Swirl marks?

[mpierich]

Hi,

On some aluminum bike parts I'm doing (after grinding out defects w/120 paper) I go: greasless 120/220/320 on spiral cotton, wet-sand with 600 paper, then emery and tripoli on spiral, then white and red on loose cotton. I change directions several times during each step. All on seperate wheels, clean between steps, etc.

When I'm done the piece is damn shiny, but in daylight a plethora of mini-scratches are evident and appear as a halo around any reflection of a light source in the surface. Are these what is referred to as swirl marks?

I tried the Caswell suggestion of buffing with powder but no joy. Any hints? I did just order some Canton wheels...would these be better for the final finish?

thanks for any help.

[thekuai]

im no expert but i believe your are not properly sanding. The reason the piece is really shinny but you can see scratches is because compounds only shine metals but they dont really remove scratches, they only make the scratches shiny. Perhaps sanding with 120 is too coarse, try going as low as 200 only. Before you do any compounds, look at the metal for any scratches, any scratches you see will be visible after polishing.

[mpierich]

Thanks, thekaui,

I always start with the finest grit possible. But when there are knicks and gouges to be removed, 200 won't cut it, so to speak. I need to start with 120 or 80-grit to grind out the defects.

The scratches I'm seeing are not in the direction I work. I work successive passes at 90 degrees to one another - these marks appear in a circular pattern so I figure they must be "swirl" marks or an interference pattern caused by my work. I don't know.

[thekuai]

swirls can also result from the use of too much compound....so go over the material again and apply compound 1/2 a second of application at a time...thats all you need.....recompound every minute or less....also dont forget to rake ur wheel with a hand saw blade every 5 applications...remember its the compound that really does the work