Minimum raceway hardness for lightly loaded needle roller bearing

[ddowns46]

Hi all, this is my first post here. I am looking for some advice.

I have an application that requires the use of a 1" needle roller bearing, .75" wide. This bearing is being used as a pilot bearing similar in function to the pilot bearings used to support the transmission input shaft in vehicles equipped with a manual transmission. To elaborate, under normal circumstances, the bearing in my application does not experience rotation relative to the shaft that acts as the raceway. With no rotation, it will experience a maximum radial load of 250 pounds. Relative rotation up to 5000 RPM under the same 250 pound load is very intermittent (roughly 5% of the total time the machine is being operated, machine is operated 20 hours per week). Mcmaster Carr lists that the bearing I would like to use is rated for 4,050 pounds at 11,000 RPM. The bearing has 20 needles and the needle diameters appear to be approximately .075".

My question is what is the minimum raceway (shaft) surface hardness that I can get away with in this application? A more general question: does bearing loading and speed have any influence on what the raceway hardness should be? First guess would be that the higher the load the harder the race needs to be, but I am no expert!

thanks,
Danny

 

[Tmoose]

hardness, and depth of hardness depends on load and needle diameter.
Also the surface finish and geometric accuracy to make the bearing happy for a long time.

The big INA needle bearing catalog used to have all the info needed.

I think inner races were available separately

 

[dinjin]

My guess is that the rollers are 63 Rc. I would assume that the raceways should be at least 55 Rc. Hardness above 63 Rc does little for life but your general statement about hardness is true. You can make something too hard and it becomes brittle. I assume you are speaking of surface hardness of the shaft rather than the core hardness. Tho your loads are light, you may have to worry about viebration and fretting corrosion.

 

[Tmoose]

Forgot to say "what does the needle bearing supplier say? "

I'd still compare a sales person's reply to the INA technical info.

 

[Fugeguy]

Unfortunately the Torrington catalog is not available on-line right now.

Sooner or later it would be here:

http://www.koyousa.com/DesktopDefault.aspx?tabid=603

The generic recommendation is for a minimum shaft hardness of Rc = 58 and a wave free surface finish of 8 microinches.

Light loading should not matter because the shaft is in effect the inner bearing race. Assuming inner ring rotation and loading why under spec the component most likely to fail first?