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I am finishing up my Columbia AH early style first style project. To complete the build, I need 4 nuts and 1 screw The screw is to hold the base of the governor in place, and the missing nuts hold the base plate and top plate to the internal works. As many of you know, thread sizes were different and 1901/1902 and the modern day equivalents don’t work.

Nuts - see pictures below for context. I need to get 4 Columbia nuts that are approximately 15/64

Screw - see pictures for context. I would like to get a machine screw that is ⅓ inch long and approximately 11/64.

Feel free to reach out to me with any additional questions. Does anyone have these?

Thanks.

The major diameter of the screw is an important measurement and I’m glad that you checked it with your caliper, however the thread type and number of threads per inch (or the thread pitch) are equally important. We’ll need to know this as well.

This looks like another job for the handy thread checking tool in this other “thread”.

viewtopic.php?f=2&t=57889

Mark

Mark,

Thank you very much for the information. I used calipers to count the threads and came up with 32 threads per inch. Seems to be a V-thread which I believe is the same as a unified thread. Does that answer your question? I’m certainly happy to provide more information if need be.

Thanks again,

John

Here's a couple of tips.

1. Don't use your caliper in fractional mode when measuring thread diameters. Not all SAE threads are "fractional", (e.g. 8-32). For example, an 8-32 thread has a diameter of .164". I kind of suspect that the thread of your screw is 8-32, but your fractional setting is too inaccurate to know for sure. Use the decimal setting, which is far more accurate.

2. Measure the thread diameter further back in the jaws of the caliper. The knife edges at the ends of the jaws are likely to fall into the threads and give you an erroneous reading. The wider back jaws will bridge the crests of the threads.

Have a look at my posting on this topic as well... viewtopic.php?f=2&t=57889

I took your advice and pulled out my plastic thread gauge. Additional measurements:

Screw - according to my gauge, it’s is a 10-32 fine thread x ⅓ inch long. Screw Diameter: 4.66 mm

Nuts - according to my gauge - ¼ inch with 28 threads per square inch, which makes it a fine thread. Diameter of the bolt to which it attaches - 6.27 mm

I am doing precise measurements, but it’s hard to be perfect. I have taken booth the nut and screw to an excellent hardware store with a reputation for matching old screws/nuts, and they had nothing in stock to match.

Am I getting closer? Need anything else…. If so, I’m happy to oblige…

John

Search GOOGLE with those thread sizes and you might have some luck...

DELETED DUPLICATE

Thanks for the advice and I think I’ve got the nuts figured out. I purchased a thread gauge and can confirm the precise measurements of the screw:

3/16-30 x ⅓ inch long. Ideally, this screw should be black (like the other one), but color isn’t a deal breaker.

Jmcmahan67 wrote: ↑Fri May 10, 2024 9:28 pm Thanks for the advice and I think I’ve got the nuts figured out. I purchased a thread gauge and can confirm the precise measurements of the screw:

3/16-30 x ⅓ inch long. Ideally, this screw should be black (like the other one), but color isn’t a deal breaker.

That would be known as a 10-30 x 5/16" screw.

You can make any screw black with Birchwood-Casey cold gun bluing or heat it with a torch and drop it into motor oil...