Pneumatic Sanders: A Cushy Way to Smooth Curves
For sanding curves and contours, it's hard to beat a pneumatic sander. These inflatable sanding drums conform to curves, so you're a lot less likely to flatten a flowing form when you only want to smooth it. Use these tips to put a pneumatic drum sander to work in your shop.
You'll get pumped up for sanding with this drum You'll probably spend in the neighborhood of $70-$80 on a pneumatic drum sander. When you buy the drum, you need to know whether you'll use it on your lathe or drill press. Most drums come with a mandrel for lathe-mounting; some require an adapter kit for drill-press use.
Before you inflate the sanding drum, slide the sanding sleeve onto it. (Replacement sleeves cost about $15 for five.) Inflate the drum until it feels firm, but not solid-drum hard. Later, you can bleed some air to fine-tune the firmness to the job at hand.
A valve-stem extension (available from an auto-parts store) makes inflation easier on some drums. We sliced about 1⁄8 " off the bottom of the plastic extension so it would screw onto the stem and fit down into the hole around it, as shown at left. After inflation, remove the valve extension, and cap the valve stem to keep sanding dust out.
A bicycle pump, left, works fine for inflating the drum—it only takes a few strokes. Beware of high-pressure air from your shop's air compressor; you might blow out the drum's air bladder.
Pneumatic Sanders: Simple to set up
It's simple to set up your new pneumatic sander You can install a pneumatic sanding drum between centers on a lathe, as shown at below, or chuck it in a drill press as shown above. Drum installation is relatively easy, following the manufacturer's instructions.
A typical pneumatic sanding drum comes with a mandrel for lathe mounting. A fitting at one end features diametric kerfs to engage the lathe's two-or four-prong spur drive center.
For the tailstock end of the one shown (from Woodcraft Supply, 800/535-4486), the manufacturer suggests you cut off the tenon on the nylon fitting supplied for the tailstock end, and support the drum end with a rotating tail center. For surer centering of the drum, we turned a simple tailstock fixture to receive the fitting's 3⁄8 "-diameter tenon, shown in the photo above and the Tailstock Bearing drawing. (For continuous or heavy use, using the rotating tail center would be better.)
For drill-press mounting, chuck the tenon on the drum's top fitting into the drill-press. To keep the drum running true, be sure to clamp the bottom support fixture supplied with the drum firmly to the drill-press table. (For our drum, we drilled a hole to receive the drum-end pin in a piece of scrapwood large enough to clamp at both ends, shown below.)
Now, you're ready for some contour sanding Run the drill press or lathe at 1,200 to 1,400 rpm for sanding with a pneumatic drum. The soft surface can make the drum grabby, so hold the work firmly. Sand on the lower front quadrant of a lathe-mounted drum. And remove the lathe's tool rest for sanding; don't try to brace the workpiece against it.