Exact Physical Sizes of Threaded Metric Rods or Bolts

Hi John,

It's not a 10mm thread as it would measure very near 10mm outside diameter.

The nearest I can work out is it MIGHT be 7/16 Outside Diameter by 20 Threads per Inch which is UNF. Try and get a nut with a known thread and try it.

Hope this helps.

Best of luck,

John

You are right. I used a cheap plastic thread measuring tool that Bolt Depot sent me for free on an order. After reading your comment I broke out my Starret guages. The 1.25 metric ALMOST fits except after about 10 turns you can see a tiny ride up whereas the 20 TPI fits snugly end to end. Stupid me. The fitting came from an English sailboat wire rope rigging eye kit so I assumed metric, got a good fit on the plastic guage and then went off track. those guages go to the trash can as of now.

I couldn't find a 7/16 x 20 nut around here for the test but 7/16 = .4375 and my major diameter is .428 so this might be the correct fit. A precise mechanical drawing of a 7/16 x 20 bolt showing tolerances will confirm this. I hope there isn't a close Whitworth (English) thread to further confuse the issue.

Thank you very much.

John

From Sleepy,

do not throw those gauge blocks away, they will be very useful!

Make sure that you have some Imperial ones as well!

If I lived a little nearer I would make you an offer for them! As it is I had a relative visiting the Dominican Republic recently!

More than 50 years ago I had to learn how to use Slip Gauges very accurately to set coupling loops on 2GHz filters, five cavity if my memory serves me aright, Thus four coupling loops to be set on each production filter; after I had calibrated the system so that a given centre frequency provided a set of coupling parameters for each filter. As well as input and output couplings.

Turned out that nobody in the production team could handle it so that I was down to do the lot; I cannot now remember how many there were but they were for a major continental Microwave Relay system. Each loop had to be set accurately with slip gauges and then soldered with minimal solder. The position as well as the size of the loop.

Then tune each filter, Dishal's method, using the VSWR of the filter on a swept measurement. Tighten a lock on each cavity screw and then done!

I lived around 25 miles away, left home at about 7 am and cycled the 25 miles to work, slaved away on these filters all day, stopping briefly for a sandwich at lunch, leaving to cycle home around 8 pm.

After 3/4 weeks of this. (7 day weeks) I was getting extremely tired ! To the extent that I was allowed 30 mins rest around 3 in the afternoon! There was a very tight deadline on the whole project and there were teams working all over the place.

My first aquaintance with Slip Gauges and I loved the precision that one could achieve, around 1 thousand of an inch for each coupling. I nearly bougt a set on eBay recently!

I believe that I saw a set of Optical Gauges for sale recently, well beyond my budget and I cannot remember what the tolerance and steps were. This was my ( as an EE) first introduction to the Mechanical side of my career.

Sleepy

I don't think this will quite help you, since the thread sizes aren't exactly right, but maybe you could start here. You might contact them to see what else they offer, or if they have a supplier they use that could help you.

http://www.edmundoptics.com/onlinecatalog/displayproduct.cfm?productID=1378

http://www.edmundoptics.com/onlinecatalog/displayproduct.cfm?productID=2787

With 10.9mm OD and 1.25mm pitch, threads seems to be 7/16"UNF only which are standard for tube fittings.

Your requirement of inch to metric coupler is not unique. Genrally these are standard product in instrument fittings. You can try at http://www.swagelok.com/

Try a non standard M11x1.25 (the size exists and 10.9OD will suit it). This is provided you are sure it is metric.