silverfox4 Posted March 10, 2018 Author Report Share Posted March 10, 2018 Hi Roger, Thanks for confirmation. I do have a tap on order from Amazon - taken longer than usual to deliver, so maybe dredging the South China sea for one... Alf Quote Link to post Share on other sites
stuart Posted March 11, 2018 Report Share Posted March 11, 2018 Hi Alf, you can get a 5/8 x 13tpi tap made but it does not exist as a standard thread form (anywhere in the known or unknown Universe). The 16mm x 2mm fits OK. Roger Oh yes it does, I have one here, bought off Ebay a few years ago. It therefore follows it cant be the only one. Stuart. Quote Link to post Share on other sites
AlanG Posted March 11, 2018 Report Share Posted March 11, 2018 Oh know It doesn't. Well it does actually... https://www.ebay.co.uk/itm/41-British-Made-Second-Imperial-Hand-Tap-Tapping-Drill-5-8-x-13-Thread/371848536866?hash=item5693e66322:g:DagAAOSwpDdU-IXe Alan Quote Link to post Share on other sites
stuart Posted March 11, 2018 Report Share Posted March 11, 2018 Oh know It doesn't. Well it does actually... https://www.ebay.co.uk/itm/41-British-Made-Second-Imperial-Hand-Tap-Tapping-Drill-5-8-x-13-Thread/371848536866?hash=item5693e66322:g:DagAAOSwpDdU-IXe Alan See, told you so! Stuart. Quote Link to post Share on other sites
RogerH Posted March 11, 2018 Report Share Posted March 11, 2018 Hi Stuart, this is all very fascinating. I have a listing of all the thread forms used - tiny little threads with 400tpi up to 6" threads with just a few TPI It is not 100% comprehensive but covers a great deal and that bl**dy 5/8 x 13 isn't there. So what is it. Why make a special when money is tight. Roger Quote Link to post Share on other sites
silverfox4 Posted March 11, 2018 Author Report Share Posted March 11, 2018 Very strange, I do see the UK Ebay listing, as Stuart points out, but over this end the only one Amazon.ca has is a BSF 5/8" -14 Alf Quote Link to post Share on other sites
stuart Posted March 12, 2018 Report Share Posted March 12, 2018 Hi Stuart, this is all very fascinating. I have a listing of all the thread forms used - tiny little threads with 400tpi up to 6" threads with just a few TPI It is not 100% comprehensive but covers a great deal and that bl**dy 5/8 x 13 isn't there. So what is it. Why make a special when money is tight. Roger Maybe to try to make the thread form closer to that of the switch so its more oil tight. Stuart. Quote Link to post Share on other sites
RogerH Posted March 12, 2018 Report Share Posted March 12, 2018 Maybe to try to make the thread form closer to that of the switch so its more oil tight. Stuart. Hi Stuart, yes I can see that but why did the original switch manufacturers use an odd thread. 5/8BSF is 14 tpi and if there is a French connection then M16 is 12.7tpi Very odd indeed. It is interesting how they pop up on ebay now and then. Roger Quote Link to post Share on other sites
silverfox4 Posted March 12, 2018 Author Report Share Posted March 12, 2018 I was checking stuff about the overdrive (wow pressure required is 490 psi), and on page 2.304 reference Fig 5 for the overdrive isolator switches, it notes that the thread is 16 mm x 2 mm. Go figure.... Alf Quote Link to post Share on other sites
Tom Fremont Posted March 12, 2018 Report Share Posted March 12, 2018 13 TPI equates to 0.07692" each, which number is different from 2mm by....0.002"! The same discrepancy holds for 5/8" and 16mm. For a short run of thread like these switches employ they ought to be functionally equivalent. Perhaps the taps could pass for each other as well... . Cheers, Tom Quote Link to post Share on other sites
silverfox4 Posted March 12, 2018 Author Report Share Posted March 12, 2018 Valid point Tom, as IRCC think there are only three threads. The debate now is why the metric vs SAE (BSF?) situation arose in 195X - it seems the switches might well be metric to start with; who knows. Alf Quote Link to post Share on other sites
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.