Odie
Panning for Montana gold, with Betsy, the mule!
There is a reason why router and shaper bits are run at super high speeds.....speed makes for a cleaner cut until the sharpness of the cutting edge is the undermining factor. Another consideration is carving tools are used in a extremely slow cutting speed, comparatively speaking. If a carver is getting clean cuts, the sharpness is the most important determining factor, along with direction of cut according to wood grain (presentation). A lathe turner doesn't have the luxury of high rpm, so an equilibrium between speed and sharpness is a critical factor. Most bowls are done "cross grain", and because of that, there is more resistance to the cut with the end grain, than it has with the long grain. There is nothing you can do about this, but you can minimize it's effect on your ability to get the cleanest cut possible.
Another consideration, is the inherent vibration at a given rpm, compounded by the harmonic vibration created by the cutting edge as it cuts the wood. These things must be taken into consideration, as well......because any vibration of the wood at all, will prevent a sharp cutting edge from achieving the cleanest cut that is possible under the most desirable of conditions. You may not achieve the most absolute perfect of conditions, but getting as close to it as possible should be the goal. Generally, the faster the rpm, the more potential for high intensity vibration there is to spoil a cleanly executed cut.....this would be the inherent vibration between spinning wood, and lathe ability to absorb it......while the harmonic vibration can be felt, seen and heard through your senses. One source of vibration can be adjusted through variation of rpm, while the other can be manipulated through adjusting tool presentation while in the act of turning.....(this is the heart of spiritual turning)
As a newbie, I tended to run lathe rpm at speeds that I'd currently consider potentially hazardous.....but, surface speed does allow a cleaner cut with a tool that isn't as sharp as it could be. A newbie might think this is his "eureka" moment, but he still has a few things to learn yet! At the very center of the foot, or very center of a bowl interior, you should be able to get a clean cut right up to the very center. This is the kind of sharpness that carvers expect, and if you can't do that, then you either didn't start with a sharp enough tool, or you have let it get too dull before taking a trip back to the grinder (or re-hone).
The equilibrium is reached when a combination of best rpm, sharp tool, best presentation, along with using your senses to make presentation adjustments as necessary.
-----odie-----
Another consideration, is the inherent vibration at a given rpm, compounded by the harmonic vibration created by the cutting edge as it cuts the wood. These things must be taken into consideration, as well......because any vibration of the wood at all, will prevent a sharp cutting edge from achieving the cleanest cut that is possible under the most desirable of conditions. You may not achieve the most absolute perfect of conditions, but getting as close to it as possible should be the goal. Generally, the faster the rpm, the more potential for high intensity vibration there is to spoil a cleanly executed cut.....this would be the inherent vibration between spinning wood, and lathe ability to absorb it......while the harmonic vibration can be felt, seen and heard through your senses. One source of vibration can be adjusted through variation of rpm, while the other can be manipulated through adjusting tool presentation while in the act of turning.....(this is the heart of spiritual turning)
As a newbie, I tended to run lathe rpm at speeds that I'd currently consider potentially hazardous.....but, surface speed does allow a cleaner cut with a tool that isn't as sharp as it could be. A newbie might think this is his "eureka" moment, but he still has a few things to learn yet! At the very center of the foot, or very center of a bowl interior, you should be able to get a clean cut right up to the very center. This is the kind of sharpness that carvers expect, and if you can't do that, then you either didn't start with a sharp enough tool, or you have let it get too dull before taking a trip back to the grinder (or re-hone).
The equilibrium is reached when a combination of best rpm, sharp tool, best presentation, along with using your senses to make presentation adjustments as necessary.
-----odie-----
