materials

[calixt0]

Ok So I'm starting to do research on materials for a form 1 can. Ive read alot about Ti but not sure my lathe will handle it (1940's logan lathe). I'm not super experienced but understand threading and basics. should I be considering stainless or another material.. this will be for a 6.5 creedmoor and maybe 270 win or similar.


Thanks for your time and advice

[fishman]

Stainless is even more difficult to machine than titanium alloy

[jnjproto]

I prefer 17-4, easy to machine and one step heat treating. Titanium or chrome moly tubing.

[ECCO Machine]

Boring Ti with drills or end mills, reaming it or tapping it are difficult, but it's not difficult to cut or single point thread. I do a lot of secondary ops on a little Atlas 618. The stuff welds easily, too. You just have to turn the gas up, as it needs more shielding than carbon or stainless steels.

An all Ti can is definitely going to save weight. It's just expensive.

Stainless is even more difficult to machine than titanium alloy

Depends entirely on the alloy and the particular operations. 416 cuts like butter, but stringy, sticky, work-hardening 304 will give one fits. 17-4 has pretty good machinability, but is fairly difficult to tap.

[fishman]

I've had more trouble with 17-4 than with g5 Ti. Neither are that difficult if you keep your tools sharp, cut slow, and apply coolant contiunously, or between passes. I cut both with high speed steel, despite some claiming that its not possible or practical.

My statement was in regards to grades of stainless that are highly suitable for silencers. I should've been more clear.

[ECCO Machine]

I've had more trouble with 17-4 than with g5 Ti. Neither are that difficult if you keep your tools sharp, cut slow, and apply coolant contiunously, or between passes. I cut both with high speed steel, despite some claiming that its not possible or practical.

My statement was in regards to grades of stainless that are highly suitable for silencers. I should've been more clear.

HSS can do it, but you have to keep speeds down and use coolant or cutting fluid.

I use carbide almost exclusively, and work on 1-3/8 to 1/5/8" diameter 17-4 at 500-700 RPM most of the time, although I thread at 350 and part off at 160. I also cut aggressively, .080"-.100" deep (single depth; radius) and feeding at 30-50 IPM with CNMG cutters. But that's on my 3 HP 17 x 60 lathe; a light machine like a Southy heavy 10 or Grizzly 12" would not do that well. Larger machines let you get away with things like that, as well as coming straight in on threads rather than using compound at 29.5°. That's why I tell people to get the biggest, baddest machine they can fit/afford.

[fishman]

I cut at half those speeds and 1/5 that depth. My machine is TINY though. (Pics in signature link)

I always thread straight in but I only take .001" off per pass.

[calixt0]

I've had more trouble with 17-4 than with g5 Ti. Neither are that difficult if you keep your tools sharp, cut slow, and apply coolant contiunously, or between passes. I cut both with high speed steel, despite some claiming that its not possible or practical.

My statement was in regards to grades of stainless that are highly suitable for silencers. I should've been more clear.

Fishman can I pm you I have more questions on your can design.

[fishman]

I've had more trouble with 17-4 than with g5 Ti. Neither are that difficult if you keep your tools sharp, cut slow, and apply coolant contiunously, or between passes. I cut both with high speed steel, despite some claiming that its not possible or practical.

My statement was in regards to grades of stainless that are highly suitable for silencers. I should've been more clear.

Fishman can I pm you I have more questions on your can design.

Absolutely

[ECCO Machine]

I cut at half those speeds and 1/5 that depth. My machine is TINY though. (Pics in signature link)

I always thread straight in but I only take .001" off per pass.

Yeah, can't take big bites with a Sherline! They're high quality machines, but you can only get so much rigidity out of a lathe that fits in a backpack. My 4 jaw chuck weighs five times what an entire Sherline 4100 does.

What they are great for is secondary op stuff, namely finish work. I don't do my baffles entirely on the two ton Rahn-Larmon lathe; final passes and polishing are done on an Atlas 618. The big critter maxxes out at 1,020 RPM, and has more vibration than I care for above 800. But the small Atlas I rebuilt hums along silky smooth at 2,000 RPM and higher. I have a Hardinge HCT as well, and they don't come any smoother except maybe a Monarch 10EE, but it's pretty much become a dedicated barrel threading and chambering machine these days.

[BinaryAndy]

Ti: light, expensive, difficult

17-4: very strong, cheaper, somewhat less difficult

4130, 4140, 4340: strongest, dirt cheap, easy to machine, needs heat treat and protective coating

For the tube your only good options are Ti and 4130, unless you go tubeless or make a tube from solid bar.

[calixt0]

Ok so whats the best place to buy Ti?

[fishman]

Ok so whats the best place to buy Ti?

I use titanium joe

[ECCO Machine]

Ti: light, expensive, difficult

17-4: very strong, cheaper, somewhat less difficult

4130, 4140, 4340: strongest, dirt cheap, easy to machine, needs heat treat and protective coating

For the tube your only good options are Ti and 4130, unless you go tubeless or make a tube from solid bar.

4000 series chromoly steels are not the strongest unless you use a low temper, and even then it only has a higher UTS than 17-4, but still a lower yield strength, and will be more brittle. Factor in the better thermal properties and corrosion resistance, it's easy to see why virtually all manufacturers use 17-4 and none use 4140.

Ok so whats the best place to buy Ti?

Get tubing from tiger titanium

Shop ebay for 6/4 round bar

[T-Rex]

This guy has great prices on Ti. He's in Israel so shipping isn't cost effective on small orders.

[Rich V]

Ti: light, expensive, difficult

For the tube your only good options are Ti and 4130, unless you go tubeless or make a tube from solid bar.

4000 series chromoly steels are not the strongest unless you use a low temper, and even then it only has a higher UTS than 17-4, but still a lower yield strength, and will be more brittle. Factor in the better thermal properties and corrosion resistance, it's easy to see why virtually all manufacturers use 17-4 and none use 4140.

Anyone have a source for 17-4 seamless tubing or pipe?
Lots of places sell it if you are willing to buy a truck load but finding it in smaller quantities has proved impossible.

[T-Rex]

Anyone have a source for 17-4 seamless tubing or pipe?

Several members with SOT's have offered to sell other members small quantities.
I'm not going to call them out, because I don't know if it was a forever offer, but I'm sure a small search could prove fruitful.

[BinaryAndy]

4000 series chromoly steels are not the strongest unless you use a low temper, and even then it only has a higher UTS than 17-4, but still a lower yield strength, and will be more brittle. Factor in the better thermal properties and corrosion resistance, it's easy to see why virtually all manufacturers use 17-4 and none use 4140.

If 4140 and 17-4 are heat treated to the same yield strength, 4140 will have a higher UTS and a significantly higher elongation at break, meaning it's less brittle. 17-4 in the H900 condition (the strongest available) has a yield strength of 200 ksi and elongation at break is 7%. 4140 can be heat treated to 250 ksi with an elongation at break of 11%, and it retains a greater percentage of its hardness and strength at high temperatures and conducts heat better than does 17-4. 4150 and 4340 are slightly stronger yet. Yes, heat treated 4000 series steel is the strongest readily available material suitable for suppressors. Granted, 17-4 is a very close second and has the benefits of corrosion resistance and simpler heat treatment.

[Rich V]

Anyone have a source for 17-4 seamless tubing or pipe?

Several members with SOT's have offered to sell other members small quantities.
I'm not going to call them out, because I don't know if it was a forever offer, but I'm sure a small search could prove fruitful.

I know one SOT member here that switched from 17-4 to 316 tubes because of supply issues and cost. Another posted they had some but never replied to my IM or direct e-mail to their web site.

I'll gladly pay a premium for a few feet of 1.5in OD 17-4 tubing if anyone has or knows of a source.

[mr fixit]

4000 series chromoly steels are not the strongest unless you use a low temper, and even then it only has a higher UTS than 17-4, but still a lower yield strength, and will be more brittle. Factor in the better thermal properties and corrosion resistance, it's easy to see why virtually all manufacturers use 17-4 and none use 4140.

If 4140 and 17-4 are heat treated to the same yield strength, 4140 will have a higher UTS and a significantly higher elongation at break, meaning it's less brittle. 17-4 in the H900 condition (the strongest available) has a yield strength of 200 ksi and elongation at break is 7%. 4140 can be heat treated to 250 ksi with an elongation at break of 11%, and it retains a greater percentage of its hardness and strength at high temperatures and conducts heat better than does 17-4. 4150 and 4340 are slightly stronger yet. Yes, heat treated 4000 series steel is the strongest readily available material suitable for suppressors. Granted, 17-4 is a very close second and has the benefits of corrosion resistance and simpler heat treatment.

How does 4140 tube compare if it is not heat treated? I have seen more than a few builds mention using 4140 for tubes. Just wondering how well it would work for a centerfire rifle in say .223 or .308?

[BinaryAndy]

I have not been able to find a source for 17-4 tube in quantities any less than a mill run of several thousand pounds, and I've spent a great deal of time searching.

4140 isn't available in tubing either, but 4130 is. If it's annealed it's nearly as strong as titanium, 60ksi. If it's cold worked and not annealed it should be a bit stronger. At high temperatures it will be significantly stronger than titanium, but titanium will be lighter.

Heat treating 4130 roughly triples its strength. Without heat treat it can work just fine, but it's not a great choice and you'll have to end up with a heavier tube.

[ECCO Machine]

How does 4140 tube compare if it is not heat treated? I have seen more than a few builds mention using 4140 for tubes. Just wondering how well it would work for a centerfire rifle in say .223 or .308?

Not favorably. Chromoly steels derive most of their strength from heat treatment. Annealed 4140 has only slightly higher yield strength than 1018 mild steel.

That's where 17-4 stainless and 6/4 Ti really shine: They are 75% as strong in the annealed state as treated. Annealed 6/4 is 128 KSI and annealed (H1150) 17/4 is 105 KSI yield. I have no qualms about using untreated 17-4 in a number of applications.

[BinaryAndy]

How does 4140 tube compare if it is not heat treated? I have seen more than a few builds mention using 4140 for tubes. Just wondering how well it would work for a centerfire rifle in say .223 or .308?

Not favorably. Chromoly steels derive most of their strength from heat treatment. Annealed 4140 has only slightly higher yield strength than 1018 mild steel.

That's where 17-4 stainless and 6/4 Ti really shine: They are 75% as strong in the annealed state as treated. Annealed 6/4 is 128 KSI and annealed (H1150) 17/4 is 105 KSI yield. I have no qualms about using untreated 17-4 in a number of applications.

That's all true, but neither 17-4 nor 6Al4V are available in tubes. Aermet 340 and Maraging alloy 300 have yield strengths over 300 ksi, which is equally irrelevant to the discussion of silencer tubes. 3Al2.5V (Grade 9) Ti is available in tube form, but the yield strength of that is only 72ksi, a little more than annealed 4130 and almost exactly the same as DOM steel tube.

Anyone can find all of this information. Just go to matweb.com and search for the material you want to know about. Yield strength and elongation at break are probably the most relevant properties to silencer construction, in both cases higher numbers are better. Charpy impact, fatigue strength, and yield strengths at elevated temperatures are useful figures as well, but much harder to find.

[ECCO Machine]

That's all true, but neither 17-4 nor 6Al4V are available in tubes. Aermet 340 and Maraging alloy 300 have yield strengths over 300 ksi, which is equally irrelevant to the discussion of silencer tubes. 3Al2.5V (Grade 9) Ti is available in tube form, but the yield strength of that is only 72ksi, a little more than annealed 4130 and almost exactly the same as DOM steel tube.

6/4 tubing is out there, but I've not ever seen it in the sizes & thicknesses we need. We also don't really need it, though. I've gone as thin as .028" wall on magnum rifle rated monocore cans of mine using gr. 9, no issues. I've built pistol cans with .028 wall and threaded it 40 pitch, still good to go. My most recent prototype is a 9" .30 cal rifle can with .035" gr. 9 tubing, threaded 36 pitch at both ends, fully welded 17-4 stack. It's good so far with heavy semi auto fire, although I haven't punished the 14.5 ounce suppressor with my machine guns yet. .023" gr 9. wall is a favorite of mine for rimfire cans.

Point being, while the high carbon chromoly, Maraging and tool steels will easily exceed 3/2.5 and 6/4 in just about every mechanical property, they aren't needed and, for many of us, the weight is not wanted. Which is why the industry overwhelmingly chooses Ti for housings except for the most heavy duty critters, or the cheap ones.

[Rich V]

I have not been able to find a source for 17-4 tube in quantities any less than a mill run of several thousand pounds, and I've spent a great deal of time searching.

Snip

Same here Andy. Many places have an impressive listing of size/wall thickness of 17-4 seamless but only sell in big lots.

Given the the yield strength difference between 17-4 H900 and 300 series SS one could cut the wall thickness in half using 17-4 and still have a can with ~2x greater strength than the 300 series SS at full wall thickness from RT to 1000F.

Would be nice to have a 223/308 can with 0.030 in wall that was as strong as a 316 SS @ 0.100 in.

Maybe I'll bit the bullet and turn a 17-4 bar into tubing. Should be a lot of fun boring that one.