Hock on sharpening: a turner’s perspective
Here are some comments from a turner’s perspective on Ron Hock (2009) The Perfect Edge: The Ultimate Guide to Sharpening for Woodworkers (Popular Woodworking)
The sharpening bible for me has been Leonard Lee’s book (1995) Complete Guide to Sharpening (Taunton Press) which is written in a clear and enaging style. It’s one of the rare technical books I’ve read cover to cover.
Both Hock and Lee are renowned makers of edge tools and both books cover a wide range of tool sharpening methods. Both books reproduce microscopic images of tool edges which bring sharpening into the realm of evidence based practice and out of myth and folklore. I have three Veritas (Lee) planes which are beautifully made, and one of Hock’s plane irons in a Stanley #6.
Lee’s chapter on turning tools however suggests a less than close acquantance with the craft but makes the fair point that the topic deserves a book in its own right.
Hock also makes the fair point that turning is machine work in which the operator holds the blade while the machine moves the work, and so the demands made on the tool will far exceed those made on bench chisels and plane irons. Being more recent, Hock does justice to the many commercial sharpening jigs and machines now available. He acknowledges the greater innovation in turning tool production than in flatwork tools. Indeed, powder metalurgy, cryogenic treatment and exotic alloys are now available to us. Doug Thompson in the US is producing affordable cryo treated tools with a high vanadium content to reduce abrasion damage to the edge.
And indeed turners do expect more from their tools than other woodies. We want to remove more wood between sharpenings; our edges take a pounding particularly with truing faceplate blanks; and many hundreds of times a minute when turning a bowl our edges may alternate between cutting long grain, cross grain and end grain. Our toolshafts sometimes extend considerable distances beyond any support and edge chatter is not uncommon.
Hock will raise some eyebrows with his assertions that a standard grey grind wheel will work fine for grinding, with care, and that cooling a tool with water between passes on the wheel will not cause damage.
Both Hock and Lee cover the sharpening of various kinds of turning tools including bevel angles. Hock’s chapter has extensive phtographs covering machines and jigs. Lee’s goes into more detail, with useful drawings of gouge grinds and types of parting tools. He provides a sketch of a simple home-made angle setter for a grinder platform.
What is disappointing in the Hock chapter is its ignoring of the studies done on the value of fine grinding and honing of tool bevels. He simply states that most woodturners use their tool off the dry grinder, and while this is true, an ‘ultimate guide to sharpening’ should be focussing on leading edge treatment (ahem). The seminal comparative test was done some years ago by Robbie Farrance and published in the UK mag Woodturning, issue no. 70. More recent studies, published in American Woodturner, were probably not available to Hock when he was writing, but they confirm that finer edge treatments cut cleaner and last longer than those straight off a dry grinder. And Lee’s book makes the same point.
A gap remains on test-based treatment of scrapers. On the Australian WW forum I’ve posted microscopic images of dry ground and burnished edges, and a practical test of those, along with top-lapped treatment, is still on my to-do list. In a recent article in Aust Wood Review, Raffan opts for top-lapping. Lee is a fan of rolling an edge with his burnisher; I’m still experimenting with this as such an edge requires a different technique: faster lathe speed and more careful tool presentation. And my images revealed that while the burnished edge is more even than a burr, it was by no means consistent across the full edge. Maybe that’s my lack of skill.
The matter of turning tool sharpening is complex, involving metallurgy, wood grain structure orientation and composition, bevel geometry, tool presentation, and speed pressure and heat in cutting. Our edges have to penetrate fibres (either by crushing and breaking or by severing), lift and separate them from their neighbours, all at high speed.
Anyone with a general interest in sharpening will find either Lee’s or Hock’s book of great benefit. I find overall that Lee’s book is a richer source of insight and techniques. But IMO turners would benefit more from Darlow’s Fundamentals of Woodturning as a starting point for their sharpening journey and then consult Lee.
There appears to be a tendency for turners to jump from dry grind treatments only to the expensive Tormek system. That system is actually two technologies: slow, fine reverse wet-grinding followed by honing, and an extensive set of jigs to hold tools. We can learn from flatwork ‘darksiders’ that the two need not be sourced in the one package. Here are some off-the-cuff ideas. Jigs can be placed in front of any array of abrasive types and carriers, eg. fine grit dry grind wheels followed by honing wheels using bench grinders, workheads or indeed the lathe as the power source. The Tormek Bench Grinder Mount opens up just this possibility but any 12mm rod and some metal butchery will take Tormek, Jet or Scheppach jigs. A Tormek or Scheppach profiled leather honing wheel, or home-made MDF wheels, can be charged with Aluminium Oxide compound (better than Chromium dioxide for HSS acc to Lee) and mounted on the lathe or drill press. And of course there are flat stones and slipstones of varying grits. An alternative commercial method of honing on the lathe is the Sorby system.
For someome with a talent for tinkering, a Scheppach wet wheel can be had for $55 here in Australia from Hare and Forbes and be mounted in a home-made rig with bath. IME this wheel cuts quicker and with less clogging than a Tormek. It will wear quicker too but is only a fraction of the big T cost.
And why would you bother with all this? To get the best possible finish off the tool. The 60 grit ‘tool’ is tedious, a threat to fine detail, and wood dust is carcinogenic.