Threaded Suppressor Adapter

wnchstrtnfldvlle

wnchstrtnfldvlle

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Well, got the lathe back up and running and was looking for a project to start on that would test my abilities to follow a set of drawings. Then the other night we discovered an armadillo den between the neighbor's house and ours. Which made me think about suppressing my Mk4. I don't have a .22LR suppressor, but I do have an Omega 9K that accepts a threaded adapter. The only really critical dimensions are the threads. 1/2-28 UNEF for the muzzle, and 1.125-28 UNF for the suppressor side. But I did measure out the original 5/8-24 adapter to use for the drawings. Aluminum rod for the practice round, then either 4140 or 416 stainless for the final part. I haven't even started trying to figure out which would be the better option so any advice would be appreciated.

Preliminary design stuff
IMG_5552.jpg

I'm also trying to get better at CAD, so here is the attempt. I did have to look up a couple things, but the majority I was able to remember how to do.
IMG_5555.jpg

Chucked up in the lathe and turned to the 1.200" overall diameter. As you can see that is steel. I attempted to thread away from the chuck without rewatching the Joe Pie video, and ended up cutting left-handed threads, lol. So now it's a restart with the 4140.
IMG_5559.jpg

A couple questions.

1. What strategy do you guys use when setting up to hit the Y-axis dimensions? Do you face it then mark that the zero, then watch the DRO while traveling towards the chuck to hit the mark? Or would you work your way backwards from the 1.2" ring turning to the major diameter and then face off before starting the 1.125-28 threads?

2. How do I get the threading insert (or HSS tool) to reach the centerline for threading? Pic below for clarity, but there's no way that I can see to get the insert at the proper level. I run out of travel way before. In the Joe Pie video, it looks like he has a shop made adapter that allows for higher placement on the tool post. Any ideas?
IMG_5560.jpg
 
You can try running the threading tool right side up, but from the back side of the part, assuming the cross feed will allow for that.
(lathe in reverse, carriage traveling away from the headstock)

Also on the workflow, I would probably machine the larger thread first, then make a mandrel and cut a female version of the larger thread to hold the part for making the smaller thread. If you do not remove the mandrel it should maintain perfect concentricity.
 
1. Along the spindle axis is Z, not Y. I do as much as I can in one setup to maintain concentricity, and to minimize figuring out workholding on short parts. In the case of your adapter, I would face, set the Z position to 0, then work my way from Z0 to whatever I need to turn. I would not part off before threading, much easier to do it while still attached to the bar, and you know it is concentric to what you just turned.

2. I use a Mesa gooseneck threading tool for threading away from the chuck. A smaller toolholder can work too when mounting it upside down, you probably don't need for such a big tool for threading unless you are doing really course threads. I don't recall what Joe used to set his tool higher, but a block of the appropriate thickness should work fine.

This is the Mesa tool https://www.mesatool.com/product-page/gooseneck-threading-tool
 
Ischgl99 said:
1. Along the spindle axis is Z, not Y. I do as much as I can in one setup to maintain concentricity, and to minimize figuring out workholding on short parts. In the case of your adapter, I would face, set the Z position to 0, then work my way from Z0 to whatever I need to turn. I would not part off before threading, much easier to do it while still attached to the bar, and you know it is concentric to what you just turned.

2. I use a Mesa gooseneck threading tool for threading away from the chuck. A smaller toolholder can work too when mounting it upside down, you probably don't need for such a big tool for threading unless you are doing really course threads. I don't recall what Joe used to set his tool higher, but a block of the appropriate thickness should work fine.

This is the Mesa tool https://www.mesatool.com/product-page/gooseneck-threading-tool
Click to expand...
And I knew that about the Z-axis, lol. The DRO has the Y on it, and I just got used to that.

Your plan sounds about like what I was going to do.
- I'll turn the major diameter for the larger thread, thread it.
- Then bore out the inner portion. (I didn't want to thread on the thin wall left if boring first.
- Then I'll turn the backside of the 1.200" ring for the hex wrench flats.
- Then turn the .860 diameter for the barrel side.
- Then bore the minor diameter for the 1/2-28.
- For these threads I may just tap it using the tap and follower setup in the lathe. I think that will be the best bet. But I may try to single point it to see if I can figure that out. One more skill to practice.

Thanks for the reply
 
They make right and left hand threading tools as well as boring / threading tools . Makes threading a breeze if you don't trust your capabilities .
 
First, a slight digression - can you (or someone) post a link to the referenced Joe Pie video? I really like JP, but I haven't stumbled across that one. I have only threaded conventionally (toward the headstock), which eliminates some of the problems you mention.

Aluminum would probably be fine, forever, but I'd do steel myself.

I usually face, set up a parting tool, touch the faced surface with it, then move back the desired amount + the width of the facing tool and cut a thread relief. You *will* want a thread relief in this application no matter how you cut the thread. For the sake of axial alignment, your can needs to butt up against a squared surface, as does the adapter.

It's not a precision measurement, 20 thou either way isn't going to make or break it. I'm not saying you should be sloppy, just trying to inject some realism so you don't overthink it.

Who in the heck threads a suppressor 1.125" x 28?!? I've threaded dozens of barrels for suppressors and never run across that.

I'm assuming that's one internal thread and one external. Just drill, thread outside, thread inside, part off and done. Maybe throw the nearly finished piece in a collet for a cleanup face - that step not having any impact on your concentricity.

GsT
 
Here is the Joe Pie link.
Joe Pie Threading Video

As far as the adapter being regulated, I will have to look into that. I do know that the adapters for oil filter suppressors may get you in trouble so it's a valid concern. In my case I don't know that it would matter since I've already got the suppressor with the other adapter.
 
GeneT45 said:
It's not a precision measurement, 20 thou either way isn't going to make or break it. I'm not saying you should be sloppy, just trying to inject some realism so you don't overthink it.
Click to expand...
Understood. It's more to just practice hitting dimensions. The overall goal is to start chambering my own barrels, so I thought this would be a good project to start practicing.
 
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