View Full Version : Harbor Freight Grinders don't suck...
04-09-2008, 08:56 AM
O.k. they do suck, but I was fartin' around in the garage yesterday and decided to open my HF grinders gear box. Others had said that they may need some more grease. So I opened it up and yup, just as others had said, there was little grease and what was there was spun off the gears to the outer edges of the gear box. So I packed they thing full of grease, put it back together, and WOW what a difference. It is about half as loud as before and the terrible rattling it used to have in the gear box is gone. I was truly amazed and actually thought hey I should get a couple more of these which is rarely something you hear about HF items. It still does not have the power of better tools but it runs great now. Heres the real test of the change, I turned it on last night after 9pm once I packed the gear box with grease and my wife did NOT immediately run to the garage and yell at me for making a racket at night. If you have an HF grinder, do it, it works wonders!
Now, grease... I used high-temperature brake drum grease, I also had some multi-purpose lithium grease. What's the difference really? Is grease just grease?
04-09-2008, 09:09 AM
Not that it makes any difference on that grinder, but the gearboxes on grinders are not supposed to be packed full, it keeps the parts from dissipating heat. Same as wheel bearings on a car, you never pack the whole hub full of grease.
But anything that makes a Horror Fright grinder last longer is probably fair game.
04-09-2008, 09:47 AM
You grease your brake drums?
04-09-2008, 10:03 AM
No idea, I have only done drum brakes once and that was like 15 years ago. But the grease says brake drum grease on the container. It's blue??
04-09-2008, 10:39 AM
It's axle bearing grease for cars with drum brakes. :)
Disk brakes need higher temp grease.
04-09-2008, 10:56 AM
Ya know, I've wondered about the gearboxes on tools before. I guess they aren't sealed up, so it wouldn't work, but I would think that a little gear lube or heavy weight oil would make it run smoother. Maybe not, though.
04-09-2008, 10:59 AM
it is not sealed nearly enough to put any kind of oil in it. But the grease worked great, it's not completely FULL to the point of oozing out but just the large voids filled up.
04-10-2008, 01:04 PM
You grease your brake drums?
Gets rid of the brake squeal. (Actually oil or grease usually softens the lining and makes them really grabby - like when the rear axle seals were leaking on my old F-250)
04-10-2008, 01:26 PM
Yeah, a little good grease will help those things....probably full of animal fat when they come from China. I opened up a HF grinder one time and discovered the spindle rode in a bushing. Funny thing is, the ID and OD matched the standard bearing used in a lot of older alternators, can't remember the # right now. After I put that bearing in, the grinder sounded like a Dewalt. The motor burnt up a couple months later, but the head was still nice and smooth.
04-10-2008, 08:32 PM
I took two grinders apart tonite..one from HF and one from Northern. The HF grinder had grease in it but it had spun off the large gear. The Northern was basically dry. I got all of the old grease out I could and repacked it about 3/4 full with red wheel bearing grease. WHAT a difference it made in the sound.
Thanks for posting that. I had just bought these and not used them. Im sure they will last much longer now.
BTW...the HF grinder is built much heavier than the one from Northern
04-11-2008, 09:28 AM
I took the HF grinder apart after regreasing it and packed it FULL of red grease. Talk about smooth. The only problem is when the gearbox heats up the excess grease pushes out past the seal ( if there is one) in the output shaft. I would only pack the gearbox about 3/4 full max if you do this. It makes a real mess if you use too much and I think the heat would be an issue.
04-18-2008, 08:10 PM
Now if y'all can tell me how to quieten my HF chop saw...
04-21-2008, 06:54 AM
I don't think this had anything whatsoever to do with the grease being put in the bearing box, but this weekend my grinder burst in to flames.
I was cutting some 3" x 18" x 3/16" bar in to 3 pieces, so basically I was making 2 18" long cuts through 3/16". Just as I was finishing the last cut the grinder burst in to flames in my hand. It started inside and I believe it was the motor windings that caught fire. Fire was was coming out of the vent holes so I disconnected the power, threw it down and pumped the inside with the fire extinguisher before the whole thing started on fire.
I don't think I am going to bother with anymore HF grinders. I just bought a Hilti DAG-450 and a Bosch 1711 as replacements. Hopefully these should give me no problems.
04-21-2008, 08:32 AM
I wonder how different that model is from the model with the switch offset to the left. I've got 3 of them and have even used one to cut a 3'x7' piece out of a 4'x8' sheet of 1/8" aluminum and didn't even notice it getting warm. I guess that was one of the bad apples, huh?
04-21-2008, 03:42 PM
I have the same grinder (heh, HF lovers eh?) and mine is holy terror loud. I have some High-Heat Moly Disc Brake grease (black in color, VERY slippery), and red disc brake grease that also claims hi-heat.
My question is this: my gut tells me the more expensive black Moly grease is better for the application, but I must admit I don't really know. Any thoughts on this?
Thanks in advance :).
04-21-2008, 03:44 PM
I opened mine up the other day and since I had it open went ahead and replaced the grease. Frankly, at 10k rpm, the grease doesn't stand a chance of sticking to the gears anyway, and ends up just packing the space around the gears.
04-21-2008, 04:20 PM
The one I relubed was dry. There wasnt enough grease in it to have ever mattered. Ive got enough in it now that it runs quiet. I went back into the case and yes some of the grease is pushed away from the gears. BUT, there is enough of it in the gear box that it wont ever run dry.
I think it well worth taking 15 minutes of time to do it.