Chisel set up and aside for softwoods

[Tony Wilkins]

Do any of you have a chisel (chisels) set up with a lower bevel angle for use on pine and other soft woods? If so, what angle and chisel do you choose for this?

[Brian Holcombe]

Not usually, I find that if they’re very sharp the standard bevel angle is fine.

[Derek Cohen]

Not usually, I find that if they’re very sharp the standard bevel angle is fine.

Agree. My bench chisels are 30 degrees since they may be tapped with a hammer. My paring chisels (Japanese) are 25 degrees. No need to go lower.

Regards from Perth

Derek

[Stewie Simpson]

Keep an open mind gents. 10 degree convex bevel (measured from the center point of the curve. W1 steel. Parring both Cypress Pine and Aust.Jarrah. The cutting edge did not fold or chip, but required a light work out on the loaded strop to complete the parring work on the Jarrah. Am I recommending we all ignore the western standard of 20 degrees for parring chisels. No. But don't expect a parring chisel that's been hollow ground at 20 degrees with a light micro bevel to hold its edge for too long.

[Patrick Chase]

Keep an open mind gents. 10 degree convex bevel (measured from the center point of the curve. W1 steel.

For edge life all that matters is the angle at the very tip (say, the last 1/100" or so). Do you happen to know how convex that bevel was?

[ernest dubois]

For edge life all that matters is the angle at the very tip (say, the last 1/100" or so). Do you happen to know how convex that bevel was?

And what lies behind this 1/100th has no relevance?

[Derek Cohen]

Stewie, I am curious to know why 10 degrees? I might add the same question for those who believe any especially low angle is beneficial - at what point is the apparent edge penetration more important than edge holding? How many strokes are acceptable before rehoning such low angles - 2, 3, 4?

Regards from Perth

Derek

[Patrick Chase]

And what lies behind this 1/100th has no relevance?

Not to edge wear, which is what Stewie was addressing. It obviously matters to strength and stiffness, but I'm not surprised that Stewie found 10 deg to be adequate in those respects.

[ernest dubois]

Not to edge wear, which is what Stewie was addressing. It obviously matters to strength and stiffness, but I'm not surprised that Stewie found 10 deg to be adequate in those respects.

And strength and stiffness have nothing to do with edge wear?

[Brian Holcombe]

Paring is pretty low impact Ernest, I've experienced it being more critical for chopping.

[Patrick Chase]

Paring is pretty low impact Ernest, I've experienced it being more critical for chopping.

Indeed. Chopping imposes high compressive load that might cause a low-bevel-angle blade to bevel, though even there I'd bet that the critical angle is a lot lower than most people think. You don't hear about people breaking the tips off of their 20 deg Ray Iles mortise chisels, after all.

[Patrick Chase]

And strength and stiffness have nothing to do with edge wear?

They do, but bending moment in the blade increases linearly from edge to handle, so the loads out at the tip are smaller than a lot of people think (provided you don't apply high twisting loads, which you shouldn't). The tip is subject to compressive loads, but a 10 deg bevel would be able to withstand those for paring.

Also, if the bevel is continuously convex like Stewie's and if the first 1/100" is pitched at, say, 20 degrees, then we know that the next 1/100" isn't going to be much less than that, etc. If you honed a 10 deg primary bevel and then put a very thin higher-angle microbevel on that then you might have a problem with buckling/folding, but that's not what he did.

[John C Cox]

And strength and stiffness have nothing to do with edge wear?

For most chisels - the thickness adds stiffness against prying and twisting and impact... If you have a very very sharp edge and a very careful technique - you can shave wood without the need for great thickness back in the body of the chisel.... For example - your sharp pocket knife shaves wood well - yet these are usually quite thin... Even a razor blade will work if you are careful....

As Brian notes - the additional thickness is very useful for chopping...

[ernest dubois]

For most chisels - the thickness adds stiffness against prying and twisting and impact... If you have a very very sharp edge and a very careful technique - you can shave wood without the need for great thickness back in the body of the chisel.... For example - your sharp pocket knife shaves wood well - yet these are usually quite thin... Even a razor blade will work if you are careful....

As Brian notes - the additional thickness is very useful for chopping...

Yes it adds this stiffness but the mass behind the cutting also is a buttress supporting and absorbing, and including another thing I just thought, dispersing not only pressure from impact but heat generated by friction, also a contributor to the break down at the edge, which is another way of saying wear. The mechanics of abrasion always involves stress on the steel structure and in not just some mysterious force working against the edge.

[Patrick Chase]

Yes it adds this stiffness but the mass behind the cutting also is a buttress supporting and absorbing, and including another thing I just thought, dispersing not only pressure from impact but heat generated by friction, also a contributor to the break down at the edge, which is another way of saying wear. The mechanics of abrasion always involves stress on the steel structure and in not just some mysterious force working against the edge.

Err, no.

Heat is simply energy, and energy is force times distance. The amount of heat that can be generated by cutting with a chisel is therefore strictly limited by how hard you push the chisel and how far it moves while being pushed (and in fact much of that energy input is absorbed by deformation of the wood rather than as frictional heating). There is no way that paring could possibly create enough heat to matter, particularly when you consider that steel is very conductive.

The part about "stress on the steel structure" seems to me to be hand-wavy pseudoscience. Tool steel at Rc60 has a compressive yield strength of about 300,000 pounds per square inch. It really doesn't take much cross-sectional area to resist the sorts of forces involved in paring. More practically and as somebody else pointed out, the fact that thin-bladed knives can be used for fairly hard work tells us a lot.