MC Engine Cases - Frustration Building

[rickt]

I have reviewed the online manual, read several books, and viewed at least one instructional video. I have done a fair amount of metal polishing over the years and have generally had pretty good luck polishing stainless. On the other hand, my success rate with MC parts has been rather poor. Currently, I am working on three engine cases from a 70's era cycle that I'm restoring. I removed the residual polymer coating from the cases with garden-variety paint stripper and wet sanded the cases with 1500 Meguiar's followed by 2000. I then went to spiral sewn and tripoli on my bench grinder. I got a decent shine but numerous small scratches and the dreaded HAZE remained. I then switched to a loose wheel with white rouge and didn't really see much improvement (direction of small scratches would change direction depending on the orientation of the buffing wheel - haze remained). I took the case to the garage and tried a 4" spiral with tripoli on a dye grinder followed by a loose wheel with white rouge - NO improvement.

So, am I missing some very basic skill with this polishing project? I'm not sure what these cases are actually made of - some type of alloy I assume.

Any advice would be greatly appreciated and certainly help to ease the frustration level.

rickt

[jrow]

rickt,

You didn't mention any cleaning steps before or after changing buffing compounds or buffs. Did you rake your buffs? After each buffing step clean your metal with either Acetone or Brake cleaner, then wash in Dawn dish washing liquid and water. Use a different buff for each compound. It sounds like your not getting enough heat in the metal for the compound to work. The small scratches should buff out with either Emory or Tripoli on a sewn buff, then clean and switch to a loose buff with your white compound. It that doesn't work try an Airway buff and Emory or Tripoli.

John

[mpierich]

If you started with 1500 grit, I'd be surprised if you got rid of any scratches at all, unless of course the cases were in mint condition to start with.

That being said, I've taken to skipping the tripoli altogether since it usually seems to leave more haze than shine; then again, if your 1500 job was sufficient, tripoli might be the next step. I usually go from 400 straight to emery, then white. I seldom get a _completely_ scratch or haze-free surface, but I've never had any major complaints.

[rickt]

Thanks for the input. Cleaning after the use of the tripoli might be part of my problem. I have not done a good job of this in the past. Usually, just a wipe with a cotton towel - sometimes I will use a degreaser solvent. I will try to clean more thoroughly between compounds.

The cases were not in bad shape after removing the polymer coating. Not knowing any better, I thought it would be a good idea to do some sanding with the fine emery paper. I'm pretty certain that the tiny scratches I'm seeing are caused by the wheel since turning the piece 90 degrees shifts the scratches 90 degrees. It was my understanding from what I have read that the white rouge would remove these small scratches as well as the haze. Is my thinking incorrect?

I also see that Caswell sells a "blue" rouge. Would this be a better option for eliminating the scratches and haze? The Caswell online manual suggests the use of corn starch or talc on wet metal as a final step. Does anyone have experience with this?

rickt

[mpierich]

I haven't had a chance to test it, but I feel that a slower speed wheel should be used for the final step(s). I think fast speeds make the wheel fibers slap the metal too hard and cause scratches no matter what compound you use. You could also try a canton wheel.

In _my_ experience the blue doesn't do much except that it's good for polishing plastic. I've also tried the talcum thing with no success, but perhaps others have had better luck.

[jrow]

rickt,

Along with what mpierich stated, try a Canton wheel. I would also try some hand polishing using either Mothers Mag wheel polish or some Simichrome. These may take out the scratches you are seeing!
What are your plans on protecting the metal after you have it polished, so it doesn't oxidize?

John

[rickt]

John,

I'll give the Canton wheel a try. About the only way of slowing things down that I know of is to use a variable-speed drill with a 4" wheel or maybe rig up something with my drill press.

I haven't tried Simichrome (yet) with these pieces, but my past experience indicates that once you have a good shiny finish, Simichrome can help maintain it, but it doesn't help much getting rid of micro-scratches and haze. Even so, it can't hurt to try it again.

As far as a post polishing coating, I've tried a couple of automotive-type clearcoats in the past (acrylic urethane catalyzed paints). The problem with this approach is that these products need somewhat of a rough surface to bite into. The better the polishing job, the less likely the coating is to stick. What I do now is just give the shiny pieces a touch up polishing (maybe Simichrome with 0000 steel wool) a couple of times a year. All of my bikes are stored inside and rarely see wet weather, so the oxidation problem is not terribly serious.

rickt