How to properly polish alloy

[Tim754]

Think the title says most of it, Still use stitched or unstitched mops ? which colour polish stick for alloy, aluminium , copper etc. and are there any short cuts as I seem to spend a lot of time for results that are not anywhere as good as some I have seen on the forum or in the flesh.  I have my polishing mops set on an eight metric inch dual end bench grinder. Thanks Tim754

[LWC82PE]

Tim, i can help here, allow me a day or 2 to write something up.

[Maicojames]

I buff some aluminum, nasty work, but looks really nice when done.

As for the buffs, you will primarily use a stitched( spiral sewn) buff, and typically a loose sewn buff for final polish. There are so many opinions on process for home polisher, it is amazing. Generally, though in practice one would want to remove all pits etc by sanding to P400 wet, then lightly with P600 wet-you may need to start with powersanding with coarser grits, though I would not reccomend coarser than P120-as the the scratches left by coarser grits are tough to remove.

You must clean part between each grit, then sand at 90 degrees from the last grit-this way you will remove all scratches. I begin with spiral wheel ( 8" or  6" depending upon part- 8" wheel is on large machine, 6" is on smaller machine)-with a black compound-then finish with a loose wheel and wht compound. Again hre you must clean part of all residue between stages etc., only one compound for one buff(mop?).
  The time to finish is quite variable on the part, size condition, complexity. Some small parts, like Amal levers polish right up with the black compound, no sanding in most cases-others like Bultaco lower fork legs take a ton of powersanding, then wet block sanding with P320, P400-this could be lessened if they were machined down slightly to remove most of the nicks and corrosion pits.  Still on Bultacos, the engine covers, can be real tough too-they are die cast-and porous-that is when you remove any material to polish/buff you often expose pinholes-you usually can burn  a hole right through to find out they are permeated in the casting.( I know the hard way)-these are some parts that simply will not finish out really nice without welding up pits, aluminum solder fill, or plating.

Interestingly, many sand cast Maico parts I  have done were actually more solid, once I removed the casting flash-and smoothed they polished out nice. Also it has been my experience that the Asian die castings, and CZ die castings are much less porous than the Spanish and buff out nicely. Hopefully, this give you something until LWC can put an article together-do seraches and read everything you can for now.
 James

[LWC82PE]

here is my bit. some bits i didnt mention are the same as as what Maicojames has said

There are a number of ways you can polish alloy but here is just a few of my methods. That work. Maby others have different methods

Starting with a  pretty common set of Japanese KYB/showa fork sliders

First if you have a lot of corrosion clean the part with alloy cleaner or bead blast it with glass beads. Make sure you use clean beads and do the rough cast areas that haven’t been polished around near the axle mounts and any cable guides. This will give it a shiny look very close to the look when it was new.

If you have got really deep gouges, get these filled in with a TIG welder. I’ve never had to do this yet. Most times I can get most marks out with very course sand paper, hand files, small sanding disc in a grinder or the under (loose) side of a sanding belt on a belt sander. Use white wax on any powered sander so the discs/belts don’t clog up with alloy. Then I work my way to about 320 or 400 wet and dry on these deep areas. Once the really deep marks are out you can start polishing. If you want you can sand a lot more of the finer scratches out with wet and dry paper if you have time. The original finish on most Japanese fork sliders is a brushed sort of finish and not mirror finish, but if you want mirror finish I can tell you how to do that too. The original finish on most Japanese sliders is done by a Sisal wheel. I’ve got one of them but I’m not satisfied it gives the same finish as the wheels they used 30 or 25 years ago. The first wheel I start with is a really hard compound light grey wheel, I’m not really sure what its called but I think it’s a 3M and its not a mop type wheel and it lasts for ever. I guess I would call it a hard ‘scotch brite’ wheel as it looks similar to the material in a green Chux or Scotchbrite scouring pad. This wheel is good for removing medium size/depth scratches, but will leave some finer ones. Try to polish with the scratch and along the length of it and not across the scratch. If you go across it this tends to keep opening the scratch up wider.

After this wheel I go to a softer compound darker grey ‘scotch brite’ wheel. I currently have been using them in 3M brand. We probably go through about 1 a year. They will wear out quick if you really lean into this wheel and polish sharp edged objects. Every time one of these wheels wears and we go to get a new on the supplier has always superceeded it and we can never get the exact same wheel we had before which is annoying. They are always changing.

This is the wheel I use to get that nice original brushed/satin type finish on fork sliders. For the final run only move the piece over the wheel very lightly and try to do it all in on direction. You will have found you couldn’t get in around the axle mounts. Where you have bead blasted it will a light silvery grey cast look. I usually then rub over these parts by hand with a fine steel wool or a scouring pad, this just gives it a little more shine and closer to the original shiny cast finish. Now the polishing is finished.

If you got no power tools this process can be done with course dry sand paper and working your way down finer with wet and dry sand paper. You can get results just as good by hand. Then try finishing off with a green scouring pad. It will give a very nice finish, but will be a tad more shiner than original, but wont be mirror. I have found the best scoring pad for my work is the Chux heavy duty scouring pad. They come in packs of 3 and are a green angled rectangle shape. Ive tried all the other brands but like this one the most.

If you want mirror finish on these sliders or any other alloy part then follow the same steps but after the green scotch brite pad or about 800 or 1200 wet and dry if your doing it the hand way then use Reflection brand polish in a tube. It’s the best hand polishing paste I’ve ever used and really works very well. It will be possible to get mirror finish with this but will take a little longer.

If you got the powered polishing tools, after the soft darker grey scotch brite wheel I use a stitched soft cotton type mop with a blue polishing compound, then polish away. This gives outstanding results, but it will depend on the condition of the alloy. You can polish till your blue in the face but still not get the results you are after. You get this problem with porous alloys with hundreds of pit marks and the more you polish the more pits appear, they just don’t go away. I only get this problem on british alloys, the jap stuff doesn’t have this problem. Also if alloy had a lot of white corrosion on it in the beginning from moisture, even though you have thought you have removed it with previous steps once you start going for a mirror finish you will still end up seeing some corrosion marks. This is annoying for sure but it’s really deep in the alloy and doesn’t go away no matter how much you polish the more you polish the more it opens up the pores in the alloy where moisture has been trapped. After this mop some marks may show up. Go back to the soft scotch brite wheel  and go over these marks again, then re-polish with the stitched mop.

After this stitched mop I then go to a un-stitched mop of the same material. It’s basically a calico material stuff. I also use the same polish stick on this. Polish away till you can see your reflection and your done!

So these steps can be applied to most alloy parts like rims and engine side covers. most japanese alloy parts were very roughly polished and ive seen NOS 650 Yamaha side covers and seen how rough they are polished. I got some brand new Kawasaki KYB fork sliders and I’ve also seen what they were like originally too. Sometimes it a bit hard to polish to 100% like the original Japanese stuff as a lot of it is done very rough and quick and to be honest it doesn’t look very good and looks crap. If you were to polish a set of side covers on a japanese engine to what they would be like from the factory 9/10 people would think it looks crap and doesn’t look polished properly. So I tend to make exceptions and polish Japanese engine covers to a finish a bit better than original. Most of the british stuff, is highly polished to a good standard anyway so that’s not a problem.

For the GP BSA I’m restoring the clutch cover had the worst corrosion id ever seen. It had a big section of really deep (5mm) corrosion. Most people would of chucked it. We had other covers but they had inspection covers and this original GP cover didn’t have any and was right for the GP. We had nothing to loose. The cover was really thick so we just ground out all the corrosion and worked our way down to finer sanding discs. Amazingly it come out and there is still enough meat in the cover. Sadly I haven’t got any before photos to show you. Its one of those things where you get all excited about doing the job and seeing if you can fix it and before you know it your halfway through the job and thinking bugger, I should of taken a photo of what it was like before hand.

[Tim754]

Many thanks Lads , I seem to have all the required items here but was not following all the steps. Cheers and once many thanks. Tim

[Maicojames]

LWC, you can also get the satin finish on Jap sliders often by polishing to about a no 7 finish, then you can install a sprecific wheel for this( Caswell in US has them) to get the marks back in. Alternately, you can sand with P800-P1200 in a 45 degree pattern -with an oil based solvent as lubricant( careful-use the rubber gloves here for sure). BTW Always use eye protection, a respirator-or at least a dust mask with alow micron rating, gloves( change them often I pick up six packs from Harbor Freight, as the compound gets on your gloves-and back on your work)-the parts get really hot while buffing. 
LWC, I think we do it about the same method, but perhaps the compounds, buffs, and vernacular are different for Australia and US.

[LWC82PE]

yeah theres no real one and only set way to do it. i use big thick welding gloves when im working on a big piece for ages as its really too hot to handle. for certain parts i prefer to do the process by hand with wet and dry and then a scouring pad.

[carbyman]

HEY ALL NOT SURE IF THIS WILL HELP YOU GUYS I HAVE A MACHINE THAT DOES MASS FINISHING/ POLISHING
WHAT YOU END UP WITH IS A NICE POLISHED FINISH BUT STILL RETAINING THE ORIGINAL FINISH LIKE CASTING MARKS ECT
IT WONT POLISH TO A MIRROR FINISH BUT MAKE IT LOOK ORIGINAL AND NATURAL
I MET SOME GUYS AT A MATES BIKE WORKSHOP AT LIVERPOOL SYDNEY JUST BEFORE XMAS THEY WHERE FROM NOWRA AREA I THINK  AND INTO VMX AND WHERE BLOWN AWAY WITH THE FINISH ON PARTS A HAVE DONE OFF MY SPARE KX250C1
THERE IS NO INFO ON MY WEB SITE ABOUT IT BUT CALL ME OR DROP AROUND AND TAKE A LOOK IT MAYBE WORTH IT
www.xtremefuelsystems.com.au
THANKS NIGEL

[LWC82PE]

well im happy that i can get all the correct finishes that i need. what do you mean by a 'mass finishng machine'

[carbyman]

ITS A LARGE ROUND MACHINE HAS A CHANNEL THAT HOLD THOUSANDS OF STAINLESS STEEL BALLS SHAPED LIKE A SPACESHIP/ FLYING SOURCER AND THEY VIBRATE AROUND WITH THE PARTS VIBRATING AGAINST THEM (WITH NO DAMAGE OR MATERIAL LOST)
THIS PROCESS HAS BEEN AROUND FOR A LONG TIME BUT WE HAVE JUST BOUGHT OURS TO POLISH OUR HOLLLEY CARBURETTORS TO THE SAME AS WHEN YOU BUY A NEW HOLLEY CARBURETTOR
ITS TRUE NAME IS STEEL BALL BURNISHING / MASS FINISHING
THE PARTS COME UP BETTER THAN NEW
FOR INSTANCE THE HEAD OF MY KX250C1 IS CAST AND IT LOOKS LIKE IT HAS BEEN BEAD BLASTED AND CLEAR COATED WITH OUT HAVING TO PAINT AND IT LAST FOR AGES THE CLUTCH SIDE COVER CAME UP TOPS AS ITS A SMOOTH FINISH ANYTHING ALLOY CAN BE DONE HUBS TRIPLE CLAMPS ENGINE CASES ECT ...

[yzhilly]

G'day Carbyman have you got some pics ,of the machine and parts ,before /after .thanks

[Doc]

I 'always' use good ol' elbow grease..nothing like it for a bit of elbow exercise when 1 does not drink  none of those nancy pansy machine's or polishing gizmo's here and I'm very happy with the results..there is such a thing as being overly polished which is a common mistake made. Mirror finish on some parts doesn't look so great.  Most Jap forks for example don't look so good if overly polished. Some steel wool, a sheet of wet and dry, a tin of Silvo and I'm set to hook in..surprisingly it doesn't take long. It's all in the prep which I use wet and dry if steel wool is too slow..most engine parts I polish were painted from the factory but the sanding off of the black alone is all the prep the alloy will need to polish up to a high 'bling' 

[DJRacing]

Geez Doc ya dont sand the paint off do ya? Try 'Tergo stripper' or 'Dads stripper' and the paint will be gone in about 5mins, and then just wash the part with lots of cold water. Its already for polishing then and your elbow will thank you for the less sanding , and of course its up to you what ya do with all that extra elbow grease you'll have

[carbyman]

LIKE I SAID ITS NOT A HIGH FINISH LIKE A MIRROR JUST A GOOD SHINY FACTORY LOOK IT KEEPS ALL CASTING MARKS IE NUMBERS LETTERING LOOKS A1
I WILL TRY AND ADD SOME PICS TO MY WEB SITE IN THE MEAN TIME EMAIL ME AND I WILL FORWARD A FEW PICTURES TO YOU GUYS INTERESTED
 
[email protected]
 

[YZ250H]

Hey LWC,

Any chance you can tell us what product code is on those 3M wheels.  I am going to set off down the path of doing things your way.  I have looked at the 3M website, but there are a number of options.  If you had the product codes it would make things a lot easier as they are a bit expensive and I would hate to buy the wrong ones  .

Any help appreciated
Cheers