pushing compound about on aluminium

[whistule]

I am having trouble with the famous cloudiness during polishing. Usually I have no problems but for some reason (I think it may related to air temperature in the workshop) the wheel is depositing compound on the aluminium. This always comes in 2 forms :- either dark blotches (which is solved when I apply more compound to the wheel) or cloudiness because the wheel is not taking the compound off the surface. The part itself gets really hot when I'm polishing but the temperature in the workshop at this time of year is around 6degC (43 degF). I was wondering if anyone else was having this problem or perhaps the compounds were designed to work at room temperature?

I am using 2 stacked 8 in. wheels on a 2900 rpm 3/4 hp spindle with a tripoli and white compound stages on spiral sewn and loose cotton wheels respectively.

[BrianKidd]

Good question, I am also getting the same results as you, I'm not sure what the tempature of the workshop is, usually somewhat cold lately but the work piece does seem to heat up quite a bit. Same thing with the black blotches too with too little compound. I'm really new to this myself so I know I do have a bit to learn but it does seem pretty universal with the problems with polishing aluminum. I have quite a few components to polish and don't want to screw them all up.


B.Kidd

[whistule]

Lets see if we can work it out...

When I put compound on the wheels they seam to go through a cycle:-At first they deposit compound on the surface and then they start taking it back. I always find myself trying to cover more surface in the latter part of the cycle so that I can lift off all the compound deposited before the 'blotches' start to appear. I'm only pushing the compound against the wheel for a couple of secs and raking before applying more compound. One thing that did cross my mind was that my rake (which is just the saw blade method) might not be penetrating deep enough to make the wheel 'fluffy' enough. How are you raking your wheels?

[whistule]

I noticed if you've got a clean wheel it will take the compound off in no time at all - of course the wheel will only stay clean for so long.....dam! Good idea with the test - unfortunately it seams to be cold all the time at the moment over here! Marsfroggie mentioned a while back that heating up the compounds beforehand helps so I've been trying that and it certainly does make a difference. Do you find the new A14 and A15 compounds are better than standard compounds?

I wonder if its not about getting things just right i.e. raking, compound application, polishing times, s.f/min etc. When you say '6K' what wheel diameter is that on? How often/long do you rake and how deep are the teeth? I'm running at about 6900 surface ft per minute and raking as hard as I possibly can to get the wheel to 'fluff up'. I've found the 'saw blade' rake I am using is not great to honest - the points blunt down too quickly and bend.

The whole spray/immerse and clean thing is obviously a well discussed question on this forum. Any paper towels I have touched the aluminium with have scratched it and become more obvious with anodising. I'm just waiting for an ultrasonic cleaner (all-be-it not big enough to do my parts all at once) but it will be interesting to see how good it is at removing compound - any recommendations for cleaning solution to run in it would be most welcome.

[tomg552001]

Whistule, you could always take some nails and hammer them through a board to make your own rake. It'll be much stronger, and will probally clean the part a little better than a saw blade. When i do my polishing, especially on more dense peices, i always keep a hand held propane torch handy, that way i can heat up parts slightly so they take compound better and clean up easiar. I have also found that, a certain amount of cloudiness is expected with polishing aluminum. From examining other parts, even polished SS, it seems that from certain angles, there is still a slight haze. My personal test is bringing it outside in the sun, if you can see a haze, than it needs more time on the buffer. Good luck!

[whistule]

Only trouble with that is you need some sun. You got any 'sun' for sale caswell?

Thanks for those ideas.

I've been polishing and anodising all day and it's think it's fair to say it's driving me absolutely mad. Two weeks making up ten parts and I have just ruined 2 of them with the anodising....

[whistule]

Now I've recovered from the loss I can think straight again.

Tom, Re: propane torch....I would have thought you'd move to a bigger mop / more powerful buffer to get the heat by friction? My thinking is that they've been polishing since way back when factory heating was pretty basic so the compounds really should be able to work with the friction of the wheel alone. What do you think ??

How do you clean the polishing compound off the part? As I am getting more experienced at this I realise you can minimise the compound residue by getting the wheel in the right 'nick' and getting the strokes right but I can never get it completely clean. I've tried loads of things. Touching the part with a cleaning cloth always leaves scratches because as you clean the part off the compound takes to the cloth and scratches as you wipe.

The other ways I can see are steam cleaning(of which I know little), a dishwasher or an ultrasonic cleaner. I tried out a dishwasher but just with 'dishwasher' solution and it didnae work. Thinking about the expense of big ultrasonic cleaners I bought a wee dinky one and tried dipping just a bit of my parts in - first in meths with little result and then in SD-Klene 416(one of of caswells degreasers) and the compound came off fantastically. I am wondering if a proper degreaser in a dishwasher would work or if I need to fork out the coin for a big enough ultrasonic machine.

[tomg552001]

I use a heavy duty buffer, but i sometimes do find it helpfull to blast the part with the torch to get it super hot, and remove the excess. This isnt as much with the bench buffer, but more with felt bobs and smaller wheels etc. Another important part of polishing, is like you said the strokes. Use a heavy pressure with the direction of the wheel to remove excess and really color, than use less pressure with the wheel to even out the finish. Like i've said, i think some cloudiness is expected, and ive learned to deal with it. Also make sure you use even, slow strokes to allow the wheel time to cut, color, and remove the excess. Polishing is purely experience, as you get more into it you'll pick up little things that work for you. Good luck!

[whistule]

Yeh, it is renowned as 'black art'. It's funny that we are on a polishing forum but few of us are actually talking about the polishing itself more about products - I guess it's difficult to describe and actually what you want is for the polishing wizard to pop up and show you how it's done! Thanks for the tips Tom.

[tomg552001]

Yep, very very slow forum.....6 months ago, itd be weeks inbetween posts! Do you have a digital camera? Snap some pics of the problem, it might help more people to chime in.