pmurdock
08-06-2009, 11:22 PM
ok.. so I want to make a few bearings.. these are thrust bearings.
See wikipedia for photo of what I'm talking about
http://en.wikipedia.org/wiki/File:Thrust-ball-bearing_din711_ex.png
all the faces of the bearing require 32 Ra finish.. no prob on the a CNC lathe.
What I do have a question about is the raceway. I would like to get a raceway with a finish of 8 Ra or better. I'm wondering what the general consensus is on achieving that?
I will start with 8620 steel machine everything to size (except the raceway - which I imagine I should oversize? how much is needed) then send it to the heat treaters for case hardening (carburizing - case depth - any recommendations?) and then mount it back in the lathe and hard turn the raceway.
Now I have been looking at some Kennametal inserts (wiper technology). See Kennametal catalog here (http://www.kennametal.com/images/pdf/US/Sections/KMTL-Lathe_Tooling_Catalog_4010/KMTL-lathe_4010_complete.pdf;jsessionid=WSIAILQJIWM2RLAUCYOSFEVMCQFB0IV0) see page A20-A23
These inserts claim a potential Ra of 1 which I find hard to believe, but makes me think that 8 Ra just might be possible. Anybody have any experience machining to these type of surface finishes? I'd like to do them in house if possible and can't justify buying a grinder just yet. :)
How about a round insert like an RCMT - perhaps those might do the trick - though I don't see any PCBN or DIAMOND versions of the RCMT.
Perhaps machine to size or + 0.0002 or so and then only worry about polishing the raceway after case hardening (read that in a post by HuFlungDung).
cheers!
Paul
See wikipedia for photo of what I'm talking about
http://en.wikipedia.org/wiki/File:Thrust-ball-bearing_din711_ex.png
all the faces of the bearing require 32 Ra finish.. no prob on the a CNC lathe.
What I do have a question about is the raceway. I would like to get a raceway with a finish of 8 Ra or better. I'm wondering what the general consensus is on achieving that?
I will start with 8620 steel machine everything to size (except the raceway - which I imagine I should oversize? how much is needed) then send it to the heat treaters for case hardening (carburizing - case depth - any recommendations?) and then mount it back in the lathe and hard turn the raceway.
Now I have been looking at some Kennametal inserts (wiper technology). See Kennametal catalog here (http://www.kennametal.com/images/pdf/US/Sections/KMTL-Lathe_Tooling_Catalog_4010/KMTL-lathe_4010_complete.pdf;jsessionid=WSIAILQJIWM2RLAUCYOSFEVMCQFB0IV0) see page A20-A23
These inserts claim a potential Ra of 1 which I find hard to believe, but makes me think that 8 Ra just might be possible. Anybody have any experience machining to these type of surface finishes? I'd like to do them in house if possible and can't justify buying a grinder just yet. :)
How about a round insert like an RCMT - perhaps those might do the trick - though I don't see any PCBN or DIAMOND versions of the RCMT.
Perhaps machine to size or + 0.0002 or so and then only worry about polishing the raceway after case hardening (read that in a post by HuFlungDung).
cheers!
Paul