I say they have never been common in the automotive industry. The American companies now are largely using metric the same as much of the world has for a long time. Before they went metric, below 1/4’’ they used number fasterers, #10, #8, etc. Maybe the 3/16’’ specification was always around, but why start using something in place of a more common fastener?
I think it was over 10 years ago I first ran into a 3/15’’ screw. I needed to replace a #10 screw in my chain saw. Now there really isn’t that much difference, 0.190’’ vs. 0.1875’’, but when going into a tapped hole in an aluminum housing, you don’t want a sloppy fit.
Who done it? I smell the work of the ISO. For an engineer designing new products or a manufacturer building them no big deal. So we make it harder to repair our existing stock in order to make it easier for foreign countries to sell in our market?
I don’t know how common 3/16-32 screws were, but they were more common than they are now. They are now considered obsolete. I doubt anybody has “just started” using them for anything.
Auto parts stores sell them for the same reason they sell anything. They are/were used on cars and they occasionally wear out and need to be replaced.
No, I never saw a 3/16’’ screw until at least the 90’s. As I said in my OP, American cars used #10 screws until they went metric. None of the cars needing screws ever used 3/16’’.
As for metric, Yes the 5 mm screws are nearly the same, but their 0.8 thread pitch is much coarser than a 10-32.
The #10 was the standard for most of the 20’th century and now all you can find is the 3/16’’.
No, they are different, close but different. Although in this sloppy era, I can see mislabeling. So you buy a 1/4’’ and it really is a #14 and doesn’t fit right.
That is another problem, #12 and #14 wood screws coming crawling out of the wood work after years and years of obsolescence.
Found mounting directions (PDF) for Arctic brand snow plows that call for 3/16-32 screws. Also have run across them on some old Brit stuff. This chart seems to support the notion it is a British norm.
Sorry thelabdude, I sell screws for a living and absolutely nobody is pushing the use of 3/16-32 screws, and they have not replaced 10-32. In 15 years I have gotten maybe 3 calls on 3/16-32 screws and they were all to replace screws on old cars or antique sewing machines. They are currently not used in fabrication at all.
If you can’t find 10-32 screws you’re not really looking.
You see them because nobody buys them. Buy them out at that store and I will bet you 6 bits they will never replace them.
I work part time at a parts store and we are also a limited hardware (auto specific for the most part) store.
That also would include someone wanting 2 dozen 3-16" x 2" screw that I will call a “Stove Bolt” and when I source it I find them 100ea and then 75ea sit on the shelf forever.