Angle grinder questions

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Boo2

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Hi,

Following a lead here I went out and bought a 125mm angle grinder from Lidl and I have a couple of questions :

Firstly, is it normal for the grinding disks to have a bit of runout ? The supplied cutter disk has almost 1mm of runout but I substituted a diamond wheel and it seems to be the disk not the machine.

Secondly, can you use the normal cutting disks on ally as well as steel ?

Finally, has anyone used an angle grinder to polish the gel coat of their boat ? I see you can get polishing mop kits for them and I wondered how well they work ?

Thanks,

Boo2
 
as polishers they will not be successful, since the rotation speed is too high, and the buffer will 'burn' the GRP. For cleaning you need 3 to 800 rpm max.
 
sarabande said:
as polishers they will not be successful, since the rotation speed is too high, and the buffer will 'burn' the GRP. For cleaning you need 3 to 800 rpm max.
Click to expand...

Agreed. No way would I try polishing with an Angle Grinder. Typically an angle grinder uses 4 inch discs. If you take the saftey guard off you could use bigger sponges/mops but it would just be too fast.

If using the angle grinder for cutting metals then purchase some of the really thin discs. 0.8mm/1.0mm. If you try cutting alloy with the thicker discs they would soon clog.
 
There should be no run-out. At the speeds that angle grinders rotate this could be quite hazardous. Check the seating for a foreign object

Grinding aluminium and other non-ferrous metals will clog the wheel and can cause damage. I do it but check the disc frequently.

My grinder has a speed control and I guess it could be used for polishing at a slow speed, although I have never tried. It is great with a flap wheel at slower speeds.
 
It sounds as though you have a badly made disc! It's not unusual for cheaper tools to be mostly good but with poor accessories - in this case, throw the duff disc away before it shatters!

I've used the standard cutting and grinding discs on just about every type of metal and FRP, but it may be worth looking at better suited discs for extended use on a particular material. They are always (?) sold as just metal cutting/grinding discs, but you may find some better than others on aluminium.

Polishing your hull requires a slow running mop or it will burn the surface. In its normal form an angle grinder runs much too fast, but it can be slowed using a dimmer unit. There was an article on this in PBO a couple of years back.

Rob.
 
You can cut aluminium and steel, but not with the same disk - if a disk has iron oxide particles on or in it, and you start cutting aluminium, you may experience the thermit reaction close up, which could result in the disk getting a lot hotter than it was designed to do, and/or tiny globules of molten iron being thrown off the disk at high speed.
 
Thanks for the replies, I will try to source some thin cutting disks where the mfr mentions aluminium suitability.

Boo2
 
I don't know if it applies to the small angle grinders but on my large one the clamp nut(?) has to be put on the right way round. It goes one way for a grinding disk and the other way round for a cutting disk. If it were screwed on the wrong way round for the type of disk it would quite likely cause 'runout'.
 
Grinders great tools!
agree about the 1mm wide discs they are very good[but only for cutting]!
as cannot take a side load
good deals on fleebay
i cut everything with them[not glass]...:P
also good with sanding discs
but do be very careful they can easily injure
got the t shirt but nothing too serious like a lost finger...or major...:) artery cut
 
Cutting discs are flat, grinding disks are slightly offset. If you are cutting a lot buy quite a few discs because they wear out quickly and they don't cut very fast when they are only two inches across! The only "injury" I've had off mine was when de-rusting my bike frame with a wire brush wheel. The bristles fly off and go straight through your clothes! Angle grinders spin far too fast for polishing, I think the polishing wheel would fly apart. If not it would burn what you are trying to polish.
 
Wear leather builder's gloves.
Wear goggles, or better still a visor (about £7)
Look for this Logo on the disc.

cuttingdisc.jpg


If it hasn't got it, they may not be very good.
Don't let them get damp, they will fall to bits when you apply pressure.
Most can be bought in tins of 10 which keep them dry.

1mm are really much better. Stands to reason really as you are only cutting a 1mm slot in the metal, not a 3mm one.
 
As everyone has said so far, forget it as a polisher - WAY too fast. However, it's probably also worth mentioning that small angle grinders (and I imagine this will be especially true of a Lidl one!) are not rated for continuous running, so you'd be likely to burn it out quite quickly if you used it for (say) more than 30 seconds at a time in any given minute.
 
I disagree with the admonitions against the use of angle grinders for gelcoat polishing...provided the grinder has a decent speed control and is used at the lowest rpm, and providing the job is kept wet (which most cutting compounds should be, anyway). Water from a trigger-action spray bottle is ideal. I've done two hulls this way with good results and no 'burning'. 3M (and not doubt others) do hard foam pads for the job.
 
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