Shot peening

Hmmmm polishing and shot peening are completely different, the process's are different and so is the end result.

Polishing/lightening helps reduce weight and mostly helps take down stress risers and cracks that might already be there from the casting from the factory but when you polish you take away the surface hardening that's why you need to shot peen as well.

Shot peening is a process of small steel shot being hurdled at your rods that is like being struck with a ball peen hammer only smaller causes the surface to stretch and the dimple compresses the metal underneath, remember that metal fatigue cracks start where the surface is in tension, NEVER where it's in compression.

I'll touch on some key points of peening:

The maximum compressive residual stress produced just below the surface of a part by shot peening is AT LEAST as great as one-half the yield strength of the material being shot peened.

The peening compressive process is beneficial in increasing resistance to fatigue failures, corrosion fatigue, stress corrosion cracking, and erosion caused by cavitaton.

To create the dimple the surface of the material must yield in tension below the surface, the material tries to restore it's original shape thereby producing below the dimple a hemisphere of cold worked material highly stressed in compression.

Nearly all fatigue and stress corrosion failures originate at the surface of a part but cracks will not initiate in a compressively stressed zone, now because the overlapping dimples from shot peening create a uniform layer of compressively stress at the parts metal surface, shot peening provides considerable increases in part life.

Let's not get into Laser Peening that goes 4 times deeper than normal shot peening.

So as you can see Peening and Polishing are completely different and you should ALWAYS shot peen after you polish.
 
Thanks Taylor. That explains alot! What is the best method for polishing?
 
Gonna make me bust out my notes again huh Kevin? I can't take all the credit I do alot of research before I do something nowadays and with lots of help from different companys and notes and sending rods off that's what I've come up with, there was a company online that I got alot of tech from I'll try and dig up the name. Are you wanting to do them yourself or send them off? They are a pain and time consuming but will save a little money. Weren't you going billet? Most billet rods will come shot peened as well.
 
dont the bolts need to be in the rod to properly heat treat and resize?
 
I want to go billet. But circumstances have changed and I dont think I can afford it this year. With the state of this "awesome running" engine that I bought it is costing way more than what I can afford.
 
rawdog said:
dont the bolts need to be in the rod to properly heat treat and resize?
Click to expand...

To resize, yes. To heat treat no. the metal needs to be able to move and do whatever it wants to, then the parting lines may need touched up if they do move. sometimes they do, sometimes they don't.
 
Cryo or heat treat? Which is better? I am imagining that you would do the shot peen before you would either heat treat or cryo?
 
Heat Treat. Not sure which order honestly. Bowdil does it and I never asked what order they do it in.
 
Heat treating relaxes the metal to a natural state, doing away with stress, cryoing will align metal within itself, but keep it in a stressed state.
That is what i have gathered.. if i am wrong please say so!
 
ahh,,, how hot do they take them too? I will have to find someone that can do that for me,,, not likely something you could do in your oven I imagine
 
No Kevin you won't be able to heat treat at home, I'll try and dig up a site that had some good tech on heat treating and cryo.
 
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