Rough angle grinder

[droopsnoot]

One of my angle grinders feels "rough" - there's noticeable drag when I turn the disc manually compared to the other grinders that I have. I expect if I carry on using it, it will seize up at some point. I took it to bits on the basis I've nothing to lose, and the sections feel fine in isolation. There's a chance that the plastic "cup" that the back bearing (the one furthest from the angle end) was in wrongly, but I've fixed that now and it's still dragging. But, in this photo, it seems to be as if the grease is everywhere except where it needs to be:

The crown wheel and pinion (not sure if that's the correct term, but they look like those bits from an axle) are almost completely dry. Should I grease them? Or is it just time to accept that this is why the previous owner was getting rid of this grinder?

 

[Pond frog]

Every angle grinder I’ve opened up has been like this with grease everywhere except where you want it . I normally just added more and hoped for the best

 

[Turbo]

Add some grease to the head but leave room to let the grease expand as the head heats up.

Check all the bearings individually in the head and the motor. They may feel fine now but when they are under load it may be a different story.

 

[droopsnoot]

Cheers, I'll have a play. I didn't want to just stick a load of grease in only to find that there's a reason that bit is dry.

 

[nickk]

All my 15 grinders appear the same,centrifugal force throws the grease outwards.

 

[MattF]

Once the grease warms it'll flow somewhat.

 

[brightspark]

All my 15 grinders appear the same,centrifugal force throws the grease outwards.

just take them apart and scoop some of the grease up with your finger and blather it over the gears job done , dont over pack with grease and use the proper stuff . if its 2 thick it wont do the gears or the motor any flavors and pull the speed down

 

[Brad93]

You need to use a grease with the correct drooping temperature point, it needs to go semi fluid at the working temperature of the grinder.

When people repack their grinders with any old cv joint grease that's the worse thing you can do.

 

[Bravheart]

Re grease it and fit new brushes in the motor.

 

[hotponyshoes]

If you are turning the disc it's normal for them to feel notchey.
I guess it's because you are driving it against the syncromesh?

If it's apart try turning it from the motor end and it should feel smoother.

I've worn out a few grinders in my time, never had the gears wear out.
I've even got one head that's on the 3rd grinder now. It's always the motors or control electronics that give out first so I wouldn't be overly worried about greasing them

 

[Erie Fred]

I add a small squirt of 75w90 in there.

 

[Turbo]

I add a small squirt of 75w90 in there.

Would that not just run out past the input shaft. They don't normally have a seal on the input.

 

[sardine]

You will have drag from the brushes, take them out and see how the bearings feel on their own. Or replace the bearings anyway if it's had a lot of use, they don't cost much and changing them before they fail is a good thing.

Pond Frog is right, I've repaired loads of grinders and everyone had no grease on the gears but plenty in the housing doing nothing.

 

[eddie49]

I add a small squirt of 75w90 in there.

Similar here - I use Hypoid EP90 diff oil.

 

[frank horton]

it's not a Dewalt is it......
I got an as new one in a garage sale.....lucky it was cheap.....
what a pile of poo....only used with a flap wheel now.....
I only buy Jenuine Jap made corded tools now....
amazing work they do for such a crude tool.....
My Hitachi'e are over 20 years old now.....BUT I do have one for every style of wheel.....lets say 15 units.....hahaha.....
they were on a pallet sale years ago for £80 per box with a 9" and a small one....think I bought 10 boxes......

 

[Wildefalcon]

Funnily enough, I've switched back to Hitachi or hoki-koki or whatever they are called now.

 

[Mark 5]

One of my angle grinders feels "rough" - there's noticeable drag when I turn the disc manually compared to the other grinders that I have. I expect if I carry on using it, it will seize up at some point. I took it to bits on the basis I've nothing to lose, and the sections feel fine in isolation. There's a chance that the plastic "cup" that the back bearing (the one furthest from the angle end) was in wrongly, but I've fixed that now and it's still dragging. But, in this photo, it seems to be as if the grease is everywhere except where it needs to be:

The crown wheel and pinion (not sure if that's the correct term, but they look like those bits from an axle) are almost completely dry. Should I grease them? Or is it just time to accept that this is why the previous owner was getting rid of this grinder?

You don't say type and how old.

My guess it may well be the bearings, either end of the armature, these can be removed and pressed on and check the brushes at the same time.

Either the grease is old and/or it's the wrong type and this does matter as does the amount, once it warms up, it gets around so over filling is not good, the head needs a good cleanout but it ain't that bad.

From the photo the gears look ok.

 

[tom2207]

I use tungsten di sulphide in with molly grease and seldom have bother in at that end of my grinders , its the brushes end that I seem never to be out of , although a blow out with the airline helps them stay fresh .

 

[MetalMonkey]

The grease will be spun off the gears so it will always be sat in the housing when you open it.
When you start using it, the grease warms up and turns more liquid and gets flung around the gearbox and lubricates the gears.

As brad says, you need to use the right type of grease.
Just packing the thing full will do more harm than good as it bogs it down and get very hot.

 

[droopsnoot]

Cheers all. I forget the make, but it's something cheap, Power something maybe, I was given it with some other power tools a while back. There's definitely play in the bearing that sits just inside where the disc is attached. I've put a bit of grease on the gears but haven't tried it since - rotating it by hand it does seem smoother, I didn't pack it, just a bit over the surfaces. But, I just used some grease I had lying around, so maybe I should clean that off and just move some of the grease back onto the gears from the outside. I can't say whether the grease that's in the photo is the original, I've no idea what the previous owner did of course.

I thought it felt rough when rotating by hand in comparison to my other grinders, rather than just in isolation. I don't feel confident in using it as it is, just in case it does something drastic while it's in my hand - I had one years ago (a cheap Aldi one) that seized and somehow managed to undo the disc, which flew across the workshop and landed somewhere. I presumed it was the momentum that did it, but I can't be sure. I may well take it to pieces and see if I can get bearings for it - it was free to me, and is only a low-cost brand, but it's interesting to see if it can be saved / improved. Brushes seem to have plenty of life in them.