68mm right/right on a 70mm right/right Shell?
 

Hello im currently replacing my Botton bracket for a new one.
my old one Is italian style right/right 36 x 24tpi - 70 mm

I can only get right/right 36 x 24tpi - 68 mm

​​​​​​my question Is if i can use the 68mm in the 70mm Shell?

Are you in Arkansas, US or Argentina? If the US, and if your LBS won't order the right part, I'd recommend Bike Tires Direct, Modern Bike, Velo-Orange, or even Amazon as a source.

If you're in Argentina, I can't help.

Im from argentina. I can only get 68mm, same thread.

Viva el Peru!

The Italian shell inner diameter is 1.375 in. ISO is 1.370. Your ISO BB will likely be a loose fit threadwise.

...sometimes they work OK, if it's a sealed unit. But you need to be mindful about getting the correct spindle length, so your crank arms don't end up too close to the chainstays and interfere.
As a last resort, you can get someone with a BB facing tool to take off a mm on each side of the shell, making it a 68mm BB shell.

But Italian threaded bottom brackets have been sized to fit 70mm shells forever. So I have the feeling that there is something else going on here, of which I'm unaware.

AFAIK, I cannot buy an Italian threaded bottom bracket unit that will be sized for anything except a 70 mm shell. I've used one of those once in a 68mm shell that was rethreaded larger to Italian threading because of damage. It worked fine.

My DS has been rethreaded for Italian threads due to cross-threading by the previous owner or his mechanic. When I wanted to install the TA Cyclotouriste BB, it was apparently cheaper and easier to by a French BB and axle, an English NDS cup, and an Italian DS cup. It's been working for 38-40 years ago.

So, for an Italian BB in Argentina, web order from Europa or USA?