I'm trying to identify a bolt size / thread, not out of a VW and unlikely to be metric as it's to fit a tread in an old machine manufactured in Scotland, I have a bolt that fits reasonably well and have measured the pitch with a screw pitch gauge ..(28) and the OD of the thread is 5.4 mm, pretty sure that's exact OR .2126 inches (by my conversion calcs.) Using some identification charts I found (Google is my friend) the nearest I can come up with (though not exact) is an American (?) UNF, although it's unlikely I would think as it's an English or at least Scottish machine, I have a 1/4 Whitworth die (at least it has 1/4 W20 stamped on the body of the die) and that wont fit, too tight and an NF28 die and that's no good either, too loose.
Does anybody out there in help-full land have a clue to help.
The only place I can see where I may be off track is that while the bolt I have, I don't have a nut to fit, does run into the threaded part all the way to the bottom (15 mm) I can't be sure that it is a really good fit, feels OK but I'm not positive
Thanks in advance
Don

I would suggest B.S.F British Standard Fine but the pitch would need to be 26 tpi for that O.D.

edit rechecked my tables and it could be 7/32 B.S.F which is 28 tpi with an od of 5.55mm

Have a look here, donn :-

http://www.tracytools.com/taps-and-dies 

I had a similar problem with my Minerva. There was a thread I had not heard of called UNS.....1/4 UNF is 28 TPI, 1/4 UNC is 20 tpi - 1/4 UNS is 24 TPI !

If you need 1/4 UNS taps & die, you can borrow mine. Good luck.

Quote:

Originally posted by HappyDaze Have a look here, donn :- http://www.tracytools.com/taps-and-dies  I had a similar problem with my Minerva. There was a thread I had not heard of called UNS.....1/4 UNF is 28 TPI, 1/4 UNC is 20 tpi - 1/4 UNS is 24 TPI ! If you need 1/4 UNS taps & die, you can borrow mine. Good luck.

"Special", I think.....it was a new one for me.

I think Harley Davidson used UNS threads.

Ok, thanks for that fellas, I'll head off to the bolt suppliers armed with that info on Monday, Saturday just before closing I took a punt but came home with the wrong gear.

7/32 BSF looks like it.......however [just to confuse the issue], there is a metric 5.5x0.9 thread which is VERY close.

BSF thread angle is 55 degrees, Metric is 60 degrees.

We'll the good news is that it sure looks like 7/32 BSF, the bad news that it's no longer made or not available, depending on who you ask, so I've got the job of drilling and tapping a new thread.
Thanks for the help

Hhmmmm.
I had our local WA bolt and fastener companies all tell me I couldn't get metric fine M18 (common in Euro). They also told me that you could no longer get SAE 10/32 or 8/32 (I use them here at work on old NASA shite).
What that translates too is they either haven't even heard of them and are too bloody lazy to look, or they haven't got suppliers who stock them.

I found them on Ebay no worries.

Well Modnrod, I'm not even going to look, I've already tapped the new thread and I don't want to find out that I didn't look hard enough.

Quote:

Originally posted by donn Well Modnrod, I'm not even going to look, I've already tapped the new thread and I don't want to find out that I didn't look hard enough.

For future reference a copy of machinerys handbook has every thread ever produced and you can pick up a copy off amazon fairly cheap , you don't need the latest so an older version is fairly cheap and it has a lot more useful information than just thread types
Cheers

sure its not a BA thread as in 0BA 1BA etc