Threading help please

[tobnpr]

Maybe this will help explain: This is not my pic, just one I found with a quick search on the internet, but this shows the 3 parts im making:
View attachment 508279

Exactly.
The part at bottom right is what you're referring to, correct?
That's turned/bored/threaded out of solid stock, not tubing.

 

[Investigator]

Exactly.
The part at bottom right is what you're referring to, correct?
That's turned/bored/threaded out of solid stock, not tubing.

My friend, I'm confused now. I never said it was out of tubing

 

[tobnpr]

So, I have 1" rod and 1" tube. I'm making a screw in cap. The tubing is machined as shown in the drawing.
I need to find the major diameter of the external threads on the rod so I can turn it to that dimension then thread. The minor diameter of the internal threads can't be less than .900"

I honestly couldn't understand what was referring to what, and I still don't follow the profile you drew for the muzzle end of your barrel. You said the muzzle is threaded 1/2-28, but you have a relief section ahead of the threads dimensioned as .860, which sure as hell is larger than the minor diameter of 1/2 threads. That's obviously not your muzzle in the top drawing, but I don't know what it is.

I'm not trying to be difficult, I honestly can't follow your sketch- it doesn't relate at all to the photo of the end caps and tube you posted.

 

[Investigator]

I honestly couldn't understand what was referring to what, and I still don't follow the profile you drew for the muzzle end of your barrel. You said the muzzle is threaded 1/2-28, but you have a relief section ahead of the threads dimensioned as .860, which sure as hell is larger than the minor diameter of 1/2 threads. That's obviously not your muzzle in the top drawing, but I don't know what it is.

I'm not trying to be difficult, I honestly can't follow your sketch- it doesn't relate at all to the photo of the end caps and tube you posted.

OK you are confused. let me walk you through it. First let's look at the admittedly horrible drawing i posted:

First and foremost there is no barrel in this drawing, no gun part, no firearm part nothing except exactly what it says. The top section is my depiction of a 1" solid rod of CRS I got from the big box store. I will take that solid steel CRS rod which at the moment is 36" long and put it into a 5c collet through the headstock of my lathe. I will profile it, as I will describe in a moment, and thread it at 28tpi.

The bottom sketch is supposed to represent some round tubing I have with measures 1"OD with a .065" wall, and .868" ID. (yes i know the numbers are off, but the wall thickness is what was listed on the tube and the ID is what I measured with my bore gauges) This tubing is 4140 (I think because it's what I had on hand) and is about 12" long. That piece of tubing will go into the lathe in the same 1" 5c collet, and the end will be trued, and then bored to an ID of .900" for a depth of .480". That .900" ID area will need to be threaded to 28tpi so that the cap from the solid 36" rod in the top drawing will thread in and fit.

If you will again look at the top drawing of the solid CRS rod, you will see at the southern end as drawn a section that is shown as .868" OD. That section will actually be turned to about .865" so that it will slide into the ID of the tube which as not been bored. SO THAT when threaded together it will form an integrated spacer for the first baffle.

Now, when all of that is completed, I will cut the tube to length and repeat those operations on the new end of the tube as well as making another endcap for the new end of the tube, thus producing:
*1 suppressor tube
*1 proximal endcap
*1 distal endcap.

And if my math is correct at no time during the foregoing operations will a gun or gun barrel or gun part or grease gun or gun or firearm of any kind be touched, machined, drawn, fondled or (dare I say) even imagined.

It's a tube and 2 caps.

 

[redgrouse]

Investigator, Your original sketch and request is clear enough to me, however you say the barrel thread industry standard is 1/2" x 28 UNEF -- well this side of the pond it's 1/2" x 20 UNF and has been possibly since the first sound moderators came about ? but I can verify it has been so for the last 60 years and I have fitted a great many, mostly of similar proportions to those you propose 1" dia x approx 5" long

Going back to your original question regarding the OD of the male thread, you need to turn it to 0.9387" +0.000" - 0.005" and thread to 28tpi -- I would suggest you thread to internal first to a thread depth of 0.019" 0.021" then use this as a gauge for the external thread. Calculations were made using a standard 28tpi UN thread and adding or subtracting the difference of your proposed 0.900" ID thread as required -- OK it may not be exactly to a particular standard but will suffice for you needs.
Hope this helps !

Here are a few links that you may find useful

https://www.alliedtitanium.com/technical/threads/unef/UNEF_Threads.pdf

This one you put in the diameter you want in Inches BUT it gives the answers in millimetres !!! so use 0.0397 as the factor to convert to proper sizes !

Unified Inch Screw Thread (UN UNC UNF UNEF) | Thread Specification

Unified Inch Screw Threads (UN|UNC|UNF|UNEF) profile, dimension and tolerance. 1-64 UNC, 2-56 UNC, 3-48 UNC, 4-40 UNC, 5-40 UNC, 6-32 UNC, 8-32 UNC, 10-24 UNC, 12-24 UNC, 1/4-20 UNC, 5/16-18 UNC, 3/8-16 UNC

www.threadspecification.com