One Bevel, Two Bevels, Three Bevels, More?

[Jacob]

In fact if you use a jig for long enough initially set at say 25º, without adjusting it, it will produce a rounded bevel.

At what stage when working a flat bevel on a flat stone does the roundness happen?

The removal of metal at each sharpening when using a jig is small, certainly not enough to alter
the angle.

So (as almost everyone knows) the bevel
when using a jig stays flat, and is the same angle each time. SImple.

Impossible. Every pass shortens the blade slightly and hence alters the angle. Barely noticeable with just a few passes, but a fact nevertheless. If you keep going you get a rounded bevel.
This may be another feature of jig sharpening which confuses the enthusiasts and sends them off into more rounds of bevel counting and frantic flattening. :lol:

 

[Benchwayze]

I never strop. Unless you count a few flips on the heel of my hand. I like to finish with a few strokes along the edge of the stone, with the iron overhanging, so only the first 3/8" or so of the face gets 'flattened'. (I don't lift the rear of the blade as per David's Ruler trick. I might be thinking wrong, but I can't see how that doesn't result in something approaching a knife edge.) After that the heel of my hand just removes the tiny wire-edge,

My way has always worked for me. As for bank balances, I don't worry about anyone's balance but mine. What people spend is their affair. Not mine.

 

[Phil Pascoe]

Agree totally, B. I can sharpen my tools perfectly well. I couldn't give a damn how other people do it really, although sometimes it gives a laugh.

 

[Woodmonkey]

Every pass shortens the blade slightly and hence alters the angle. Barely noticeable with just a few passes

Alters the angle (by an infinitesimally small amount) yes, rounds over the bevel, no. That is just plain wrong. When you get to the end of the stroke you will have taken a tiny amount of metal more from the tip than from the heel thus as you say fractionally changing the angle. It will still be flat though.

 

[bugbear]

Every pass shortens the blade slightly and hence alters the angle. Barely noticeable with just a few passes, but a fact nevertheless. If you keep going you get a rounded bevel.

You're simply wrong. If one continued to grind away for ages (why?) on a coarse surface, the angle would indeed very slowly steepen as the blade shortened, but the bevel would remain flat; steeper but still flat.

Even if one starts with a convex bevel (one where the arris is a lower angle than the cutting edge), the flat grinding plane would simply grow from the edge until it meets the arris.

You could demonstrate this simply and rapidly to yourself with a piece of wood on your belt sander. Try it!

BugBear

 

[GLFaria]

This thread has been fascinating, if only for showing that feelings and emotions play so great a part in sharpening! :lol:

But it looks like people are now running around in circles, doesn't it? :wink:

 

[Jacob]

Every pass shortens the blade slightly and hence alters the angle. Barely noticeable with just a few passes, but a fact nevertheless. If you keep going you get a rounded bevel.

You're simply wrong. If one continued to grind away for ages (why?) on a coarse surface, the angle would indeed very slowly steepen as the blade shortened, but the bevel would remain flat; steeper but still flat.

Actually it'd depend on where the pivot point was, according to the design of jig.
But steepening angle most definitely. Which is why you don't need multiple bevels with a jig ; course grind at 30 and go straight to fine hone without taking it off the jig, will give you a slightly higher angle and a "micro" bevel hooray! This also gets you around the problem of aligning a straight edge with a flat stone, which can mystify people.
Not that I bother with all this faffing about myself.

 

[carlb40]

This thread has been fascinating, if only for showing that feelings and emotions play so great a part in sharpening! :lol:

But it looks like people are now running around in circles, doesn't it? :wink:

After the first page of posts - any thread to do with sharpening or involving Jacob normally does. :roll:

 

[Jacob]

This thread has been fascinating, if only for showing that feelings and emotions play so great a part in sharpening! :lol:

....

Yers they do seem to get a bit shirty :roll:
I think there's probably a link between obsessive sharpening and personality; defensiveness and a tendency towards irritability and sarcasm. :lol: :lol:

 

[bugbear]

Every pass shortens the blade slightly and hence alters the angle. Barely noticeable with just a few passes, but a fact nevertheless. If you keep going you get a rounded bevel.

You're simply wrong. If one continued to grind away for ages (why?) on a coarse surface, the angle would indeed very slowly steepen as the blade shortened, but the bevel would remain flat; steeper but still flat.

Actually it'd depend on where the pivot point was, according to the design of jig.
But steepening angle most definitely.

Yes, yes. If one ground away for hours, the angle would eventually steepen. No one ever does this, of course, but give the (odd) hypothesis, the (odd) conclusion clearly follows.

But you said:

In fact if you use a jig for long enough initially set at say 25º, without adjusting it, it will produce a rounded bevel.

Now, I am of the opinion that the bevel would stay nice and flat, and simply get steeper as the tool wore away.

Where would the roundness come from, in your understanding of the geometry of jigs?

BugBear

 

[Jacob]

...
Yes, yes. If one ground away for hours, the angle would eventually steepen.....

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, the other being that there's nothing to stop you raising the angle of the tool and rounding over the edge, which you would imagine a jig would prevent.

 

[Cheshirechappie]

But you've forgotten the critical factor, BB. Jacob's oilstone has a surface reminiscent of the inside of a soup-spoon. THAT'S where the roundedness comes from. :lol:

 

[Woodmonkey]

Every pass shortens the blade slightly and hence alters the angle. Barely noticeable with just a few passes, but a fact nevertheless. If you keep going you get a rounded bevel.

[/quotecourse grind at 30 and go straight to fine hone without taking it off the jig, will give you a slightly higher angle and a "micro" bevel

This is the problem isn't it, people arguing for the sake of arguing. From one post to the next it's gone from "sharpening using a jig makes a rounded bevel" to "sharpening using a jig makes a micro bevel". Well clearly it's neither, using using a jig gives you one consistent bevel every time. Perhaps that's why Jacob seems to dislike jigs so much, they seem to confuse him....

 

[Spindle]

Hi

Seven pages - no consensus, (as per usual), why not limit sharpening threads to one or two pages :roll: :twisted:

Regards Mick

 

[bugbear]

...
Yes, yes. If one ground away for hours, the angle would eventually steepen.....

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,

Fascinating. By rougly what amount, do you think, in degrees? I'd hate to think you were worrying about nothing, or just raising obscure points to distract from:

In fact if you use a jig for long enough initially set at say 25º, without adjusting it, it will produce a rounded bevel.

BugBear

 

[Jacob]

...
Yes, yes. If one ground away for hours, the angle would eventually steepen.....

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,

Fascinating. By rougly what amount, do you think, in degrees? I'd hate to think you were worrying about nothing, ......

I'm not worried at all. I don't use them. A blessed relief! But the answer is that the more you grind/hone without resetting the blade the steeper the angle. Sooner or later it'll get to 90º! PS if the jig isn't in the way etc

 

[MMUK]

Some say he sleeps with a sharpening jig under his pillow and that he dreams of scary sharp stones. All we know is he's called Jacob :lol:

 

[Jacob]

Some say he sleeps with a sharpening jig under his pillow and that he dreams of scary sharp stones. All we know is he's called Jacob :lol:

I've got a website you know. Somewhat out of date I admit.
I'm not really obsessed by sharpening except that it is central and fundamental, and (paranoia showing here) there has been a huge conspiracy of misinformation in recent years and a lot of people seem to believe that simple freehand sharpening is impossible. In fact any pineapple can do it.

 

[Benchwayze]

I'm not worried at all. I don't use them. A blessed relief! But the answer is that the more you grind/hone without resetting the blade the steeper the angle. Sooner or later it'll get to 90º! PS if the jig isn't in the way etc /quote]

Despite this flaw, the blades must be sharp enough to function, or woodworkers wouldn't use the jigs. So if you are right, then maybe the angle of the 30 deg bevel isn't so critical after all. Which is also the basic flaw in hand sharpening Jacob. No matter how expert you are, the angle doesn't remain constant, hence your rounded bevel. At least, so I've found. But the edges still function. If occasionally they get too steep, or too rounded, I re-grind.

Repeating myself: Whether you use a jig or not, maybe the angle isn't quite so critical as we think? I dunno. I just make sure my irons and chisels cut like they should. If I get a flat bevel first time, it's a bonus. :mrgreen:
:?

 

[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!