Rack mount equipment screw size question.

[xwarp]

So it appears that the standard screw size for the screws used going into the rack itself is 10/32.

But apparently, the screw size for the mounting of ears to the test equipment itself is not the same?

Are these M6 because 10/32 doesn't seem to want to screw in.

Thanks!

[Monkeh]

So it appears that the standard screw size for the screws used going into the rack itself is 10/32.

But apparently, the screw size for the mounting of ears to the test equipment itself is not the same?

Are these M6 because 10/32 doesn't seem to want to screw in.

Thanks!

Haha, standard.

There is no standard for what manufacturers use to assemble their equipment. There isn't even one for the racks.

[The Soulman]

Ear to rack in the EU is mostly M6, ear to gear is not standardized in any way, as far as I know.

[notsob]

A picture of the rack would help - the made in USA racks that I've seen have tapped screw holes in the rack vertical rails, the Australian ones have punched square holes and require a "cage" nut to be fitted

[threephase]

That M6 caged nut approach is what I have come across in the UK.

Kind regards

[cvanc]

Here in the States the rack rails can be either 10-32 or 12-24.

Ampex and RCA, I think, were the 12-24 crowd, and most everybody else was 10-32.

As for the ears to the equipment?  No standard at all.  Could be English, could be metric.

[floobydust]

Hammond has always been 10-32, but they also sell 12-24 and M6 rack hardware.

[chris_leyson]

Here in the States the rack rails can be either 10-32 or 12-24

Interesting, so why switch to a fine pitch 10-32 instead of using 10-24. Just wondered out of curiosity, been slowly building up my small collection of UNC and UNF fastners.

[xwarp]

The screws for the rack are in fact 10-32 on mine.

What I thought might be standard, apparently is not. What I was trying to find out was the screw size for a HP 34401A, which are apparently M4-0.70 screws.

[Gregg]

Here in the States the rack rails can be either 10-32 or 12-24

Interesting, so why switch to a fine pitch 10-32 instead of using 10-24. Just wondered out of curiosity, been slowly building up my small collection of UNC and UNF fastners.

10-32 machine screws are stronger mostly because of the root cross section compared to 10-24.  Historically a lot of the older racks were made of aluminum and 12-24 fasteners fit the niche of having coarse enough threads not to easily cross thread or strip and strong enough to do the job.  10-32 was mostly used with steel racks and with the snap in captive nuts that fit in the rectangular holes on some racks.  10-24 fasteners were used a lot in softer materials like carburetor bodies.
Standards, there are lots to choose; but the three will fit most: M6; 12-24 and 10-32
When I have to rack equipment, I take along an assortment of all 3 types and a tap for each thread and a 1/4-20 tap with a few fasteners to match.  Stripped 12-24 holes can easily be tapped to 1/4-20 and save the headache of relocating things.  Wide masking tape makes a good chip collector when tapping out holes in racks.

[TimFox]

Here in the States the rack rails can be either 10-32 or 12-24

Interesting, so why switch to a fine pitch 10-32 instead of using 10-24. Just wondered out of curiosity, been slowly building up my small collection of UNC and UNF fastners.

6-32 unc, 8-32 unf, and 10-32 unf are the popular choices for nos. 6, 8, and 10 machine screws in American electronics.  I was told that this is because one can re-tap a stripped 6-32 to 8-32, and 8-32 to 10-32 when needed.

[tkamiya]

Mine has square holes where caged nuts goes in.  I use 8mm screws.  Also available are 6mm.  Obviously, they are not exchangeable but works fine because cage nuts always comes with screws.  I avoid using Imperial as much as I can.

[boffin]

I see 3 sizes on a regular basis

#10-32 (which is pretty standard for North American Racks)
M6
M5 (which is really really close to #10-32, but not quite, which makes it a pain)

Also on occasion #12, but not nearly as often as the M6

In our office we tend to use the 1st two, and rarely anything else.  I'm trying hard to break people of habit of just tossing all rack screws into the same box <it's not an easy battle>

[chris_leyson]

@Gregg and TimFox thanks for the heads up. Obvious when I think about it in a little more depth.

[coppercone2]

Consider getting thread gauges or making your own by gluing/welding standard size bolts to little sticks/rods with clear labels on them. A thread gauge will typically have a go/no-go but even a simple one can be a useful shop tool.

Just go to Lowes and buy one of each bolt along with some dowels.. the easy way is to drill a hole in the dowel, cut the head off the bolt and glue it into place. HIgher quality would be brazing or welding them to little rods with knurling or something.

Or MCMASTER.

You can also kinda use taps but if its close but no cigar you might damage the thread with a sharp tap. A bolt will simply get stuck.

Good enough for chassis work (but if your doing screw terminals or electrical contacts you should get real thread gauges). These have a benefit because they are extremely cheap and you can make them long/skinny if you select the right dowel, so you can get it deep into a chassis hole some where (you won't have a problem making one thats a foot long with a 1/4 inch dowel). The machine shop ones are kinda stubby usually. And since they are double sided, its not super ergonomic because you end up being poked by a screw thread when you install it (not like a real handle)

Gluing a thread into a dowel, giving it a bit of lacquer, putting a label on it and then covering with clear heat shrink will make something pretty nice and very cheap


Another option that won't really work too well but will kinda work in a pinch is to get bolt samples and put them in one of those screw drivers that has some of those holding pincers on it meant for screw insertion.

https://content.artofmanliness.com/uploads//2010/02/screwholder.jpg