I've owned my Black and Decker "Professional" angle grinder for many years, maybe 30? It's only a tiddler which takes 100 mil diameter discs but it's been very reliable and, although used intermittently, it's done a power of work over the years. I've never done any maintenance on it and as I don't have need of it just now I thought I'd dismantle it's gearbox and repack it with grease - I've seen lots of people doing this on you tube videos and I've repacked all the electric drill gearboxes I've owned (except my newest one which is still very, well, new).

So, having removed the screws and prized the casing apart, Imagine my surprise when I saw this:



Not even a wee dod of grease to be seen anywhere! The inside of the casing is spotless! This is obviously how it was assembled and, looking at the condition of the gear teeth, which are immaculate, this is how it's meant to be. Once I'd overcome my surprise I started looking more closely. The teeth show no sign of bluing (which might indicate overheating) and I can tell you it's done some serious grinding in it's time. Also the armature pinion bearing and the much larger bearing on the bevel wheel are both of the sealed type so don't rely on exterior grease and spin very nicely with no signs of roughness:



The bearing in the bottom of the end casing which supports the other end of the bevel gear is of the oilite bush type so I'm not going to slaister any grease in here or on the gear teeth but I am a little tempted to apply a few drops of oil to the bush - question is what oil? I think I'll google oilite bearings for advice.

And now my question to you folks is has anyone had their angle grinder in pieces and if so was it's gearbox "dry" like mine? Having regreased electric drill gearboxes - I've never stripped one and found it not to contain grease - I'm finding this very strange.

Oh, there you are, Oilite site says "ISO VG (SAE 30)" Wonder if my lawnmower engine oil will do the job - It's a straight SAE 30!

I was going to suggest that maybe it was covered with a light oil when new and the oil has dried out/burned off over the years leaving it looking like there was nothing there.

Generally a grinder is something you can buy so cheap (~£10 sometimes) and I use so infrequently, I never bother to do maintenance and would just bin it if it failed but they don’t really fail.

Even hard grinding you don’t put a lot of pressure on internal parts, they have a single gear, the crown wheel being large spreads the heat/pressure from any high torque situations so as a consequence they don’t need much looking after.

I’d probably give it another light oil and leave it at that.

Normally if they do go wrong it’s the motor burning out. I’d suggest the motor would burn out long before you could exert enough force to damage the gear box on a properly made machine

Thanks Andy. Yes, all that sounds very plausible. When I was a motor vehicle trainer the workshop next to mine trained welders. They had many grinders, one for each booth plus spares. I don't think any maintenance was ever performed and they just chucked them when they failed.

I'm going to give that bush literally a couple of drops of the lawnmower "lifeblood" and I like your idea of a very light application of oil to the gears - just enough to "dampen" them as, obviously, 90%, or more, of it's going to get flung off.

Pugglt Auld Jock said:

Thanks Andy. Yes, all that sounds very plausible. When I was a motor vehicle trainer the workshop next to mine trained welders. They had many grinders, one for each booth plus spares. I don't think any maintenance was ever performed and they just chucked them when they failed.

I'm going to give that bush literally a couple of drops of the lawnmower "lifeblood" and I like your idea of a very light application of oil to the gears - just enough to "dampen" them as, obviously, 90%, or more, of it's going to get flung off.

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Hi Jock, different tool, I have an electric corded drill Black and Decker that belonged to my father, must be over forty years old still working. I keep it for sentimental reasons, I still use occasionally, but I have others. When I was a welder Jock we used air grinders. Not to messed about with, but there was always some clown switching on the wrong airline. Happy days, we were young and I thought nothing could happen to me..

When ever I have used a angle grinder the gearbox usually
sounds like it's running dry, now maybe I know why.

Aye Jim, young and invulnerable eh? When I worked in workshops there was often some really stupid prank going on involving airlines and the bodyshop guys were always blowing the "catty" dust off their overalls with it at the end of the day. All so very dangerous but I didn't really appreciate just how dangerous until I became a trainer and did all the health and safety stuff.

Electric drills? Like most of us, I would think? an electric drill was the first power tool I bought. It was a Black and Decker with blue body and grey gearbox casing - single speed, no hammer action. I was still, very infrequently, using it up until maybe 5 years ago when it expired gently with a smell of burning and lack of rotation. I felt absolutely terrible when I dropped it off at the council recycling centre. Like I was betraying an old friend! Because it was single speed and pretty wimpy, I soon bought a "friend" to keep it company. A more "beefy" 2 speed jobbie but still without hammer action:



Then I got much more adventurous with my DIY and realized a hammer drill was a must. So I bought one of these:

https://www.ebay.co.uk/itm/353477843914?hash=item524cebdbca:g:0I4AAOSw-RNgiWuh

It's variable speed too which made it very useful for use when drilling metal and I thought I could use it to drive screws, but it wasn't good at that. These two drills, with the old blue one pretty much being retired, were my main weapons for many years. Then my oldest boy bought an absolute wreck of a flat down in the Lieth dock area (now very trendy - he made a real killing when he sold it) which we gutted back to walls and floor boards and completely revamped with new kitchen, bathroom, etc. During this refurb I wrecked two Lidl battery drills before buying my present, and very reliable, Ryobi 18v jobbie but more to the point the variable speed Black drill started making a noise like a chipped tooth in it's gearbox. By now the Ryobi was mostly taking the strain so that didn't matter too much.

Then, one day whilst shopping in Aldi (might have been Lidl?) I spotted this Humongous SDS jobbie. You can see how big it is in relation to the old B&D:



We had almost finished the flat by then but we needed to remove the hot water storage tank and alter some masonry around where it was fitted and I reasoned I could more easily do it with this (it's got rotation stop for chiseling) also it was pretty cheap, which worried me, but hey, you only live once! It's an absolute animal, drills holes in brick and concrete in seconds and knocks stuff about violently when used in chisel mode. The big problem with it though is it weighs an absolute ton and after about 15 minutes or so of taking the weight and the violent hammer action it is capable of you just have to take a rest. Because of this I only really use it for "big" jobs so I think it'll outlast me comfortably.

Now with the Flat all done I got to thinking about my black variable speed drill which was making the "ticking/clicking" noise from it's gearbox. "had it for quite a while haven't I" I thought. "Time to treat myself to a new one especially as this is the one I use most" I bought this:

https://www.machinemart.co.uk/p/clarke-con1200-contractor-hammer-drill/

I'm very pleased with it so far and although it's not variable speed I find I don't miss this facility at all.

There's a last wee "twist" - Haha! - to this story which is that shortly after I'd bought the yellow Clarke drill a young family moved in at the end of our street. I'd chatted with them and they turn out to be very pleasant. So, when, a couple of weeks later he knocked on our door I was feeling kindly disposed towards them. "I'm told that you're a bit of a DIY man" he said, "don't suppose you could lend me an electric drill could you?" My immediate reaction was to say no - I've learned over the years that people often don't treat tools with the same reverence I do and if they wreck your tool it can lead to problems and ill feelings. But I suddenly remembered the old black drill which was still working but noisy. I lent him that having explained it might break and he said that he'd buy me a new one if he broke it (which I wouldn't have taken him up on in the circumstances) He kept the drill for nearly a week and I heard it several times obviously doing some serious work. When he handed it back I gave it a check over and tried it with a drill in a piece of scrap wood. The noise had gone and it drilled as well as it ever had! I can't explain it but it was very welcome and, as I now had the new yellow drill, I gave the black one to my older boy whose cheap battery drill had just expired - it's still going fine.

Pugglt Auld Jock said:

Oh, there you are, Oilite site says "ISO VG (SAE 30)" Wonder if my lawnmower engine oil will do the job - It's a straight SAE 30!

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Of course it will...

I ran out of SAE30 for the two stroke mix the other day. Looked at my 0W30 for the Panda and decided near enough is good enough. Mixed this with the little bit of mower oil and tipped it into my (new) hedge cutter. Started first pull, ran smooth and smoke free so as I suspected it seems to work. Not that I'm going to waste the expensive jollup any more than necessary mower oil is cheaper!

The bevel gear in an angle grinder runs at very high speed. Locally applied grease or oil would just be thown off.

Robert G8RPI

Pugglt Auld Jock said:

Then, one day whilst shopping in Aldi (might have been Lidl?) I spotted this Humongous SDS jobbie.

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AH ha. Big Bertha as I call mine. Very decent power tool. My chuck disintegrated a while ago, but I managed to acquire anothe free so that was good.

I did some calculations as practice for my N&V competent person cert a few years ago when it was new. Daily vibration dose is likely to be achieved in.... wait for it. Yep that right you just overdid it... (18 seconds a day max safe dose on hammer and chisel.)

As a DIY tool, when you don't use it every day or for massive periods its a really good thing but its good to know not to overdo it. I did however work side by side with a builder friend removing render from brickwork. He was using a modern Bosch SDS drill of about 1/3 the size, and it was far better! He was laughing at my massive drill and pulling my leg rotten. I the end I had to tell him proper men need to use a man sized drill and that his looked like a womans drill! That shut him up for a little.

I used to have a Black & Decker professional angle grinder with plug in power cord for easier disc changes. It said the gearbox had sintered gears which did not need lubricant though I did add some driveshaft moly grease. Eventually the switch failed. I replaced it with a Makita which destroyed itself when the spindle lock fell into the gears. I now have grinders from Aldi and a Lidl - both doing the job for very little cost.

g8rpi said:

The bevel gear in an angle grinder runs at very high speed. Locally applied grease or oil would just be thown off.

Robert G8RPI

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Point taken. I think literally a couple of drops down the sintered bush and I might just dampen the gear teeth with oil, more to ward off corrosion than anything else?

DaveMcT said:

I used to have a Black & Decker professional angle grinder with plug in power cord for easier disc changes. It said the gearbox had sintered gears which did not need lubricant though I did add some driveshaft moly grease. Eventually the switch failed. I replaced it with a Makita which destroyed itself when the spindle lock fell into the gears. I now have grinders from Aldi and a Lidl - both doing the job for very little cost.

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Yes, a Lidl or Aldi holds great attraction for a "throw away" like this. Following on from having bought my new Clarke drill from Machine Mart I'd be very tempted by this: https://www.machinemart.co.uk/p/clarke-115mm-45-angle-grinder-230v/ I've also found the Clarke branded stuff to be well supported for spares. They regularly send me VAT free days too so I try always to buy then which makes quite a big saving.

Well that's it all back together again with precisely 2 drops of SAE 30 on the sintered bush and 3 drops spread round the inner rim of the bevel gear teeth so it will throw out the first time it's spun up and so coat the teeth.

Gave it a quick "wizz" and, unsurprisingly, it sounds exactly the same as it did before, - dry gears running without lube, as someone said above - which is how it's always sounded