Skew the Plane, Lower the Cutting Angle

[Ron Hock]

Nicely done! It's a difficult thing to visualize but you made it simple. 

I tried to do the math, with John Whelan's book's help, in my blog entry over a decade ago: https://hocktools.wordpress.com/2010/03/...-the-skew/. I worked so diligently only to have Warren Mickley correct me (and John) that our trig was wrong. We were rescued by the link in the last comment posted: https://investigationsblog.wordpress.com.../#more-248. I'm still surprised that it's so complicated.

[CStan]

Planing straight across the grain is often recommended when reducing a board's thickness to prevent it tearing out (difficult species). Skewing the plane is just a variation of that. If planing straight down the board is planing at zero degrees, and planing straight across the board is 90 degrees, then skewing is somewhere in between those two numbers depending on how much you skew the plane. The plane blade is hitting the fibers at some angle other than straight on, in this example arbitrarily set at 0 degrees. This is how I visualize it.

[Arlin Eastman]

Well done Mark on the video and explaning it with the props.

My question is not should all plane blades be sharpened or adjusted to this degree?

[MarkSLSmith]

Well done Mark on the video and explaning it with the props.

My question is not should all plane blades be sharpened or adjusted to this degree?

Arlin, 

I'm not sure I understand your question but I'll give it a shot.  

One interpretation of your question is that you want to sharpen the bevel of the plane blade (its a bevel down plane) so that it lines up with the effective cutting angle (the lower angle shown in the video).  This would require sharpening the blade to a very small angle and the strength of the cutting edge would be poor.

A second interpretation of your question is that if the effective cutting angle is, for example, 35 degrees then you want to sharpen the plane blade so the bevel is also 35 degrees.  This would be ok as long as you don't mind the larger angle on the bevel (assuming your normal bevel is 25 to 30 degrees), I assume it would take a bit more effort to push the plane, skewing or no.  On the other hand, I'm not sure the combination of larger bevel angle and skewing the plane results in an advantage.  

A larger bevel angle would decrease the clearance some, albeit perhaps not seriously.  It is worth noting the bevel angle and the resulting clearance angle are mainly important in the context of the plane and the frog, and are not  affected much by the effective cutting angle.

In either case, I think you just want to stick with the bevel angles that you are used to.

If your question meant something else, please say so.  

Thanks,
Mark

[Arlin Eastman]

what is the best way of the way you explained it to make me look smart is the way I meant it.  





I was just thinking instead of skewing the blade to the board just lower the sharpening edge to match the cutting angle of a skewed plane.  If this question does not make me look intelligent then skip it.  

[omark]

I will never get, if the slicing is more than lowering the cutting angle.
If you just push it skewed but straight forward, there ist no action of microteeth like in sawing.

That is very useful remark, thanks. I have to admit I believed that skew results in 'sawing' but after reconsidering you are clearly right.

The additional effect in addition to lowering the angle might be a result of wood fibers flexibility interacting with micro-teeth (but I may be wrong about that).

[MarkSLSmith]

what is the best way of the way you explained it to make me look smart is the way I meant it.  





I was just thinking instead of skewing the blade to the board just lower the sharpening edge to match the cutting angle of a skewed plane.  If this question does not make me look intelligent then skip it.  

Hi Arlen,

I think you have just discovered low angle planes!  

Just kidding.  But actually your question is a good one.  That would be a logical step.  You can lower the bedding angle of a bevel down plane some (maybe 10 degrees at most), but then you run out of clearance angle.  So you turn the cutter over and make a bevel up plane.  

But you probably don't have some of the other advantages that people have mentioned above, so maybe you don't gain as much as you might have thought.  And then there's the whole issue of the absence of a chip breaker.  

I think you started down the right track, but my opinion is that it starts looking like an apples and oranges comparison before too long.  

Mark