Old and unusual screw sizes

[joecb]

Hello all. Following up on a discussion about old/ obsolete American Standard Screw sizes… I found my reference chart for sizes from #2 to #30 . This from an old fastener manufacturing company. When measuring the diameter of the thread, remember that the thread will be a few thousands smaller that the nominal body size.

Hope it will be useful and prevent problems from “almost alike” fasteners.

Joe B

• This topic was modified 2 years, 7 months ago by joecb.
• This topic was modified 2 years, 7 months ago by Mumbles.

[Mumbles]

That’s a handy chart and thanks for posting it!

And there are the #14 screws Johnson used on their rope sheaves which commonly get mistaken for being 1/4″.

What is the length the last column would be referring to?

[joecb]

The lengths in the last column, are the standard range of lengths that this company , The American Screw Company produced.

Joe B

1 user thanked author for this post.

Mumbles

[The Boat House]

Early Johnson had an odd shear pin Dia. as
well. I haven’t had any luck finding brass rod
that size.
Tubs

[pm-t2]

The screws used in the earlier Johnson rope sheaves are 10-30 screws. My South Bend lathe has no setting for cutting 30 threads per inch. My Cardiff does, but I don’t have the necessary headstock gear for it. I bought a 10-30 die from a place in Michigan for 11 dollars US. I use it to make new rope plate screws, and also made screws that work with my puller kit so I don’t have to hammer on the flywheel nut to get the flywheel off.

But here’s one for you. Check out the slotted hex-head bolts that are used to fasten the cylinder castings to the crankcase. They are 20 TPI but the major diameter measures at about 0.260″, whereas most 1/4″ fasteners measure a few thou under 0.250″. Using a regular 1/4-20 fastener is not recommended for that particular application.

Hope it helps, but it’s somebody else’s fault if it doesn’t

Best,
PM T2

1 user thanked author for this post.

T....in Wisconsin

[joecb]

Dear Prime Minister … 0.260 (that be 6.604 mm for some of you guys) is likely the #16 -20 from the chart, body diameter of 0.268

Joe B

[The Boat House]

This is the little bugger. Luckily they don’t
get the attention that the flywheel screws do
so they are, normally, still in good condition.
Tubs

[Buccaneer]

I ran across an odd size thread today, on the 1925 Elto Lightwin, model C,
on the water outlet tube that goes thru the exhaust manifold.
I had no tap or die for this one.

The thread OD measured .388, and it has 27 TPI.
I didn’t even know my thread gauge has 27 tpi, let
alone hear of that thread.

Prepare to be boarded!

[joecb]

One encounters 27 tpi on some pipe fittings, with out going down to the shop to measure, I’ll bet that that is a 1/8 NPS ( National Pipe Straight) as opposed to the common 1/8 NPT ( Tapered) , both are 27 TPI. I think that if you go to a lamp supply store , you will discover that the common threaded tube in most light fixtures is 1/8 (27 tpi) NPS

AND yet another caution… careful that there is a British 1/8 pipe that is 28 TPI

All this is great fun , and we haven’t even gotten into the metric and Whitworth stuff yet.

Joe B

[Buccaneer]

Joe, I should have thought about the pipe thread possibility!
The specs I found are pretty close to what I have…….

Nominal Pipe Size (inch) – 1/8″ NPT
No. Of Threads Per Inch – 27
Outside Dia. (inch) – 0.405

Prepare to be boarded!

[Author]

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