Simple Guide To Sharpening Lathe Tools
Just as important as learning how to use lathe tools is learning how to sharpen them. Here you'll discover the basics of sharpening lathe tools.
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Woodturners create round or cylindrical objects from wood with a lathe. Having the right lathe accessories is critical to woodturning success, but buying tools like a roughing gouge, bowl gouge, skew chisel and others is only the first step.
It’s just as important to keep those tools razor sharp and in good working order. Dull woodturning tools won’t carve shavings properly as your workpiece spins, leading to rough, unsatisfactory results. If you’re interested in giving woodturning a try, keep reading for a detailed guide on sharping lathe tools.
Tools and Materials for Sharpening Lathe Tools
Sharpening lathe tools is precise, skill-dependent work. With the right equipment and approach, anyone can learn. But there are lots of ways to mess up if you attempt to sharpen without the right tools.
Give yourself every chance of success by investing in the following pieces of equipment:
A must for all sharpening jobs involving a grinder.
You’ll use this on nearly every lathe tool you sharpen. More on this later.
Bench-top grinder with adjustable tool rest table
A good bench-top grinder is the foundation of all your lathe tool sharpening work. Get one capable of slow speed (around 1,800 revolutions per minute). Choose a well-reviewed model with a solid base that can be bolted or clamped onto your workbench. And be sure the grinder you choose has a wide, adjustable tool rest table built in.
Cool grind wheel
I always sharpen my lathe tools with a cool grind six-inch aluminum oxide wheel. Cool grind means the stone is softer than typical grind wheels, so it won’t heat your tool as quickly. There’s a tradeoff: Cool grind wheels wear out faster.
Lathe tool sharpening guides
These grinder accessories aren’t strictly necessary, but they’ll make it much easier to set and maintain the correct sharpening angle for your various lathe tools.
Wheel dressing tool
If you sharpen steel tools regularly with any sort of grinding wheel, you’ll need to start by dressing the wheel with a diamond-faced dressed tool. Dressing restores the flat, crisp edge of the wheel and removes bits of steel that worked their way into the pores of the stone. This process is necessary to keep your wheel sharpening properly.
Tools with a bevel on only one side (mainly gouges for woodturning) sometimes form small burs of steel on the back of the blade during sharpening. Leaving these will limit your tool’s sharpness, which is where slip stones come in. Use them with a bit of water to wear that bur away as a final step after grinding. I find a 1,000-grit water stone works well for this.
How To Sharpen Lathe Tools
You’ll know your lathe tools need sharpening when you notice small, ragged tears in the fibers of the wood you’re turning. Another sign: If your tools can’t slice a sheet of paper cleanly, with no tearing or resistance, they need sharpening.
The two biggest dangers are letting your tools get too hot as you hold them against the grind wheel, and sharpening at the wrong angle.
Never leave any lathe tool in contact with the grind wheel longer than 10 seconds. Too much heat could permanently soften the steel, preventing the tool from holding a razor-sharp edge. Grinding the bevel of a lathe tool at the wrong angle risks making the edge too thin and delicate, or not sharpening it at all. That’s why being slow, careful and diligent is crucial when sharpening lathe tools. Precision really matters.
Here’s how it’s done:
- Weat safety glasses. Be sure there are no shavings, sawdust or other flammable material anywhere near where you’ll be sharpening. Sparks from the grinder could start a fire.
- Dress your grinding wheel for several seconds with a flat stone dressing tool until the surface is perfectly flat and the corners crisp. Be sure there’s no metal residue remaining from previous sharpening jobs. The flatness of the dressing tool will shape the wheel correctly, as long as you hold it firmly and squarely against the wheel’s surface. You’ll know when the metal residue is gone because the surface will be clean, evenly colored and porous.
- Color the beveled edge of your tool with a permanent marker. This bevel will form a specific angle — around 40 degrees for most skews, 30 degrees for a roughing gouge, 50 degrees for a bowl gouge and 40 degrees for a flute gouge.
- Hold the tool firmly against the tool rest, adjusting the rest so it’s 1/16-inch from the wheel. Position the tool to gently touch the grinding wheel with its beveled edge. If you have a set of lathe tool sharpening grinder guides, this is the time to set them up for the tool you’re sharpening first. If not, you’ll need to set the tool rest table to the correct angle, then ensure you hold the tools firmly against it as you sharpen. This method takes more skill and care than using guides, but is certainly doable if you take your time.
- With the grinder turned off, turn the wheel slightly by hand. If the wheel scratches off the marker across the entire bevel, you’ve set the tool rest angle correctly. If not, adjust the angle until it does.
- With your tool rest table locked in place at the correct angle, pull the tool away from the wheel slightly and switch on the grinder.
- Holding the tool firmly against the tool rest with your thumb and move it back and forth slowly with your other hand, pressing moderately against the grinding wheel. The exact movement varies by tool. For skew chisels, it’s a gentle, side-to-side movement. For gouges, it’s a medium-speed rotation from one side of the rounded beveled edge to the other.
- Remove the tool frequently during sharpening and test its temperature with your finger. It should never become too hot to the touch.
- Sharpen each tool for no more than 30 seconds total before trying to slice a sheet of paper. That should be enough.
- Finish your gouge sharpening by running a round-edged water slip stone through the concave section at the back (the flute) to remove any burs that formed during grinding.