Thread: Flat Grind Versus Hollow Grind

Jim posted: Geez , I hope those parts come tomorrow, the stress cracks are starting to show...

Can only be microfractures.

Macrofractures = a rant and is too much the gent for that.

Good wrap , thanks.

There is a group that debate, argue and discuss the process.

And then there is another group that actually do it.

Which group you belongem?

Cheers

Tim

Originally Posted by Tim the Timber Turner

Which group you belongem?

I do, when I can.

When I can't, I ask.

And, if I'm asked, I say what I can do.

But, don't mind a discussion when I'm not doing...

Originally Posted by artme

I keep having trouble with Windows Explorer making and keepin g contact withe forua.

I posted on this yesterday and it obviously fell ver the edge.


To me it stands to reason that a flat grind - at the correct angle of course - will be sturdier and longer lasting.
After all is has more metal supporting it.

It may be your Internet Service Provider. Mine is ATT and at noon or quitting time I cant get on or it drops out.



Mozilla Firefox is a better browser. Mozilla Firefox Web Browser

A few things must have Explorer to work.

Originally Posted by NeilS

I do, when I can.

When I can't, I ask.

And, if I'm asked, I say what I can do.

But, don't mind a discussion when I'm not doing...

LOL. So to bookend your thread Neil (you can't get off so easily despite the wisdom and wit!) what's your take on the issue you raised?

Originally Posted by rsser

So to bookend your thread Neil ... what's your take on the issue you raised?

1. With only a few exceptions, most of us have not actually used a flat grind on which to base our comments, me included.

2. Some hand hone the tip and heel flat on their concave grind and offered comments based on that being a short flat bevel. However, at that length the difference between a flat and concave grind would be infinitesimal.

3. There was mixed views on flat vs concave bevels on skews. Our most experienced spindle turners prefer a concave grind.

4. Most saw a concave grind for turning the outside of bowls an advantage.

5. Most saw single grinds (concave or flat) as a problem on the inside of bowls. Some resort to grinding off the heel while others just use a smaller gouge for 'turning the corner'.

6. There was discussion on grind angles, the most significant point (IMO) was that a flat grind will change the bevel angle (slightly more obtuse) which should be taken into account. 's comment, "angles really don't matter as long as the tool is sharp and you have the ability to change to suit the angle", summarises my own take on this.

7. Discussion on honing to create a sharper edge and saving trips to the grinder, although of interest, was off-topic. It is understandable that it came up as it was raised by the Jon Siegel article.

8. There were other points that were raised which were also off-topic, many of them valuable in themselves, but again didn't throw any light on the primary topic.

9. My conclusion from the discussion is that there are some advantages to the concave grind, but that they are not so significant to make it indisputably better. An experienced turner should be able to adapt to a flat grind.

Thank you everyone for their contributions.

By oversight I've ended up with 2 of 3/8" beading and parting tools, both with fairly long bevels. One was done on the Sorby ProEdge and had a flat bevel, the other was hollow ground with an 8" grind wheel.

So for a test both got a lick or two on each bevel with a very fine diamond hone to take off any burrs. I do this with any tool that's got to cut Radiata Pine or other softwoods cleanly.

I cut flats on a spindle piece of that Pine with light fine peeling cuts.

My immediate impression was that the flat bevel was easier to control.

Then I alternated between the two and found no difference.

Maybe the initial impression was a Hawthorne effect. Maybe I'd unconsciously compensated for the hollow grind when alternating.

Inconclusive but interesting.

Is life too short to get worked up about the potential differences? Definitely.

Originally Posted by rsser

Is life too short to get worked up about the potential differences? Definitely.

Some get rather passionate - like Holden vs Ford!

Originally Posted by rsser

Is life too short to get worked up about the potential differences? Definitely.

Agreed.

Thank you for sharing your test run observations, Ern.

Originally Posted by

You did ask!

My mind is boggled. (response to 's epic post. Shortened version as my Irish computer only has a single page on screen). .

Your comment conjured up two recollections from the past. The second I have to research so I'll give you the first.

Robert Mitchum was interviewed by a journalist, who was quick to point out that it normally took two people to interview him as he had a reputation for being unpredictable and the forerunner of WPHS required backup.

For one page of the publication (I think it was "Private Eye," but not certain) RM was clearly disinterested and monosylabically replied "Yep" or "Nope" to an array of questions.

Then the journo asked him what was the strongest alocohol he ever drank. Mitchum spoke for two pages without stopping. You just had to get him on his subject.

Digression over. Back to the sharp end. I enjoy these discussions.

Regards
Paul

Originally Posted by

You did ask!


This discussion reminds me of the man watching his wife prepare the leg of lamb for roasting. She always cut off the shank and roasted it seperately.

"Why do you cut the shank off and roast that separately?" he asks.

"My mother always did it that way," comes the reply.

A week later he is around at the Mother in Laws and asks the same question.

"Why do you cut the shank off and roast that separately?" he asks.

"My mother always did it that way," comes the reply.

A few weeks later they are round at Grandmas house and he asks the same question.

"Why do you cut the shank off and roast that separately?" he asks.

"Because it wouldn't fit in the roasting dish with it on!" comes the reply.

The point of this is to show that some things are done through habit to suit a purpose that is no longer applicable.

Another exert from 's epic. I recalled my second recollection.

An experiment was conducted with five monkeys in a cage. Bananas were placed at the top of the ladder but anytime one tried to climb the ladder and grab the babanas all the monkeys were doused with freezing cold water. Soon the monkeys grabbed any simian rash enough to climb the ladder and hauled him back down.

Then the water was disconnected but the monkeys continued to self-police. Even when monkeys were replaced the newcomer was prevented from getting the bananas by the others.

Eventually none of the original monkeys remained but still any newcomer was restrained from going up the ladder. If asked why, the monkeys said,

"This is how we've always done it."

The analogy of course is the resistence to change. I guess we all need to keep an open mind and in the case of sharpening techniques and systems there may be no right answer for all situations. Sharpening like most things in life is a compromise.

Regards
Paul

(PS. (I'm out of white out) I like 's analogy, in no small part because I really like lamb shanks .)

Don't get me started Paul. Change theory and practice is a very interesting subject
and one subject to heated debate.

Originally Posted by artme

Don't get me started Paul. Change theory and practice is a very interesting subject
and one subject to heated debate.

Arthur

I agree entirely, but it wasn't my intention to hijack the thread. It was just a couple of tiny digressions inspired purely by 's epic reply.

I am hoping I am allowed tiny digressions. If not, my backup plan is a tendency to absentmindedness, which, unlike wine, is not improving with age.

If none of that is acceptable, I plead temporary, total insanity .

Regards
Paul