One Bevel, Two Bevels, Three Bevels, More?

[Trafalgar]

Charles,

I'm so sorry to hear that you are struggling with these simple concepts.

Coarse stone to raise wire edge, polishing stone to replace stropping.

I do hope you are not putting back bevels on your chisels?

David

Not bench chisels. I do have a few carving tools that have that sort of treatment but it's really more a knife edge than that little wisp of a thing to which you attribute so much magic.

You are aware I assume that you are likely the only woodworker who has ever lived that has installed, intentionally, four bevels on a plane iron?

 

[Benchwayze]

.... Whether you use a jig or not, maybe the angle isn't quite so critical as we think? ....

Of course it isn't critical. Who thinks it is, and why? (perhaps don't answer that :roll: ).
It's just that 30º is easy to hit by eye. If you can do that you can also do a bit more (35 ish?) or a bit less (25 or so) like falling off a log!

Clearly Jacob, someone must think the angle is critical, otherwise there wouldn't be so many jigs to 'ensure' that angles are "correct", nor would there be so many sold. Although, it is a good marketing ploy, maybe? (hammer)

 

[Jacob]

.... Whether you use a jig or not, maybe the angle isn't quite so critical as we think? ....

Of course it isn't critical. Who thinks it is, and why? (perhaps don't answer that :roll: ).
It's just that 30º is easy to hit by eye. If you can do that you can also do a bit more (35 ish?) or a bit less (25 or so) like falling off a log!

Clearly Jacob, someone must think the angle is critical, otherwise there wouldn't be so many jigs to 'ensure' that angles are "correct", nor would there be so many sold. Although, it is a good marketing ploy, maybe? (hammer)

They are critical but within limits - so something between 25 and 35 will do for many things, but beyond a certain point (depending on the tool and the task) the angle could be too far out - not enough clearance under a plane, or too fragile etc.

4 bevel Dave has only got to go one more step - take off the arrises and he has 8 bevels, which is a rounded bevel as near as dammit! :shock: :shock:
But is a rounded bevel an infinite series of micro bevels, or no bevel at all? Who first coined the expression "micro bevel"? It's quite recent.

 

[Benchwayze]

Well okay Jacob. Shall we say it's critical that the angles be within close limits? :roll: Something I have always maintained, even to myself.
I'm still a little disappointed when I enter a post which, on the whole, backs you up and you then instruct me on how it is! Really old chap, this is the limit! :lol: :lol: :lol:

 

[bugbear]

Not hours. Immediate effect. With every pass the angle steepens a touch.
It's one of the basic flaws of the common design of jig,
.
.
.
But the answer is that the more you grind/hone without resetting the blade the steeper the angle.

Since your maths and geometry skills seem lacking, let me help.

Even if one were to somehow remove a full 1/8" of hardened tool steel when sharpening a chisel using the Eclipse jig at 25°, the angle of the (still flat, see earlier diagrams...) bevel would still only change by a single degree.

So - even though no ever does this, it wouldn't matter if they did.

Summarising:

* when using a jig the bevel stays flat
* the angle of the bevel does not change to any significant extent during sharpening

I think some people over state the difficulties of jigs.

BugBear

 

[Benchwayze]

A similar principle applies with freehand-honing. It's highly unlikely the angle will be constant. So if it's okay to be within limits, after freehand honing, then it's okay after using a jig. It's just that with the jig one can predetermine any differences yet in theory, allow the bevel to remain constant every time an iron is placed in the jig. That's how I see it.

Yes, I have a guide I used years ago. I don't know of course, whether or not Jacob has ever used a jig. I'm sure he will enlighten us?

John

 

[MMUK]

They are critical but within limits - so something between 25 and 35 will do for many things

A 10 degree tolerance isn't exactly what I would call critical, Jacob. As an engineer, a critical item for me would have a tolerance of 0.5 degrees MAX, situation dependant.

I see what you are saying here but I think critical is the wrong word to use. :wink:

 

[Jacob]

Yes have used jigs. But made a little effort to freehand and suddenly found sharpening much easier, quicker etc - which also means sharper for longer as you aren't put off by the faffing about and the paraphernalia.
People do so overstate the difficulties of freehand; "Unless you happen to have an uncanny ability to judge and hold a desired angle freehand, some kind of assistance is definitely called for. BugBear" is complete nonsense.

 

[Jacob]

They are critical but within limits - so something between 25 and 35 will do for many things

A 10 degree tolerance isn't exactly what I would call critical, Jacob. As an engineer, a critical item for me would have a tolerance of 0.5 degrees MAX, situation dependant.

I see what you are saying here but I think critical is the wrong word to use. :wink:

Horses for courses. 0.5º tolerance essential for some things, but not others. As you say; "situation dependent".

 

[MIGNAL]

Freehand you probably can get the angle to within 2 degrees, unaided. . . . if you really wanted to. Someone with a fair amount of talent and who consciously practiced for a year or so might even be able to get it within 1 degree. That kind of accuracy is not unusual when doing something like playing a musical instrument. Let's take the example of a Cello player who has to move a hand some 12 ", yet has to have a finger accuracy better than 1/8 of an inch. No visual clues either. Easier than riding a bike to many of them.

 

[bugbear]

Yes have used jigs. But made a little effort to freehand and suddenly found sharpening much easier, quicker etc - which also means sharper for longer as you aren't put off by the faffing about and the paraphernalia.
People do so overstate the difficulties of freehand; "Unless you happen to have an uncanny ability to judge and hold a desired angle freehand, some kind of assistance is definitely called for. BugBear" is complete nonsense.

Ah - I see the discussion of jig geometry has been dropped; the good old Butler swerve.

Any number of beginners try to sharpen freehand, report initial success on a freshly ground tool, but then encounter the
(reported up and down history) problem of the cutting bevel getting steeper and steeper with each sharpening. A jig neatly cures this difficulty and allows them to get on with woodworking, with sharp, easy to maintain edges.

The more subtle advantage of a jig used in conjunction with a projection gauge (AKA two pieces of scrap plywood) is that
the same angle is hit every time; it doesn't really matter that the angle is within reason, but the consistency is important.

This minimises the amount of metal that needs to be removed to renew the edge, with both extends the life of the tools, and reduces the labour.

BugBear

 

[MMUK]

Let's take the example of a Cello player who has to move a hand some 12 ", yet has to have a finger accuracy better than 1/8 of an inch.

I knew there was a reason I wanted to go out with that lass from school :lol:

 

[Racers]

This thread needs closing, we have the same problem as every sharpening thread.

Pete

 

[Jacob]

.........
Any number of beginners try to sharpen freehand, report initial success on a freshly ground tool, but then encounter the
(reported up and down history) problem of the cutting bevel getting steeper and steeper with each sharpening. A jig neatly cures this difficulty and allows them to get on with woodworking, with sharp, easy to maintain edges.

Another much simpler cure is to stop doing it. Once alerted to this common mistake anybody with half a brain will stop doing it.
Re: hitting the same angle. This is done freehand by doing it the same way every time, as near as you can judge.

 

[MMUK]

This thread needs closing, we have the same problem as every sharpening thread.

Pete

I agree. Now I know not to ask any questions even remotely connected with sharp edges

I think I've worked out the answer to my original question though from varius replies.

The number of bevels is not important as it has no effect on cutting performance. It is purely a matter of personal preference for potential future time saving when re-sharpening.

 

[Trafalgar]

There are three techniques that appear to have the imprimatur of history:

1) hollow grind and hone on the grind using the hollow as a built-in jig;
2) hollow grind, hone slightly higher, occasionally hone on the grind to control the growth of the higher bevel;
3) round under - the Jacob Butler/Paul Seller's method. I take Seller's oral history on its face that this is how he was taught.

Any three of these will work fine. The rest are a stretch, at best. Four bevels is preposterous. A back bevel on one, SPARE, cutting iron for a smoothing plane is reasonable as long as one understands the implications and produces one that has a real affect on cutting geometry. That said, there must be thousands upon thousands who have worked without this little dodge.

If one simply needs to remove rag/fine burr on the flatside of a cutter that is not perfectly flat then just do a very slight lift ON THE STROP. There is no reason to interpose a thin ruler or any other little aid on one's finest whetstone to accomplish this stunningly simple feat. Two swipes on a strop.

 

[Sgian Dubh]

I suspect it's much harder and more time consuming to contribute anything useful to these interminable sharpening threads than it is to actually regrind and hone a whole tool box full of planes and chisels ... using whatever method you prefer. Personally, I freehand the job, which seems to work more than good enough for the wood hacking I've been getting up to for the last three or four decades.

Darn, in the time I typed this I could have honed a couple of chisels! Slainte.

 

[MMUK]

There are three techniques that appear to have the imprimatur of history:

1) hollow grind and hone on the grind using the hollow as a built-in jig;
2) hollow grind, hone slightly higher, occasionally hone on the grind to control the growth of the higher bevel;
3) round under - Jacob/Paul Seller's method.

Any three of these will work fine. The rest are a stretch, at best. Four bevels is preposterous. A back bevel on one, SPARE, cutting iron for a smoothing plane is reasonable as long as one understands the implications and produces one that has a real effect on cutting geometry. That said, there must be thousands upon thousands who worked without this little dodge.

Thanks CS, but this thread wasn't intended as a sharpening techniques showcase, just a question on the number of bevels :wink:

 

[David C]

Isn't it odd that the people who mock the techniques of others, have almost certainly never tried those techniques?

If I remember right, Paul Sellers uses three stones and a strop for his sharpening. Four surfaces.

I use two. (Not counting the periodic grinding).

Many people work on two surfaces when sharpening, I work on three.

I have taught the technique to hundreds of people who have found it most satisfactory.

David Charlesworth

"Preposterous", I think not.

 

[Jacob]

It's very odd Dave. :roll:
How did you get on with the Sellers method?