Maximum sharpening angle bd plane?

[ali27]

I am wondering what the maximum angle is that one
sharpen a bd plane iron at? Probably around 35-40 degrees
I think.

Is a plane sharpened at 25 degrees sharper than 40 degrees?

I am asking because sharpening at 40 degrees requires far less
metal removal.

Thanks.

Ali

 

[Jacob]

.....
I am asking because sharpening at 40 degrees requires far less
metal removal.

Thanks.

Ali

No it doesn't. If you want to remove say 1mm from the edge of a blade of given thickness AND to maintain the same bevel (whatever shape it is; straight, facetted, rounded) the amount of metal removed will be the same. Geometry.

 

[ali27]

.....
I am asking because sharpening at 40 degrees requires far less
metal removal.

Thanks.

Ali

No it doesn't. If you want to remove say 1mm from the edge of a blade of given thickness AND to maintain the same bevel (whatever shape it is; straight, facetted, rounded) the amount of metal removed will be the same. Geometry.

Pythagoras? a2+b2=c2

A 25 degree bevel has a ''wider'' bevel than a 40 degree bevel, so more metal must be removed in comparison? Or am I missing something?

Ali

 

[Jacob]

.....
I am asking because sharpening at 40 degrees requires far less
metal removal.

Thanks.

Ali

No it doesn't. If you want to remove say 1mm from the edge of a blade of given thickness AND to maintain the same bevel (whatever shape it is; straight, facetted, rounded) the amount of metal removed will be the same. Geometry.

Pythagoras? a2+b2=c2

A 25 degree bevel has a ''wider'' bevel than a 40 degree bevel, so more metal must be removed in comparison? Or am I missing something?

Ali

It's also thinner.

 

[Corneel]

For end grain you need a decent amount of clearance, around 10 degrees or so. Otherwise you get burnished spots in the wood and worse cutting behaviour. In long grain cutting you don't need any clearance at all as long as the blade is sharp. But I suspect the wear bevel will have bad effects pretty quickly. So better to just keep at least 10 degree clearance angle in all your planes.

 

[bugbear]

Pythagoras? a2+b2=c2

A 25 degree bevel has a ''wider'' bevel than a 40 degree bevel, so more metal must be removed in comparison? Or am I missing something?

Ali

If you assume that you need to remove a given amount along the axis of the blade (L) and that the plane has a single bevel, and the blade has a thickness (T) the metal you're removing is a parallelogram of base L and height T.

And the area of a parallelogram is simply base x height.

http://www.mathgoodies.com/lessons/vol1 ... ogram.html

So the angle doesn't matter (given the assumptions above...)

In practise, the wear patterns tend to mean that 'L' is a little larger for a very fine bevel edges, so this geometry, though lovely, is not applicable. The real world of applied mechanics tends to be complex, which is fun.

BugBear