Endcap thread length?

[cdhknives]

I thought I had plenty of threads with a 1/2" thick endcap almost full threaded 1/2-28. On final review I see the YHM barrel threading spec is .620-.670" from shoulder to muzzle. That will leave exposed threads to get gunked up in my blast chamber. I am trying to keep the weight down so adding another 1/8" of endcap thickness (17-4 steel) is something i'd rather avoid. I know I can drill and undercut to lighten it but still...

Is leaving these threads exposed on the inside of a 22lr suppressor going to lead to problems removing the suppressor later? I know there are other workarounds (like a 17-4 insert/thread adapter into an AL endcap body) but the straightforward approach is what I prefer...I am self taught and by no means an experienced lathe operator!

[John A.]

I have noticed that not all barrel threads protrude 1/2 an inch. Some longer, some shorter.

If you do happen to thread it long, will essentially guarantee that they will seat up against virtually any shoulder.

And if they "gunk up", you can always run a tap down there and clean it up.

[cdhknives]

It is the male thread getting fouled that concerns me. That could lead to difficulty even getting the endcap off the barrel, threads galling, etc.

[T-Rex]

teflon tape the threads

[tootalltom]

Would it make any sense to just create a solid "shim" to thread onto the muzzle before the suppressor is threaded on?

And, for my own education, if that type of workaround does make sense for a .22lr suppressor, should it be avoided for centerfire uses?

[cdhknives]

One workaround (which actually fixes 2 concerns...reduces weight) already mentioned is a 17-4 adapter in a aluminum endcap. Thread the ID 1/2-28 for the muzzle and the OD thread to fit the endcap...that would make the adapter easy to build to muzzle thread length since I am going to thread several barrels for this suppressor. It does make everything more complex though. I am still mulling that solution.

[fishman]

Would it make any sense to just create a solid "shim" to thread onto the muzzle before the suppressor is threaded on?

This is what I'd do.

OR
Shorten the barrel 0.2" then run a die over the threads

[ECCO Machine]

Most rimfire thread tenons are .450" or shorter, and some rimfire cans will bottom out the blast baffle on a tenon over 1/2" without a spacer.

I thread end caps or brakes .700" deep (plus .050" undercut where applicable) for centerfires, but my rimfire caps are just .500".

[cdhknives]

Thanks guys...I assumed the 1/2-28 muzzle threads would all be the same. After some more searching I find some suppressor manufacturer's diagrams for rimfire 1/2-28 are as short as .400". Much better! I will be cutting muzzle threads into a couple of pistols for my rf can...good thing I found this now!

[yondering]

Sounds like you figured it out; I was just about to ask if this was for rimfire or centerfire.

My rule of thumb has always been .400-.420" for 22lr threads, and .600-.620" for 5.56 and other appropriate centerfire calibers.

[ECCO Machine]

Sounds like you figured it out; I was just about to ask if this was for rimfire or centerfire.

My rule of thumb has always been .400-.420" for 22lr threads, and .600-.620" for 5.56 and other appropriate centerfire calibers.

I started out doing .625" on rifles, but I've encountered a few brakes that got really tight or bottomed out on tenons that long. My current standard unless otherwise specified is .450" for rimfire or pistol barrels, .550" for centerfire rifle, undercut fore and aft, with the thread crests knocked down to .003"-.005" under major dia. I use Kennametal Top Notch pitch-specific inserts only.

[cdhknives]

I am grinding my own HSS threading bit...need to work on it as it is cutting pretty ragged threads at the moment. Getting a good flat edge on a tip that small is...fun...

[ECCO Machine]

I am grinding my own HSS threading bit...need to work on it as it is cutting pretty ragged threads at the moment. Getting a good flat edge on a tip that small is...fun...

If you're going to be doing any significant amount of external threading, save yourself a lot of time and aggravation:

https://www.ebay.com/itm/TNSR16-3D-NOTC ... 0107!US!-1

Go with a few NTF3R inserts first, as they'll do anything up to 44 pitch (will cut the root deeper than necessary on coarser than 20P, but that's OK). If you find yourself doing a lot of threading in a given pitch, the pitch-specific inserts crest the threads, which not only makes them cleaner, but lets you know when you've hit depth if your major was spot on.

One of the benefits to Top Notch type inserts, aside from not having to grind your own and set angles, is that you can replace a worn or broken insert in the middle of an operation without having to stop everything and find your threads with the new cutter while the half nuts are engaged and the gear/lead screw/half nut slop taken up.

[Rich V]

I am grinding my own HSS threading bit...need to work on it as it is cutting pretty ragged threads at the moment. Getting a good flat edge on a tip that small is...fun...

If you're going to be doing any significant amount of external threading, save yourself a lot of time and aggravation:

https://www.ebay.com/itm/TNSR16-3D-NOTC ... 0107!US!-1

Go with a few NTF3R inserts first, as they'll do anything up to 44 pitch (will cut the root deeper than necessary on coarser than 20P, but that's OK). If you find yourself doing a lot of threading in a given pitch, the pitch-specific inserts crest the threads, which not only makes them cleaner, but lets you know when you've hit depth if your major was spot on.

One of the benefits to Top Notch type inserts, aside from not having to grind your own and set angles, is that you can replace a worn or broken insert in the middle of an operation without having to stop everything and find your threads with the new cutter while the half nuts are engaged and the gear/lead screw/half nut slop taken up.

Yes they work great but for the new/hobbyist user they are very easy to break.
Never stop the spindle rotation while making a cut.
Always have a full depth relief cut at the terminus.
Run as fast a spindle speed as you can control.
Use a good cutting oil.
Rigid set up is a must

I broke my share of tips learning how to use carbide thread tooling.

[cdhknives]

I use carbide for turning, and yes I have a bunch of inserts missing chips so I hear ya.

ECCO, the tool you listed seems to be a 1" shank. I have an AXA toolpost, max clamping is about 1/2" so maybe something like this would be better...

http://www.shars.com/products/indexable ... holder-1-1

I can't tell if it is just the stringy 17-4 (condition A) or my tool grinds but when I try to wipe down the threads they snag all sorts of fibers form my rags...rough as all get out but no obvious tear out.

[ECCO Machine]

I use carbide for turning, and yes I have a bunch of inserts missing chips so I hear ya.

ECCO, the tool you listed seems to be a 1" shank. I have an AXA toolpost, max clamping is about 1/2" so maybe something like this would be better...

http://www.shars.com/products/indexable ... holder-1-1

I can't tell if it is just the stringy 17-4 (condition A) or my tool grinds but when I try to wipe down the threads they snag all sorts of fibers form my rags...rough as all get out but no obvious tear out.

Those work OK, inserts are cheaper. Unless you're threading away from the spindle on the back side, though, you're gonna want a RH holder & inserts.

The faster you can run the spindle, the cleaner your threads will be. GL4/GL5 gear oil will help with clean cuts on SS. For cleaning up the threads, get some fine triangular files and run the lathe forwards and backwards while using the file in the threads with moderate pressure. Then crease 400 grit and run it through the threads. Lastly, hit the crests with the 400 grit.

[Rich V]

I use carbide for turning, and yes I have a bunch of inserts missing chips so I hear ya.

ECCO, the tool you listed seems to be a 1" shank. I have an AXA toolpost, max clamping is about 1/2" so maybe something like this would be better...

http://www.shars.com/products/indexable ... holder-1-1

I can't tell if it is just the stringy 17-4 (condition A) or my tool grinds but when I try to wipe down the threads they snag all sorts of fibers form my rags...rough as all get out but no obvious tear out.

I run a file over the threads and use a scothbright pad to polish the threads. Slow spindle speeds and less than sharp tooling can cause this as well.
I purchased a set like https://www.amazon.com/INDEXABLE-CARBID ... ools+1%2F2 these. Well worth the cost.

[yondering]

I use carbide for turning, and yes I have a bunch of inserts missing chips so I hear ya.

ECCO, the tool you listed seems to be a 1" shank. I have an AXA toolpost, max clamping is about 1/2" so maybe something like this would be better...

http://www.shars.com/products/indexable ... holder-1-1

I can't tell if it is just the stringy 17-4 (condition A) or my tool grinds but when I try to wipe down the threads they snag all sorts of fibers form my rags...rough as all get out but no obvious tear out.

I use that style as well (but a RH tool); it works really well. I got my inserts from latheinserts.com; don't know if the additional price is justified since I've never tried the cheap inserts for this tool, but after about 3 years of threading I'm still using the first insert. I use it often for light chamfering cuts as well. Hard to go wrong with one of these; I've never felt the need to thread with HSS again after buying mine.

As for threads snagging your rags - are you aware that you need to clean off the crests after threading? Do that before test fitting, otherwise a loose fit can feel tight just because of crest burrs. I use either a file or emery cloth and oil; just make sure to remove the abrasive particles before more threading passes when you use emery cloth. It leaves a nice smooth thread crest though. When threading aluminum, you can just use fine steel wool on the crests; it pulls the burrs off and burnishes the crest all at once with nice results.

[fishman]

How do you guys clean female threads? A file certainly won't work.

[ECCO Machine]

How do you guys clean female threads? A file certainly won't work.

A few passes with a threading bar held by hand while the spindle runs, then 400 grit on a finger or rolled up.

[T-Rex]

Green scotchbrite after final pass.
A cleanup pass with the mounted tool at the last setting.
Wipe threads down.
A dab of valve grinding compound on the mating threads.
Final degrease w/ brake clean.

Rough threads are bad threads

[propeine]

How do you guys clean female threads? A file certainly won't work.

I use a 60 degree triangular file all the time on them actually.

[cdhknives]

A spring pass has been standard for me with my lightweight lathe...it still leaves things rough on this 17-4. My inside threads for the tube (7075Al) were perfect. Since I'm turning to a shoulder I am in back gear-70 RPM. The next step up is 112 RPM and I'm not comfortable faster than that. I need some free time to regrind my tool and try again. The years of knife grinding comes in handy for HSS bit shaping...

Every time I use a triangle file to clean up threads they end up oversize and loose before the threads are smooth.

I use a large single cut fine file to knock off the peaks.

Still learning here...

[T-Rex]

For threading to a shoulder, try flipping the cutter and threading out (towards tailstock) instead of in (towards spindle).
It's not necessary for slower speeds or lightening reflexes , but allows you to bump the rpm's up a good bit.
I tend to do "regular setup" threads at around 200rpm.

[ECCO Machine]

A spring pass has been standard for me with my lightweight lathe...it still leaves things rough on this 17-4. My inside threads for the tube (7075Al) were perfect. Since I'm turning to a shoulder I am in back gear-70 RPM. The next step up is 112 RPM and I'm not comfortable faster than that. I need some free time to regrind my tool and try again. The years of knife grinding comes in handy for HSS bit shaping...
.

Practice, practice, practice!

The only time I use back gears is for single digit thread pitches. I thread 10-18 pitch at 355 RPM and 20-40 pitch at 525 RPM on my big lathe. I'll come within .040" of a shoulder at those speeds. The only reason I don't run 28-40 faster is that I don't like the externally lubricated gear train running that fast on a century old lathe. I do thread at 1,000 RPM on my Hardinge HCT to within .010" of shoulders, but that's an auto threader, so there's no half nuts to disengage.

If you have a micrometer carriage stop, you can use that more effectively than trying to watch the cutter come up to the shoulder with chips and smoke obscuring your view. That's how I do it; set the stop and disengage half nuts when the carriage is about to touch the stop.

Another thing you've likely encountered with 17-4 and other tough alloys is tapered threads from tool deflection; again, it takes practice, but you can get the deeper threads to diameter without oversizing the ones nearer the start by cranking on the cross slide as it's threading. It's something you just get a feel for with your machine on a given material.