Piston rod - material and threading

[kevincoxshall]

Hi all,
I am wondering what the best material is for a steam engine piston rod. I think I read somewhere about using drill rod or tool steel, but how would I put a thread on such a hard material to attached it to the piston? I think/thouht that these materials were only grindable and not machinable. So if they cannot be machined is there another classic way pistons are attached?
I'm clearly misunderstanding the basics of the steam engine on this one.....please help.
Or is the answer simply stainless?

kevinC

 

[GailInNM]

Kevin,
In the USA, drill rod refers to unhardened tool steel stock, typically sold in 36 inch lengths. It is accurately ground to size and machines quite well. Depending to the type, it can then be hardened by heatng and quenching in water, oil or air. Drill BLANKS are shorter lengths that are already hardened, most often made of high speed steel and can only be machined effectively by grinding.

I know the UK terminology is a little bit different.

Gail in NM

 

[Metal Butcher]

Hi. Which model engine are you building? What do the plans specify?
If your building one of Elmers Engines that use a threaded rod that goes into a threaded hole in the piston, than the material is not too critical. In that case brass, stainless ground, or drill rod would be fine. I would probably use drill rod (due to its lower cost and dimensional predictability) that is sold in an un-hardened state and machines very easy. It can also be hardened (drill rod) if needed in the average home shop with out a lot of difficulty.

-MB

 

[Jasonb]

I would go with stainless steel particularly if you intend to run on steam rather than air.

Jason

 

[John Rudd]

Ditto SS, use 303 grade.

I'm building a twin cylinder( Yeah will post picks some day... ;D ) and it uses 3/32 SS and needs a 7BA thread...

Cut quite easily by hand..

 

[kevincoxshall]

Thanks for the advice on this one.
The engine is my own design.
I'll start a new thread on the engine soon.
Kevin