Thread identification please.

[Monte NZ]

Could someone please  let me know the thread size of the three screws that attach the  starter pulley  on my 1924  2hp BNL Johnson…

I believe it is an unusual thread size.

Thanks in advance

/

Monte NZ

 

[The Boat House]

Do an internet search for – screw size aomci. There is more than one oddball thread on those early Johnson’s.

[RICK EICHRODT]

Monte,

I think they are 8x 30 thread size.  Chris Scratch has made some for me and I believe that is the size!

 

Rick

[Steve D]

A thread gauge tool like this has come in handy for me a number of times.

[bkrsdoz]

Rick is correct. 8-30 thread size. You can find used ones from donor motors.

I found some oval head slotted 8-32’s on EBay. They work as well.

[joecb]

I think that it’s time to post the chart again. The old ASME screw thread standards.  Use caution when encountering a thread that appears to be a 1/4 inch, note on the chart that there are three screw sizes that are real close to 1/4 inch…. some unusual thread pitches also. A micrometer and thread pitch gage is your friend.

Joe B

1 user thanked author for this post.

The Boat House

[Monte NZ]

Thanks  Tubs, Rick, Steve D, bkrsdoz and joecb for your help in sorting that problem and thanks to for the chart…..very handy…….I have printed it off for future reference.

Why they used such uncommon threads beats me!

As always, many  thanks for your input.

Monte NZ

[joecb]

Uncommon now – a- days, but optional “standards” back then. I believe that World War II industrial production boards did a lot to put the old standards to bed and introduce the current standards.

Joe B

[Author]

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