12 Replies Latest reply on Apr 5, 2018 9:40 AM by Christopher Estelow

# UNF wizard hole

Hi guys, starting to understand Solidworks and i just got problem with understanding standard wizard hole using UNC and UNF.

i've been practicing Solidworks and just started 3 days ago through self-learning via (youtube and websites tutorials)  and i just encounter a description of "6-32 UNF-2 or Unified National Fine (from google) "which should be the standard size of the hole for thread if i got it correct however i still don't understand.

This 6-32 UNF-2, can you explain it to me because i tried to search it on google but
it would be best if I ask some experts rather than guessing on my own to avoid inaccurate information.
many thanks!

my Questions are:
What 6-32 mean is it 6/32 size or is it
6 stand for 6 mm/inc and 32 means the number of thread cycle

and what does -2 next to UNF stand for?

Picture #8

Misc. Web Blueprints for Practice

• ###### Re: UNF wizard hole

6-32 is a fastener size, #6 screw with 32 threads per inch. The -2 is the thread class or fitment details.

Here is what the #6 means:

"# 6 screw is one of many US Numbers screws (where is pitch makes no difference in diameter) All Number screws are measured as follows: O.D = 0.060" + N(0.013") , where's N is the number of the screw , thus the diameter of # 6 screw is: 0.060" + 6(0.013") = 0.060" + 0.078" = 0.138"."

• ###### Re: UNF wizard hole

Attached is a pretty good article on Unified threads.

Also this:

• ###### Re: UNF wizard hole

It is a good article. Thanks.

For a long time it is bothering me. What is the importance of the Pitch Diameter in the manufacturing process?

• ###### Re: UNF wizard hole

Specifically, scroll down the GH Numbers area.   This gives a good idea on how Pitch diameter is used.

• ###### Re: UNF wizard hole

FYI:  6-32 is UNC, not UNF.  6-40 is UNF.

• ###### Re: UNF wizard hole

Good catch! didn't even notice that. That print is wrong. I'm sure any machinist would have caught that and disregarded it as an obvious mis-callout, but still, the devil is in the details:).

• ###### Re: UNF wizard hole

Walter, that's a good catch!  It is so easy to accept things as true when they are so close, kind of like how many of each animal did Moses take on the Ark?

• ###### Re: UNF wizard hole

Also, not really necessary to call out drill dia/depth, unless design calls for it. Let the shop use the standard drill size for the thread.

• ###### Re: UNF wizard hole

I agree for that part, machinists don't appreciate being told how to do their job! Although I have a lot of blanks plasma cut with tap drill diameter holes, then sent to a second shop for final thread forming and machining. It helps to have the proper diameter/tolerance for the plasma cut print. I have accidentally had them cut to the major diameter by mis-checking the "remove thread" option in the hole wizard,  which necessitated repair via inserts, or scrapping the parts.

• ###### Re: UNF wizard hole

In the attached reference doc I use there is a tab for inch threads.  It will give you all the details for min and max of the major and minor OD's for each thread. The correct callout for the thread, not including the tap drill, would be 6-32 UNC-2B. The 2 is the class for the fit and the B would mean internal thread (A is external).

Chris

• ###### Re: UNF wizard hole

many thanks with the details and files attached, i really appreciate it!

now i can easily study about thread.