.250-28 in UNF -BA what is the BA ?Like the title says

J

jrmach

Titanium

Joined

Jun 9, 2012

Location

Boise,Idaho USA

• Feb 14, 2019

• #1

Like the title says,,,what is the BA
Kind of contradictory when already specifying UNF
My understanding is BA is for the other side of the pond?????

 

johnoder

Diamond

Joined

Jul 16, 2004

Location

Houston, TX USA

• Feb 14, 2019

• #2

Mistake for 3A?

Class 3 OD thread

Seems incorrect to have both UNF and BA in the same line of text - the one being HERE and the other THERE

 

L

L Vanice

Diamond

Joined

Feb 8, 2006

Location

Fort Wayne, IN

• Feb 14, 2019

• #3

BA is British Association, a small diameter thread standard with strange diameters and pitches invented in the 19th century, probably by math majors with no machining experience. I bought the taps and dies in 1964 for convenience in building Stuart Turner model steam engine kits.

Someone who wrote .250-28 UNF is already departing from the normal designation of 1/4-28 UNF, so the BA might be similarly peculiar and probably nothing to do with the old English machine screw threads.

Larry

 

J

jrmach

Titanium

Joined

Jun 9, 2012

Location

Boise,Idaho USA

• Feb 15, 2019

• #4

johnoder said:

Mistake for 3A?

Class 3 OD thread

Seems incorrect to have both UNF and BA in the same line of text - the one being HERE and the other THERE

Click to expand...

That's what I am thinkin,,

 

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G

guest

Guest

• Feb 15, 2019

• #5

The tolerance on the major is a lot tighter than a 3A.

edit: looked again, guess that's a sort of shoulder bolt is why. Kinda fussy.

 

K

kenton

Stainless

Joined

Dec 15, 2015

Location

Illinois

• Feb 15, 2019

• #6

The cadmium plating and 100 deg angle makes me curious if it's aircraft hardware. Obviously, if it is get clarification in writing from whoever wants that bolt to cover your ass.

 

michiganbuck

Diamond

Joined

Jun 28, 2012

Location

Mt Clemens, Michigan 48035

• Feb 15, 2019

• #7

Hope that is not all given .. what is the body diameter?

 

G

guest

Guest

• Feb 15, 2019

• #8

michiganbuck said:

Hope that is not all given .. what is the body diameter?

Click to expand...

I'm reading it as .2481/.2487 for the body. Theoretically the threaded part could be as small as .2435 if the "B" is supposed to be a "3"- but it can't be over .2487, so you couldn't make the 1/4-28 UNF 3A at MMC (.250" OD).

 

C

CountryBoy19

Stainless

Joined

Aug 14, 2012

Location

Bedford, IN

• Feb 15, 2019

• #9

guest said:

I'm reading it as .2481/.2487 for the body. Theoretically the threaded part could be as small as .2435 if the "B" is supposed to be a "3"- but it can't be over .2487, so you couldn't make the 1/4-28 UNF 3A at MMC (.250" OD).

Click to expand...

Yeah, I'm wondering if the BA has some sort of significance bc the OD of the part means the thread could never be MMC on the major diameter. IE, maybe a special spec that means pitch diameter is controlled to class 3 but the major is reduced?