Maybe a British bolt?

[Cedarman]

I have a Dominion Midas moulder made in England about 20 years ago or so. A bolt has disappeared. (I have employees, happened in the last several years, and haven't needed it until now) I do have 2 of the 3 bolts needed.
In front of me now I have a bolt that the threaded length is 1 1/8", bolt size is 1/2", but here is the kicker the threads per inch are 12 instead of 13. You can take a 9/16-12 and the thread pattern matches up exactly. Take a 1/2 inch bolt and the threads do not.  Caliper reads .48 so I know it is a 1/2 inch bolt.  I cannot find a 1/2-12 anywhere.  Tried McMaster-Carr, Grainger, even a specialty bolt supply business.  No luck.

Option:  Retap at 1/2 -13 and hope it holds a 1/2-13 bolt

Option:  Drill and tap for 9/16-12 and get new bolts.

My question for anyone east of the pond that might know, "do you have bolts that are 1/2-12?" Was that a standard bolt size?

And for anyone else, do you know where I can find a 1 1/8"long x 1/2-12 bolt?

[fstedy]

You might try to see if a metric size will fit sometimes they are very close. I don't think the Brittish were still using Whitworth threads 20 years ago but I could be mistaken. I think your easiest solution would be to tap 9/16 - 12 since you wouldn't be cross threading as if you used a 1/2-13 tap. Be sure you can get both tap and bolt before you start. If you tap 9/16-12 its just a simple redrill to open the holes to the 9/16 tap drill size then retap. It should pickup the old threads and just open it up to the new size.

[Lenny_M]

 Brittish standed or Wentworth thread would be 2 I know of.
You could try a garage or dealership that work on older Britt cars
                                                              Lenny

[isassi]

Or the quickest would be to buy a grade 5 or less long half inch bolt and have a guy with a lather or machine shop cut off to length and thread for 12 tpi which according to my reference is Whitworth (not used in 40 years). Funny thing is somewhere in my collection of odds and ends, I have a 1/2 - 12 die we used for model steam engines I built when I was much younger. 

[Cedarman]

Thanks for the info.  I will post what I did and how it turns out.  If I don't post, you will know how it turned out :D :D :D

Now just why would industry decide that they needed a 1/2- 13 if they already had a 1/2-12?   To me it sounds like some engineer needed to be taken out and shot.

[Fla._Deadheader]

  Gotta justify their existence  ??? ;D ;D

[Tom]

My BSA motorcycle was Whitworth and drove me nuts. 

http://www.boltscience.com/pages/screw4.htm

http://www.jag-lovers.org/xk-lovers/library/whitworth_system.html

[isassi]

Actually American engineering was behind the times when related to the English standards. We use SAE, a newer version of SME. The Brits had a standard back in the beginning of their mechanical revolution. The Whitworth thread was 55 degrees instead of 60 as American (SAE) and typically was a little coarser, i.e. 12 instead of 13. I used to own a Broadbent engine lathe built in the '40s and the bolts and screws in it were Whitworth.

[Cedarman]

Thanks Tom, those links provided a world of info.  I have a set of the wrenches. They never did make sense to me until now.  The moulder was like brand new when I bought it about 4 years ago even though it was an old machine.  It has made me a lot of money.  Most of the bolts seemed to be interchangeable with standard bolts, but a few seemed to be very contrary.  Now I know why.  Gear shaft sizes seem to be normal though.

Since the bolt didn't need to be torqued extremely tight to do its job. I rethreaded with a 1/2-13.  Put in a new bolt and it is holding fine.  But I think I will order the correct bolts and nuts that may be needed at a later date for other spots on the machine.

[CHARLIE]

Geeez Tom....my '58 BSA Super Rocket and my '65 BSA Lightning Rocket both used Wentworth bolts. AND.....I still have a set of 4 Craftsmen open end wrenches (8 sizes) in my tool box. I don't know why I still have them...sentimental I reckon.  I also have 1 or 2 Wentworth wrenches that came in a Triumph Bonneville, T120 that was given to me when Harris sold his bike and bought a Harley Sportster.  Wonder what they would sell for on e-bay? Hmmmmmmm ;D  The Wentworth sizes never bothered me 'cause I had the wrenches.....it was the oil that leaked from the Primary Case that was the bother.  Double gaskets and lots of permatex fixed it though.

[Tom]

I think Whitworth is still available so you probably wouldn't get much for them.   You should  make a display case for them and put a little story and pictures in it for Little Charles.  You've got some twins now that will consider them Gramp's antiques.  :D

[Brucer]

According to British Standard 1083:1965, the standard threads for 1/2 inch bolts are 12 TPI (BSW) and 16 TPI (BSF). BSW refers to British Standard Whitworth, and BSF refers to British Standard Fine. These aren't commonly used anymore as British manufacturers switched to either ISO metric sizes or the UNC/UNF sizes common in North America. None of which is much help to you :(.

[scsmith42]

Cedarman, if you have any problems with the new bolt working loose, try replacing it with a stud (installed with some blue or red loctite on the former-whitworth threaded end only).  Studs usually stay put when bolts work loose.