Flat or Hollow grind

[Paul Stroik]

Which is better for turning tools - Flat grind or Hollow Grind. I use a Tormek on all of my tools. But have heard that Flat grind is better for riding the bevel. ?????

Any turners out there who flat grind their tools?

[Malcolm Tibbetts]

Paul, I actually freehand grind on an eight inch wheel in order to shape a very slight convex surface behind the cutting edge. It's unusal and takes a little getting used to, but it works for me. The big difference from the more common hollow grind is my "bevel riding" surface is immediately behind the cutting edge, not a 1/4" away. To my way of thinking, rubbing the bevel on a hollow grind increases the chances of bruising the wood fibers.

[JerHall]

not "riding" it or polishing or bruising the wood.

The classic reason for a hollow grind (apart from the fact that it is a natural result of grinding on a wheel) is that it makes accurate hand honing a breeze by bridging between the front edge and heel. This saves me many trips to the grinder, adds life to the tool, and allows me to touch up the edge to a fine degree for final, key, cuts. This is as taught by Alan Lacer.

Convexity has its advantages in being able to turn inside corners without dragging the heel it seems to me, but does ask for better tool control, and makes honing tougher. An alternative is to have a second or third hollow ground tool on hand, each with a steeper grind on hand to do such cuts, like the bottom of a bowl. That is what I use my cheap Penn State tools for, since they get relatively light use. I like being guided by a long bevel. It can also help to relieve the heel a bit to make a smooth cut while turning the corner; but I grind the relief in a consistent way, with a jig, so I can hand hone accurately.

Just a perspective. Any tool with an edge can work in many situations. It just takes practice and confidence. I turned a spin top recently with an old Plumb roofer's hatchet. I kinda liked it. Like a skew with a right angle handle.

[Tom Wilson66]

The best bevel for the tool is the one you like to use. Personnaly, I grind my tools, then use a hone to sharpen between grindings. Except the skew, which I only hone. So, when fresh off the grinder the bevel is hollow, after a few honings, it is flat at the cutting edge (1/4" away from the edge the chisel does not touch the wood), so I use both hollow and flat on the edge from one grinding to the next. Can't say I notice a lot of difference, but some people apparently do. So, again, do it your way.

[Kim Ford]

There are many camps on both sides of this issue and I don't think either way is right or wrong. I think what is more important is that you have the right style of grind for the cut you are making at the moment, that your tool is sharp and presented properly. Then decide whether flat or hollow is your choice.