Hitachi 9" angle grinder query noise and model identification

[Shabs]

I have a Hitachi 9" angle grinder 110v. It is painted blue and has a number marked on it... maybe ex hire? I bought it as a non working model and had the brushes and bearings replaced to make it work.

It worked fine for me whilst i was builing a shed... used to cut concrete block, but towards the end it has started to make this funny noise like the spining action is not smooth and maybe catching on something. It is not the disc catching so i was wondering if the bearings had gone again. What would be the symptoms for this?

Secondly Is there any way to identify what model it is without any documentation.

any comments greatly appreciated.

[Alan Campbell]

Hi, when you turn it manually, is it rough?. If so, then it is some sort of mechanical fault - it is unlikely to be bearings, more likely gears. I suspect though, that it is shorts in the armature windings, the cost of a new armature probably being greater than the machine's value. Take it to a local repair place and they will be able to tell you instantly, advise you on cost to repair or cost of replacement.

Alan.

[Shabs]

As far as i am aware the grinder is fine if turned manually. The noise is not always present. i can fire up the grinder and when i start to grind say 10 seconds later, the sound can start. It also stops before i have stopped the grinder.

I can open the grinder up to have a look around... any ideas what i should be looking at?

[Rob Morley]

Check if the commutator is worn or dirty, causing the brushes to chatter. Also check the condition of the brushes, that they're free to move and the spring tension is correct.

[Alan Campbell]

Strange...

Is the disk centre the correct size for the grinder and is the disk correctly fitted to the grinder?

It almost sounds like the disk is either loose or off centre.

Alternatively, perhaps one or more of the screws is loose either holding the gearbox to the motor housing or the gearbox cover plate to the gearbox (under the guard) so that if you use the grinder in one position, it pushes the parts together or if you use it in another, it pulls the parts apart causing the noise.

If not this, you could open it up. I would start at the gearbox end. Check the bearings are tight and have no play and that the gears don't look worn. Also check for foreign objects in the gearbox. Then check the commutator end bearing.

Let us know what you find if anything.

Alan.