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I like to have many different shapes of carving wheels and points on hand and to have them available in coarse to polish grits. Most of the wheels and points I use and make are less than an inch across. I’ve developed a way to make them that involves very little equipment and time. You can create larger wheels, but for that you'll need a larger piece of equipment with a Jacobs chuck. The Jacobs is the style of adjustable, keyed chuck found on most power drills. I use a flex-shaft for much of my carving, although for a fixed arbor I use other equipment like a watch lathe. I make wheels using all different types of wood. To help you determine what wood you’ll want to use for your wheel, for the specific job you have in mind, see “Which Wood?” on page 32 of the July 2004 Lapidary Journal. |
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Placing the bur in the hole you’ve already drilled will give you a guide, but be sure to hold the wood quite tightly so the bur doesn’t fly out of the hole from centrifugal force.
Caution: Contrary to what you might expect, it is much more effective and far safer to run the motor faster rather than slower. If the wood piece is reasonably uniform in shape, there shouldn’t be any appreciable wobble. Run your flex-shaft motor around 12,000 rpm (about 3/4 speed on the standard Foredom® or Pfingst® flex-shaft), and slowly bring the square wooden wheel-to-be down onto the rasp so that only the corners barely touch. You will want to use only enough pressure to about duplicate the weight that gravity might exert at this early stage. Obviously you’ll want to position the wood so that the cutting edges of the rasp face into the direction of the cut. Start cutting the corners. Because you’re simply removing layers at the edge of the grain, this should go pretty smoothly. If your tool jumps at all and you’re sure the mandrel is straight, it is either because you’re not running your motor fast enough or you’re applying too much pressure. After a brief time, stop your shaft and examine your cut. The corners should be uniformly rounded.
Sometimes the rasp becomes clogged with wood splinters, especially with more resinous woods like lignum vitae or teak. You can use an old toothbrush or a wire brush to clean the file, but be aware that if you aren’t careful, you can dull the edges of the rasp’s cutters with the wire brush.
Change your cutting surface to the finer side of the rasp until the wheel is uniformly round and you can’t tell where the corners were. At this stage you can shape the edges of the wheel to your specifications; a cone, a reverse cone, a curve, etc.
Once you get proficient at making wheels, it should take less than half an hour. Good luck with the carving. To see a carving executed using these types of wooden tools, see page 33 of July 2004's Lapidary Journal. |
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Making a Carving Wheel
Inspect your piece of wood to make sure there are no impurities, knots, or cracks. You want the piece to be as uniform in consistency and weight distribution as possible. It should also be well seasoned so it won’t check or crack.
Cutting off your wheel.
After making sure that there is nothing unexpected on the inside of your slice (like a check or knot), measure it as close to a square as you can get and cut off the excess so you have a piece about a 1/4" thick and 1" square. At this stage, check to see how close you came in uniform thickness. If you want to adjust the thickness, you can sand the wood using a sanding disk or whatever tools you have available for sanding wood.
Once you have a good parallel square piece, take a straight edge and mark a diagonal line from corner to corner. Mark another diagonal line working from the other corners. You should have an X on the front of your square with the lines crossing fairly close to the center. This doesn’t have to be exact. In fact, unless you’re determined to have an exact diameter, it doesn’t even need to be that close.
You’ll be using a mandrel to hold your wood on the drill for shaping and then for attaching your finished wheels and points to your flex-shaft for use. All mandrels come in two parts, the mandrel itself and the screw that goes into it. The screw holds the wood in place at the top. Put the mandrel into the flex-shaft and run it, holding your finger gently on the mandrel, towards the screw end. If the mandrel touches your finger constantly as it spins in the chuck, that indicates it is straight. If it’s bent, it can be straightened, but until then it’s useless.
At the center of the X on your block of wood, drill a hole using the appropriate bur or drill bit to match the exact diameter of your screw from your mandrel. You want to be able to get the screw through the hole without allowing any play, but not have it be so tight that you have to twist hard — screws can be fairly breakable so be careful with this.
If your wheel is too thick for the screw to reach through entirely, you’ll have to countersink the hole. I use a round Dremel® bur for this, but a standard wood drill bit could work as well, although it’s not quite as easy to control the depth.
Once you’re sure the mandrel is straight and the screw will go all the way through and grab at least a third of the thread length in the shaft, mount your piece of wood on the mandrel.
Put on your safety glasses. Hold the flex-shaft handle firmly in one hand. With the other, tightly grasp your coarse wood rasp.
Because things cut more easily when there is less surface area in contact with the cutting surface, I usually change the angle at which the wood contacts the rasp. Using the same technique as in Step 9, continue to file off the corners of the now less-than-square wheel.
After a short while your wheel will approach round as the corners are removed.
For this final process I use a standard rattail file so the final surface is smooth. Be sure your file is clean. You don’t want to leave imbedded metal filings in the wood from an unclean file.
Now you’re ready to use your tool. Put a couple drops of oil extender on the wood to help seal it and accept the diamond. Then use a small dab of your selected grit of diamond paste which will imbed into the wood fairly quickly. Once you’ve decided on a grit for the wheel, it must be dedicated to that grit size only. And you must wash off your stone between grits or you’ll contaminate the next wheel with the wrong grit. Periodically you’ll need to add more extender and diamond grit to the wheel, but the basic wheel can last years.
