How to do Proper Sanding and French Polishing on Lathe Works

Sanding

While one of the main purposes of this article is to teach methods that eliminate excessive sanding, there comes a point in most turnings where some sanding is necessary. If you use the shear-cutting methods I’ve recommended, you should be able to start sanding for spindle turning at 150 grit or 180 grit rather than 60 grit or 80 grit, which would be the case if you were scrape-cutting. Sanding facework (in most woods) starts at a heavier grit-typically 60 grit or 80 grit.

SANDING SPINDLE WORK

When sanding spindle work, the piece remains in the lathe. For beginners, it makes sense to remove the tool rest, but experienced turners work around the rest by sanding at the back of the piece. Never use a whole (or even a large) sheet of sandpaper because it can wrap around the spindle and drag your fingers in with dire results. I always tear sandpaper into quarter sheets, then fold these in half.

For spindle turnings, I generally start with 1 80 grit and finish with 220 grit, although you can go as fine as you like. The main thing is not to skip grades of sandpaper or you’ll get scratch marks on the work. By using good spindle techniques, sanding is merely a final operation to remove fuzz and make things uniform in texture for finish. Once you’ve finished sanding, its a good idea to burnish a turning with a handful of chips to improve surface finish.

SANDING FACEWORK

Facework requires a good deal of sanding even when using textbook turning techniques. An experienced turner will spend as much time sanding facework as turning it. Start with 60-grit or 80-grit sandpaper to remove the tearout in the end grain, then work up through grades to the desired finish. A common sanding schedule might run 60, 1 00, 1 50, 220, and so on. If providence allows you to start at 80 grit, then the schedule might run 1 20, 1 80, 220.

Although hand-sanding works fine for spindle work, the best way to sand face work is with a flexible pad mounted in an electric drill. The rubber pad is flexible enough for most facework. There are various proprietary systems available, one of which uses hookand-loop fasteners to attach the sanding media to the disk. Another system uses sanding circles that are backed with pressure-sensitive adhesive. A third system has a metal or plastic clutch glued to the back of the sanding circle. All three systems allow quick changing of abrasive to work up through finer grades. With the hook-and-loop and clutch systems, coarser grades can be reused if they’re not expended.

Beginners should slide the rest back out of the way during sanding (top), but experienced turners can sand opposite the rest so they don't have to remove it (bottom).
Beginners should slide the rest back out of the way during sanding (top), but experienced turners can sand opposite the rest so they don’t have to remove it (bottom).
The easiest way to sand facework is with a sanding arbor mounted in an electric d rill. Here I am using a shop-built hook-and-Ioop arbor that has sufficiently resilient padding to sand with the finest of grits without scratching.
The easiest way to sand facework is with a sanding arbor mounted in an electric d rill. Here I am using a shop-built hook-and-Ioop arbor that has sufficiently resilient padding to sand with the finest of grits without scratching.

Holding the spinning disk against the spinning work makes sanding go much faster than if you were sanding by hand. Since the disk wipes at an angle to the direction that the piece was turned, it produces a smoother surface. The important thing to remember when power-sanding is to spend enough time at the coarser grits to remove all of the tear out.

All of the clutch and some of the pressure-sensitive adhesive sanding systems are unsuitable for sanding beyond 1 80 grit because at finer grits there will be circular scratches even though the surface becomes more polished generally. The reason is that dirt and oversize sanding particles occasionally counteract the action of the majority of the sanding particles in the paper.

The solution is to glue foam rubber (I use 3h-in. neoprene rubber) to an expended pad, then glue thin, flexible sandpaper to the foam. The resilience of the foam combined with the flexibility of the thin paper allows you to sand ultra-fine grades with ease. A thin piece of garnet or aluminum-oxide sandpaper glued to the foam rubber with photo-mount adhesive works splendidly. When the sandpaper needs changing, some heat from a hair dryer will loosen the glue joint so you can remove the sandpaper.

French Polishing

This is my favorite lathe finish. It is quick to apply and dries instantly-just the finish to use on Christmas Eve.

1. To French-polish in the lathe, apply a coat of the shellac mixture to the work with a small rag or a full brush. However, you apply the shellac, be sure to saturate the work completely-don’t worry if some of it dribbles onto the lathe bed. Brushes may be cleaned completely and inexpensively with a mixture of ammonia and water.

2. Remove the tool rest, stand aside, and start the lathe. You need plenty of speed-at least 1,700 rpm. Grab a handful of shavings and apply them with firm pressure to the spinning work. Turn the shavings often since they will become saturated with the excess shellac. The shellac will melt under the burnishing action of the shavings, leaving a pleasing French polish with none of the fuss, pumice, oil, and other assorted trappings of conventional French polishing.

3. French polish is a very thin finish, yet it is quite durable, except to prolonged contact with water, which will leave a white mark. To give the finish some water-resistance and further beauty, I apply pure carnauba wax to the spinning work. Pure carnauba, which is difficult to find, is very hard and shatters like ice if dropped. Crayon the wax onto the work (left) and finish by burnishing with shavings again (right).

4. The finished piece.

Finishing

Just as the lathe can be a great aid in reducing the drudgery of sanding, it can also help in the finishing process. In most cases, turned furniture parts will be finished with whatever is planned for the rest of the piece, and a considerable amount of time can be saved by finishing them right after they’ve been turned rather than when the piece is assembled. As outlined in chapter 4, it’s a good idea to reference the turned piece to the drive center with a mark. This mark allows you to rechuck the piece with each of the center tines in the same place and maintain centering. For example, if you wanted 12 spindles, you would turn them all first, then rechuck and stain, and finally resand and finish.

Using a small rag, you can wipe on stains and most finishes while the lathe is running at a low speed. I use a rag about 2 in. square, which is small enough so that it won’t pull your fingers in with it should it get caught in the spinning work-an important safety consideration. I often burnish an oil finish with shavings, usually about five minutes after applying the finish. Since burnishing with shavings wipes across the grain, there is good filling of pores.

One finish that’s easy to apply with the workpiece in the lathe merits special mention. This is a lathe-applied French polish, which gives all the beauty of the traditional method but takes much less time and bother. To French-polish turner-style, you need to use genuine orange shellac made from shellac flakes. The canned variety has preservatives and extenders to prolong shelf life, which render it unsuitable for French polish.

I mix my shellac in 200ml plastic camping bottles, filling each bottle about one-quarter full of shellac flakes and adding alcohol to just shy of the top. I shake the bottle well and shake again every hour or so until everything dissolves, then set it in direct sunlight for at least a day. The wax and impurities settle out. I decant the liquid, which is pure orange shellac, and throw away the sediment.

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