Oddball thread help on Kamakura 6” rotary table

[Flyinfool]

I have seen where since the company is making both the internal and external thread, it is intentionally made oddball just so that no one can repair it with an off the shelf part, they must get the replacement from the OEM. I know this to be true because as a design engineer I have done it. Not my idea, just following orders from above. Same for electrical cords with a custom connector and plug.

 

[egiddings]

I’m cleaning up an old rotary table I found last year. Though the tag says it was made in Japan, all the screws and clamp handles are SAE thread. (Was that common for Japanese manufacturers in the 50s, 60s and 70s??)

Anyway, it’s the table’s center hole that’s getting my attention. It’s threaded rather than tapered. The plug seats about 60 thou below the surface and seems useful only for blocking chips. I assume if I want any center alignment or fixture pins, I’m going to have to make them. That’s fine, but I need a sanity check trying to ID that thread…

Major dia. is 23.10mm/.9095in. Threads are 60° and a perfect 1.50mm pitch. (18TPI is too small, 16 too large and my Starrett No6 never heard of 17TPI.) I’ll be damned if I can find anything in my 15th ed. MHB or the engineer’s black book with specs like that.

I guess it doesn’t really matter if I’m cutting threads on the lathe. But it’ll be my first threading project and it would be nice to find an actual standard with tolerances. Just want to be sure I’m not overlooking something obvious…

Any help?

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Looks like the guy who owned this 15th ed. before me had some difficulty with threads too…
View attachment 476755

Good afternoon, I believe I have the same or similar table. Do you have any suggestions on how to remove the center plug? Just wanted to check before I start heating and cranking on it. Thanks

 

[Weldingrod1]

Inspect from the bottom. As far as I understand, the bore is usually Morse taper.

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[yota]

I have a Japanese lathe and it's almost all SAE fasteners. my guess is that for a certain time period, the US importers could require the manufacturers to use SAE fasteners.