HF Grinder fix

[mrpizza]

A while back I posted asking about greasing up a HF 4 1/2" grinder. Well, yesterday I decided to just take mine apart and see what all was inside. I started by taking the cover off where the shaft comes out. The inner gear is attached to this cover. Inside, the bevel gear from the motor is there. It appears they use the crappiest yellow/brown grease in the entire world, and don't apply it very well. There was a ton of it jammed in the case, but barely any of it was on the gears. I cleaned ALL of this out of there. I ended up taking the whole tool apart to get at all the bearings. I took the seals off and packed new high temp grease in all the bearings. (one at each end of the motor, one in the top of the gear housing, and one in the base of the gear housing where the shaft comes through) After I got it all back together, I would say vibration is cut in half, and noise by about the same. These two pictures of the gears are as removed, before I even started taking the old grease out. See how little is on the gears!

 

[solitaire]

is this the black grinder they sell for $9.99 ?

 

[Bronson]

You get what You pay for.

 

[itsvegas]

i'll have to try this out. those grinders are pretty loud but everyone seems to love them. for $10, you can't really go wrong. i have like 6 of them and don't use them a ton but they get used and haven't had an issue with one yet.

 

[madmikeee]

Buddy of mine did the same thing, he used it once, pulled it apart and laughed hysterically at the "lack" of grease. Used some GOOD high temp grease, Packed the thing FULL and got the same results. He has been using it now steadily for MANY projects for over a year with ZERO problems.

 

[diesel research]

You don't want to "pack it full". Works better not completely packed, and will run a bit cooler. That goes for any gear/crank case...

 

[Outlawmws]

The problem with those units is the gears soon throw off the grease, and unless it gets hot enough to actually liquefy the grease, it's getting hot and making noise soon after.

I did the same repack job and a week later of incidental use, it was hot and noisy again. I opened it up and all my good grease was plastered everywhere except the gears.

Hmm,,, what this thing really needs is Hypoid gear oil. I put in some 140 wt, (I left the grease in as an added "seal" and fired it up. weeks later it seems to be holding up and so far the gear oil has not started leaking out. YMMV

 

[diesel research]

What about worm drive oil?

 

[z28snksknr]

The problem with those units is the gears soon throw off the grease, and unless it gets hot enough to actually liquefy the grease, it's getting hot and making noise soon after.

I did the same repack job and a week later of incidental use, it was hot and noisy again. I opened it up and all my good grease was plastered everywhere except the gears.

Hmm,,, what this thing really needs is Hypoid gear oil. I put in some 140 wt, (I left the grease in as an added "seal" and fired it up. weeks later it seems to be holding up and so far the gear oil has not started leaking out. YMMV

Yeah, I'm guessing the vibration and lower temps are more from the insulating qualities of the grease, not the grease actually staying on the gears. I wonder how Lucas Oil treatment would fare, since it's thick as snot, but still liquid enough to find its way back to the gears after it's shut off.

 

[diesel research]

The two problems I could see with lucas is that it foams up real bad and has zero "nutrients" or pressure additives. It is bare oil, while most lubricants use a variety of additives to achieve their goals.

Used straight, you get no additives. Mixed, it just dilutes additives.

 

[Outlawmws]

What about worm drive oil?

That would also probably do well. anything that has high shear resistance.

And I agree with you comment about Lucas. it's an additive, not a great lubricant by itself.


I used to use straight STP oil treatment in old manual steering boxes, but those are low speed gearing, so you can get away with that. but getting it inside was always a pain. had to heat it y\to get it thin enough to pour...

 

[mrpizza]

I didn't pack mine full, just on the gears and re-packed the bearings. Didn't want to waste the grease in the open spaces. I am thinking about doing my 1/2" drill I got from HF as well. Great drill, just want to make it last. I used it to drill two wheel bolts out with a 1/2" bit, and I had em out in ten minutes or so. Saved me a bunch of money over letting a shop do it, so any more work I get out of it is a bonus at this point. I will have my wife photograph that job for a full writeup. Ill try and do it tonight.