Can anyone I.D. a bolt via size? - Page 3 - UK Vintage Radio Repair and Restoration Discussion Forum

Station X · 25th Jan 2018, 2:53 pm

A 5/16" X 22 TPI BSF bolt would measure 13.335mm across the flats of the nut, which isn't too far off the 13.25mm specified by the OP.

Measuring thread pitch without pitch gauges or known threads to compare the unknown one with isn't easy, so perhaps the 20 TPI quoted by the OP is incorrect?

g4aaw pete · 25th Jan 2018, 11:14 pm

This post has prompted some really interesting information.
I've attached the measurements as shown.

Head of bolt 13.25mm
Half inch of thread (12.7mm), 10 threads or 20 TPI
Thread max diameter 7.77mm

However, I found a cycle spanner that was a fairly loose fit.
Also, rummaging through a box of loose bolts at my office, I found exactly what I needed. I imagine it was part of an office chair. It's a tight fit into the casting of the tripod & has a molded plastic disc / hand grip.

Mission accomplished.
Thank you all for inputs.

Regards
Pete

emeritus · 26th Jan 2018, 12:25 am

To me, the second photo shows 9 threads in 1/2" ( 12.7mm), which would make it 5/16" Whitworth or UNC.

Station X · 26th Jan 2018, 12:31 am

Agreed.

Radio Wrangler · 26th Jan 2018, 1:25 am

It is pitches which must be counted, and because of thread starts, it's best to set the anvil of the mike one pitch in and count from there.

David

Boater Sam · 26th Jan 2018, 2:01 am

No, not after all this debate don't you dare say mission accomplished and disappear!
T'would now seem to be 5/16 UNC if it is not very old. Whitworth is the same pitch up to 5/16 anyway but different thread form, BUT the spanner size on the spare bolt you found is Whitworth size.
So, can I conclude?
The required handwheel is 5/16 UNC and does the job.
The spare bolt you had was 5/16 Whitworth, and caused a lot of confusion!

g4aaw pete · 27th Jan 2018, 10:52 pm

Quote:

Originally Posted by emeritus

To me, the second photo shows 9 threads in 1/2" ( 12.7mm), which would make it 5/16" Whitworth or UNC.

Having looked at this again & re-photographed the thread, I can only agree with your observation!

25th Jan 2018, 2:53 pm	#41
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: Can anyone I.D. a bolt via size? A 5/16" X 22 TPI BSF bolt would measure 13.335mm across the flats of the nut, which isn't too far off the 13.25mm specified by the OP. Measuring thread pitch without pitch gauges or known threads to compare the unknown one with isn't easy, so perhaps the 20 TPI quoted by the OP is incorrect? __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

25th Jan 2018, 11:14 pm	#42
g4aaw pete Heptode Join Date: Jan 2008 Location: Birchington Kent, UK. Posts: 596	Re: Can anyone I.D. a bolt via size? This post has prompted some really interesting information. I've attached the measurements as shown. Head of bolt 13.25mm Half inch of thread (12.7mm), 10 threads or 20 TPI Thread max diameter 7.77mm However, I found a cycle spanner that was a fairly loose fit. Also, rummaging through a box of loose bolts at my office, I found exactly what I needed. I imagine it was part of an office chair. It's a tight fit into the casting of the tripod & has a molded plastic disc / hand grip. Mission accomplished. Thank you all for inputs. Regards Pete Attached Thumbnails

26th Jan 2018, 12:25 am	#43
emeritus Dekatron Join Date: Jan 2012 Location: Brentwood, Essex, UK. Posts: 5,347	Re: Can anyone I.D. a bolt via size? To me, the second photo shows 9 threads in 1/2" ( 12.7mm), which would make it 5/16" Whitworth or UNC.

26th Jan 2018, 12:31 am	#44
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: Can anyone I.D. a bolt via size? Agreed. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

26th Jan 2018, 1:25 am	#45
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,901	Re: Can anyone I.D. a bolt via size? It is pitches which must be counted, and because of thread starts, it's best to set the anvil of the mike one pitch in and count from there. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

26th Jan 2018, 2:01 am	#46
Boater Sam Banned Join Date: Dec 2013 Location: Middlewich, Cheshire, UK. & Winter in the Philippines. Posts: 3,897	Re: Can anyone I.D. a bolt via size? No, not after all this debate don't you dare say mission accomplished and disappear! T'would now seem to be 5/16 UNC if it is not very old. Whitworth is the same pitch up to 5/16 anyway but different thread form, BUT the spanner size on the spare bolt you found is Whitworth size. So, can I conclude? The required handwheel is 5/16 UNC and does the job. The spare bolt you had was 5/16 Whitworth, and caused a lot of confusion!