How do I sharpen wood lathe tools?

Question

I've had a lathe for about a year now (I have the JET 1442 with variable speed) and love it but noticed that I really suck at keeping a nice sharp edge on my tools. I have a small bench grinder I use to sharpen them, but I still just can't seem to get a good edge on my tools. Any tips or advice?

Answer 1

Be very careful with the grinder. It is only used to establish the original critical angle and to take out nicks in the cutting edge. If you use too heavy a pass and the metal changes color (metal temper color - extremely light straw, you've started to mess up - blue or dull metal color, you've really messed up), you soften the metal and it won't keep an edge till retempered or ground past the area where the coloration occurred.

Once the angle is established, you use standard sharpening stones to keep the edge, they are much finer grit and establish a really sharp edge. On a properly maintained tool with an established angle, this part is a touch-up process, not a laborious grind, and may be done several times during a turning session if maintaining a really sharp edge is necessary.

After fine stone work, you can use a strop charged with buffing compound to remove the burr (wire edge) that results from a good sharpening session. I also just used the buffing wheel on the other grinder (always use the portion of the wheel where the surface is passing away from you so the point doesn't catch and throw the tool at you).

Answer 2

I use my bench grinder to get the shape of a tool right, but final sharpening is done by hand, on something like this Diamond Hone.

This gives me better control over sharpening angle and pressure than I would get with a grinder. Diamond cuts fast too, so there's no time penalty for doing it this way.

Answer 3

• Buy a jig if you can't hold the angle yourself. It may cost a bit, but sharp tools make things fun. On the other hand, dull tools sometimes make it dangerous. You end up pushing things.

• Buy tools with carbide tips. These are usually replaceable, have multiple edges, and take a long time to get dull anyway. (I make some of my own tools, where I'll use either a carbide insert, or a hi-grade tool steel insert. These can be bought cheaply online, and tossed out when they become too short for a new insert.)

• Join a local woodturning cub. They are full of people that will gladly teach you how to grind the proper angle.

Answer 4

While learning to hone your tools is nice, first concentrate on being able to use the grinder consistently. You can get by without honing anyway for all but the very finest work. The only time I bother honing turning tools is when I am making the final passes on a difficult piece of wood.

With the grinder you should always be using some kind of support. The flat supports that come stock with the grinder are usually kind of small but they will work until you decide to invest in a better grinder and/or sharpening jig. Use a black Sharpie marker to mark all along the edge to be sharpened. With the grinder turned off adjust the supports so they are titled at the angle you want to maintain on the tool. To check the angle hold the tool up to the grinding wheel, turn the wheel by hand, and check where the black marks are removed. This is also a good time to kind of practice the motion you will need to move the tool through if it has a curved edge.

When your initial angles on the tools are established and your supports are adjusted you should be able to touch up an edge in just a single quick pass or maybe two. You should be removing a minimum of metal from the edge.

Using a coarse grit wheel (I use 60 grit) will help keep down the heat to minimize the risk of bluing the edge. If you can adjust the speed of your grinder you can slow it down as well. There are a number of sharpening jigs for turning tools that aren't too expensive (or with a little work you can copy and make your own) that would be worth looking into if you want to do a lot of turning. I would suggest taking your tools with you to your local turning club, or a Rockler, Woodcraft or similar store where someone can help show you how to re-establish and maintain the angles on your particular tools if they are way off.