The Shop => Finishing => Topic started by: rleete on January 09, 2009, 08:46:44 PM

Title: Final polish
Post by: rleete on January 09, 2009, 08:46:44 PM
Well, I'm nearing completion on my first engine.  So, I've been working hard at getting it looking nice.  Sanding with ever finer grits, and then off to the buffing wheel.  I start with tripoli compound on a spiral sewn wheel, and move to white polishing compound (sticks, not sure what it is) on a loose sewn wheel.  All well and good.  Shines up fairly nice.

But, when I get to that last bit, I can't seem to get the streaks out.  It's the last minute bit, when the light hits it just right.  More or less pressure on the wheel, more or less compound applied, nothing seems to get rid of it.  If I turn the part 90 degrees to the last buff, the streaks seem to go in that direction.  So, it is micro scratches?  What do I use to eliminate them?

Parts are 360 brass and 6061 aluminum.  Both exhibit the same hazing.
Title: Re: Final polish
Post by: Divided he ad on January 09, 2009, 09:22:35 PM
Hi Roger,

I've not got too much idea about your issue... you see...  :worthless:

Honestly... I think I know the result of which you are talking, it sounds like too much 'soap' on the wheels to me.
If the polish is too abundent on the wheel it often leaves horrible dark lines/streaks behind.

Personally, first I clean the part in brake cleaner... it is a solvent used for de-greasing/cleaning vehicle brakes. It evapourates very quickly and usually disolves the streaks (assuming they are soap)

There is also a powder to use last called Vienna lime. This removes the grease off the mop quite effectively and helps obtain a good finish.

A random E-blag post I grabbed at... Not even sure if it is value for money... It's just to show you the bag of powder you get with the kits... Also the final soft mop, being the polishing mop barely has anything applied to it other than the non-greasy bar (very light amount on the mop) and the lime!

I linked to a site in my polishing post that can help with technique... added with what I have written above that is pretty much all I know.... Maybe Bog's has more insite?

Good luck, don't polish all your hard work away... We'll figure it out  :thumbup:

Title: Re: Final polish
Post by: gilessim on January 29, 2009, 09:38:36 AM
you should try a felt wheel, when you get streaks like that it usually means that the wheel is saturated with polish as Ralph says above ,with a cloth wheel the stick polish really hangs on, you can clean them with the edge of a knife, that helps a bit but a felt wheel is much more solid so you can push harder to melt any residue, also the fibres in a felt wheel act like little hooks that clean off any scum and the used polish just falls off, hope this helps!

Title: Re: Final polish
Post by: bogstandard on January 29, 2009, 10:59:25 AM

I can't add much more, except that I also use vienna lime, but I also have an unsewn soft cotton wheel that is only used for final polishing, so there will be no heavy grease deposits on it.

Like Giles, I also use a felt wheel, but only for getting into very sharp corners, I find it rounds out a part a bit too much for my liking, I like nice sharp edges, but they do cut the metal back to a very fine finish.

I have recently purchased a mop for plastic polishing that is made up of thousands of very soft loose strand cotton fibres. I think that would be just great, with a bit of vienna lime, for getting the workpiece to it's final sheen.

Your problem, I think is just a bit of technique and wheel selection problems. The higher the sheen, the softer the touch and cleaner and softer the wheel has to be. Plus your hands, they are covered in natural grease, wash them prior to final polishing. But never, ever, use gloves or a bit of cloth for holding you parts, it is better to lose the part rather than your fingers. Professional polishers do use special polishing gloves, but that is purely for speed reasons, to allow them to hold hot friction heated parts much longer, and so allow more production. We should never be in a rush.

You might find that a manual polish with a bit of soft cotton (new t-shirt) and no polish just might rub the haze off. I am lucky in that I can obtain some very special paper cleaning cloths that are perfect for the job.

I also find that a proprietary brand of furniture cleaner and polish will bring up the surface and keep it shiny for much longer. In the UK I use Mr. Sheen, again with a super soft cloth.

Title: Re: Final polish
Post by: rleete on January 29, 2009, 01:10:55 PM
Well, I posted a bit more detail on that other site.  Seems that the problem was multiple things.  First, the white polish compound had too much cutting action.  Second, I think I had it on the wheel too heavy.  Third, I wasn't cleaning the part betwen buffing stages, and might have been contaminating the buff.  I do wash my hands during the process, too. 

Mostly, it was me being overly picky.  I stopped using the white stuff.  After getting it almost there with the tripoli, I switched to hand polish with a piece of flannel.  I also realized I needed to go a little further with the sanding, using a finer grit (what I thought was 1000 was actually 800), and now I go down to 1200 with a lighter touch.

No pics at the moment, because I haven't gotten down into the shop in over a week.  I had started a thread on my first build, which I need to update.  I'm 90% done.
Title: Re: Final polish
Post by: bogstandard on January 29, 2009, 03:26:09 PM
There are some very good tips in the very early sections on HMEM. A lot of people just ask the same question over and over again, and don't bother to search thru the old files.

You have most probably seen these pics over there, but they do explain about the finish required and the final bit about polishing.

This first one shows the finish to the metal BEFORE it is taken anywhere near a buffing machine. The buffing is only for giving a final sheen, all the hard work is done by hand well before. I find that the very finest scotchbrite pads, followed by superfine carpenters wire wool gives the finish I want before buffing. That is after you have been thru all the grades of wet&dry.


This one shows that ali can be brought up to a mirror finish. This was before the final treatment with furniture polish. After that, it becomes rather difficult to photgraph because of all the reflections.