Machining versus forming a bolt.

[blakev]

I have need for a bolt which I can not find readily available off the shelf. Can I machine the bolt from rod and expect to get properties similar to a manufactured bolt? I would machine the bolt and follow up with a heat treat and temper in effort to get the desired tensile, yield and hardness. Will I have impact strength issues? Does rolling the threads give benefit over cutting the threads?

Any input would be greatly appreaciated.

[PinkertonD]

Hi, tell us what size bolt and loads you are talking about here. Is the bolt in tension or shear?

I would hazard a guess and say every significant bolt and nut on the Shuttle was machined from solid, make of that what you will.

[blakev]

PinkertonD. The bolt is in tension. The grade class requirement is 10.9 per ISO 898-1.

With Space Shuttle bolts come hi-tech expensive materials no?

Basically I want to machine something from 4140 then heat treat / temper to get to the yield / tensile / hardness of a grade 10.9 bolt. Maybe it's not much more complicated than that. It just seems to me if you cold head or hot upset forge a head onto a bolt it is going to be stronger than machining it.

[PinkertonD]

@Blakev, forging versus machining would come down to Metallurgy and the fineness of the metal consistency and a bunch of other stuff, but if you are trying to emulate a Grade-8 bolt (ISO 10.9) then it really all is moot. Machine your bolt, make sure there is a good sized radius under the head and also a very fine lathe finish on the shank/body. Thread forming versus machining again would be moot in this instance. Do the highest level of thread tolerance you can buy a die for, or use a Go/Nogo nut for the tolerance you seek.

I can't help but feel you are wasting time on things that do not matter. If the diameter/load is that critical, go to a higher grade of material or heat treatment, or a go to larger diameter. It's a bolt dude!

Fini for me.

[blakev]

Great thanks for the input.