Starrett has some weird threads.

[woodchucker]

5/16 X 20 is a standard thread. Tap and die are available from KBC among others. $9 & $11 in catalog. Spec's are in Machinery Handbook. You can single point it. On the 15/32 , is that the rod diameter where the holder/stop goes and then is turned downed to 5/16-20? That is what it looks like in the pictures. Gotta remember that Starrett has been around since Freddy Flintstone was machining granite wheels. So a thread that was common in 1900 may be obsolete today. But if the company has already tooled up and was using it, they would continue.
Have run into this before and had other people point out what it was from their collection of notes.

Fred Flinstone, wasn't he the guy that used his feet to stop the car?
I don't want to add 5/16 - 20.. was surprised after tapping 5/16-18 to find that. Anyway, easier to make a new rod. I could have turned down the existing rod and done 18.. but I'll save it for if I ever need it.

Thanks...

 

[woodchucker]

I think Starrett started out with a meat chopper if I remember correctly . Late 1800s or so .

were you around then?

 

[mmcmdl]

I've got Starrett Mag bases with some weird threads as well WC . I just used them as chip shield holders in the past . I'm sure the rods are somewhere on the premises .

 

[Chewy]

WC, fully understand not wanting to get weird taps and dies. Just consider yourself lucky that you aren't into model steam engines. The normal stuff is ME and BA thread. USA supplies of parts and tools are limited. Biggest source is from the UK. Shipping ain't cheap.

 

[mmcmdl]

were you around then?

Absolutely not . I remember this from 7th grade .....................................the longest 3 years of my life .

 

[Bi11Hudson]

Re. The 15/32 rod: How about 12mm. . . Which is actually 0.472. With the top of the threads trimmed off 0.003 each side works out. Then there is a metric thread that comes out pretty close to 20 TPI. 1mm pitch is 25.4 TPI. . . Could be. . . I got into that problem with toggle switches as far back as the mid '60s. 1/2 was too big, 7/16 was too small. Then I discovered metrics.

Edit: I missed a point. 5/16 is so close to 8mm, a sheet of cigarette paper wouldn't fit. And the thread would be near to 20 TPI. The cap screws are so close that one will "almost" fit the other.

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[Chewy]

Bill, was it as much fun as discovering girls?

 

[woodchucker]

Re. The 15/32 rod: How about 12mm. . . Which is actually 0.472. With the top of the threads trimmed off 0.003 each side works out. Then there is a metric thread that comes out pretty close to 20 TPI. 1mm pitch is 25.4 TPI. . . Could be. . . I got into that problem with toggle switches as far back as the mid '60s. 1/2 was too big, 7/16 was too small. Then I discovered metrics.

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but 15/32 was just right

 

[Bi11Hudson]

Bill, was it as much fun as discovering girls?

Not quite, but it solved a lot more problems. If I had stayed in school, the girls would surely have been much more interesting. But growing up too early does have some up sides. They must be better viewed in hindsight though. Learning about girls from women was fun.

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[woodchucker]

Not quite, but it solved a lot more problems. If I had stayed in school, the girls would surely have been much more interesting. But growing up too early does have some up sides. They must be better viewed in hindsight though. Learning about girls from women was fun.

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Bill, you learned about girls/women, but have you figured them out yet? That's the one every man is wanting to know.