Sharpening a V-tool
Q: I rely heavily on V-tools, but when it comes time to sharpen them I’m never satisfied with the job I do. Is there a formula of some sort for this tricky sharpening task?
Ken Kupsche responds:
Most carvers consider V-parting tools among the toughest chisels to sharpen, but they’re not if you work methodically, with the right tools and a steady hand. I generally find that when it’s time to sharpen a V-tool, I’ve usually honed and stropped it far enough out of shape that it’s best to start with a clean slate. To do that, I carefully touch the cutting edge to the side of my grinding wheel (Fig. 1). Keeping the tool at 90 degrees to the wheel ensures that you get a nice, flat front edge to start sharpening toward. Only remove enough metal so that you have a complete section of the tool showing.
If you work with a light above and over your shoulder, you should clearly see a flat plane on the cutting edge when you examine the tool (Fig. 2).
Imagine this is no longer one tool but three: two chisels and a gouge. You’ll sharpen each tool independently of the others. As long as you work carefully all three will come together to form one cutting edge (Fig. 3).
Before you begin, you’ll need a fine wheel on your grinder, water (keep a cool tool or you’ll lose your hardness) and a jig to hold your tool at the proper grinding angle. I recommend a Wolverine Grinding Jig or similar shop-built unit. You’ll also need an angle checker, a variety of honing stones and a knife-edge slipstone.
Fig. 1 Carefully touch the cutting edge to the side of your grinding wheel at a 90-degree angle.
Fig. 2 Working with a light over your shoulder allows you to easily monitor your progress while sharpening.
Fig. 3 Imagine that you are sharpening not one tool but three: two chisels and a gouge.
Before you begin, you’ll need a fine wheel on your grinder, water (keep a cool tool or you’ll lose your hardness) and a jig to hold your tool at the proper grinding angle. I recommend a Wolverine Grinding Jig or similar shop-built unit. You’ll also need an angle checker, a variety of honing stones and a knife-edge slipstone.
Start by reshaping the major bevels of the tool. I usually grind my V-tools at 20 to 25 degrees. (Fig. 4) As you slowly grind, keep the tool cool by quenching in water and check the flat top to see your progress. Start with one of the chisel edges. Keep the width of that flat parallel across its entire length and stop grinding when you have about 1/64" of width left. Do the same to the other chisel edge. Now it’s time for the V point. Think of it as a very small gouge and gently roll the edge on your grinder. Move from one chisel edge to the next, watching the flat as an indicator of your progress. Stop when you match the chisel edges.
At this point I reset my jig to about 15 degrees and round off the heel of the tool. How far is just a matter of personal preference. Doing this makes it a lot easier to maneuver the tool when carving.
Grinding on the wheel is done. You should have a tool with equal bevels and edge thickness all around. Pull out your soft Arkansas stone and hone a micro bevel on all three edges. Start with one chisel, lift 5 degrees and take a few strokes. Move on to the other chisel edge, then the point (Fig. 5). Pull the burr from the inside of the tool with a knife-edge slip. A loose cloth buffing wheel can also be used at this point to quickly pull the burr and even put a final edge on the tool. Check your work with the light over your shoulder as you go. If you move slowly and methodically, you will end up with a tool that’s in better shape, and certainly sharper, than when newly purchased.
Ken Kupsche is a contributing editor to Woodcraft Magazine
Q: I love the color of purpleheart wood, but with time it turns brown. Is there a way to prevent this from happening?
Bob Flexner responds:
The color change you refer to is caused by oxidation, accelerated by light. I’m sure you don’t want to leave the wood in the dark all the time, but that is the only way to significantly slow the color change over a long period of time. The best thing you can put on the wood so that you can enjoy it in the light and have it retain its color for a while is a marine varnish that you can purchase at a marina. These varnishes contain a lot of UV absorbers (to protect the wood on boats out in the sun all day), and they will slow the color change for a while, but the absorbers wear out, like sunscreen. The problem is that you would have to build a thickness with several brushed-on coats to do any good, and the varnish is very glossy. My guess is that you want a very thin, non-glossy finish.
You will probably just have to live with the color change.
Bob Flexner is the author of “Understanding Wood Finishing”
Q: I bought a random orbit sander because I understood they didn’t leave swirl marks, but I can see them on my work. What gives?
Aimé Ontario Fraser responds:
All sanding leaves scratches. Some, such as those left by coarse paper, are simply easier to see than others. Achieving an apparently scratch-free surface depends on your sanding technique and your choice of grit.
If you’ve ever flipped a random orbit sander and watched the motion, you know it’s not random at all. The pad turns in a very precise pattern that looks like something you’d draw with a Spirograph. The loopy Spirograph circles go in all directions, and if you move the sander slowly they’ll swirl around one another until a truly random pattern of scratches results.
Hold your random orbit sander lightly; let its own weight do the work. If you press down too hard or move the sander too quickly, you’ll leave a trail of scratches that look like the loops you practiced when you were learning cursive writing.
Keep the sander in constant motion, moving all over the surface. I use a crosshatch pattern, first sanding from lower left to upper right, then from upper left to lower right, then back and forth across the grain, and finally with the grain. This ensures that the sander hits every inch of the work from a variety of angles.
If the paper is coarse, you’ll still see some scratches. Your job now is to sand thoroughly enough with finer paper to replace those coarse scratches with finer ones. And then you replace those with scratches that are finer still, until you reach the desired level of smoothness. If you keep sanding with ever-finer paper, the surface will go from dull to satin sheen. Use fine enough paper (something with a grit rating in the thousands) and you can achieve a mirror-polish finish.
It takes patience to refine the surface, even if you’re only going up to 220 grit. If you don’t sand enough with the finer grit, or if you choose a grit that is significantly finer than the previous grit, you’ll get a surface that immediately feels softer. Blowing away the sanding dust reveals deeper scratches that remain visible. That’s why you should always step through the grits when you’re sanding, and spend enough time with each to completely eliminate the deeper scratches from the previous grit.
How far you take these steps depends on the finish you’ll be using. If you’re merely painting the surface, you want a toothy finish for the paint to grab. For a super-fine finish you’ll use both a primer and an undercoat, so you needn’t worry much about scratches at all; 120 or 150 grit is more than adequate.
Stain will accentuate any deep or cross-grain scratches, so be extra diligent in your sanding. Hold the sander lightly and keep it in constant motion. Move slowly, but don’t stay in any one place very long. This keeps the scratch pattern uniformly random. Make sure each successive grit eliminates the prior grit’s scratches. Check the directions for the stain you’ll be using to determine the finest grit the manufacturer recommends, and when you’ve done that grit with the sander, do a final sanding by hand. For this, use a rubber or felt sanding block and sand with the grain for several minutes.
If your sander is working properly, following this sequence should leave no visible scratches. If you still see scratches, there’s something wrong with your sander. The eccentric weight might be loose, broken or incorrectly positioned, or perhaps the pad brake isn’t working.
Aimé Ontario Fraser is a woodworking instructor and author of “Getting Started in Woodworking”
