Can someone explain what a "USF" thread is?

[Villagelane90]

I have a vintage drawing that shows 6.990" major ID with 6.8547" minor ID and 8 threads/in USF.

 

[MattiJ]

I have a vintage drawing that shows 6.990" major ID with 6.8547" minor ID and 8 threads/in USF.

Constant-pitch series 8 UN?
Unified Thread Series 8 TPI ANSI/ASME B1.1

 

[Villagelane90]

Drawing states USF thread. I see I can purchase on Ebay some thread gauges for USF thread but don't understand what machining details are. I will look at your data and see if will work. Thanks much.

 

[L Vanice]

When was the drawing dated? In 1914, the United States Standard thread was in use. USS was probably the precursor to UNC, which generally has the same pitches. A 6" diameter USS thread had 2 1/4 TPI, so USF might describe a fine thread of the US form, which has flat crests and roots measuring 1/8 of the pitch, which would be 1/64th of an inch for 8 TPI. Or USF might stand for United States Form rather than Fine. Anyway, look at the handbook data below for 1 inch 8 TPI and use the depth of thread and width of flat dimensions. Tolerances? In 1914 they just made things to print.

Larry

 

[johnoder]

The US suggests United States Standard - which went away before my January 1940 American Machinist's Handbook came out

I see Larry types quicker

 

[MattiJ]

Based on old books that google finds its same as USS threadform = same as UN with possibly slightly different tolerances.

United States Standard thread - Wikipedia

Someone with machinery handbook should be able to dig more info. My copy is currently hiding somewhere.

 

[NRDock]

Here's a reprint of a first edition, 1914 Machinery's Handbook for $64.65. If I wasn't counting down, I'd have already bought it.

Machinery's Handbook : For Machine Shop and Drafting-room, 1914 First Edition... | eBay

 

[carlherrnstein]

That must be a old one... U.S.F.=United States Form

What is the 16 U.S.F Threads meaning ? | GrabCAD Questions

Might be best to fit it to the male thread if possible if not perhaps you could measure the male thread P.D. however, a lot of the old "standards" were kind of a rule of thumb and not super exact. Basically if the parts screwed together it was good.

It might be as simple as just bore the I.D. to the "minor I.D" and work the thread depth out to the specified Major I.D. However its probably more complicated than that.

 

[L Vanice]

Here's a reprint of a first edition, 1914 Machinery's Handbook for $64.65. If I wasn't counting down, I'd have already bought it.

Machinery's Handbook : For Machine Shop and Drafting-room, 1914 First Edition... | eBay

Those are $20 cheaper on Amazon ($44.47 with free shipping + tax).

https://www.amazon.com/gp/offer-listing/0831133708/ref=dp_olp_new?ie=UTF8&condition=new

Larry

 

[Ron Hofer]

Leave it to Larry.

 

[Villagelane90]

The drawing is 1960 vintage. I looked at the USS form but the dates did not line-up.

 

[MrSteve]

Pre WW1 USS Sellers or National Standard thread form but non-standard TPI/Pitch or non-standard diameter “United States Form” Thread? Modern UN thread form tweaked for odd diameter might interchange?

 

[calvin b]

Villagelane90, Sir (?)
Being that your print is from 1960 I think it's a unified "special form" thread. Usually the unified part is left off of "special form" designations but I think it's possible that an over zealous draftsman added it to the drawing. Hey at least you can look up the formulas in a ASME handbook and figure out what you need to make.. Kinda awkward but it's a start...
Hope this helps
Stay safe
Calvin B