Which taper for suppressor mount to brake?

[mr fixit]

Working on several cans. My plan is to make a muzzle brake and mount the cans to the brake. I think the taper lock up on the mounts is a good idea, but what taper? I believe I saw here that someone measured a Griffin mount and the taper on that was 12* included (6* on compound).

Is there a 'best' angle for the taper? Any pros or cons to using 12*. Any recommendations on other mounting options?

[yondering]

I went with 20* included; seems to work fine. I forget what Propeine used, maybe he was the one measuring the Griffin comp.

I think I remember someone else uses 25* included. Sig?

At some point the taper becomes self locking, so you may not want to go much smaller than 12*.

[ECCO Machine]

I'd go 10° or more (compound, 20°+ included). Go much more acute, things bind and gall, especially when you start introducing heating & cooling. 6° isn't a whole lot more than the rod ends and ball joints in automotive applications, and I don't think you wanna be using pickle forks & air hammers to break your suppressor loose.

[smustian]

GA Taper Mount drawing. Hope it helps.

[mr fixit]

I think R8 collets have a 17* angle (8.5 on compound), and 5C have 20* (10 on compound).

I'm thinking 20* would be about right. With that in mind, what thread to mount can to brake and tighten on taper? I've read both fine and course. I've even seen acme threads used. I'm thinking around 20tpi for the taper mount. Suggestions?

[T-Rex]

I would choose a coarse thread, possibly multi-start, over fine for probably some of the reasons an Acme would be chosen. Fine V threads are stronger than coarse and are less likely to loosen, but the taper is your lock and makes-up for the deficiency. Acme threads have much better wear properties, tolerances, and load capabilities, than standard threads. They tend to operate better in environments with dirt and debris, since the threads are thicker and wider.

If you're machine can't turn an Acme, I'd look at a 2-start, 4 Tpi, V-Thread. Although, I think you'd be fine with most anything you chose.

[mr fixit]

I would choose a coarse thread, possibly multi-start, over fine for probably some of the reasons an Acme would be chosen. Fine V threads are stronger than coarse and are less likely to loosen, but the taper is your lock and makes-up for the deficiency. Acme threads have much better wear properties, tolerances, and load capabilities, than standard threads. They tend to operate better in environments with dirt and debris, since the threads are thicker and wider.

If you're machine can't turn an Acme, I'd look at a 2-start, 4 Tpi, V-Thread. Although, I think you'd be fine with most anything you chose.

I think for my level of ability single thread is the way to go. Something maybe 16 to 20 threads per inch. On the drawing posted above it shows 375 as the length of the threaded section is that enough?

[fishman]

I would choose a coarse thread, possibly multi-start, over fine for probably some of the reasons an Acme would be chosen. Fine V threads are stronger than coarse and are less likely to loosen, but the taper is your lock and makes-up for the deficiency. Acme threads have much better wear properties, tolerances, and load capabilities, than standard threads. They tend to operate better in environments with dirt and debris, since the threads are thicker and wider.

If you're machine can't turn an Acme, I'd look at a 2-start, 4 Tpi, V-Thread. Although, I think you'd be fine with most anything you chose.

I think for my level of ability single thread is the way to go. Something maybe 16 to 20 threads per inch. On the drawing posted above it shows 375 as the length of the threaded section is that enough?

Use an online thread strength calculator. Whatever thread diameter, length, and pitch you choose, make sure it's as strong as 0.6 inches of 5/8x24

[partsguy22]

I think for my level of ability single thread is the way to go. Something maybe 16 to 20 threads per inch. On the drawing posted above it shows 375 as the length of the threaded section is that enough?

If you can cut single point threads you can do acme and with a couple minuets of practice multi start threads are fairly simple...

Go nuts and try multi start acme...2 start 5 tpi acme

[ECCO Machine]

I think for my level of ability single thread is the way to go. Something maybe 16 to 20 threads per inch. On the drawing posted above it shows 375 as the length of the threaded section is that enough?

What's the point of going to the trouble of making this system if it's gonna take just as long to screw cans on & off as direct thread? Also, the finer the thread, the harder it's going to lock onto your taper, so keep that in mind.

ACME would definitely be a good choice. ACME gives you the larger circumferential stress area of fine thread with the speed of course thread, virtually no chance of cross-threading, and better wear characteristics than standard unified threads.

If it were me, I'd probably go 8 or 10 TPI ACME

[mr fixit]

What's the point of going to the trouble of making this system if it's gonna take just as long to screw cans on & off as direct thread? Also, the finer the thread, the harder it's going to lock onto your taper, so keep that in mind.

ACME would definitely be a good choice. ACME gives you the larger circumferential stress area of fine thread with the speed of course thread, virtually no chance of cross-threading, and better wear characteristics than standard unified threads.

If it were me, I'd probably go 8 or 10 TPI ACME

The main reason for going to the brake mount is to use the brake as a sacrificial blast baffle. If/when the blast baffle is worn from use just replace it, no need for FFL/SOT or form 1. just make another. I'm not looking at this as a quick detatch. A brake in the suppressor can also help with suppression.

[ECCO Machine]

The main reason for going to the brake mount is to use the brake as a sacrificial blast baffle. If/when the blast baffle is worn from use just replace it, no need for FFL/SOT or form 1. just make another. I'm not looking at this as a quick detatch. A brake in the suppressor can also help with suppression.

OK, makes sense. On that note, some will disagree with me, but as the original manufacturer of a form 1 suppressor, you can make repairs. You just cannot make alterations (other than a small amount of shortening necessary to re-thread for end caps in the event of damage) or keep spare parts around.

Yes, brakes in the blast chamber certainly can help. I use them on some of my prototypes, although they are integral on many, so the suppressor is still a direct thread type. Just quicker and easier than worrying about precise mating surfaces for cans that I'm going to beat the hell out of in testing, likely to the point of failure.

[mr fixit]

On that note, some will disagree with me, but as the original manufacturer of a form 1 suppressor, you can make repairs. You just cannot make alterations (other than a small amount of shortening necessary to re-thread for end caps in the event of damage) or keep spare parts around.

interesting opinion. Just curious on what you base this on, and to what extent you consider allowable?

[fishman]

AFAIK, we can make repairs but not replace any parts. If my tube broke in half I could weld it back together. If I damage a baffle I could destroy it and shorten the silencer by the length of one baffle. If my barrel mounting threads got messed up I could bore them out and thread a bigger thread into the endcap.

I'm no lawyer though.

Some disagree with this interpretation. *cough* bendersquint *cough*

[propeine]

I would choose a coarse thread, possibly multi-start, over fine for probably some of the reasons an Acme would be chosen. Fine V threads are stronger than coarse and are less likely to loosen, but the taper is your lock and makes-up for the deficiency. Acme threads have much better wear properties, tolerances, and load capabilities, than standard threads. They tend to operate better in environments with dirt and debris, since the threads are thicker and wider.

If you're machine can't turn an Acme, I'd look at a 2-start, 4 Tpi, V-Thread. Although, I think you'd be fine with most anything you chose.

I think for my level of ability single thread is the way to go. Something maybe 16 to 20 threads per inch. On the drawing posted above it shows 375 as the length of the threaded section is that enough?

The above drawing is mine. Griffin uses 17-4 for their brakes I believe. I've used that mounting pattern on 5 brakes and 2 cans now and not had any issues. Shear strength of threads is easy to calculate. PitchDiameter * Pi * Length of thread gives you shear area. Pitch Diameter on 1-20 is .9675 so we get 1.14 sqin. 5/8-24 has a Pd of .5979 so we get 1.13 sqin. As long as your barrel material and brake material are the same, the 5/8-24 threads will fail first.

[fishman]

I would choose a coarse thread, possibly multi-start, over fine for probably some of the reasons an Acme would be chosen. Fine V threads are stronger than coarse and are less likely to loosen, but the taper is your lock and makes-up for the deficiency. Acme threads have much better wear properties, tolerances, and load capabilities, than standard threads. They tend to operate better in environments with dirt and debris, since the threads are thicker and wider.

If you're machine can't turn an Acme, I'd look at a 2-start, 4 Tpi, V-Thread. Although, I think you'd be fine with most anything you chose.

I think for my level of ability single thread is the way to go. Something maybe 16 to 20 threads per inch. On the drawing posted above it shows 375 as the length of the threaded section is that enough?

The above drawing is mine. Griffin uses 17-4 for their brakes I believe. I've used that mounting pattern on 5 brakes and 2 cans now and not had any issues. Shear strength of threads is easy to calculate. PitchDiameter * Pi * Length of thread gives you shear area. Pitch Diameter on 1-20 is .9675 so we get 1.14 sqin. 5/8-24 has a Pd of .5979 so we get 1.13 sqin. As long as your barrel material and brake material are the same, the 5/8-24 threads will fail first.

That's only an approximation. Finer threads are stronger.

https://www.engineersedge.com/thread_stress_area_b.htm

[propeine]

I think for my level of ability single thread is the way to go. Something maybe 16 to 20 threads per inch. On the drawing posted above it shows 375 as the length of the threaded section is that enough?

The above drawing is mine. Griffin uses 17-4 for their brakes I believe. I've used that mounting pattern on 5 brakes and 2 cans now and not had any issues. Shear strength of threads is easy to calculate. PitchDiameter * Pi * Length of thread gives you shear area. Pitch Diameter on 1-20 is .9675 so we get 1.14 sqin. 5/8-24 has a Pd of .5979 so we get 1.13 sqin. As long as your barrel material and brake material are the same, the 5/8-24 threads will fail first.

That's only an approximation. Finer threads are stronger.

https://www.engineersedge.com/thread_stress_area_b.htm

Finer threads also have a larger pitch diameter but yes it is an approximation and a pretty damn good one considering we're guessing at almost everything anyways.

For reference
1-8 PD = .9188
1-12 PD = .9459
1-20 PD = .9675

That link doesn't seem to take into account the length of threads or I'm reading it wrong.

[mr fixit]

The above drawing is mine. Griffin uses 17-4 for their brakes I believe. I've used that mounting pattern on 5 brakes and 2 cans now and not had any issues. Shear strength of threads is easy to calculate. PitchDiameter * Pi * Length of thread gives you shear area. Pitch Diameter on 1-20 is .9675 so we get 1.14 sqin. 5/8-24 has a Pd of .5979 so we get 1.13 sqin. As long as your barrel material and brake material are the same, the 5/8-24 threads will fail first.

I think that 1-20 would be fine for me, especially since you have used it successfully already. I don't feel the need to re-invent the wheel.

Looks like you used 12* included, and I saw where SIG uses 25* included. I guess pretty much anywhere in that range should be fine.

Right now, I think I will go 1-20 external thread with a 20* included angle......20/20 should be easy to remember for the next time down the road I add a brake for another gun.

[fishman]

The taper lock on my integral can is 60° or 30° on the compound. The thread is 28 tpi.

I'm sure those smaller angles will work great, but so will a bigger angle.

[ECCO Machine]

The taper lock on my integral can is 60° or 30° on the compound. The thread is 28 tpi.

I'm sure those smaller angles will work great, but so will a bigger angle.

That wider angle doesn't really act as a lock, though; it's too obtuse to create bind without a lot of torque. It's behaving more as direct thread with better alignment characteristics.

IMO, 20°-30° included is pretty optimal. I use 20°, and it creates a good lock without being so much that metal galls. The .30 cal totally Ti can I just did has a 20° included taper on a Ti brake with 1/2" of 1"-12 TPI thread. 6-1/2 turns to install, won't loosen on it's own, but not terribly difficult to remove.

[fishman]

The taper lock on my integral can is 60° or 30° on the compound. The thread is 28 tpi.

I'm sure those smaller angles will work great, but so will a bigger angle.

That wider angle doesn't really act as a lock, though; it's too obtuse to create bind without a lot of torque. It's behaving more as direct thread with better alignment characteristics.

IMO, 20°-30° included is pretty optimal. I use 20°, and it creates a good lock without being so much that metal galls. The .30 cal totally Ti can I just did has a 20° included taper on a Ti brake with 1/2" of 1"-12 TPI thread. 6-1/2 turns to install, won't loosen on it's own, but not terribly difficult to remove.

Using such coarse threads, i would agree, a more acute angle is ideal. with finer 28 tpi threads, 60* gives a solid lock, a lot more than just threading on a direct thread device.

[BinaryAndy]

A fine threaded bolt is stronger than a coarse threaded bolt due to the larger minor diameter, but that is not true of the threads themselves. Coarser threads are stronger than finer threads. On a silencer tube you want relatively fine threads because they weaken the tube less, and for a direct thread mount you want fine threads because they're less prone to loosening. For a taper mount like we're discussing here, you're not gaining anything by using a fine thread.

[fishman]

For a taper mount like we're discussing here, you're not gaining anything by using a fine thread.

Yeah, I didn't choose the thread pitch, bushmaster did. Mine has tapered mount attached to the barrel separate from the existing muzzle threads; it is certainly an oddball exception to the rule. For a traditional taper brake, fine threads are easier to cross thread, require more turns, and offer little to no advantage.

[BinaryAndy]

And in your case with a relatively obtuse taper, a course thread might be more prone to loosening on it's own. A 60 degree taper would hold on and align better than a square shoulder, but it wouldn't lock itself in place like a 20 degree taper would. Your approach of using a larger angle with finer threads makes sense.

To clarify, my comment wasn't aimed at you, I just noticed a few comments about fine threads being stronger than coarse and wanted to bust that myth. It's A common misconception even among engineers. A fine threaded bolt is stronger, but the threads themselves are slightly weaker.

[fishman]

Each thread is weaker but you can fit more of them in there. Two threaded areas of the same pitch diameter, one fine and one coarse, will be the same strength. But if the two threads have the same major diameter, the finer thread will have more shear area due to its larger minor diameter. Its splitting hairs. Like andy said, the real advantage comes from having a thicker bolt because the fine threading removes less material.