[Norm Dresner]

AFAICT, 8-36 UNF and metric M4x.7 screws and nuts are totally
interchangeable.

Are there any other pairs of metric and US screw threads that can substitute
for one another?

TIA
Norm

[Mark Rand]

On Sun, 15 Feb 2009 18:21:08 GMT, "Norm Dresner" wrote:

AFAICT, 8-36 UNF and metric M4x.7 screws and nuts are totally
interchangeable.

Are there any other pairs of metric and US screw threads that can substitute
for one another?

TIA
Norm

Not metric, but UNC threads of 3/16"(10-24) and above are identical to
Whitworth apart from the thread form with the notable exception of 1/2". This
leads to the confusion that some people think that 1/4" and 3/8" camera tripod
threads are UNC (they aren't, they have always been Whitworth).

regards
Mark Rand
RTFM

[Steven J Masta]

Norm Dresner wrote:
AFAICT, 8-36 UNF and metric M4x.7 screws and nuts are totally
interchangeable.

Are there any other pairs of metric and US screw threads that can substitute
for one another?

I frequently confuse M5x.8 with 10-32 - 5mm is roughly .197 inch and .8
pitch is 31.75 TPI.

Steve

[whit3rd]

On Feb 15, 10:21*am, "Norm Dresner" wrote:
AFAICT, 8-36 UNF and metric M4x.7 screws and nuts are totally
interchangeable.

Are there any other pairs of metric and US screw threads that can substitute
for one another?

Yep, I've seen gear clusters on a bicycle with either 1 mm (25.4 tpi)
or 24 threads per inch, and either will fit any hub.

It doesn't work out well at ALL, though: the mismatched
threads result in a six-thread fit having two in tension, two
out of contact, and two in compression. The two in tension
fail (because the compression plus the load is too much
force), then it's one thread in tension, two out of contact,
and one in compression... which also fails.

Most bicycle shops are aware of the problem, and have thread
gages. Even I learned the lesson, after buying a few hubs.

The hub issue is less than 1% mismatch, and your example
of 8-36 and M4x.7 is (nominally, in thread pitch) similar. It might
work if the materials stretch enough without fracturing, but
it'd be nice not to depend on that.

[Norm Dresner]

"whit3rd" wrote in message
...
On Feb 15, 10:21 am, "Norm Dresner" wrote:
AFAICT, 8-36 UNF and metric M4x.7 screws and nuts are totally
interchangeable.

Are there any other pairs of metric and US screw threads that can
substitute
for one another?

|Yep, I've seen gear clusters on a bicycle with either 1 mm (25.4 tpi)
|or 24 threads per inch, and either will fit any hub.
|
|The hub issue is less than 1% mismatch, and your example
|of 8-36 and M4x.7 is (nominally, in thread pitch) similar. It might|
work if the materials stretch enough without fracturing, but
|it'd be nice not to depend on that.

The 8-36 and M4x.7 are 0.8% apart and, at least for the 1/2" or so that I
need, are, if my calculation is correct, about .0001" different after the
..5" interval which, I don't think should matter that much for most things.

Norm