shaft material for needle bearing 1

[atkt1123]

Hello,
I using a needle bearing on a 416 SS shaft. I need a hardness RC 41- 45 for this application. The heat treatment is distorting the shaft hence I am looking into a different material which can be hard enough for needle bearings. Also pre hardened hardness on this shaft is RC 29 is that good enough for needle bearing use. What is the general practise in the industry when using needle bearings.....
Thanking you in advance.

 

[EnglishMuffin]

I wouldn't dream of running a needle bearing directly on a surface that wasn't hardened & ground. Apart from accuracy considerations, you need a very good surface finish - otherwise you may get rapid surface fatigue failure. You should have a shaft Rockwell hardness in the high fifties for most applications - especially if you want to achieve the manufacturers life ratings. There is a grade of Stainless which is used for bearings - AISI 440C, and you can harden this up to about 60Rc. However, because you may not want a completely through hardened shaft for other reasons, you may have to investigate ways of achieving local hardening. I suppose you could get away with a softer shaft if it was a very lightly loaded low speed application, but I wouldn't skip the grinding. I am assuming that you are talking about running the needles directly on the shaft, of course. If you use an inner race, shaft hardness is not so important.

 

[Carburize]

I have seen applications where, because of space constraints no inner race can be fitted, the surface of the shaft where the bearings run is carburized. Obviously you will need to select an appropriate carburizing grade to give all the other properties you need for the design 17CrNiMo6 (18CrNiMo 7-6)might just about make the core strength/hardness you are looking for?

 

[MASSEY]

For steel shafts we use 8620 vac. degassed case hardened and ground with the the non-bearing surface drawn back.

For Stainless Steel we use 440C which thru hardens, the non-bearing surface is drawn back and the bearing surface is ground.

 

[unclesyd]

A little late.

Try Thomson Industries:

http://www.thomsonindustries.com/Sections/Products/products_main.asp?PC=2000000&GI=1

There Case 60 shafting is outstanding.

 

[splitbearing]

I know this is a bit late, cos I just joined the forum.

In rolling bearings which do not have inner or outer ring to provide a raceway, the rolling elemets run directly on the shaft or housing bore. The shaft or housing should be designed as a raceway.
Material for rolling bearing raceways:
Through hardened steels to DIN 17230, eg.100Cr6. These steels can also be surface hardened.

Case hardening steels to DIN 17230, eg.17MnCr5 or 16MnCr5

Steels for flame or induction hardening to DIN 17230, eg.Cf54 or to DIN 17212, eg.CF53.

Heat treatment of materials. For case hardening, flame or induction hardening steel, the following must be ensured:
a surface hardness of 670 +170HV, a sufficient hardness depth Eht or Rht. According to DIN 50190 the hardness depth is the vertical distance from the surface where a reference hardness of 550HV is persent. It is measured on a finish ground shaft and should correspond at least to the lower values given. It must be >=0.3mm.
Case hardening Eht>=0.078.Dw

further information can be obtain from

http://www.ina.com