[dhcarguy]

I came acrossed old receits from previous owners and one from the engine shop has under Discription of work done: engine magnafluxed and shot peened.
What exactly does shot peened entail?????????
Thanks, Dave

[SWEETJUDGE]

its like sand blasting to clean parts but a shot is used not a sand

[67drake]

I thought shotpeening was used to change the surface of the metal to prevent cracks and make the part stronger?

[SWEETJUDGE]

shot peening also stress relieves. CAST IRON Heads & rods are very common shot peened pieces.

will not make it stronger. ahhhh heads are shot peened to clean them the best to hunt for cracks as an example......

most shops use ovens to bake the oily greasy engine parts than shot peen to truley clean all surfaces.....

[dhcarguy]

So , I take it that shot peening is a much better way to clean the metal, and also helps in finding any defects in the parts???
Thanks for the responses, Dave

[b-man]

The shot peening does what it describes. Using tiny steel shot balls it peens over any microscopic surface cracks to remove these imperfections, thereby reducing chances of failure. It will also serve to harden the surface and relieve stress. It's more than just a cleaning operation.

[Bill Meyer]

Since the EPA has taken away the use of most cleaning chemicals, many shops now use the "shake & bake" method of degreasing/cleaning. The block is heated to about 500 degrees for an hour, then put on a rotissarie for 30 minutes and blasted with shot. Next, the block is shaken and tilted/rotated to get the shot out. Usually, when they come out, they look like they were just made!!
If you are not boring the block,however, the edges can roll over causing problems. Also, always check the lifter bores as they may have rolled edges and need a quick reaming to get the proper clearances. We like to put the old bearings in the block with the mains to keep these surfaces true. - Bill -

[Schurkey]

There is a HUGE DIFFERENCE between blasting a part with steel shot to CLEAN it, and blasting it to make it STRONGER.

The common process is to use the steel shot for cleaning. The shot does not hit the part hard enough to provide surface compression. You don't get a stronger, more reliable part, you just get a clean one.

Shot blasting for actual surface treatment is a rare thing; at least around here.

[Dragncar]

There is shot peening and there is "military grade" shot peening.With real shot peening you get a strip of metal that was in with the parts that you paid to get shot peened.It gets shot peened and has a curve to it and the marks from the shot peening you paid for as "proof" of the job done.It must be done with brand new shot.I paid 200$ to get that sort of shot peening on my SD rods by the same place that shot peens the turbo fan blades for F-17 jet engines.It is not just a cleaning.

[Will]

Too many people, and shops, use the term "shot peening" when what they really mean is "shot blasting" or "shot cleaning."

The "shake & bake" process whereby parts are baked at high temp to turn oily gunk to carbon then blasted with metal shot to clean them is probably the best way to clean parts that's come along in a long time. You get a part that looks like a fresh casting. However, this does NOTHING to alter the surface structure of the metal. I have had shop people insist this is "shot peening", but it's not.

The word "peen" is defined thusly in this context:
–verb (used with object)
2. to enlarge, straighten, or smooth with a peen.
3. to strengthen (a metal surface) by light hammering or by bombardment with steel balls or shot.

The surface of a shot peened part will not appear as rough as a fresh casting. Casting lines will generally be flattened out and the surface will have a uniform dimpled look, almost like a golf ball. This is because large shot was used at a high enough pressure to slightly deform and compress the surface of the part. This is not what's done to clean the part, this is a different process used to remove surface imperfections, stress risers, and to improve the strength of the part.

If you have any doubt as to whether a part has actually been shot peened or not, compare it to another part that you know hasn't been shot peened. The difference in appearance will be obvious. Back before we had reasonably priced forged rods, sanding the parting lines off the beams of stockers then shot peening them was the best bet for a street or street/strip buildup.

[HWYSTR455]

Shot peening is done in a 'tumble drum', correct? That would be the difference from blasting. That was my impression, have had parts shot peened, though never really researched the process as to how it actually was done. I also am under the impression that for different materials you use different types of shot, size & material.

[Skip Fix]

I think some of my old Chevy Hi Perf factory books even talk about specific spray patterns to use for rods. It is different than just cleaning.

[Will]

Originally Posted by HWYSTR455

Shot peening is done in a 'tumble drum', correct? That would be the difference from blasting. That was my impression, have had parts shot peened, though never really researched the process as to how it actually was done. I also am under the impression that for different materials you use different types of shot, size & material.

Nope. How are you gonna hit the surface of the part hard enough to "hammer" it if all you're doing is tumbling the part around in a drum? A tumble drum is for cleaning parts, not for shot peening.

Again, shot peening literally deforms and changes the surface texture of the part.

[HWYSTR455]

Like I said, wasn't sure, but the weight of the part and shot could be enough to hit it, or was my thinking. Guess I'll look into it, just from the knowledge aspect, since most parts these days (in my builds) won't require it. How does one get even coverage if it's sprayed? And control the impact? Yeah, think I'll have do do some research, satisfy my curiousity!

[Mr. P-Body]

Shot-peining is a process where the entire surface of a metal part gains an evenly stressed layer by bombarding the part with steel or lead shot at high velocity. It's very good for forged rods and cranks. It's pretty much a waste of time and money on cast parts.

The cleaning cabinets that use good stainless shot, can have a minor effect of shot-piening if the parts are left in it long enough. It is not a substitute for "real" shot-piening. (there's been a "debate" over the spelling of the word "pien" or "peen", but one cannot buy a "ball-peen" hammer... so I guess it could go either way) Generally, one must go to a metal treatment shop, not an automotive machine shop, for "real" shot-piening.

FWIW

Jim

[smagnotti]

Steel shot and high velocity and a realy soft set of cast iron sb chevy heads that lost almost 3/16" of meat all around made my jaw drop after just 20 minutes in a shot peen cabinet.

[Jack Gifford]

Interesting topic. I'd seen shot-peened parts, but hadn't witnessed the operation. I would have assumed that a media-blast cabinet would work as well as any.

Originally Posted by Mr. P-Body

... one cannot buy a "ball-peen" hammer...

Sure you can. But, please understand that this is all merely trivia, since peen/pien/pein will all be clearly understood. 'Peen' (from German Pinne Pane) is the predominant spelling, with 'pein' shown as alternative spelling in most dictionaries (which say 'see peen' for the 'pein' entry). 'pien' isn't generally acknowledged.
And, even more trivial, is the fact the 'peen' is also a noun- meaning the rounded end of a hammer head.