-8 Stainless Steel, 70,000 psi
Offers excellent corrosion resistance; it may be mildly magnetic.
Alloy 20 Stainless Steel, 80,000 psi
Also known as Carpenter 20, it's nonmagnetic and especially
resistant to stress corrosion.
300 Stainless Steel, 80,000 psi
Meet more stringent specifications such as military
specifications. All are passivated (a nitric acid treatment that
creates a passive film to protect the stainless steel from oxidation
and corrosion).
316 Stainless Steel, 80,000 psi
Offers even better corrosion than 18-8 stainless steel. It
contains molybdenum, which increases resistance to chlorides and
sulfates. It may be mildly magnetic.
450 Stainless Steel, 170,000 psi
Offers more corrosion resistance than alloy steel.

Unrated hardware, Class 2A, has a 60,000 psi strength.
Grade 5 with a zinc plating is double the strength at 120,000 psi.







If you want strong, buy HoloKrome screws. I believe J&L is in the UK.







http://www.microfasteners.com/index.cfm







Try a company like Fastenall for good screws.







http://www.mscdirect.com







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Christopher Tidy wrote:

That's not the answer to the question I asked above. Please read it
again.


Time to get a life, Christopher.















Best wishes,

Chris




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John Doe wrote:

Time to get a life.



Hope you find it before it's too late. PLONK


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
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John Doe wrote:
Christopher Tidy wrote:


That's not the answer to the question I asked above. Please read it
again.



Time to get a life, Christopher.


Well, it was you who lowered the tone of the discussion. I asked a
reasonable question, which you refused to answer.

I'm inclined to think that you are putting screws into untapped holes,
but for some reason refuse to admit it. It's a strange attitude if you
actually need a solution to your problem.

Best wishes,

Chris

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On 2008-02-26, John Doe wrote:
"DoN. Nichols" dnichols d-and-d.com wrote:

We are trying to figure out exactly what the conditions are
under which the screws are breaking,


And I'm trying to tell "we" that it really doesn't matter.

and a lot of the initial answers
were addressing the implied condition that the screws were
breaking before they were fully into the workpiece


Better to go with the stated condition, that the screws were
breaking with too little torque. Since you don't know how much
torque I apply, you'll just have to take my word for it.


If the breaking torque is being reached before the head comes
into contact, *I*, at least, have to assume that you are trying to form
threads by screwing the screw into an unthreaded hole, which is not what
it was made for, and it *will* break.

I've never seen you *deny* that you were doing this. Clearly
deny that, and we will consider other things.

And 6-32 are *very* weak screws, and if made of the typical
zinc-plated butter steel which is used for the blister-pack stuff sold
by most home user hardware stores, they certainly will not survive being
used to *form* threads.

If you want to form threads -- either get the screws made for
the purpose (you're not likely to find them in Lowes), or get a
thread-forming tap. Note that when you are *forming* threads, you need
a larger tap hole than when you are using a normal thread cutting tap to
make the threads. If you try to use the tap drill for a thread cutting
tap, you will even break a thread forming tap as it clogs up with too
much metal.

We make suggestions, and you attack. ISTR that you came in
with
a similar behavior a couple of months ago or so.


And you're planning to tell your imaginary kill file friend on me.


I think that I did wind up tossing you into the killfile at the
time, but I changed newsreaders and am starting over. You are getting
very close to going into it again.

We're *trying* to help, and to do that, we need to understand
the precise conditions under which the screws are breaking. You
seem to have later suggested that the holes are properly drilled
and tapped, but it is not totally clear that was what you said.


I've said this several times already. I'm asking about bolt
strength, not about methods. Talking about methods is misconstruing
my original post. I mentioned the method because it happened to be
how I determined that the bolts on using are crap. Doesn't matter if
I am holding the small end of the bolt in a vice, the bolt breaks
too easily. How else am I supposed to determine bolt strength? Why
isn't that method okay? What other method would you suggest for me
to get an idea of bolt strength? Screw it into a correctly tapped
hole?


Yes -- and then measure the torque needed to break it off. Or
screw it in to normal torque and pull up on the plate held down with the
screw and measure the breaking point. Screwing it into an untapped hole
is putting stress on it in the wrong places, and it is of course going
to fail.

Little pressure -- or before you even get the screw in far
enough for the head to contact? This is the kind of detail which
can make a difference in you getting useful answers.


I've gotten plenty of useful answers about screw strength, IMO,
probably at least enough already. Some people aren't inclined to
give useful answers. Some people just don't know (for example, folks
living in the UK when asked about "USA chain stores"). Some people
just want to talk about fastening stuff, and that's okay with me.


Well ... my first answer to you told you where *I* would go to
buy the good screws -- before it became apparent that you will probably
similarly break good screws by similarly mis-using them.

When you have this many people asking you to clarify your
question, it must mean something other than that you are communicating
clearly.

DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---
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DoN. Nichols wrote:

snip

I've never seen you *deny* that you were doing this. Clearly
deny that, and we will consider other things.


This is what I've been trying to establish. It only requires a yes or no
answer, but he's unwilling to give one. I don't think we can help him
any further unless he provides a proper, unambiguous answer.

Best wishes,

Chris

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