Nuts and Bolts

[MrAl]

Hi,


Recently i was at the dollar store and picked up a set of nuts and
bolts. The package was not marked as to the sizes of the nuts and
bolts but there were 100 pieces so i thought that was a pretty good
deal.
I got home, opened the package, and found that (to my surprise)
all of the bolts had enough matching nuts and they fit perfectly.
I expected to get a roughly equal amount but planned on missing
some nuts or whatever.

So anyway, the sizes APPEARED to be 8-32 and 10-32, but after
trying a standard 10-32 nut on the package bolt it was very
tight, and the package nut was so tight on the standard 8-32 bolt
that it wouldnt fit at all.

Any idea how i can verify what sizes these are without buying any
new hardware? I have a good 1" micrometer, but the size differences
in diameter are very small like 0.003 inches and the threads
per inch vary by only a tiny fraction too: 32 TPI for standard,
31.75 TPI for the metric.

I usually use American Standard bolts and nuts.

[MrAl]

Hi again,


Right after posting this i came up with a way to compare the
8-32 to the M4-0.8 metric thread.
Taking an 8-32 bolt and an M4-0.8 bolt (i had the 8-32 and
the M4-0.8 i am assuming is the size from the new package)
the M4 threads fit into the 8-32 threads almost perfectly
when you try about 1/4 inch of threads or less, but anything
over that (like 1/2 inch) and the threads 'ride up' on each
other as if they were 'surfing' each other, meaning they dont
'grab' each other like two of the same kind of bolts do.

The 10-32 and the M5-0.8 (or at least that's what i am guessing)
has a closer tolerance however, only about 1 part in 1000 difference.

[sghioto]

MrAl,

Assuming they are standard metric sizes I would just go down to Ace Hardware and find the matching nut in their metric bins. Are you suggesting they're some "off the wall" size that only works with the nuts supplied?

SteveG.

[MrAl]

MrAl,

Assuming they are standard metric sizes I would just go down to Ace Hardware and find the matching nut in their metric bins. Are you suggesting they're some "off the wall" size that only works with the nuts supplied?

SteveG.

No, i think they could be metric but i was hoping for a quick test
without buying any new hardward (ACE is several miles away
and it's snowing bad here today so i cant go today and probably
not tomorrow either) and that might not help anyway.

I am pretty sure now that the 8-32 look-alike is really M4-0.8
but still not sure about the 10-32 look-alike which i think could
be an M5-0.8 bolt, and the funny thing is that the 10-32 nut
seems to fit but it's very tight, and as i said the thread TPI is
very very close between the metric and standard bolt so buying
a new nut might not help either (i do have 10-32 nuts BTW, but
no other M5-0.8 nuts if that's what they are).

So my problem now is reduced to trying to tell the difference
between a 10-32 and an M5-0.8, and as i said the difference
in diameter is very small too so the difference is lost in the
noise field of the tolerance, which means it's hard to determine
even with a highly accurate diameter measurement, unless of
course i missed something.

[sghioto]

MrAl,

If you have a tap and die set you could re-tap the nuts for 10/32 and 8/32 screws but that seems like a waste of time. At this point might as well just keep in a seperate bin marked "Dollar Store" size. You only payed a buck for em right? You get what you pay for.

Steve G

[cdenk]

They are likely to be metric sizes (all or in part). There are several US standard sizes in that size range that the nut fits the other family, and the machine screw won't fit the the nut or visa versa. I have run into that numerous times lately, and when putting spares that I am unsure of back to storage, I try both the screw and nut.

[dacflyer]

i used to and still do, save nuts and screws from old scrapped stereos etc, when they were built ofmetal frames etc. i am talking about the big honking pioneer stereos, tape decks etc. a lot of them screws were great for replacing other missing screws etc, but i was never really able to find a size on them, not even in the hardware store, it was as if the screws were a special secret size and thread cut.. knowhatimeanvern?

[Janitor Tzap]

i used to and still do, save nuts and screws from old scrapped stereos etc, when they were built ofmetal frames etc. i am talking about the big honking pioneer stereos, tape decks etc. a lot of them screws were great for replacing other missing screws etc, but i was never really able to find a size on them, not even in the hardware store, it was as if the screws were a special secret size and thread cut.. knowhatimeanvern?

You do that too!
He he he....
I've got an old coffee can filled with bolts, nuts, screws, and fasteners.
I think the weirdest thing I've come across was a reverse threaded bolt, and nut combo.

Any way......
Those Bolts & Nuts probably are metric.
The local dollar store here also has those Bolt & Nut Packs.

But, I've run into bolts that the thread pitch or cut,
is just different from the standard ones in the hardware stores.

I had an RC car that used bolts in the front suspension.
I broke one of the bolts.
I thought I'd just go up to the local hardware store and get another one.
Wrong!
The bolt threading was way too different, then what the hardware store had.
I ended up going to the hobby store, and paying $1.50 for four bolts.


Signed: Janitor Tzap

[MrAl]

Steve:
Yeah, i got what i payed for i guess.

cdenk:
Yes, i seem to be having a problem with the near 10-32 size.

dac:
I keep a few of them too. I think most of mine are somewhat
standard though.

Janitor:
I am starting to think that this near 10-32 size is just that:
"near 10-32 size" and is not really 10-32 and not M5-0.8
either, but some off beat size made perhaps in China where
the standard may be slightly off (as usual).


All:
I made a slight mistake with the near 10-32 size bolts/nuts
as the thread is closer to 32TPI than 0.8 metric. It's
really strange that's for sure.
The near 8-32 are really M4-0.8 threads as i pointed out,
but these near 10-32 threads are almost real 10-32 but
very very slightly off so that a real 10-32 nut fits
but it's very tight until you wind it down the bolt a
bit, then back out, then back in, in which case it gets
a little looser. This leads me to believe finally that
they are just poorly made 10-32 bolts and poorly made
10-32 nuts. Luckily they do fit each other quite well,
so are still usable...just not with any other off the
shelf 10-32 hardware. Strange!

Here's a drawing of what was happening when i tried to
fit a real 8-32 bolt to a real M4-0.8 bolt. The threads
are slightly different so the first 1/4 inch or so fits
into the threads of the other, but after that the threads
start to ride up on each other because of the eventual
change in phase. It turned out to be interesting...
Note that the situation shown in the lower most drawing
gets worse as the length of the bolt increases, so that
eventually there ends up being at least two threads
which wont interlock at all and so force one bolt to
perfectly 'ride' the threads of the other bolt, so that
no interlocking at all takes place. In this case you
can easily 'slide' the two bolts along each others
lengths without feeling too much 'drag'. With two
bolts that have the same thread you could never do
that because they get caught in each others threads!
I think this is a good test, but if you find anything else
let me know.



Here is some numerical data showing the thread 'peaks' of both
types of threads side by side, with all dimensions in inches.
Note that after 0.25 inches the difference between the two
threads is only around 2 thousandths of an inch, yet this
still prevents the threads from interlocking nicely.
For bolt lengths shorter than this however, the threads might
appear to interlock because there isnt enough difference
yet for the threads peaks of one bolt to be forced up out of
the valleys of the other bolt.

[Lenp]

Al,

Quality bolts for the most part have their threads made by cutting, on a screw machine while cheaper bolts are often made using rolled threads. There are differences in quality and finish. Use a microscope or high power lens and look at the thread. It may be obvious if they are rolled.
I have had long bolts that have the nut bind partway up, because the pitrch of the bolt drifts

It seems that the US imports a lot of junk grade consumer geared low end materials. Maybe that's why they were mated with nuts since they are out of tolerence!

A few years ago I purchased a sheet of MDF from Lowes. It was not a 48 X 96" sheet, it was oversized in each direction, even the label said, I believe 49 X 97! Lowes said I was getting more wood for the same price and offered to 'trim' it if I wanted to bring it back! I'll told them that it would be a disaster if someone tried to use it on studs at standard spacing, but Lowes was clueless! It must have come from someplace where their math for metric to US was poor. They may still sell it, I haven't looked.

Len

[Robert Reed]

Hi Lemp
I ran into this sizing difference several years ago when I first started purchasing MDF at the local lumber yard. They explained that since this material was used mainly for counter tops and such, it was made slightly oversize to trim for a clean edge. That made a little more sense to me. Also they said the same sizing is used in particle board many times for the same reasoning. Of course the people at Lowes would have no idea about this as they are not true lumber yard or construction knowledgable.

[Dean Huster]

Regardless of whether it's metric or English/SAE, it has to be a standard size, and M4-0.8 is not! Here's standard ISO Metric sizes around that area (all are "coarse" threads):

M3-0.5
M3.5-0.6
M4-0.7
M4.5-0.75
M5-0.8
M6-1

M5.5 is only available as a constant pitch thread with a pitch of 0.5 mm.

I've had similar problems with the 10-32 vs. a similar ISO and with 8-32 as well. A metric and an SAE thread gauge is a very helpful tool with working with hardware.

Dean

[Lenp]

Robert,
Thanks for that info, It does make sense.

The lumber business is indeed unique, selling 2x4's that are smaller, sheet goods that are larger and penny sized nails that cost dollars...the list goes on.

Len

[MrAl]

Hi again,


Len:
Yeah mine binds as soon as you put the nut on, but after turning
back and forth a few times it loosens up a bit. That makes
me think it's just crummy threads.

Dean:
I'm also having a bit of a problem figuring out what size thread
my LCD panel monitor takes. Recently i decided to make a home
built mount for it so i can tilt it easier, and so i needed some
bolts for the (quote) VESA STANDARD mounting hole pattern.
The manual just says "M4" and doesnt give the thread pitch,
and even M4 itself seems to thick for the screw holes in the
monitor, and when i call the hardware store they say they
only have M4-0.8, and i thought M4-0.7 was the standard size too.
I still havent figured out what size it takes. Maybe i'll start
a new thread about that.

Len & Robert:
Yeah the lumber sizes have always been 'interesting' ha ha.
Everything is always undersize. I think the last time they
made a 2x4 that was actually 2x4 was 100 years or more ago.

[CeaSaR]

Maybe i'll start a new thread about that.

Would that be a "New Thread" thread??

Sorry, I couldn't resist.

Have a safe and happy holiday everyone.

CeaSaR