Thread: Flat Grind Versus Hollow Grind

Compared with flatware workers, turners tend to use higher grind angles. This is about edge durability.

One wrinkle with low nominal grind angles is that the smaller the wheel the lower the actual angle is near the tool tip - cos of the greater hollowing effect. This can make a diff. down at the 25 degree mark; less so at higher angle all other things equal. That is something to consider with bench chisels and plane blades where you're aiming for the lowest grind angle consistent with edge retention.

One thing that we share with flatware workers is that when we skew bevel-rubbed edge, typically a skew chisel, the cutting angle is effectively lowered for a given grind angle.

As for hollow v flat bevels, it seems this debate has been around for a while, and there are some turners whose views I respect who are convinced that flat is the way to go.

When the Xmas madness is over I'll do some more tests. I'm not expecting to find much difference but remain open; and say that cos in a lot of my turning I'm making unconscious adjustments to the variables in play. It would be interesting to have some testing done by a newbie.

Originally Posted by rsser

Compared with flatware workers, turners tend to use higher grind angles. This is about edge durability.

One wrinkle with low nominal grind angles is that the smaller the wheel the lower the actual angle is near the tool tip - cos of the greater hollowing effect. This can make a diff. down at the 25 degree mark; less so at higher angle all other things equal. That is something to consider with bench chisels and plane blades where you're aiming for the lowest grind angle consistent with edge retention.

One thing that we share with flatware workers is that when we skew bevel-rubbed edge, typically a skew chisel, the cutting angle is effectively lowered for a given grind angle.

As for hollow v flat bevels, it seems this debate has been around for a while, and there are some turners whose views I respect who are convinced that flat is the way to go.

When the Xmas madness is over I'll do some more tests. I'm not expecting to find much difference but remain open; and say that cos in a lot of my turning I'm making unconscious adjustments to the variables in play. It would be interesting to have some testing done by a newbie.

Ern

Thanks for that.

It was what I was expecting, but because I do minimal turning (tools handles are 99% of it and no bowls at all) and about half my tools are home made from spring steel I don't really have a good basis to make judgements.

Regards
Paul

Originally Posted by Bushmiller

... but not as sorry as he will be if the guard should suddenly wear through .)

l

.......

This by rsser:

When the Xmas madness is over I'll do some more tests. I'm not expecting to find much difference but remain open; and say that cos in a lot of my turning I'm making unconscious adjustments to the variables in play. It would be interesting to have some testing done by a newbie.

And the reference to Richard Raffan's multifaceted bowl gouge leads me to say:

I think that when a person starts turning and have had no hands on training, but have done a lot of reading they will have a tendency to sharpen the perfect, endorsed by Famous Turner tool at a given number of degrees of angle, on the perfect grinding system, and present the tool to the rotating timber at the prescribed angle, and wonder why it doesn't make those bushels of streaming curlys like the guy doing the demo.

After a person has spent hundreds, or thousands of hours, at the lathe they can grab most any tool, give it a few swipes on a reasonable grinder, present it to a rotating piece of timber and make a stream of curlys.

After a person has spent enough time turning they do not think about angles, but present the tool and adjust up or down, twist left or right, and it cuts.

It becomes unconscious, automatic, and one does not even have to look at what is going on. It can be felt.

Maybe in 100 years that will come to me with the accursed skew. I make 25 bowls for each spindle. The only spindles I make are tool handles for myself.

Wolverine Grinding Jig & Accessories

An oft quoted line used by me at the start.

Originally Posted by

....An oft quoted line used by me at the start.

You must mean this bit.... "Professional turners don't behave in a predictable fashion" . . . . . or maybe my speed reading missed something!

Originally Posted by Paul39

After a person has spent enough time turning they do not think about angles, but present the tool and adjust up or down, twist left or right, and it cuts.

It becomes unconscious, automatic, and one does not even have to look at what is going on. It can be felt.

There in lies the answer to this whole discussion.
Jim

Not having read back through all the posts, is it the case that only one post reports a side-by-side comparison?

See also post #53 here: https://www.woodworkforums.com/f8/rob...ml#post1585407

With a couple of skews now with bevels ground flat (in the interlude between Xmas shopping and cooking) I'd offer some more observations.

Note, these are 'end-on' tests, not side by side. The skews were 1/2" and 1.25" with a straight cutting edge.

Planing cuts were easier to control.

Shallow curves were distinctly easier to form.

Found no diff. with shallow V cuts.

Beads: hard to tell. With me rolling beads is mostly about confidence and that varies day by day.