Planetary Pinion Gear on Forklift Hub: Acceptable Play???

Clark Hurth/Dana Spicer 212 Super Tractor axle.

Planetary gears in the hub being replaced, and one of the four pinion gears came without the inner bore finished (which is also the roller bearing outer race). It was never ground. Due to time crunch, I got good measurements and finish bored the gear. Bore arrived .0154 undersized, so I just needed to skim that off.

I practiced on one of the the old gears, with consistent results, perfect finish. Took off .002 per pass, then .001 per pass consistently.

On the new one, same great finish... BUT! On the last spring pass, (no cross slide adjustment; just reversing back out), my boring bar took a nice initial cut and removed .005 instead of just under .001 as I was repeating before. It is now .005 oversize.

Noticable play when bearing assembled and installed on shaft.

My dumb question: Is this a major no-no to use as is? I know the forklift's weight doesn't rest on this planetary system, just drive from axle shaft to wheel. I think I already know the answer, but would love to hear scolding/advice.

.005 might as well be a mile when you add in the words "bearing" and "gear".

With three planets in there I think I would assemble it up and give it a test drive. If it's going to cause trouble, you will feel a binding when driving it. If you feel it binding buy another gear and fix it, if no binding use it as is.

Thanks for the answers. I really should just get the new gear.
Second post is very temping... I'm scared of metal particles ending up in the other bearings if this one fails.

i might be imagining things but i believe the planet gears to share torque equally need to be radially located on the planet gear carrier with no slop, or, equal slop between the gears. if one is loose its not going to be loaded.

The pinion gear which meshes with in your case, 4 planet gears, those 4 planet gears ensure that the gear is not going to experience any huge radial forces because the gear is constrained by them. so you could very plausibly fix your problem with .002" shim stock and locktight.

however..

one of the four pinion gears came without the inner bore finished (which is also the roller bearing outer race).

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this sounds like you're talking about the planet gears. if the gear is the roller bearing outer race, then you need a ground finish right? if you're pressing a roller bearing outer race into the gear, then you could still fix this problem with shimstock and glue if the glue can handle the pressure.

if you're talking about the center pinion gear then the radial forces cancel out and there isn't significant load on the roller bearing. if you're talking about one of 4 planet gears then that's different.

TheOldCar said:

Thanks for the answers. I really should just get the new gear.
Second post is very temping... I'm scared of metal particles ending up in the other bearings if this one fails.

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"Fail" just might could also involve jamming or locking-up whilst handling a load in a critical situation, so, yazz - prolly not worth the risk.

Just out of curiosity, how big is the assembly, is it still a stocked item anyway, and if so, what kind of costs are involved for a store-bought replacement?

Foto? Link?

A lot of needle-roller bearings are available as cage-with-rollers only, to be used with appropriately hardened and finished inner and outer members supplied by end-user and integrated with other parts, roller assy with inner race only (not very common), and rollers with outer race only.

Quite possible you could find an outer-race, or an off-the-shelf assembly of rollers with appropriate ID to fit the shaft you have, so you could grind or hone another 20 or 40 thou out of your gear and end up pressing the assembly in for a perfect fit.

INA has one of the better needle-roller-bearing catalogues.

Very good point about risk.

I am so frustrated I messed up the bore when I bored the unfinished gear. I need to get some pictures.

The forklift is not huge, but big for us. 12,000 lb. max load, made to run always in 4wd (which makes no sense to me). The gear is one of the 4 planet gears and was the only one that they forgot to grind ID.

The inside bore of this gear also serves as the outer race for the bearing rollers/needles, with a center circlip keeping the inner race and both rows of needles in place. Once the Assembly-Goo'ed-together innards are slid down into the gear, that circlip springs out, snapping into a small center groove in the bore, and the gear & bearing assembly becomes one. The setup cannot be disassembled after that. Then you just slide the assembly onto its shaft.

I don't think I could make use of shim material; If I wanted to make use of this same gear, I can only imagine boring it oversize and pressing in a sleeve, which would need to be hard, and use "dutchman" screws or pins at the joint. Then I would need to finish the bore size.

Impatience!

I like magneticanomaly's idea!

I WANT to do what ronf said. Heck, the axle showed no signs of failure in 14 years of harsh abuse until we opened it up.

But this much noticeable play when I tilt the gear screams "get another gear".

For how shredded the insides of this hub was, I couldn't believe no noise or shake was ever noticeable. We only took it apart because the seal needed replacement. Wheel bearings were completely breaking down. I say hub was shredded, but really the planet gear bearings were all still intact. Heavy metal flake sure had piled in on the bottom, though, mainly from the wheel bearings. That of course was starting to wreck planetary assembly.

TheOldCar said:

For how shredded the insides of this hub was, I couldn't believe no noise or shake was ever noticeable. We only took it apart because the seal needed replacement. Wheel bearings were completely breaking down. I say hub was shredded, but really the planet gear bearings were all still intact. Heavy metal flake sure had piled in on the bottom, though, mainly from the wheel bearings. That of course was starting to wreck planetary assembly.

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No reason to not 'honour the threat' and replace outright. Both sides if there are two.

If you bought it NEW? 14 years ain't bad. If you bought it USED? Might it be 30 years?

May be pricey. Surely could beat buying a new(er) FL when you can probably count on another 14 years - maybe more.

If you bored that gear the id wasn't hardened and your bearings/bearing seat wouldn't have lasted long anyway. magneticanomaly has it right, size the bore for an outer race for the bearing.

You need to check your gear to see if it completely missed the hardening process as well as final id sizing. If the teeth are softer than the other gears, replace the gear rather than sleeving it.

ID is quite hard, same as the old one which survived well. The old one I practiced on is still very hard. The gears are surely thru hardened, since they are so small, and a file can't scratch them anywhere. The new one is just as hard, whether after boring or on the teeth.

I only had success with very light cuts and a positive insert. I didn't think carbide would even work, and especially didn't expect a sudden .005 bite. It looks like 100% user error.

The gear is around 3.5" OD. I expected to have removed the hardened layer, too, until I did my redneck "hardness testing". Much slower feed and speed than I'm used to, but it would remove .001 (and a sudden .005) so beautifully. I think I didn't account for the the spring pressure of my short boring bar against the bore, and the different angle my insert contacted the metal as I reversed.

When I say they cut beautifully, I don't mean like butter. Could only take little bits.

How many hundred other identical axles out there are working
everyday with WAY more than .005 -wear- in all 4 gear bores?
If the arrangement is what I'm visualizing, I say RUN IT.

I should be getting a replacement gear and bearing kit from the supplier. I explained what happened, and he had no clue what I was talking about. Still trying to explain it, but new ones are on order. 3 weeks out...