how do I slow the revs on an angle grinder - for polishing hull

Modulation

Modulation

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Top sides pretty chalky so I've got a winter project ahead with the cutting paste. I've got an angle grinder which can be switched to polishing/surface cutting mode. The trouble is /forums/images/graemlins/shocked.gif the minimum revs I can switch to is 1100 - way too fast for doing polishing work on the hull, as it will overheat it, causing discoloration.
It's a 240v grinder.
Does anyone know of a way to slow it down to a more suitable 200 revs?

Thanks
 
I don't think you can. The motor will burn out. I tried years ago with a variable resistor and the angle grinder didn't like it.

Hire or buy a polishing machine.
 
You dont, you buy or rent a proper polisher.

If you use a machine that runs too fast you stand a chance of burning the surface. If you try to reduce the speed with some current reduction device on the grinder then the motor will not have the torque necessary to drive the polishing pad, the resistance on the motor can cause that to burn out.

The reduced speed of a polisher is obtained through gearing.
 
oh dear oh dear oh dear.

I have one of these very very similar "polishers" sitting in my garage, used once - THEY ARE RUBBISH !

Honestly, you get what you pay for and I wouldn't recommend the Meguiars one either.

Tenner to a good home Oh sorry, I'll put it on the For Sale section !

Adrian
www.cleanandshiny.co.uk
 
You'll get a good polisher from Machine mart for about £70, that's about the cheapest for a machine that will last and do a proper job
 
Get one made by Rupes, Metabo or Sealey. If you're suprised by Sealey all the bodyshops use them. Go to a Motor factors or better still a bodyshop/spray equipment suppliers.
 
You do not want a polisher. A polisher is for polishing, not compounding. What you want is a purpose built, low revving, compounding tool. These are fitted with a sponge which, having dampened, you add compounding paste - eg Farecla.

Even at low revs the sponge will get hot as it dries so your must be careful not to damage the gelcoat.

Unfortunately I can't tell you where to get one - I bought mine in Malta - not very convenient for Norwich!
 
Polisher/compounders, same thing! The one I recommended can be fitted with various grades of sponge for different paint/fibreglass surfaces. It's a variable speed professional tool. The sponge is kept cool by the use of a fine mist water spray.
 
I take it you will be using proper closed cell compouding mop and polishing paste such as one of the 3M or Farecla products. That's what you will need for the job you describe.

The mops and a limited range of compounds are available from Screwfix but the only suitable sander/polisher they listed in 2004 (my catalogue's a bit out of date) was £170. A vehicle refinishing suppliers would probably be the best place to buy the compounds and the mops though.

My mop is actually marked (at least the box is) max speed 2500 rpm and I used an old 2 speed B&D drill, that was once my father's, on its slow speed (900rpm). I slowed that a bit lower with an electronic speed controller, although that was not really necessary. I found it quite satisfactory and I restored my hull from a dull pink to a bright shiny red. It looked so good that some people thought it had been painted.

The drill may not be the best machine for the job but it is a hell of a lot cheaper than £170.

If you really want to use a polishing machine then you should be able to hire one but I think you will find they are arm achingly heavy and you will have to rig up some sort of support from the guard rails to take the weight.

Work on a small section at a time, no more than 1m², and keep the mop wet at all times (an old trigger spray bottle is good for this).

I used a medium grade compound and did not find any advantage in going over a second time with a fine one although some coarse grade was useful for some of the bad bits. Note there are different mops for the different grades.

Finish off with a good wax polish (not a silicone one though) and a lambs wool polishing mop if you want to gild the lily and maybe seal the surface a bit.

Good luck it takes a while, allow 2 days for a twenty footer, but if done well the results can be spectacular . Dark blues come up really well.

PS protect your neighbours boat from the mess spun off the mop or you will not be popular and don't park your car too close.


Sorry post overlapped and therefore repeated what was said in the previous 2 posts.. Must learn to type faster.
 
Sheesh! me and my big mouth!

Well, in my defense, what I was trying to do was make sure he didn't use a disk grinder. Hey Ho! I know you are now watching. /forums/images/graemlins/blush.gif

I have an old polisher which I used when I played with old cars! /forums/images/graemlins/tongue.gif

Tom
 
If you are buying a polisher compare weight as well as price. I got a decent quality automobile one but working it against the side of a vertical hull (whilst on a step ladder) starts to get a bit painful after five minutes
 
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