Thread: Metal polishing problem

Originally Posted by neksmerj

I have a dedicated grinder set up with left and right handed tapered spindles. On one side is a stiff bristle buff, on the other a soft calico buff.

On the stiff buff, I use a dark grey compound, and green compound on the soft buff.

The problem I'm having is a black residue is being left on the metal part I'm polishing. The same happens using the green compound.

The residue has to be wiped off with kero or turps.

What am I doing wrong? I'm sure I didn't have this problem some time ago when parts would come up with a mirror finish right off the buff.

Any comments on my technique?

Ken

Hi Ken,

Polishing can be an art form! I'd use a lighter touch and work across the part so that any compound residue is worked across the part away from the clean area.

Also, maybe you might have too much compound on the wheel?

Polishing can be a whole discipline in itself, and I'm sure there are a few on the forum that can add ( or subtract ) a bit more...

Regards
Ray

Thanks RayG,

Maybe the buffs need dressing, if that's the right term. It's possible they are overloaded with compound.

What would be the best way to "dress" them? I thought maybe a card file, but I can imagine that being ripped out of my hands taking my fingers with it.

How about holding a file against the buffs? Sandpaper maybe?

Ken

The tang of an old file is a good wheel dressing implement.

Hi Ken,
My younger brother runs his own metal polishing business in montrose, I don't think that's very far from you. I am sure he could set you straight.

Phil

I thought that the black residue was the nature of the beast. I have polished almost every common metal over the years and have always had to deal with black funk on the workpiece. As you say, Ken, kero or other common solvents seem to carry it away.

If its going by air invent some plausible deniability, then blame the nearest youngster. That gambit has always worked for me.

Hi Greg,

Maybe I should just put up with the problem, and use a good quality scotch to remove the residue, after sampling the nectar first.

Welcome back to Mel, where's the coffee?

Kennearth

I just clean the wheel with an old large flat blade screw driver, they need it often when your doing a bigger job as they get loaded up with compound and what your polishing.
Your missing the intermediate stage of a stitched mop with brown compound.

If the part is bad I sand, then a sisal mop with grey compound, them a stitched mop with brown compound, then a loose leaf mop with white or green compound and I wash the part with turps between each stage.
If it's not to bad I just use the brown on a stitched mop and them the white or green on the loose leaf mop.
I wash the part at the end and finish off with autosol by hand, but if you clean the mop then re do the part you shouldn't get much if any compound on it.

Do as Ray said and work the job on the mop with it pushing the compound to the part to be done, this will let you see what you have done.

Dave

Did quite a bit of metal polishing in a former job. Too much compound on the mop is usually the reason for your problem.

Nev.

Ken, I suspect too much compound on the buffs, simplest way to clean is to dress the wheels.

We used to have a commercial dressing stick that was timber about 450mm long, with turned handles each end to grip. The centre section was rectangular about 35 x 70 cross section and 250 long with metal teeth inserted in it to tease the fabric of the buffs. You could probably achieve the same with 50mm bullet head nails driven into a similar piece of hardwood and trimmed back to protrude about 8mm. Unit is very firmly gripped and slowly presented to and worked across the edge of the buff. If the buff has not been conditioned this way, it may be lacking in free fibre and not work well, resulting in more compound being added to try to get it working, and then having compound deposits on the work. Here is a link to a similar unit on a UK site

Once the buff is broken in, we would trim any excessively long fibres with sissors to avoid flaying, and wear the rest to a working length by working the edge of the buff against the edge of an old file to abrade the loose fibres to a uniform length, typically 1.5 -2mm for a hard buff and 3-4 for a soft buff.

Other issues may be to low a working temp caused by lack of speed, particularly if working from a bench grinder. Polishing shops typically run 5HP + polishing lathes with 350-400mm wheels at 2800RPM, so surface speed and heat and much greater than can be achieved with a bench grinder. Low temp/low surface speed inhibits self cleaning, at higher surface speeds and temps the compound sofftens a lot and the buff can throw excess, at lower surface speed/temp it tends to clog the buff.

For polishing away from a polishing lathe, typical machines are 3HP 8000-10000RPM barrel grinders (Hitachi is commonly used) working 200mm buffs.

Hope this helps

Must be doing something right, getting likes on this as I edit it.

Originally Posted by Greg Q

I thought that the black residue was the nature of the beast. I have polished almost every common metal over the years and have always had to deal with black funk on the workpiece. As you say, Ken, kero or other common solvents seem to carry it away.

+1 to that.

I am an impatient prick and generally overload my buffs to try to speed up the job. It never works.......

A mate of mine makes armor and he can spend hours polishing one plate. Me? i give it 5 mins and then throw in the towel.......

Originally Posted by neksmerj

I'm sure I didn't have this problem some time ago when parts would come up with a mirror finish right off the buff.

Have they worn down, so the surface speed is now reduced enough to make a difference.

Nev.

G'day Ken,
Like a few of the other blokes I always figured the black stuff was just part of the process.
I usually rub if off at regular intervals while polishing as it comes off a lot easier when the part is still hot.
I never use turps, kero, etc as this also takes away the waxy coating that buffing leaves behind which preserves the shine and is a great rust inhibitor if the part is steel.
It works great for keeping flywheel rims shiny on old engines too.
I only use turps or thinners to remove the wax if I want the part to develop a patina.
Cheers,
Greg.

If you want to get technical the problem is too much compound on the job, but when I worked as a polisher ( to learn the trade)
all the pro's said don't worry about it does not cause any problems as you just clean it off before the final creme polish