Thread question, #8-32 NC?????

[Bigmon]

Seems like always something catching me off gaurd?
I used a #8-32 tang bolt on a project this week and in the process off all the Ins-and-outs I must have damaged the male threads on the bolt cause it was binding somewhat.
Knowing that I should have that size DIE in my tool box I stopped in a local hardware and picked up a USA made DIE by IRWIN HANSON.
But I noticed it was marked #8-32 NC. ( dont that mean National Coarse??).
I asked the hardware man about it and he said it seemed odd to him also, but must be ok as he had none marked NF for National Fine.
He did have #10-32 NF.
Anyway I tried to trace the bolt threads and it was very tight., but I could do it by hand with the bolt in a vice.
But once traced it is clear to see that the bolt diameter is slightly smaller, even by the naked eye.
Am I missing something here in the world of small diameter threads??
Isnt #8 a size no matter the thread and doesnt the 32 mean 32 threads per inch, and why would that matter regarding a diameter???
Probably end up buying new tang bolt.
But I am doing all this as a learning project.
But I do want to learn what is happening here before I start on expensive stuff?
Thanks in advance for any help.

[Stophel]

8-32 is 8-32.  Now one manufacturer might make theirs tighter or looser than the next, but it's still 8-32.

Now, if it is a split die, there is a screw in it where you can open it up or tighten it just a little bit, to make your screw tighter or looser.  I always have my dies opened up as far as they can go so I can cut the threads on the bolt as large as I can so it is tight in the threaded hole.

 

[okieboy]

 An 8-32 is an 8-32 and in size #8 a 32 TPI thread is coarse (NC or UNC). For a UF in size #8, you would use an 8-36. As to how "loose" or "tight" a thread is, that is determined by the Thread Class. There are thee classes of fit for Imperial threads, 1A/1B (loose), 2A/2B (medium), and 3A/3B (tight). the A stands for external threads, the B stands for internal threads.
 Most of the screws you get from the hardware store are class 1, the lock and tang screws that you have are almost certainly class 2, class 3 threads in their maximum condition will actually interference fit (very few people ever deal with class 3 threads).
 The die that you purchased was probably, if not adjustable, a rethreading die for an 8-32 class 1. If had been a threading die, as opposed to a rethreading die it would have been adjustable and you could have creeped up on the fit that you wanted as Stophel suggested.
 Correcting small damages to otherwise correct threads can also be done with a thread file or carefully with a sharp triangular needle file (standard imperial threads have a 60 degree angle, British Whitworth threads have a 55 degree angle).

[Acer Saccharum]

Okie is correct about 8-32 being National Coarse (NC). The National Fine (NF) is 8-36.

10-24 is NC, and 10-32 is NF.

[Bigmon]

Thanks for the information guys.  It is very informative and interesting.
The DIE itself is NOT a split die.
The packaging says nothing of any kind of "fit"??, nor does the die itself??
As is the screw makes up uk in the trigger plate, but is noticably sloppy.

Thanks again

[P.W.Berkuta]

May I suggest you try these people for your taps, dies, & other items -- <http://www.toolsavings.com/> --- they have a WIDE selection and great prices

[Stophel]

I hate sloppy fitting screws myself, BUT, it's just a tang bolt. No worries.

[Bigmon]

I have been away from building for 30 or more years and in that time have lost bout all my gun type tools as well as eye sight, and forgot allot also.
I have picked up some components and am trying a couple  builds with this stuff and then I am going to try and build a few nicer pieces, to the best that I can.
But I can say I never saw such a difference in these threads when they are both supposed to be the same #8-32.  Much more and they wouldnt even work.
But my Dad always said I was tooooo particular.
I already know next time I can I'll be getting new bolt.
But this brand new DIE is not right, if the screws are right??  And the screws match up well with a couple taps I have so I'd say the Die is wrong.
I hate to return stuff but it is a matter of princiole.  But I cant even blame it on Chinese made, its marked USA.
Thanks again ya'all

[P.W.Berkuta]

Just because it is USA made does not mean it is correctly made --- I have a Greenfield die (#10-32) that has NO threads cut into the die. It looks like a good die but it has NO threads . As others have already said use the "split die" so you can adjust the fit to the bolt/screw .

[flehto]

When I was toolmaking we had split, adjustable threading dies  and very rarely ever  adjusted them. So when am order of #8-32 lockbolts was rec'd which were oversize, I went to Menards and bought a cheap #8-32 threading die which was non-adjustable, but which worked perfectly.  I think sometimes we over think so-called problems.

I want any screw in any one of my builds to turn easily....but w/ a proper amount of thread engagement....since then I have bought a #6-32 threading die from Menards and this too has worked well.  Both the #8-23 and #6-32 sizes are used in my builds....no longer use #10-32 screws because I think they're overkill.....Fred

[Stophel]

Just about the only time I use a 10-32 screw is if I somehow screwed up an 8-32 hole and I need to go bigger.

[JLBSparks]

Is there a possibility that the screw is metric? m4 x .7? That would explain it looking smaller in diameter and difficult  to run the die by hand.

   -Joe

[jerrywh]

 You need to google up a thread chart and hang it on the wall in your shop. A good thread chart will show you all the tap drill sizes and clearance drill sizes also.

[WadePatton]

You need to google up a thread chart and hang it on the wall in your shop. A good thread chart will show you all the tap drill sizes and clearance drill sizes also.

I picked up a Machineries Handbook for 1 usd at a sale a few years back.  For anyone who doesn't know, this thick little book covers nearly everything you could ever want to know about metals and working with them, some engineering and other materials as well.

Also complete coverage of drills and taps and threads thereof.



____My buddy bought the Bridgeport.

Wish he'd get it set up already!

[JLBSparks]

#8 machine screw diameter is 8 x .o13" + .060" = .164".
m4 x .7 machine screw will be .157" diameter and 36 threads per inch.
Subtract .005" diameter for clearance (approx.).

   -Joe

[Old Ford2]

Just because it is USA made does not mean it is correctly made --- I have a Greenfield die (#10-32) that has NO threads cut into the die. It looks like a good die but it has NO threads . As others have already said use the "split die" so you can adjust the fit to the bolt/screw .

P.W.
You have been in the business long enough, that you should know, that the die you have is for forming unthreaded screws, so that they will be ready for threading 
Please be informed 
Fred