By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by Allendale May 23

7/16" X 30 tpi thread

Anybody able to identify?

All Topics | Latest Posts

Search for:  in Thread Title in  
Swarf Maker05/10/2017 18:05:27
63 forum posts
4 photos

I don't want people to spend hours trawling the net or whatever, but I have not been able to identify this thread standard. It is used to adjust clutch lift on a whole series of pre-WW2 motorcycles that use the smaller of the Burman gearboxes. I am completely confident of the sizes quoted as the measured diameter is 2.5thou under 7/16" and the Moore and Wright Whitworth 30tpi gauge fits snugly along its entire length. I can readily deal with both internal and external single point screw cutting for replacement components, so it's no big deal. I am just intrigued as to whether there is a standard that applies. Also interesting that 30tpi doesn't seem to appear very frequently. Anybody know this one off-hand?

Chris Evans 605/10/2017 18:39:21
1395 forum posts

I play around with pre war bikes and do come across a few manufacture specific threads. A lot of 1920s Douglas motorcycles had 25 TPI threads and not the more usual 26 TPI cycle thread.

alan lloyd 305/10/2017 18:50:30
avatar
150 forum posts

The vintage motor cycle club will have the answer i'm sure, burman gear boxes were fitted to many old motorcycles as i'm sure you know already, good luck

David Standing 105/10/2017 19:58:03
1201 forum posts
45 photos

Prior to the BSC/CEI standard, it was a free for all and as stated above, manufacturers went with whatever suited them. 7/16 x 30 is unlikely to fall into any standard.

Swarf Maker05/10/2017 22:49:03
63 forum posts
4 photos

Thanks chaps. Good to know that I am not alone in unearthing these obscure threads. It's a bit of industrial archaeology in a way and is useful when restoring things to understand a little of the likely thinking of the day. I have come across the Douglas specials myself but such things always make me wonder, was this a ploy to keep a hold on the spares supply market or was the designer being careful to ensure that the chosen thread met exacting engineering criteria? I suspect that it's best not too think too deeply and just get on with recording such original features, reproducing them when the pain is not too great, and modifying things if that is the most appropriate course of action. For this job things will remain as designed.

All Topics | Latest Posts

Please login to post a reply.

Magazine Locator

Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!

Find Model Engineer & Model Engineers' Workshop

Latest Forum Posts
Support Our Partners
Eccentric Engineering
Warco
Ausee.com.au
ChesterUK
Eccentric July 5 2018
TRANSWAVE Converters
Sarik
emcomachinetools
Allendale Electronics
Subscription Offer

Latest "For Sale" Ads
Latest "Wanted" Ads
Get In Touch!

Do you want to contact the Model Engineer and Model Engineers' Workshop team?

You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.

Click THIS LINK for full contact details.

For subscription issues please see THIS LINK.

Digital Back Issues

Social Media online

'Like' us on Facebook
Follow us on Facebook

Follow us on Twitter
 Twitter Logo

Pin us on Pinterest