Why are sharp tools important?

It seems fairly obvious that sharp tools are necessary to be successful at woodturning, and very often a dull tool, or at least one that is not as sharp as it should be, is the reason for bad experiences. But have you ever considered why? I would like to suggest three reasons, though there may be others that I haven't identified yet.

1. The most obvious is that a sharp tool will cut the wood cleaner. The wood fibers are more likely to be cleanly sliced by a keen edge than a dull one.
2. A sharp edge can pick up a fine cut. A section through a sharp edge looks like two surfaces coming together at a fine point which is capable of removing fine shavings. When the tool becomes dull, that fine point becomes rounded off, and can only pick up a cut that is thicker than the rounded edge.
3. A smaller force is needed to push a sharp tool through wood. There is an equal and opposite reaction, the rotating wood trying all the time to throw the tool backwards. A dull tool will see a larger backwards force, and will be harder to control.

Item three is perhaps the most important. A tool that is difficult to control may not cut in the direction you want it too, making it difficult to refine the shape of fine curves. If you have to push the tool forwards, you may just end up pushing it up and over the wood you are trying to cut. And if the wood succeeds in pushing the cutting edge backwards, the bevel may lift off the surface and a catch may result.

Sharp tools and lathe maintenance

Every woodturner knows the importance of keeping their gouges and chisels sharp, but what other tools need occasional maintenance?

The two things that I tend to forget are drill bits and the tailstock. I do a lot of drilling on the lathe, typically several thousand operations a year. I use mainly brad-point bits when making bottle stoppers and weedpots. If the flutes of the drill bit get clogged with wood chips, the drill gets hot, and a lot of effort is needed to feed the drill into the wood. Sharpening a brad-point bit is quite straightforward on the grinding wheel, and uses less skill than sharpening a gouge. After touching it briefly to the grinder, check that both tips project equally far forward by holding the bit up to a try-square. Keep the angles of both bevels the same, and if the brad itself needs attention, be sure to keep its tip central.

I just sharpened my 3/8" bit today, and it now cuts cleaner chips and requires less force on the tailstock hand wheel to feed it into the wood. It feels like it is cutting better, and the chips seem to eject from the hole much easier. While I was in the maintenance mode, I also cleaned the flutes of the drill bit and even carefully gave them a polish with an old buffing wheel loaded with Tripoli. Anything that helps eject those chips is worth doing. I can now run the lathe a bit faster too.

One problem with using the tailstock for drilling is that it puts a lot of stress on the tailstock spindle where it bears on the striker plate. Periodically I strip down the tailstock and clean out all the mess and file away any scarf that has been thrown up. Recently I left it too long between services, and had great difficulty disassembling the tailstock. Its not a pleasant job, but much easier to do before the tailstock jams up. A good indicator that things are not quite right is if the tailstock spindle becomes hard to wind in or out under no-load conditions. I use powdered graphite as a lubricant, the same as I do for chuck maintenance.