10-32 vs 10-24 Just curious why 10-32 is more popular when NC is more common.

Anyone know why 10-32 NF is the common screw size for a No 10, and not 10-24?

Since most all common screws are NC why is it we change for this size only????

Happy New Year.

It's not. Go into any Home Depot and they only carry 10-24.

GregSY said:

It's not. Go into any Home Depot and they only carry 10-24.

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Most of the Home Depots I go to do have 10-32 but you have to dig for them in there is a limited selection.

As for the original question the 32 tpi do have greater holding strength in thin and or soft materials, also don't strip out as easy in soft alloys.

Plus if it's a tough material to tap a 10-24 is much more prone to breaking. Kind of like a 6-32 tap is not everyone's favorite.
And your right about the big box stores, lots of 10-24 screws, very limited selection of 10-32.
Another gripe is that the standard socket head cap screw selection is always in SS, not high tensil steel. Metric is all in steel though.
I hate the big box stores, don't carry what you need and they put most everyone else out of business.

Mr Bridgeport

Ziggy2 said:

Most of the Home Depots I go to do have 10-32 but you have to dig for them in there is a limited selection.

As for the original question the 32 tpi do have greater holding strength in thin and or soft materials, also don't strip out as easy in soft alloys.

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Hmmm-I've always been under the impression that soft alloys do better with coarser threads.

So most of what I fix is 10-32 , not 10-24. I get most of my screws from McMaster. Sometimes others. I have always noticed that 10-32 is what most manufacturers use , rather than 10-24..

I prefer steel, black oxide, although I do have SS, but use it for environmental needs..

Still curious why manufacturers do 10-32 when the rest of their screws are NC as well.

Another factor is that a lot of 10-32 get used in electrical work: ground screws, terminal blocks, etc. The fine thread will take in a metal outlet box, provide an easier to control and less likely to back off terminal screw, etc. Also a stronger cross-section than 10-24.

I come from a professional electronics/radio/TV background and I almost never saw a 10-24 in use there. But 10-32s are used all over in electronics. Only one example is the mounting rails in standard electronic racks almost always have 10-32 holes. We would buy the mounting screws by boxes of 1000. Those mounting screws are usually a combination of an oval head with an integral imitation of a countersunk washer to provide a wider head to better grip the usually slotted holes in the equipment being mounted. There are many other examples of fine threads being used in professional, electronic equipment.

I am not aware of how this usage started in professional electronics. And you could order non-standard mounting rails with the 10-24 threads, but almost no one ever did.

One curious thing that I have seen is some equipment from other countries (metric countries) came with M4 screws and nut plates that fit behind a set of three 10-32 holes in the rails. The M4s had a nominal OD of 0.1575" and would fit through a 10-32 hole if a #21 (0.159") tap drill was used. However, they would not fit through a 10-24 hole if the standard #25 (0.1495") tap drill was used. I do not think this was the original reason for 10-32s, but it is interesting. And curious.

One possible reason for the use of fine threads is the predominance of sheet metal over thicker castings. It is desirable to have more than one full thread in a hole and many of the professional style, electronic devices were constructed with sheet metal. Thicker castings are quite rare in this type of equipment. Even those mounting rails that I mentioned above are normally made from sheet metal, rolled to shape.

EPAIII said:

Only one example is the mounting rails in standard electronic racks almost always have 10-32 holes....And you could order non-standard mounting rails with the 10-24 threads, but almost no one ever did....

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I agree with everything you posted.

I have found that while AV racks are tapped for 10-32 screws, most server racks use the 12-24 screws, with clip nuts.

I never really could figure out why 10-24 just wasn't that popular. My industrial supply in Tennessee had around 10,000 SF dedicated to fastener warehousing for Rockford®, Unbrako®, Allen® and a hand full of the cheaper brands. Millions of fasteners and not a single 10-24 stocked, SHCS, FHCS, SSS, RHMS, etc and notta single 24TPI in anything unless special ordered and then it had to be case quantity.

Fast forward to now and we've been doing the finishing machine work on the facial recognition camera housings for Walmart and some genius decided the 4 holes that close the camera housings are 10-24 x 3/4 SHCS yet the mounting pads for the electronic boards are 4mm. Talk about a head scratcher! I finally asked one of the engineers why and they said per thousand the 10-24 were about $.20 cents cheaper verses the 10-32. At first I just thought cheap bean counters then realized theres over 11,000 Walmarts world wide and each store gets around 100 cameras so thats 4.4+ million screws. Who would have thought an electronics engineer would think to price screws by thread pitch.

g-coder05 said:

At first I just thought cheap bean counters then realized theres over 11,000 Walmarts world wide and each store gets around 100 cameras so thats 4.4+ million screws.

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So they saved $880 worldwide, at the cost of having a hard-to-get component in one of their widely-used devices.

I'll betcha it costs them more than what they saved, in the long run. In fact, probably in the first year it'll end up costing them more.

In a fastener that small, a 24 thread looks like a club while a 32 thread looks like a fine wine...it's all in the eye of the inventor.

Stuart

So they saved $880 worldwide, at the cost of having a hard-to-get component in one of their widely-used devices.

I'll betcha it costs them more than what they saved, in the long run. In fact, probably in the first year it'll end up costing them more.

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Thats the least of their problems. They were pneumatic inserters to put the screws in. They snapped hundreds of heads off before switching to manual inserting. I was thinking the problem was actually the pitch being courser the screw torquing was happening to fast and thats what caused the snapping. Glad I didn't get the assembly contract!!

EmanuelGoldstein said:

So they saved $880 worldwide, at the cost of having a hard-to-get component in one of their widely-used devices.

I'll betcha it costs them more than what they saved, in the long run. In fact, probably in the first year it'll end up costing them more.

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This is what happens when either the people in charge of initial cost are not coupled to the people in charge of maintenance, or they don't plan to do maintenance (I'm giving them the benefit of the doubt that they know what they're doing to begin with). It wouldn't surprise me if they plan to throw away any malfunctioning units (or charge them back to the supplier who will then throw them away). In the event that they do a field repair I wouldn't be surprised if they just put it together short a screw if one is lost during the process.

I'm actually surprised they didn't pick some odd custom length as well. I used to work at a place that went through somewhere around 30 to 35 million screws/year, 25M of which were one part number. Even at 1/10th that quantity the cost is highly corelated to the weight and if you need any coatings or other process steps. Something like a custom length. We would do things like change a screw length 500 µm to solve a space issue. The cost of tooling fell away in the noise, and the price would typically adjust by the same % as the weight change, assuming there was sufficient notice to use up old stock, tooling, etc. You wouldn't have wanted to source a replacement for any of our parts, but if you're to the point of taking out one our screws you're going to be replacing the entire unit anyways.

jccaclimber said:

I'm actually surprised they didn't pick some odd custom length as well.

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That's actually a good point, and I can be pretty naive when I try. It isn't always about the actual total cost, it can be about who has to pay which part of the cost. And if that ain't you, whoopee ki yo ki yay !

It's a jungle out there

Of course its not just the screws. Its everything. Mostly I guess with larger unit savings. But all the small gains add up.

Corporate culture to sniff out the savings at specification time.

Analysing lifecycle costs is too complex. Especially so in a world where complexity and reliability is generally high enough that replace rather than repair makes sense because fixing is a significant percentage of the new unit cost.

Clive

You will never find a 10-24 on an Indy Car or high end sports car, 10-32s everywhere, 10-24s not a one.

High end sports cars are still imperial fasteners?

As for the electrical/electronics world....looking to any electrical manufacturer on how to do something mechanical is asking for a beating. History is full of electrically sound devices that fall apart, leak water, and generally don't stay bolted together.

The Home Depot that is less than one mile from me had zero 10-32 hardware with the noted exception that you can buy green, slot head crews of 3/8" length in the electrical department if that happens to be your need. But a 10-32 nut? Or common screw? Nope. It's one of those 'ask me how I know' things......you have to go another mile to Lowes where you can buy from a small selection of bagged screws that are about $1 per screw.

GregSY said:

.... a 10-32 nut? Or common screw? Nope. It's one of those 'ask me how I know' things......you have to go another mile to Lowes where you can buy from a small selection of bagged screws that are about $1 per screw.

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Tru-Value has a row of those little plastic drawers with a decent selection of fasteners, all different kinds, in different materials. Kinda expensive if you only buy five but hey, they have stock.