How tight?

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cdhknives
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How tight?

Post by cdhknives » Tue Mar 13, 2018 10:07 am

When machining baffles how tight do you secure them in the stack? In other words, do I have the endcap start contacting the baffle stack with a half thread left to turn, one thread of compression, hit it on the nose so the endcap contacts the baffle stack and the tube shoulder at the same time, ???? Mine will be 'standard' 60 degree cones, first up (but not last!) is a 22lr. Obviously the baffles need to be lightly compressed by the endcap to prevent them from rattling around in the tube but we don't want the endcap not seated against the tube's shoulder, and I can think of 2 ways to do this: Either an o-ring in the end to compress as you torque the endcap or precise machining to leave the baffle stack slightly longer and therefore compressed directly by the endcap. Is there another option I am missing? Welding is not an option for me, only lathe turned parts... Thanks in advance!
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T-Rex
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Re: How tight?

Post by T-Rex » Tue Mar 13, 2018 11:01 am

I stopped using a shoulder on the end cap, some time ago. I just didn't see a point in it as directly relating to your question. I make all my parts, before the tube, and measure their combined length. Machine the tube about .06 longer, with the rear cap inserted as I'm machining the distal threads. Insert all components and tighten the end cap. Machine the tube to meet the end cap.
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fishman
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Re: How tight?

Post by fishman » Tue Mar 13, 2018 11:29 am

I like about .005" of compression
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Enfield577
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Re: How tight?

Post by Enfield577 » Tue Mar 13, 2018 1:46 pm

As mine go out to customers all over and you never really know what they will do with them, I ensure that the stack is 0.02" to 0.030" longer so the end cap will always do them up tight, same as most manufacturers out here. particularly in the US where I understand you can't easily remake bits, If they were to wear or crush over time you would end up with loose stack....not good.

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Re: How tight?

Post by ECCO Machine » Tue Mar 13, 2018 4:33 pm

It really depends on what the can is for, what materials you use, the treatments they receive, etc. An aluminum K baffle stack is gonna squish a lot more than a stack of hardened 17-4 cone baffles. Likewise, an aluminum housing will stretch more than steel or Ti.

I like a pretty small gap, think large ones look like dooky, so I leave the last baffle a bit long, then assemble everything into the housing and tighten the cap with the wrench to the appropriate torque for the particular can. Then I measure the gap, and cut the last baffle back to .005" proud of the difference. That's with gr 9 Ti housings and aluminum cone baffles. If I were using aluminum tubes or K baffles, I'd leave the baffle .010" long. With 17-4 baffles and Ti tubes, I take them to within .002"-.003".
Enfield577 wrote:As mine go out to customers all over and you never really know what they will do with them, I ensure that the stack is 0.02" to 0.030" longer so the end cap will always do them up tight, same as most manufacturers out here. particularly in the US where I understand you can't easily remake bits, If they were to wear or crush over time you would end up with loose stack....not good.

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You could always do what I do and offer steel shims.
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cdhknives
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Re: How tight?

Post by cdhknives » Tue Mar 13, 2018 5:30 pm

I'm not afraid of shims, but would rather reduce parts count where I can. Still, a shim is cheaper than scrapping and remaking a baffle!

I had visualized cutting the first and last baffle shoulder at an angle and wedging o-rings to seal the threads from getting gunked up...but that is probably not worth the hassle.

The first can will be an AL tube for 22lr but the second will be more multiuse...likely my first try at machining Ti.
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Re: How tight?

Post by ECCO Machine » Wed Mar 14, 2018 12:25 am

cdhknives wrote:I'm not afraid of shims, but would rather reduce parts count where I can. Still, a shim is cheaper than scrapping and remaking a baffle!

I had visualized cutting the first and last baffle shoulder at an angle and wedging o-rings to seal the threads from getting gunked up...but that is probably not worth the hassle.

The first can will be an AL tube for 22lr but the second will be more multiuse...likely my first try at machining Ti.
What kind of baffles are you planning on? Cone baffles will pretty well seal themselves. K baffles won't, but I've never had a problem with carbon or other deposits in the threads on disassembly, and you'd need to wipe the threads anyway after driving the baffles out.

Seriously consider using Ti, as you can go much, much thinner. Ti is 68% heavier than Al, but when you can use less than half the thickness, the net is a lighter can. It also allows a tad more internal volume for the same OD. I use .023 wall on my monocores, .035 on my stacked baffle rimfire cans. The monocores are 2.9 ounce .22 LR only, the stacked aluminum baffle cans are 4.0 oz and rated for 22 mag and .17 HMR, and the stacked 416 stainless baffle cans are 5.7x28 pistol and .22 Hornet rated.
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