Buffing, Grinding, and Sanding
Q: I want to buff small metal items like flatware and jewelry items, maybe even watches. I got a flex-shaft machine, but I could use some help in figuring out how best to use it. Is this the right tool, or should I have bought a bench-mounted machine? Do I need to sand everything first, and if so, what grits do I use? Do I need to keep changing the angle I buff at? What do I do about all the dust and lint it throws everywhere? How big should the wheels be, and am I supposed to change speeds for different compounds?
A: One-inch wheels are about as large as you can use on a flex shaft, but with a fixed-shaft motor, you can use larger wheels. If your motor has, in addition to the flex shaft, a fixed buffing arbor, you could use, say, a three-inch wheel, which would cut faster and a bit smoother. If all you’ve got is the flex shaft handpiece, then the 1 inch wheels will be fine. It’s just sometimes a bit slower, or harder to get larger surfaces evenly buffed.
Bigger is better with buffing motors. You do want, generally, a 3450 rpm motor, not a slower one, unless you’re planning on using 8″ or larger buffs. (For your smaller items, that would probably not be needed.) The motor should be solidly mounted so it cannot move, and is usually fitted with tapered threaded spindles to easy hold and switch buffs. If the spindles come to a good point, you can use virtually any small buff, or if, like many spindles, they’re a little blunt at the end, you can get chucks that will go on the end that themselves will then hold small buffs and brushes.
While the flex shaft can give good polishing on small areas, it won’t work if you need to cover larger areas. Because the flex shaft can only cover a little at a time, it’s difficult to get uniform surfaces, and you’ll gend to get uneven spotty polishing. Don’t get rid of the flex shaft. it’s great for detailing. But if you’re doing any quantity of serious polishing, the bigger machine is almost certainly required. Most polishing lathes intended for buffs up to about six inches run at 3450 rpm. Some buffing lathe motors offer a dual speed switch with 1725 as the slow speed, but it’s not as common or offered on all buffing motors. But 1725 rpm is the common speed of utility motors, like in washing machines, so you can use them as buffing motors in a pinch.
One advantage of a bigger motor setup is that it’s then easier as well to rig up a vacuum/suction setup to catch the buffing dust. And a face shield too, is a good idea, especially for beginners. They’re easier to work in than safety glasses in some instances. The fixed motor allows you to hold the item more securely, since you’ve got both hands free. You’re not limited to six inch wheels with a buffing motor. Switch to smaller wheels if you need to. And buffs are not your only option. Brushes, ranging from 3 to 4 inch diameter on down to half inch diameter, are very useful and versatile. The follow a detailed surface better than a buff, get into details, and cut quite quickly if frequently charged with compound. The small ones fit on a specialty spindle, called a MK spindle (the most common brand of these small brushes is the MK brand, but there are others too.)
Sometimes, if the marks to be removed are deep, you’ll need to sand first. Alternatively, use a buffing compound that’s got more “cut” to it than a rouge. Rouge compounds generally are used for final buffing, not so much for initial smoothing. You normally start with a cutting compound like tripoli, or for coarser cutting, greystar compound), or for a bit gentler cutting, a “white diamond” tripoli compound. Your white rouge will have some “cut” to it, but not much. If you do need to sand your parts, 400 or 600 grits are usually sufficiently fine. On some metals, or if you wish to avoid having to use a coarser cutting compound, you can go much finer. Rouge will take out a 1200 sandpaper finish fairly easily, for example. When sanding, be sure to fully remove all traces of marks from coarser papers before moving to the next finer grade.
You do want to be varying the angle, in order to avoid drag lines. You’ll notice an apparent reduction in luster at first, because varying the wheel’s angle gets new rouge compound from the wheel to the work. Stay there a moment, and it shines up again. Use less rouge as you near the final polish, and this won’t happen so much. But do still vary the buffing direction as you work.
All new cloth buffing wheels throw off a lot of lint. It’s normal. As you use the wheel, those looser outer threads go away, and the wheel generates less lint. Plus, by then you’ve added more compound, and the binders in the compound tend to hold the wheel together. But in general, the lint and dust is normal for buffing. It’s one big reason why fixed buffing motors are usually fitted with a dust shield and vacuum system to suck up the lint and polishing dust. With a flex shaft system, you can approximate this, to keep your work area cleaner, by setting the hose of a shop vac or vacuum cleaner behind your buffing area. It’s noisy, but it will help. In either case, be sure to wear a dust mask to keep from breathing in the lint or buffing dust. Without a good dust collection system on a buffing setup, you’d otherwise end up inhaling a good deal of the dust, if not the lint, and that’s not a good thing.
By the way, felt wheels and brushes are also good ways to buff, each having different capabilities and results. Both felt wheels and brushes are mostly free from the lint problems, though both still generate buffing dust (the brushes especially). Felt wheels are the cleanest to use in this regard, are quicker cutting, but harder to use especially if you’re trying to get an existing smooth surface polished, since felt wheels cut more, and tend to give their own shape to the surface, rather than following the existing surface. This is good if you’re trying to get a nice sharp flat edge on an object that is starting with a sanded or ragged edge, but not so good if you’re trying to keep the original curves and contours.
In general, you polish at the highest speed that’s possible for your machine. Higher speed doesn’t reduce the quality of polish, and works faster. What you’ll want to do as you approach the final stage is use less pressure, and less compound. If you wish to reduce the speed, then do so, but that’s up to your personal preference. Remember that most pros polish on full-sized buffing motors, and these run at fixed speeds. On those, if you want slower buffing action, you use a smaller buff, but you’re already using small buffs, so you’re not getting very high surface speeds on the flex shaft anyway. The finer rouge compounds (red is the finest) give a higher polish due to the composition of the rouge. They have a slower cutting rate, which correlates with their finer particle size. You don’t need to slow down unless you find that it’s simply cutting too fast for you. Some work on fine details will require you to slow down so as not to buff off too much, but I doubt this is an issue for what you say you’re doing.
Also, with either setup, do some reading on proper polishing technique. Buffing and polishing can, in a beginner’s hands, be one of the most dangerous processes in a jewelry shop. Almost all of the most serious accidents I’ve seen in the jewelry business have involved buffing and polishing. That means danger to both the jewelry, and to the person doing the work. In particular, pay attention to how you hold the piece, so if the buff grabs it, it can be pulled out of your fingers without taking the fingers along for the ride. Pinch the work between fingers, don’t loop fingers fully around an item, for example. And present the work to the buff so the buff is moving “off” the item, not “onto” or “into” an edge, which is then more easily snagged and pulled. Cloth buffs are the most dangerous. Felt wheels and brushes are much less likely to snag. But you can’t get away from a cloth buff entirely. For the final finish, a soft unstiched muslin buff will give the finest and highest polish.
By the way, do be careful with buffing watches. If you don’t have some decent level of knowledge about watches, you can do a lot of damage both to the watch and to its value with indiscriminate buffing. In particular, in many cases, the watch movement should be removed before the case is buffed up, or you won’t be able to properly clean the buffing compound off after buffing. For what it’s worth, know that many jewelers who’ll happily repolish old jewelry will refuse to go anywhere near a watch unless the person requesting it is a watchmaker who’s able to disassemble the watch for buffing, and reassemble it later, and has the knowledge to choose which watches are suitable for this treatment and which are not.
As I said, most pros would be leery of buffing many watches, but for those that do need buffing, most pros use a fixed polishing lathe. That term describes a fixed larger motor, with tapered spindles, usually mounted with a dust collection setup. Flex shafts are good for doing touch up polishing on small areas, often prior to doing the rest of the polish work on the full-size machine, but about the only jewelers who’re polishing the whole piece with a flex shaft are the ones either doing such small detailed work that nothing else is needed, or those who simply don’t have a proper buffing machine. That’s not uncommon with, for example, students or those just starting out. But the simple fact is that for most buffing, it’s safer, faster, and more effective to use the larger machines.
by Peter W. Rowe M.F.A., G.G.