304 vs 316 Stainless Plate Dropouts

I’m getting dropouts cut by sendcutsend and I figured I’d go stainless and leave them unpainted. They offer both 304 and 316 options for stainless plate. 316 is superior in strength and is only a couple dollars more for what I’m doing.

Are there any reasons I should go with 304?

I’ve been using Weldmold 880 - anything I should be aware of when I weld the 4130 stays to the stainless dropouts?

As a side note, getting the dropouts made from 304 stainless is cheaper than 4130. I always assumed stainless would be more expensive.

Thanks for the info!


316 is a bit more corrosion resistant. If it’s only a couple dollars more I’d go for it.

Get some 309L filler instead. I posted about this the other day.

The biggest thing when welding is take your time and let it cool down as much as you can. Carbide precipitation will happen if it stays too hot for too long.


I am also surprised. If I were to generalize, stainless is less hard, has lower strength, and is more ductile than 4130.


The X factor is 4130’s heat treating, which I wish more tube suppliers will be more clear/transparent about.

Maybe someone with materials or build experience can chime in with the correct choice for dropouts?

I am working on a track dropout design, couldn’t decide between 4130 vs stainless, and ended up using both :rofl:

For the sliding dropouts stainless is nice. Since there won’t be any paint on the mating surfaces.

But interesting thing about 4130 dropouts, we generally assume it is being used in the annealed state (or close to it) after welding. So in that case, mild steel still works just as well.

Without post-welding heat treatment, mild steel and 4130 are effectively the same. Their modulus of elasticity is very close, so in normal use there’s not much difference.
That’s why paragon (and most others) make their machined dropouts from 1018.


That is a cool look to have the minimal stainless at the mating areas, reminds me of older Italian steel frames.

The strength difference between 4130 and 304 or 316 seems negligible for dropouts. Since the cost is about the same I can’t think of a reason not to use all stainless.