thread parameters

[lawson4]

Can anyone tell me the Pitch dia, Minor dia and Major dia for #6-48 and #8-40 threads, internal and external?
I can buy gages and taps and dies, but I can't find dimensions.
Can someone help me out?
TABIA (thanks a bunch in advance)

lawson4

 

[terry264]

If you don't have the proper equip. for measuring these, i.e. pitch mikes, etc. it won't do you any good. The gauge itself should be marked as to it's diameters. The "go gauge" and the "no-go gauge" have their min. and max. thread diameters marked on them. Any good machinist's handbook should have the drill size (before tapping) and info. like that.

 

[lawson4]

terry264, thanks for the reply.
I need the information to put on a drawing. Our standards require it. The Machinery's Handbook doesn't have these listed as they are not Unified National threads; they're considered specials.
I have a request for the info from a gage company, but I usually get info from THR faster.

lawson4

 

[terry264]

Hi lawson4, WOW, I see your problem. Did some searches for you, just nosey I guess, can't find a darned thing. Where I used to work had all this stuff, unfortunately they are out of business now. This was a faucet co. (Sterling) which was bought up by Kohler and moved all over the US in different places. I used to do QC there, among other things, and we set our own ring gages and had some state of the art measuring equip. there. If I can think of any way to get your info. I'll get back with you.

 

[Jim K]

I had much the same experience. I have known for years that 6x48 is a size that is used almost exclusively in the gun industry, and it doesn't seem to appear in any of the standardized lists or charts. 8x40 is at least on the charts but without full information. So I can only say good luck. I'll keep looking and see if I can find anything.

Much of this kind of thing is the result of the gun industry being about the first modern type industry in the U.S., and indeed in the world. There were no standards; the gun companies made their own screws, gauges and taps, to whatever specifications they felt was needed for a particular application. (Another example is the .236x60 threads on M1911 grip screw bushings.)

Jim

 

[3sixbits]

Now for a trip on the "Way-back machine" Many of our so call gun screw sizes come from the bicycle days of early America. Starrett used to list this as a bicycle screw thread and pitch gauge. When doing a search try thomasnet.com. Of course the be all, end all, is to contact Starrett via the net. Try Starrett.com. Good luck!

 

[lawson4]

I hope I will get a call from Southern Gage with answers to my questions. If not, I'll let the QC people find the information they require>

Thanks for the replies.
I'll post if I get an answer.

lawson4

 

[Jim K]

FWIW, S&W (1851) and Colt (1836) were around a long time before bicycles. But many gun companies also made bicycles or vice versa, Iver Johnson being one, so it would not be surprising if the same odd screw sizes had been used in both industries.

Jim