Frame polishing....same process...2 different finishes? HELP

[bairdmotorcycles]

Looking for a little advise and I cant seem to find any help with other posts. I am polishing a aluminum motorcycle frame and have the desired finish already on the tubular front portion of the frame but I can not seem to match the finish on the cast area around the foot pegs from the weld on back despite using the same process. The front is absolutely a mirror and I have only hit it up to the spiral/brown combination. The cast area, tho shiny, is not achieving the same finish as the other section separated by a weld. I started the cast process with 80 grit, then 220 grit, 400 grit, 800 grit with a DA sander, to wet sanding by 800 and then 1200 on the cast section and started with 220 on the tube section. I don't think the prep is the problem as I don't have any scratches or pits/waves etc but I am not sure. Could the jump between 80 grit and 220 be to large? But after 1200 the cast section of the frame looks just as good as the tube section. I have done other pieces to mirrored finishes with aluminum but this is giving me fits. This is the first time however I am not using the 3/4 polishing machine I purchased on Caswell because I don't feel like holding a 70 lb frame all day. I have been using a 1 7/8 electric polisher/buffer which gave me a brilliant shine on the tube section. Right after sanding I went directly to the spiral/brown (tripoli) and then the loose/white combo. The tube section is perfect but the cast section is hazy when closer then 3 or 4 feet after hitting both with loose/white. I then re-sanded from 400 up to 1200 wet and have now tried several different combos of loose with black magic rouge, aluminum high luster a-14 and a-15, blue rouge on the cast section and can not get the same mirrored shine. I have even tried the 4 inch wheel rather than 8 inch I have been using, as well as switching to a 7 inch air angle sander with 4500 rpm and a die grinder with 20,000 rpm which both bog down if too much pressure is applied and I still get haze. The cast part also seems to be pitting or becoming even less smooth with the tripoli/spiral wheel. I have cut and colored in every way or angle imaginable but still no change. I clean the stages with mothers aluminum billet polish and use separate rakes not to contaminate the next stage. So what do you think? Prep problem with the cast compared to the tube which was already pretty smooth? To much/little pressure? To slow/fast of speeds for the cast area? Why would the cast have a completely different shine than the tubular section when using the same exact process? Can I get the cast area to the same brilliant shine? Any help would be greatly appreciated!!

[pickleboy]

i will try to make as much sense of this as i can for you and also try not to be long winded. first off the 2 materials, even though both alum. are very different. the cast is hot poured as you would steel in a liquid form. the tube section is cold drawn in this it means that the grain structure is different. the tube has a dirrection of grain and the cast does not. the cast also has the possibility of having pits in it under the surface that are minor defects in the process. nothing you can do about that. cold formed (tube or forged billet) is allways going to get a better shine due to the material being denser. as for your process it sound good. the possibility is that the 2 different pieces may never match. when i have done cast in the past i have had the same problems. keep watching this thread and others will chime in and give some good advise. also give a look at the top of the polishing forum at the sticky on polishing motorcycle frames 101 and look at syco's frame. maybe you can get a idea as to what to expect there. hope this helps a little bit and best of luck bro.
cliff

[mpierich]

Only thing I could add is that yeah, after the 80 grit you should go to 120 as the next step.

I used to think I had to follow the formula all the way to red rouge, but every piece of metal is different. I finished a sportbike wheel last night and after starting with 80/120/240/320 the wet with 500, I hit it with emery and is looked great. No tripoli at all. I could have finished it off with white rouge but it's for a rider not a show bike. As some others have notide, the tripoli does seem to produce a haze sometimes. In future I will probably use it only to freshen up a previously -polished piece.

You _will_ find pits (bubbles) in any cast parts. Unless maybe theywere made for NASA...

Oh btw, the greaseless compunds can save you a lot of sanding.

[bairdmotorcycles]

Thank you both for the advise. I think I am going to re-sand yet once again back to 120 or so and hit it possibly with the spiral/emery to see what happens and then maybe right to the loose white. The haze is just to much to make me happy with it. I own a motorcycle shop and understand the difference in materials especially cast when it comes to chrome plating but its just to different of finishes for me to be satisified with it leaving the shop. Dont get me wrong, it looks good but not good enough for me. Plus I know it can be done as I painted another bike with both sections perfectly mirrored. I read a post in the forum dated a few years back where the individual sanded with wd40 rather than water when wet sanding and he claimed it helped. Anybody know anything about this? Or if you can provide any other information or suggestions please do so. Once again thanks!

[pickleboy]

i have used wd40 and it did not seem to be that much better. not disputing but for me it seem to be the same. i have also read here that the best thing would be kerosene. this makes a little sense due to the heavy oil content. maybe try that.

[fizlfry]

Two different finishes

Hey,
That looks EXACTLY like the problem I am having as we speak!!!!
Look at this pic, http://www.caswellplating.com/bbs/al...php?pic_id=513
and tell me if it looks kinda like that?
I have also been scratching my head.....
I have been using dish soap in the water, (just a little) and it really seems to help. It seems I have to get new water more, but, sands better.
About the different finishes.....
I have been able to get a little better match with going over the Brown like, 10 times.... No black emery/sisal, just sanding, then brown/spiral...
I am using a Makita 2500RPM drill, and the Caswells 4" wheel.
I resanded more than once too, so, dont feel bad!
Hang in there

[bairdmotorcycles]

I also use the liquid white rouge mixed with water when I wet sand to help it. I am going to re-sand yet again and try a few different processes today. Thinking of doing sisal/emery right to white/loose or maybe right to white/loose because the brown/spiral only seems to make it worse off. Probably trying the red as well. Heck I dont know....just going to keep going until I am happy which may be never but I have a feeling the customer will want his frame back sooner than later. But I will let you know what I find out.

[rides20]

...going from 80 right to 220 is a mistake that could quite possibly be the only one in this case. When I did an R1 frame, i used 60 grit to get most of my "shaping" in..then onto the 80, then 100, 150, 220 on the DA..then start wet again with 220 to remove DA marks and replace the "grain"...adding the 100 and 150 in there still removes alot of material, which is probably where your scratches are "hiding"...try it out on a small spot, and let us know!!!

[bairdmotorcycles]

That would seem to make sense but I am not sure thats the problem I am having unless I am horribly wrong. I have the finish I want but I can still see swirl marks from the wheel when the frame is directly in the sunlight or at certain angles. When its not in the direct sunlight (inside or shade), its nearly perfect and looks absolutely great and reflects like a mirror. But in the direct sunlight its a different story. Many customers have commented on the fact that they can not believe its not chrome because of the shine and how good it looks but I am a prefectionist and want to know if I can get it any better then this and do away with the slight haze in the direct sunlight left by each pass of the wheel. Its as if it traces the movement of the wheel across the frame like footprints in the sand but only shows up with direct sunlight. Any suggestions? I can see if I cant post some pics.......

[fly]

If you try a 3m type of disk it will help with the swirls, go to maxtools.com and look at their grinding disk they have the sand paper disk and the 3m disk get the med. and course 3m disk and then try your white, or blue rouge with a loose cotton wheel on a 7"or 9" grinder.

[mpierich]

I have the finish I want but I can still see swirl marks from the wheel when the frame is directly in the sunlight or at certain angles. When its not in the direct sunlight (inside or shade), its nearly perfect and looks absolutely great and reflects like a mirror.

Look for the "NASA" post. It seems aluminum's softness makes it almost impossible to attain a true optically perfect surface, hence the swirl marks. They drive me nuts, but as you say the customers don't seem to mind. The ones who do are really looking for a chrome job, which is hard enough to take on a perfect polishing job.

[bairdmotorcycles]

I may try a few more things but I think it may very well be as good as its going to get. Thanks for the help!!

[customandsound]

bairdmotorcycles
check your pm's

[bairdmotorcycles]

you mean rpm's correct? I was using a big electric 1 3/4 hp buffer/polisher with 3400-3600 rpm and a air polisher with 4200 rpm. I was using a 8in wheel at first but then realized the rpm was more than the recommended speed so I switched to a 4in wheel (which should put me in the recommended range) and I think it got better. The more I seem to be learning the more it seems the marks are impossible to completely rid the piece of but I want to minimize it the best I can. I know it can get better because I had another frame in my shop that was done by another shop that had less swirls. Should I use the powder as suggested as the last and final stage to help? Or is there another product which helps minimize swirl marks at the finals stages other than the wheels (mushrooms or something)? Thanks in advance!

[sswee]

bairdmotorcycles,
I think he means.
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