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Hello, i've been lurking a while here and finally joined up. Hope this is the right place to post this type of question. I have a need to make some automotive roller camshafts for a niche market I have developed. I need to use 8620 steel as the material to make the round lobe blanks from, but am getting conflicting input from several of the cam companies that will be finish grinding and heat treating the camshafts for me. One company says that 8620 is 8620, and HR or CR is fine and they have never in close to 60 years of business ever had any issues with that. Another has said that it must be aircraft/aerospace grade 8620 with no exceptions, bearing grade will not work at all and have seen many failures from billets made from that form of it. So I guess my question is, can the heat treat process be different enough between these cam companies to require different grades of the same material, is this a smoke screen to confuse by the one company to let them make the billets(with the correct material) instead of me, or is there really a need to use the aircraft/aerospace grade instead of the run of the mill bearing grade or lesser grade type for this application. Thanks for your time guys....
Cold rolled has more mechanical stress left in it than hot rolled. There probably needs to be stress relieving in your process. I would stress relieve before starting and again before finish machining with hot or cold rolled.
The heat treat guys are probably worried about distortion during the hardening process.
8620 is a good case hardening steel. It has an unhardened core after case hardening for more strength.
Dick Z
DZASTR
On my end I am just providing the cam company a roughed in round lobe cam blank. They then rough grind the round lobes to a pre-determined spec above the final dimension and then have the cam blank heat treated. They then straighten and finish grind all the bearing journals and lobes to their final dimensions. These camshafts are almost 29" long, so I don't know if stress relieving is part of any cam companies process to complete the final product. But I guess the main question still is the bearing grade 8620 not acceptable for this application, and is the aircraft/aerospace grade the only alternative.
Is there a large difference in the price of the aircraft quality material? I have no idea about 8620 camshafts.
However, I did have a problem with D2 tool steel. The purchasing dept bought some cheap run of the mill stuff that didn't comply with the specs I required. The edges of the cutting dies chipped. Too much sulfur in the cheap D2 formed carbide inclusions when they were hardened.
Dick Z
DZASTR
No there isn't a huge cost difference, at least in my area. There is some aerospace industry relatively close by, so that type of material grade is easily obtainable as well.
So the Aerospace stuff has no real negative. Make everybody happy, use the fancy stuff.LOL
Dick Z
DZASTR
Yeah, the main issue is that I can get the bearing grade material in-town, and the aerospace material will require a little road trip to pick it up. So if it makes them happier to have the better grade to start with then I might as well get it. Thanks Richard.
Old Chevy inline 6 iron wonder?Originally Posted by Racer-Dude
Yep, the 250 and 292 engines.
Interesting. I'm working on a derivitive. Check your PM.
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