I am in the middle of a engine rebuild on my car, so while I have all the parts out, I want to polish all the aluminum I can see under the hood. While I am not a total noobie, these are the first cast aluminum pieces I have really dealt with. I did motorcycle frames and extruded or already "flat" surfaces.
I will have a picture of the cover and the other msc parts up tonight. Basically they are rough cast parts. On the valve cover there a lot of deep scratches, and alot of the surface looks like a clay desert dried up. With a lot of little cracks and what not. The casting is just very rough. To make it harder, there are a lot of tight spots and places a da will never touch, and I will just be there all day and burn through tons of sanding drums on my die grinder. I have to remove a lot of aluminum to flatten out the surface prior to buffing.
I just found out about this greaseless abrasive stuff from this website. That seems to sound like the ticket. In my head, 80 grit I know will take alot of the surface down, and the flexible wheel and bobs will get right into the tight spots... but I just donít know how much material these materials will actually take off.
Where do you think I should start?
I would start with the "search" thing at the top of the forum...
I cant seem to locate my digital camera at the moment. But here is a link to the cover I am dealing with.
I ordered a ton of stuff.
Greaseless 80 - 400 grit.
The cartridge roll kit and 10 extra rolls.
A bunch of sewn wheels for the greasless.
15 felt bobs.
I actually 2 hours away form them, so UPS ground should only take a day or two. Cant wait!
I understand physics rather well. I guess the answer I was looking for was something along the lines of "80 grit greaseless on a spiral sewn wheel with light to medium pressure, for 20-30 seconds on a work area will remove aprox how deep of a scratch.
Sorry if I got off on the wrong foot.
Anyway. I received my order yesterday. and the stuff is amazing. I used the 80 grit stuff on a spiral 6" wheel, and used a hairdryer to speed up the layup time on the greaseless. A single application cut down the bare casting on the intake manifold plenum with surprisingly light pressure. in about 5 minutes I covered about a 3X6" area before I had to reapply. I was blown away at how much material it would remove, and yet how flat and smooth it left the surface. in about half an hour I did the entire plenum in 80 and then hit it with the 120. The 120 finish appeared to be what the results of a 220-3X0 grit sand paper would yield.
So far so good, ill post up some pics tonight.
there is no exact science that will say how much material in how much time will be removed , too many variables , type of aluminium castings ,some softer than others , what you call moderate pressure could be light pressure for me , size and width of wheel, speed of wheel ,how dry is the greasless on the wheel , part shape,.
when you change grits try to polish on a different angle when possible , that will help cut the previous polishing lines and it will be easier for you to see if you removed all the polishing marks left by the previous grit
Very true on the other variables. I guess my initial question was answered by my experimentation with the stuff last night.
i will just continue posting my results here and see what else can be done to improve on it.
The changing my cut directions is a great tip. Thanks!
I'm also new to polishing, and want to polish my rough cast motorcycle engine cases. I understand the principles, but how do you use the "hairdryer to speed up the layup time of the greaseless". Any advice would be appreciated, and which grit compounds did you use after the 80 grit greaseless?
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