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TM reader Kyle writes:

“After receiving a new angle grinder for Christmas, I looked through the owner’s manual and discovered that Craftsman recommends that the tool be relubricated from time to time. The manual says that this should be done by Sears technicians only. What’s being lubricated, and is it possible for me to do this myself without destroying the grinder?”

We’re hoping you can shed some light on this. We have a Metabo and a DeWalt in the TM shop, but neither has required any service to date. And — maybe badly — we’ve always thought of $60 angle grinders as throw-aways. Also, does your different-brand grinder require this type of lubrication as well?

Kyle reports his grinder is the Craftsman Professional 4-1/2″, model number 900.264370 (pictured above).

The Grinder [Sears]


22 Responses to Reader Question: How To Lubricate An Angle Grinder

  1. Nick Carter says:

    Usually they mean getting some grease around the bevel gears in the angle head, you should (but that’s not always a given) be able to remove the head from the body and squirt some fresh grease in. Rarely have I see one that didn’t have grease inside, even after years of use. Any bearings are likely of the “sealed for life” type, which means that you would replace those if they lost lubrication.

  2. rick says:

    Probably a good idea, probably would help every few years. but my $20 grinder from harbor freight has lasted for years. It is super loud, but so is any other grinder. It came with spare brushed. Cant help but theing when they die its just time to replace since they were lost probably 5 min after I opened the box.

    I would rate this as “good to do, but cost/benefit makes it unlikely to be done”

  3. Jerry says:

    I’m with rick on this one. I actually have 2 HF angle grinders. One from many years ago and one from about 2 years ago when I forgot to toss the original into the truck for a job. Cheaper to buy another than to go home for one. Both work fine after a lot of very heavy use. I mostly use them for cutting rather than grinding. I remember those extra brushes. HF gives those with a lot of tools. Never needed them though. Yep! They are noisy but what are you using it for that don’t make more noise anyway?

  4. KMR says:

    I cannot kill those cheap $10 blue Harbor Freight angle grinders.

    A have one that has been used to grind concrete for hours without the motor failing – the on/off switch got stuck with concrete dust, but it didn’t stop running. A few years later I was digging post holes for a fence and found some large tree roots 3ft down. I duct taped this same grinder to a pieces of PVC and installed a 5″ trim saw circular saw type blade. I eroded the roots away using this method… very messy, wear eye and face protection. Still didn’t kill the grinder.

    On off switch stuck on to this day, but grinder still works. Now has a knotty wire brush on it and used for undercoating removal from chassis and inner fenders.

    I’d say for $10, it’ll cost me more in time to open up the housing to lube it then it does just to buy a new one if it _ever_ dies.

  5. Rich says:

    Oh, my god. Using a cheap angle grinder to cut tree roots–that’s brilliant. I can’t tell you how many days of my life have been lost to chopping roots by hand.

  6. James says:

    Take the disk off and undo the screws on the bottom of the head, it will pop open to expose some angular gears, stick some grease in there and reseal the sucker back up. The armature is supported by sealed bearings so they wont need grease unless you feel it upon yourself to attempt this surgery. The design is very typical of some makita and dewalt grinders.

  7. fritz gorbach says:

    I bought six of the HF Grinders and took them out of town on a job where I had to clean an old cooling tower down to bare metal before patching leaks and epoxy coating. 6 grinders didn’t last three days of constant use, while my old dewalts and milwaukees lived through the job despite previous years of work.

    This is not to say the HF Grinders arent a good value. We bought the six for about 8 bucks a piece and kept some of the worst wear off of our favorites, and for less than one name brand, they served their purpose. That being said, I know several people who have the HF grinders as seconds or occasional users, and they have had no problems. Guess they just couldn’t handle all day constant use like the others.

    I have broken the shaft lock on my dewalt, and broken the shaft locks on two of my bosses craftsmans, but each time I have passed them on to our inhouse machinist/motorman, and within an hour or so, he repairs them. He somehow puts in a larger tab and then mills out the slot it rests in to fit.

  8. fritz gorbach says:

    Oh, and yeah, when you open those heads, they are always full of grease.

  9. paganwonder says:

    Yeah they said I needed to lub my Skilsaw M77, which has seen very heavy use since 1984 without a single problem, squirted some grease in the gear box in 1994 when I found a tube of grease in Dad’s garage. I doubt I’d treat a relatively cheap grinder any better.

  10. D. Eldridge says:

    I actually had to use the extra brushes on my HF 4.5″ grinder. I dropped the grinder from about 4 feet onto a concrete floor. Heard some rattling, took it apart and found the pieces of the broken brush. I pulled them all out, cleaned and re-lubed the bevel gears while i was in there, replaced the brushes and still works great!

  11. Jim says:

    Speaking of HF grinders. A hot deal and a helpful add-on. See P/N 90450 and 45921 at HF website.

  12. buckshot says:

    I never understood the idea of not fixing tools that were capable of being cheaply and easily repaired. So what if it cost $8, if it can do the job keep it going and use the savings on something else.

  13. BC says:

    @buckshot When your hourly rate is $100, it’s not worth it to spend half an hour on an old tool unless you need it NOW. You just grab a new one next time you’re close by HF.

  14. PutnamEco says:

    BC says:
    When your hourly rate is $100, You just grab a new one next time you’re close by HF.
    Hundred bucks an hour and using Harbor Freight??? WTF go get some real tools that will last long enough to do the job, and you owe it to your customers to have a reasonable amount of back up tools with you so as not to hold the job up.That way you can fix them on your time. Quality tools are worth repairing. You can fix them in your down time or donate them to someone who will. Some tool repair guys will take them off your hands, if your not willing to pay to have them repaired. When I make decent money I support my local tool supply house by having them repair the tools that I don’t have the time or inclination to fix. If I know I’m going to be using an small angle grinder on the job for any significant amount of time, I bring 4 of them. I usually have three on my truck, one cordless, one beater for masonry or wire brushing nasty stuff, and one newer one for everything else. They and their associated hardware/discs take up hardly any room at all, only one small gate mouth bag.

    Re:You just grab a new one next time you’re close by HF.

    It is that mentality that is making it near impossible to find any decent American made tools and why we have such high unemployment.

  15. rick says:

    Well, not to tangent this, but harborfreight is 100% chinese tools. How about home depot? Suspect they are nearly the same. And also watch for the made/assembled. Most tools there are made in china, lots of the others are made in china, assembled in the USA. I would like to buy USA, but will not spend much more for it espically when i am getting a similiar product. (cheap items i will happily buy chinese…. things my life depends on(scuba gear), nope).

    Maybe a good article here would be a side by side, tested to the destruction HF grinder v. USA grinder. I would be interested. How many hours under load does it last.

  16. Angle says:

    I Mechanical I liked the design (angle grinder), but when I went to buy one was surprised by the idleness of grinding with the knowledge that the work was not heavy and the most surprising is that the grinding did not pray it was counterfeited by a company (King Force) by a Chinese company has held the same type (angel grinder), a bad, knowing that this type of grinding PT244A.

  17. Peter Apicella says:

    Some grinders will come with a spare set of brushes. It is an easy task to replace them. And you will know when as you use the tool it will let you know. It will sputter, shake and make some real unusual noises. As far as lubrication goes, I have not come a cross very many that come equipped with oiling or greasing points. I am a believer that if you are a person who wants to keep his tools by all means oil and grease if possible. Please remember to wear you face shield and gloves. Play safe.

  18. Richard Walker (BSc Phys) says:

    Has anyone actually answered the question asked “How to lubricate their angle grinder-gearbox-”
    Well guys, having been an engineer (electrical and mechanical) for over 30 years I’m impressed by how many of you ‘professionals’ are proud of the fact that they ‘abuse’ their tools.
    A bad workman always blames his/her tools, so I was always led to believe.
    Well to answer the question: After removing the disc and guard, most grinder heads can be disassembled by undoing the part of the gearbox holding the output shaft. Having done that (usually just 4 screws) the end of the gearbox and the large bevel gear can be removed. You will usually find the grease still in there, but stuck all around the cogs and none on them! If grinder is still fairly new you can scrape off most of the thrown off gearbox grease and mix a ‘FEW DROPS (2 or 3)’ of gearbox oil with it then push it all back in. This will, in future, enable the grease to settle back and re-lube the cogs/bearings rather than just sit round the outside of the gearbox housing.
    This procedure will take about 5 min’s, if you’re not totally incompetent, and will make your grinder quieter, longer lasting, more efficient and won’t get so hot.
    So at $100/h that makes the work cost $10. But than as I can already hear you say ‘Time is money’. So maybe you’re right ….Bin it and get a new ‘Chinese’ one. I’ll stick to my trusty 10 year old ‘lubricated’ Dewalt, which has now seen 4 new sets of brushes, but apart from that is still as good as gold. :o)

  19. Fred says:

    Richard Walker, we have a Makita that threw off all the grease and chewed up the gears, so cannot use to relube since it was full of metallic particles. Owners manual refers to Makita Grease N. No.1. Do you know what is an equivalent grease to this? Stuff looks like Vasoline.

    • PutnamEco says:

      I have had excellent luck with Stihls high-performance gear lubricant. String trimmers have very similar operating parameters as angle grinders, and this grease is readily available at your local Stihl dealer.

    • ambush27 says:

      I would say wheel bearing or chassis grease.

  20. David Hammond says:

    High temp wheel bearing grease but not chassis grease.

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