10-32 versus M5???

[rwm]

I learned something amazing today that I probably should have known years ago. Perhaps all y'all already know this but I will enlighten those who do not.

A 10-32 and and M5 coarse screw are almost identical! I mean so close that I cannot always tell them apart with a caliper and a thread gauge. Depending on the thread class they may even mate with the incorrect opposite and work just fine.
After some research I have determined the following:
The major dimeter of a 10-32 is 0.183 to 0.189". The major diameter of an M5 typically measures near this range or minimally larger. My stock is 0.190!
The pitch of a 10-32 in mm is .794mm. The pitch of a M5 coarse is .800. These are too close to see visually. If you engage a metric screw in a 10-32 socket it will make multiple revolutions before binding. For a short thread like a nut you may not even notice.
Also, the socket on my 10-32 cap screws accept a 4mm hex key perfectly!
As far as I know, other sizes are not nearly this close and never interchangeable.

M5 and a 10-32


Don't mix up your stock!
Robert

 

[rwm]

After some experimentation, all of my 10-32 screws will thread into M5 nuts and don't feel too sloppy. Only some of my M5 screws (with smaller ODs) will fit in my 10-32 nuts.
Robert

 

[brino]

I stumbled over another one lately on small set-screws; #5-44 is so very close to M3x0.5 I could not tell them apart.
I could make them both thread into both a metric and imperial thread checker!

I have been meaning to make up an excel chart of the common imperial and metric fasteners with both diameter and pitch columns and then come up with a formula in another column to represent how close of match they are. I think having that would help me in the shop when I am trying to determine an unknown thread.

-brino

 

[markba633csi]

There's another one: 8-36 and I believe 4mm or 4.5 can't remember which. Nearly identical. The 8-36 is just a hair fatter IIRC
-M

 

[mattthemuppet2]

yeah, they're almost the same but they're not. I usually find out I've got one in the wrong draw because it either won't thread into a matching nut (M5 screw, 10-32 nut) or the nut is so loose that it feels like it's going to fall off (10-32 screw, M5 nut). It's a real bugger to sort them by eye.

 

[rwm]

Any body ever run a M5 tap through a 10-32 hole to convert it? I may need to do that and I want to know how it will work out?
Robert

 

[matthewsx]

That's a good reason to buy a package and not throw old ones into a drawer. If it was me I know I'd find one that didn't quite fit and bugger up the threads on something I cared about.

Yes, I have boxes of old hardware I use quite a bit but more and more I find myself just buying the right fastener for the job. Saves lots of headaches....

John

 

[matthewsx]

Any body ever run a M5 tap through a 10-32 hole to convert it? I may need to do that and I want to know how it will work out?
Robert

It'll probably work

 

[RJSakowski]

A 5/16-24 thread has an o.d. of .3125" and a pitch of .0416" and an M8-1.00mm has an o.d. of .3150" and a pitch of .0394"

 

[Bi11Hudson]

Long(!) years ago, I was replacing Lucas (Prince of Darkness) electrical components on a motorcycle. I used Japanese, probably Suzuki, handlebar switches. Having "mislaid" the original screws, I scrounged around to find something to fit. As it happened, Nr 10-32 was tight but fit good. At the time, I didn't know metric vs imperial threads. But it worked and I stuck it in the back of my mind that some sizes were (almost?) interchangable. 5/16-24 vs 8mm is another I have run across helping with automotive work.

.