Billet or forged aluminum??

dennisn

While recently looking at hubs I noticed that some were listed as forged and others listed as machined from a solid billet. My gut tells me that forging will produce the stronger hub.
At least I think I read that somewhere. Tried a web search for billet but it didn't really answer my question of which one is stronger. Anyone.

rake

i read on a whhelbuilders site forged such as shimano are stronger. but its unclear to me when they say cnc 'd it could have been forged and then cnc'd afterwards or just cnc.

dennisn

rake wrote:

i read on a whhelbuilders site forged such as shimano are stronger. but its unclear to me when they say cnc 'd it could have been forged and then cnc'd afterwards or just cnc.

That's kind of my question too.

Monty Dog

A forged billet should be stronger provided it's done correctly because in the process of forging it should ensure that the alignment of the grain structure is optimised for the shape and stresses on the part - whereas billet will have a homogenous structure and allowances may have to be made for things like hub flange / radial stresses. Forging has the disadvantage of being more expensve as it is a 2-stage process, whereas with modern rapid-machining techniques, a modern lathe can bash-out hub shells to a high tolerance in minutes.
My experience of design and manufacture of precision engineered parts, our preference was always to start with a forging - particularly for things like high-pressure or high-stress components. We did experience some valves made from billet that had a habit of blowing-up whilst doing a 500bar hydro-static test for approvals because of the irregular grain structure and inclusions in the billet.

dennisn

Interesting stuff. I sort of had the idea that it would be a clear cut answer, but as with most cycling things that proves not to be the case.
Thanks, interesting reading.