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sickboy
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3,544 Posts
Discussion Starter · #1 ·
I've only ever done frame builds and mods out of mild steel but am throwing around the idea of building a full frame out of stainless. what do y'all use or recommend using when building stainless frames as far as tubing diameter, gauge and stainless grade? It would be a trellis style frame I would be building.
 

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lɐʇuǝɯᴉɹǝdx&#4
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3,516 Posts
I'd expect you'd use essentially the same dimensions. Stiffness and strength is very similar to normal (mild / carbon) steel. Unless you were packing on extra steel to tolerate corrosion, I don't see how using stainless would change the build requirements. Obviously working techniques will differ... have fun machining that stuff!
 

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sickboy
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Discussion Starter · #3 ·
what about the grade of stainless? 304 vs 306 etc etc? also does it have to be seamless tubing?
 

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lɐʇuǝɯᴉɹǝdx&#4
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Dunno- all the strength / elasticity numbers for grades of stainless I saw were pretty similar. I also totally ignored (and don't know about) is fatigue life. Its possible that stainless is better (or worse) when it comes to withstanding fatigue, needs heat treatment to do so, or some such. Like I said, just looked at some rough elasticity / strength figures.

I'm pretty sure if you want the best strength / weight, chromoly or aluminum is the way to go. Both require special handling and heat treatment to actually deliver the benefit the alloys allow.
 

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moron with a hammer
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119 Posts
Bicycle frame builders do it from time to time, but usually only with lugged, brazed frames, and usually only with the rear triangle. It doesn't have the fatigue life of mild steel or chrome moly, especially once welded. You can go thinner than mild steel with the tubes, but that aggravates the embrittlement issues. Practically, you end up with a frame that's heavier than chrome moly in order to keep it in one piece. The only benefits are cool looks and corrosion resistance.
 

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sickboy
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3,544 Posts
Discussion Starter · #7 ·
Yah the cool look is what I am thinking of. May sound douchey but would be sick to have a fully tig welded stainless trellis frame all bare or clear powder coated.

I.E. the new cfl3 frame jesse james just came out with. 100% stainless.

 

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I bang metal
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2,779 Posts
stainless is general harder than mild steel, this means you can use lighter material to get lighter weight. The down side is that when a material is hard it is brittle, so instead of things bending they just snap off.
 

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HipsterKillerGarage
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6,484 Posts
Have a good jig and move around alot. If you run your welds all in one area at once and move linearly the frame will be so tweaked you won't believe it.

Run the material the same dimensions as mild.

Keep the heat right where it needs to be. Straw yellow and you're good. Start getting a lot of blues and purples everywhere and you're cooking the chromium. ;)

Also, fwiw, stainless is softer than mild. It is more brittle when overheated though.

Run 304 tube with 316L filler and you're good to go.

Have fun and be safe.
 

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watches you sleep.
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9,116 Posts
Im planning on having a subframe made from SS so this is all really good to know. The OD and wall thickness is smaller and thinner than what I would have used if it was mild steel. Sorry to hi jack the thread but Jamals posting in here and I'd really like to get His opinion since I never see Him around here anymore. Is this good enough to use for a subframe only supporting my weight?



PS I have boney fingers for what its worth. Cant remember the measurements off hand.
 

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re-tarded
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1,283 Posts
Looks like maybe 3/4 16ga? If so I'd expect it to be fine with a decent design.
 
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HipsterKillerGarage
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6,484 Posts
Im planning on having a subframe made from SS so this is all really good to know. The OD and wall thickness is smaller and thinner than what I would have used if it was mild steel. Sorry to hi jack the thread but Jamals posting in here and I'd really like to get His opinion since I never see Him around here anymore. Is this good enough to use for a subframe only supporting my weight?



PS I have boney fingers for what its worth. Cant remember the measurements off hand.
You'll be fine. Just pay attention to triangulation. TIG welding with minimal heat will be a good route to go, and make sure you don't leave undercut on something that thing. Just asking for cracks. You have to consider that any point of undercut reduces the material by the depth of the cut, and on something thin already it it's pretty significant.
 

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I bang metal
Joined
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2,779 Posts
Have a good jig and move around alot. If you run your welds all in one area at once and move linearly the frame will be so tweaked you won't believe it.

Run the material the same dimensions as mild.

Keep the heat right where it needs to be. Straw yellow and you're good. Start getting a lot of blues and purples everywhere and you're cooking the chromium. ;)

Also, fwiw, stainless is softer than mild. It is more brittle when overheated though.

Run 304 tube with 316L filler and you're good to go.

Have fun and be safe.
eh, you either use it or lose it.... Thanks for correcting me. Also glad to have you around again.
 
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