Removing casting/forging lines on suspension parts?

[JeffP1167]

I want to polish my C4 suspension parts but noticed they have a elevated 1/8" wide casting/forging marks on the sides and other areas. Can these safely be ground down or could it affect the strength of especially the a-arms?

 

[Twin_Turbo]

Yes, grind them oi ff..no prob

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[rtj]

I want to polish my C4 suspension parts but noticed they have a elevated 1/8" wide casting/forging marks on the sides and other areas. Can these safely be ground down or could it affect the strength of especially the a-arms?

I just polished a Procharger volute and found that an electric die grinder with 3M scothbrite pads worked great. Did the inside of my new hd rear end cover the same way. Probably not the best for removing those ridges.

I think harbor freight sells the arbor and disks I used.

 

[SuperBuickGuy]

yes, we've been doing it for years to strength connecting rods - grind the parting seam off, then polish the piece.... of course, it's not for show... or at least we hope it's not for show (if you can see the rods on the outside on the engine, generally speaking something bad may have happened)

 

[mrvette]

yes, we've been doing it for years to strength connecting rods - grind the parting seam off, then polish the piece.... of course, it's not for show... or at least we hope it's not for show (if you can see the rods on the outside on the engine, generally speaking something bad may have happened)

I have heard of that being done to strengthen a part, but I have NO concept as to WHY it works....makes NO sense to me....

anyone for a explanation??? please!!!:bonkers:

 

[Twin_Turbo]

Remoces stress risers, be sd t shotpeened after polishing.

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[JeffP1167]

so my a-arm need to be shotpeened after removing these risers or whatever they are called ??????

 

[SuperBuickGuy]

yes, we've been doing it for years to strength connecting rods - grind the parting seam off, then polish the piece.... of course, it's not for show... or at least we hope it's not for show (if you can see the rods on the outside on the engine, generally speaking something bad may have happened)

I have heard of that being done to strengthen a part, but I have NO concept as to WHY it works....makes NO sense to me....

anyone for a explanation??? please!!!:bonkers:

Parts tend to crack where they're jointed together example: a paper with a rip, if the rip is started, no matter where you pull on the paper (on either side of the rip) afterwards, it will continue ripping there.

As for shotpeening - I think it's still a good practice, but heavens does one of my machinist friends argue against it. While he agrees it makes a forged part stronger, he thinks that by the time you're done grinding the seam, shotpeening, resizing, and cleaning the rod you could have bought a better rod that doesn't have the issues (h beam)....

 

[SuperBuickGuy]

so my a-arm need to be shotpeened after removing these risers or whatever they are called ??????

no

shotpeening is shooting ball bearings at the material at high velocity to heat and vibrate the metal into a more natural alignment of the atoms. Where forging squishes (to use a technical term lol), it doesn't give the metal the same density throughout so the atoms (for example) on the outside of the forging are closer to each other then in the center. by shotpeening you let the material relax a bit and mix more thoroughly (and I am not going for technical, just trying for a birdseye view for the layman).

shotpeening realigns the molecules in cast iron - those arms are aluminum so shotpeening would probably cause more damage then strengthening.

Also, grind the seam off, don't go into the arm - the point of the grinding exercise is to create a thicker point from which a rip could start, it is not to make the arm symetrical

 

[rtj]

I always thought shot peen was for steel. As, it's too easy to erode aluminum.

 

[MYBAD79]

shotpeening would be great but polishing alone is good enough ... well, with "good enough" I mean better than before.... the casting lines are causing weak points, just like any surface imperfection....

when you're done polishing with 600 grit, take some chrome polish to that A-arm, you'll be amazed