1/2 x 28 UNF .........does it even exist?

mofosheee

mofosheee

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Lost in this rabbit hole. Rebuilding a vintage motorcycle engine and task with making various unobtainable threaded fastners.
I've searched the internet and am able to find data on 1/2 x 28 UNEF taps and dies. For reference I have been using;

1/2 - 28 UNEF : Thread Dimensions (Machining Doctor)

1/2 - 28 UNEF : Basic Thread Dimensions (Pitch, minor & major diameters, depth, lead), Tolerance range for all applicable classes and much more
www.machiningdoctor.com www.machiningdoctor.com
& I search for; 1/2 x 28 UNF taps and dies on Ebay or Amazon .................only UNEF flavors display.
I cut 1/2 x 28 threads on my mill........... and my 1/2 x 28 UNEF tap is reluctant to thread into this hole.
No data on 1/2 x 28 UNF or does it exist?

Thank you forum!
 
mofosheee said:
I search for; 1/2 x 28 UNF taps and dies on Ebay or Amazon .................only UNEF flavors display.
I cut 1/2 x 28 threads on my mill........... and my 1/2 x 28 UNEF tap is reluctant to thread into this hole.
No data on 1/2 x 28 UNF or does it exist?

Thank you forum!
Click to expand...

You are correct, 1/2 inch, 28 threads per inch are (UNEF) Unified National Extra Fine. There is no such thing as 28 UNF.
How did you tap the threads on your mill? You have a down feed for 28 TPI? If you have a 1/2-28 UNEF why do you not just use it? Or are you just asking where to find 1/2-28 fasteners? Randal answered that question.
 
RandyM said:
You are correct, 1/2 inch, 28 threads per inch are (UNEF) Unified National Extra Fine. There is no such thing as 28 UNF.
How did you tap the threads on your mill? You have a down feed for 28 TPI? If you have a 1/2-28 UNEF why do you not just use it? Or are you just asking where to find 1/2-28 fasteners? Randal answered that question.
Click to expand...
Yes, with a single point cutter, my software allows for 1/2 x 28 TPI.
yes, I have 1/2 x 28 UNEF tap and die. The parts I am trying to duplicate are 1/2 x 28 UNF
Mc Master & Carr does not have UNF because as you said, "there is no such thing" except for my vintage bike :)
Thank Randy and Rabler for the help!
 
mofosheee said:
Yes, with a single point cutter, my software allows for 1/2 x 28 TPI.
yes, I have 1/2 x 28 UNEF tap and die. The parts I am trying to duplicate are 1/2 x 28 UNF
Mc Master & Carr does not have UNF because as you said, "there is no such thing" except for my vintage bike :)
Thank Randy and Rabler for the help!
Click to expand...
I am sorry, but you cannot duplicate something that does not exist.

We're trying to help. Sounds like we need more info.

markba633csi said:
British bike?
Click to expand...
I think Mark is on the right track. You may need to duplicate something British. Good luck.
 
mofosheee said:
Yes, with a single point cutter, my software allows for 1/2 x 28 TPI.
yes, I have 1/2 x 28 UNEF tap and die. The parts I am trying to duplicate are 1/2 x 28 UNF
Click to expand...

The parts you are trying to duplicate are not UNF if they are 1/2-28. If they are described as 1/2-28 UNF, then one half of that statement is incorrect. Typo, oversight, or otherwise.

A half inch UNEF threaded fastner automatically has 28 tpi, there is no other UNEF half inch thread. A half inch UNF fastener automatically has 20 tpi, there is no other UNF half inch thread. And a half inch UNC fastener automatically has 13 tpi, there is no other half inch UNC thread. Although there was another, now obsolete US standard (outside of Whitworth) for 1/2-12 that shows up in a lot of older US made stuff, which you might could actually run into one day. just to keep you on your toes.


Bottom line-
If you have measured this, and KNOW that the 1/2-28 description is correct, then UNEF taps and dies are what you want, the UNF part is wrong.
If you have not measured this, you need to measure one part or another to confirm what you actually have, because at least one half of that description is incorrect.
 
MrWhoopee said:
I have also seen the designation 1/2-28UN, which is a standardized 28 tpi series. It's the same as 1/2-28UNEF.

28-Thread Series, 28-UN and 28-UNR

www.efunda.com www.efunda.com
Click to expand...

I see stuff tagged that way often. In hardware grade stuff, that's all that matters. You've got the diameter and pitch already, single start is safe to assume, UN makes it a unified basic form which gives you the angles and limits, they'll all work together, and anything you do to it that's "fancier" (more engineered....) is (essentially) irrelevent in hardware grade.
 
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