Bridgeport Mill motor locknuts

[Yankeefarmer]

Can anyone tell me what size thread is used on the locknuts for the motor on the step pulley (Series 1 J head, I believe) machines? I haven’t been able to find that info in any web searches. Reason I’m asking is I have a Bridgeport-like vertical mill on which previous owner(s) have cobbled up the locknuts quite badly, and I’m looking to freshen it up to facilitate speed changes. The locknuts on mine use a 1/2-12 tpi thread, which I’m assuming is a Whitworth (BSW) form, although I have read that some machinery makers used a 1/2-12 of the UNC thread form. My machine is a Pearson S, which was likely manufactured in Italy.

TIA for any info.

 

[laser3kw]

Your goto source for Bridgeport stuff is H&W machine in Fort Worth IN.
Here is a link to their resource page. Page 64, is it item 39?

Bridgeport parts diagram link

Their prices for OEM replacement parts are real reasonable.

 

[Yankeefarmer]

Your goto source for Bridgeport stuff is H&W machine in Fort Worth IN.
Here is a link to their resource page. Page 64, is it item 39?

Their prices for OEM replacement parts are real reasonable.

Thanks for your interest and help.

No, it’s items 41 and 43, the stud and the adjusting nut. My problem is that my parts look just like that, but I don’t want to buy them and find that the thread is wrong for my machine. I’d rather buy them than spend time and money for the tooling to make them on my lathe.

 

[laser3kw]

The stud should have a 3/8-24 size on the top according to the nut description assuming that 39 is the nut. Wouldn't hurt to call them and pick their brain, they may have knowledge of how close your machine matches a Bridgeport. I'm sure they have "seen it all" or close to it.

 

[Monza Harry]

1/2-12 is no longer a "standard " thread, but it does show up somewhat frequently on items from metric countries ie; the Hobart magnetic ground (China). This was a common thread a long time ago. With some searching you should be able to source something usable/modifiable. Harry
From Amazon Canada in Stainless: https://www.amazon.ca/dp/B077GLY9CQ/?tag=atomicindus04-20
P.S. BSW isn't the same system and I'm not sufficiently informed to help with that.

 

[Yankeefarmer]

Thanks, Harry. Yeah, the difference is in the angle of the threads, 55 degrees vs. 60 degrees. I’ve got a tap and die on order, and plan to just fabricate what I need. I found studs at a shop in Australia, but the gent there tells me he doesn’t ship international on orders under $100.

 

[C lectric]

A 1/2"-12 is a legitimate but VERY old thread which was superceded to 1/2" - 13 for the national standards coarse.

 

[Yankeefarmer]

Just to close the chapter on this thread, I bought a BSW tap and die on Amazon for about $30, and using some steel rod I had on hand from other projects, fabbed up everything I needed to replace the mangled hardware that was on my mill.

Thank You to those that responded. Of course, we still don’t know what Bridgeports used.

 

[TheEquineFencer]

PM OccupantRJ , he rebuilds them and knows BP inside and out.

 

[Firebrick43]

Your goto source for Bridgeport stuff is H&W machine in Fort Worth IN.
Here is a link to their resource page. Page 64, is it item 39?

Bridgeport parts diagram link

Their prices for OEM replacement parts are real reasonable.

Just don't get something rebuilt from them. They do **** work. Or at least they did on the machines that I have seen them rebuild.