Bearing and Shaft material specs

ducky1 · Mar 29, 2020

I am going to make a shaft 25MM OD with a 6205 bearing on one end and will be running in a needle bearing on the other end. This shaft is for a mower deck quill with the 6205 will be at the pulley end and the needle bear will be on the lower end. The distance between the two bearings is 2.5"
Question - What hardness will I need to run this shaft in that needle bearing and expect some longevity. The OEM application has no ability to lubricate but we will be adding a grease fitting to the quill housing when rebuilding.

Garwood · Mar 29, 2020

The shaft will need to be case hardened/carburized and ground for the needle bearing.

You can get needle bearings with inner races. That might be the way to go for you or pick a better style of bearing?

ducky1 · Mar 29, 2020

Thanks
Did not realize that type of bearing was available. Let me go look.

Phil in Montana · Mar 29, 2020

What about a seal to keep the gunk out, I would use 2 ball bearings with seals...Phil

ducky1 · Mar 29, 2020

Phil in Montana said:
What about a seal to keep the gunk out, I would use 2 ball bearings with seals...Phil

OEM uses a 6205 double seal and a double seal needle bearing and it runs till it dies.
When we rebuild these we use a 6205 and remove the inner seal and remove the top seal of the needle bearing and add a grease fitting to the quill housing and all our problems go away. Machine was designed for idiots/lazy people and we do the maintenance and keep on going.

atomarc · Mar 29, 2020

The inner race (IR) to shaft fit is critical as well as it's what keeps the IR in place on the shaft. This typically requires a shaft turned to the OD for a light press or shrink fit for the IR. Needle bearings are much fussier than standard roller bearings. I would have a look at a cartridge bearing with a squeeze-lok retainer. Many different ways to skin the cat but some are much better than others.

Application RPM and working environment will lead you in the right direction.

Stuart

ducky1 · Mar 29, 2020

OEM used a double seal 6205 and a double sealed needle bearing. Lasted as long as the MFG wanted it to. The problem is they over built the rest of the tractor and it seems to last forever if you take care of it.
We remove the inside seal of the 6205 bearing and the top seal of the needle bearing and add a grease fitting to the quill and life expectancy go thought the roof. Just trying to keep this equipment running.

ducky1 · Mar 29, 2020

atomarc said:
The inner race (IR) to shaft fit is critical as well as it's what keeps the IR in place on the shaft. This typically requires a shaft turned to the OD for a light press or shrink fit for the IR. Needle bearings are much fussier than standard roller bearings. I would have a look at a cartridge bearing with a squeeze-lok retainer. Many different ways to skin the cat but some are much better than others.

Application RPM and working environment will lead you in the right direction.

Stuart

I looked at this option and it will not work because this end of the shaft can not be reduced in size to accommodate to sleeve. Hardening should not be a problem.

Milland · Mar 29, 2020

For direct contact needle bearings, you should check out the engineering data offered by the major manufacturers like IKO and INA. Considering the job these shafts have to do (if I understand correctly, are they driven on one end and hold the blades on the other?), then you want to do the job right, which means a tough steel hardened to 55-60RHC with a fairly deep case and properly ground to diameter and surface finish.

You also need to understand the differnece between full compliment needles, and caged. Full means all the needles that will fit in the outer sleeve are used, caged means fewer needles and load capacity, but higher allowed running speeds. Even control of the ID diameter of the carrier the bearing is pressed into matters, too tight and you'll shrink the ID of the needle assembly, potentially binding on the shaft.

Be aware of fatigue risks from wear notches and out of balance condition, you don't want fast spinny things with blades on them cracking and coming free in use (why you want a tough, not just hard steel for the shaft).

LKeithR · Mar 29, 2020

Milland said:
For direct contact needle bearings, you should check out the engineering data offered by the major manufacturers like IKO and INA. Considering the job these shafts have to do (if I understand correctly, are they driven on one end and hold the blades on the other?), then you want to do the job right, which means a tough steel hardened to 55-60RHC with a fairly deep case and properly ground to diameter and surface finish.

You also need to understand the differnece between full compliment needles, and caged. Full means all the needles that will fit in the outer sleeve are used, caged means fewer needles and load capacity, but higher allowed running speeds. Even control of the ID diameter of the carrier the bearing is pressed into matters, too tight and you'll shrink the ID of the needle assembly, potentially binding on the shaft.

Be aware of fatigue risks from wear notches and out of balance condition, you don't want fast spinny things with blades on them cracking and coming free in use (why you want a tough, not just hard steel for the shaft).

Yup, needle bearings are wonderful things They're compact and they'll carry impressive loads for their size
but they can be fussy little buggers--all the required parameters need to be right or you're going to have
premature failure issues...

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Bearing and Shaft material specs

ducky1

Plastic

Garwood

Diamond

ducky1

Plastic

Phil in Montana

Stainless

ducky1

Plastic

atomarc

Diamond

ducky1

Plastic

ducky1

Plastic

Milland

Diamond

LKeithR

Stainless

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