adrianphu123 73 Posted January 31, 2015 Hey guys, just a quick question about polishing connecting rods, I've polished the sides of the rods to get the ridge down, as well as most of the casting surface pattern off the entire width. Just wondering if it thats time to stop? I dont want to take too much material off. I've also polished the tops of the beams as shown in the photo. Is that okay or have i cocked it up? All grinding and sanding was done parallel to the beam, not across it. Thanks, adrian Share this post Link to post Share on other sites
slydog 7,873 Posted January 31, 2015 OK generally rods get shot peened/blasted first to induce a harder than normal case.The polishing after wards helps to line out some of the grain of the metal and makes em look good. I'd stop when your removing move than the outer of the top casing. This is usually done on engines that will cop sustained big RPM's when aftermarket rods are not allowed or a option. 2 gerg and Outback Jack reacted to this Share this post Link to post Share on other sites
wagoon 2,429 Posted January 31, 2015 You need to be careful when grinding/linishing or polishing steel because if the steel becomes to hot to touch you have changed the surface hardness. I do hardness testing at work and have to get a polished finish and had on occasion over heated the steel which has changed the hardness result. The more course the grinding disc the less heat is put in but if using fine grade flap disc or linisher belts the job will heat up very fast. It is best to hold the steel in your hand without gloves(DON'T use a grinder in one hand while holding the job in the other) if possible as it takes only a few seconds to over heat the steel if there is already heat in it. 4 Thom, gerg, Outback Jack and 1 other reacted to this Share this post Link to post Share on other sites
slydog 7,873 Posted January 31, 2015 That is all top info there Ryan... 1 wagoon reacted to this Share this post Link to post Share on other sites
wagoon 2,429 Posted January 31, 2015 I wouldn't quite go that far sly. Hardness testing is one of the most frustrating parts of my job because it is so easy to stuff a test from over heating the steel, just need more patience. Worse part is if you overheat the surface you have to remove a small layer to then test underneath which I'm guessing would be a bad thing on con rods 1 gerg reacted to this Share this post Link to post Share on other sites
gerg 10,871 Posted January 31, 2015 I've read that after polishing, you get the rods shot-peened to compress the surface grain and make the structure uniform all around again to eliminate stress risers (any straight lines across it) Apparently, it should look rough like the rest of the rod. Some even say not to touch a forged rod at all, such is the importance of the surface grain.. If heating it up is a problem, maybe hand-filing is the go, with plenty of lube to keep it cool. Share this post Link to post Share on other sites
wagoon 2,429 Posted January 31, 2015 The process you use comes down to the makeup of the steel as all of these steels will be technically alloys as the will contain several different alloying elements which makes them suitable for the job. For example at work when we temper a steel (temper removes the brittleness of the steel but also makes the steel tuff) we try and keep the temperature lower so as not to reduce the hardness, but there are steel that the hotter you temper the harder it gets. 1 Outback Jack reacted to this Share this post Link to post Share on other sites
