shot pein ?

when shot peining items, what is the guage of shot used, and the typical air pressure ?
as always, TIA.

anyone ?

Well, you obviously haven’t tried googling shot PEENING....

now that you mention it, no.
i guess i need spelling lessons !
thanks.

Why do research when you can have someone else do it for you.

Me thinks that those in the know, the shops who do that, are not going to share their procedures on the interweb

Shops that share get more customers.
People value if someone shows experience in a field and what they are doing.

Of course trade secrets which gain you a nice profit over local competition could be considered private, or just go into too much detail which canbe irrelevant for an outsider.
But the average customer mainly likes to know / be shown you have experience in your field.

It is all written down somewhere. I did some shot peening 30 years ago and there was a measurement method involving a strip of metal which you peened and then you measured how much it curled up. That gave you a number. Then you looked in the book and it told you what number to shot peen connecting rods. We shot peened factory rods after they had been deburred on a big sanding roll. That was 30+ years ago and I wouldn't waste my time with any of that crap these days. Now I just call Summit for some chrome moly BB Chevy rods and give them a credit number. The rods show up in 2 days and I bolt them in the engine.

Yeah, and the rods are stronger and cost about as much as grinding and peening would !

FWIW, a few years back I bought a sack of shot and dumped it in my blast cabinet (home made). The intent was not so much to remove stress risers but rather to give a more uniform appearance to some cast parts that I'd ground the flashing and parting lines. The shot size was S170 which is quite small and the cabinet is a siphon feed. I run it at from anywhere from 70 to 100 PSI and it worked fine and yielded the results I was after. But not knowing the intricacies, I'd never peen parts for anything other than a cosmetic finish. For those curious, unlike most blast media, shot does not remove any material, it merely changes the surface profile.

Bad information on the Internet has cost me a lot of money. I would at least like to get the viewpoint of folks that are here.

If I can find the process standard we used at Chrysler I’ll send it to you.

In the meantime I would read up on the practice - a fair amount of info on the web exists.

You would be surprised how many items get peened in passenger car and truck production.

Seems like it would almost be impossible to do any harm shot peening no matter what method the OP used vs doing it correctly, unless OP used rock salt, cannon balls or similar.

Please correct this if I am overlooking something..

Nobody wants to get shot in the pein.

plus the fact some of you know your way around the keyboard searching thing WAY better than this old fart.
also as mentioned, other's viewpoint on subjects count far more than what is printed on the webs because of actual experience. [real life]
lots of times theory and practice are two different things.
thanks to those who are attempting to expand my knowledge on this subject.
[and i don't think being shot in the pein would be much fun. ]

The process has been around for decades,as mentioned it's a process of finishing a part with air and fine metal particals.The purpose is to give a part a consistant uniform finish an to remove and residual flash as well as give the surface a finish void of any irregularities.This process was used in most all military specs for part realiability.Most know that any type of irregularity in the surface of a critical part can be the beginning of a crack or other type of failure.With all this being noted with the new processes of finished material from casting,forging and billit parts seldem need shot peening.Also the quality of the raw materials made with the new techonology help eliminate inperfection in the product.This process also helped in materisl testing giving the part a visiable consistant surface to inspect with the different process such os x-ray,zyologo,and magnetic partical testing.

As I understand, it induced stress parallel to the plane of the part surface. This reduced the chance of a stress fracture beginning at the part surface. Anyone else have a different understanding of how it works?

Ask 4 different metallurgists the same question and you will get 5 different opinions.

But all the ones I asked about peening all said pretty much the same thing.

Every forging, casting or stamping benefits from peening. All of them. Regardless when they were made - 50 years ago or last week.
(Forged cranks, rods,etc. are made pretty much the same way as they were 50 years ago).

Peening builds compression stress at the surface. This is a good thing.

Shot peening is a cold working process used to produce a compressive residual stress layer and modify the mechanical properties of metals and composites. It entails striking a surface with shot (round metallic, glass, or ceramic particles) with force sufficient to create plastic deformation.[1][2]
In machining, shot peening is used to strengthen and relieve stress in components like steel automobile crankshafts and connecting rods. In architecture it provides a muted finish to metal.

https://en.wikipedia.org/wiki/Shot_peening

Hey 340, Wiki first states that it adds compressive stress then later says relives stress. Thats the stuff that i'd like to get to the bottom to. Which one add/relieve? An old mentor of mine that was McDonnell Douglas ball bearing top dog said it added stress. I'm on same page as Transman.

There is no universal answer, it just depends on the process that the factory follows. Typically the internal stress from forging would be taken care of by tempering. Then the part is machined, heat treated and shot peened. But engineers are free to experiment with different process flows so there might be someone somewhere who decides to shot peen after forging but before machining. In that case the shot peening would relieve internal stresses.

Years ago (1988 or so) I had three different new sets of forged steel H beam rods for BB and 426 Hemi motors I wanted magged, a set of Eagles, a set of CAT and a set of Carillo for the hemi. I took all three sets of rods to my crankshaft grinder, Wilson Bros Grinding in Ontario, CA and ask Ron if he could tell me what brand they where (none of them where in the boxes they came in and none of them had markings that he could see when I placed them on the bench before he came over to look at them. he said that the one set was Carillo and when I ask him how he knew that he said because they where the only set double shot peened I didn't see that but he did

I use to shot peen the transverse torsion bars back when we were developing the old F-body... the pressure
and shot size varied based on the material you were working with.. with those torsion bars if they werent
shot peened they would explode at the bend every time when I would try preload then... the shot peen was
a stress reliever...we tried multiple sized shot and even different sized shot on a single bar.. the peening also
compressed the steel to assist the strength of the steel... also you can double peen or more... I also use
to shop peen (douple shot peen) my viper rods

There are several good answers here and I didn't write the Wiki page. I'm thinking if you have some residual tensile stresses on the surface of a part, then peening would add compressive stresses to relieve the tensile stresses. My SWAG on the matter. Now I'm wondering how a machinist can tell if a part was double shot peened?

Answer:
https://www.shotpeener.com/library/pdf/2013029.pdf

interesting article mr340.
thank you.

So this thread then begs the question, shot peen then cryo, or cryo then shot peen?

Can we just take him out a shoot him ???

We use to shot peen the last thing

Check out WPC treatment, it's micro shotpeening. It's a big boasting point in Japanese tuning shops of how much power they can make on factory bone stock parts, they use WPC on everything.

That WPC is pretty wicked! Thanks for sharing!