jonhall Posted September 8, 2019 Share Posted September 8, 2019 I've just bought a tobacco tin of useful looking brass nuts bolts and so on and have a number of nuts that appear to be close to, but not, M3.5 or 4ba. Any suggestions what size/thread format they might actually be? Thanks Jon Link to post Share on other sites More sharing options...
RLWP Posted September 8, 2019 Share Posted September 8, 2019 How about 6-32UNC or 6-40UNF? http://www.carbidedepot.com/formulas-tap-standard.htm That would be very annoying! Richard Link to post Share on other sites More sharing options...
brack Posted September 8, 2019 Share Posted September 8, 2019 6-32 or 4-40 are very commonly found in computer cases and drives, but are more commonly shiny silver in colour. I appreciate this is a weird question, but are they old? Might give some clue. Link to post Share on other sites More sharing options...
Guest Lyonesse Posted September 8, 2019 Share Posted September 8, 2019 UNF 6-40 is .136 in diameter and 40 TPI. 4BA is .142 in diameter and 38.5 TPI, so close-ish. The unified thread standard has been around since the end of WW2. At one time, I believe, it was called the ABC (America-Britain-Canada) standard. Link to post Share on other sites More sharing options...
jonhall Posted September 8, 2019 Author Share Posted September 8, 2019 yes very old brass - I'd expected ba if i'm, honest - a known 4ba screws in a couple of turns before stopping - i'm wondering if they are just a little miss formed? Thanks for suggestions so far Jon Link to post Share on other sites More sharing options...
RLWP Posted September 8, 2019 Share Posted September 8, 2019 6 minutes ago, jonhall said: yes very old brass - I'd expected ba if i'm, honest - a known 4ba screws in a couple of turns before stopping - i'm wondering if they are just a little miss formed? Thanks for suggestions so far Jon 4BA is the highly convenient 38.5 tpi* so chances are they're 6-40 UNF Bet you could screw a 4BA screw in until it suddenly shears off. I've played this kind of game before Richard * doesn't seem to be a convenient metric pitch either Link to post Share on other sites More sharing options...
spikey Posted September 8, 2019 Share Posted September 8, 2019 Another possibility, particularly since they're brass, is one of the weird threads that used to be used by clockmakers. Link to post Share on other sites More sharing options...
Nearholmer Posted September 8, 2019 Share Posted September 8, 2019 Are they too small to be 3/16" BSF? Link to post Share on other sites More sharing options...
jonhall Posted September 8, 2019 Author Share Posted September 8, 2019 1 hour ago, Nearholmer said: Are they too small to be 3/16" BSF? Not sure - I don't have a 'known' 3/16" BSF to try them with. Thanks for all the suggestions. if anyone could use them for the cost of postage I'll happily pop them in a jiffy bag - most of my grandfathers (and therefore my) stocks are BA, so I can't really use them. Jon Link to post Share on other sites More sharing options...
RLWP Posted September 8, 2019 Share Posted September 8, 2019 37 minutes ago, jonhall said: Not sure - I don't have a 'known' 3/16" BSF to try them with. Thanks for all the suggestions. if anyone could use them for the cost of postage I'll happily pop them in a jiffy bag - most of my grandfathers (and therefore my) stocks are BA, so I can't really use them. Jon 3/16 is 0.188", 40 thou bigger than 4BA. 0.040" is near enough 1mm* - you'd spot that Richard *or 3" at 4mm to the foot Link to post Share on other sites More sharing options...
jonhall Posted September 9, 2019 Author Share Posted September 9, 2019 12 hours ago, RLWP said: 3/16 is 0.188", 40 thou bigger than 4BA. 0.040" is near enough 1mm* - you'd spot that Richard *or 3" at 4mm to the foot Oh no - its definitely not that then, the known 4ba bolt can be screwed in one turn to the unknown nut before it gets stuck, so they are very close size wise. Thanks, Jon 1 Link to post Share on other sites More sharing options...
tom q vaxy Posted September 9, 2019 Share Posted September 9, 2019 could they be Japanese Industrial Standard fastenings? https://trimantec.com/blogs/t/thread-identification-guide Link to post Share on other sites More sharing options...
michl080 Posted September 9, 2019 Share Posted September 9, 2019 Morning Gentlemen, I find THIS table very useful and complete. I guess the strange language is no problem. Michael Link to post Share on other sites More sharing options...
RMweb Gold tomparryharry Posted September 10, 2019 RMweb Gold Share Posted September 10, 2019 There used to be a cycle thread size as well, somewhat close, but not quite, Ba sizes. I've never used it myself, but the old timers knew about it. Also, some of the ME sizes are quite fine. Cheers, Ian. Link to post Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now