[OP]
Contributor
Regarding the ramped board ...
I had a close look today. The ramp does work against the skew, however we are talking 4 degrees here, and the blade is skewed 20 degrees.
I would conclude that the ramped shooting board is to be used with a straight bladed plane, where it will reduce the jarring on impact. The skewed blade of the #51-type (LV and LN) will work best on a flat shooting board.
Regards from Perth
Derek
Member
I partially agree with this, which also means I partially disagree ;-)Originally Posted by Derek Cohen
A skewed blade on a shooting plane used on a shooting board, has 3 benefits
- lowered angle
- spread wear over more blade (basically the hypotenuse at 20 degrees)
- entering the cut progressively
Of these 3, angling the board could negate the 3rd one, completely at 20 degrees, but have no effect on the first one, it can also improve on 2.
/p
Contributor
Do you think a reverse-ramped board (where the raise is in the back as opposed to the front) would help any with a LV/LN skewed blade? Any clue where the magical "the gains are minimal" point is?
Just curious here. . .
The Barefoot Woodworker.
Fueled by leather, chrome, and thunder.
Member
Yeah...that would be me.
I'm sorry.
I am never wrong.
Well...I thought I was wrong once...but I was mistaken.
Member
I am not speaking for Derek but I see several things going on here which influence what ultimately could be a subjective perception.
Reduced cutting angle, this is due to blade skew... And I hope we all agree that ramping the board in either direction has no effect here.
Initial shock or jarring, this is influenced by both skew and ramp. On a straight blade, optimal entry would be a board at 45 degrees. Except of course there is not enough blade width to accommodate hardly any boards at anything more Ghana few degrees on a ramp, but let's ignore that. Similarly at 20 degree skew a board at 25 degrees is optimal for this factor only... Initial jarring.
Another aspect is width of cut, also influenced by both skew and ramp angle, more width more force needed. Ramping in the usual direction reduces width of cut with the minimal optimal at 20 degrees (remember this also increases the initial jarring on a 20 degree skew to the maximum). Any more angle (or any less) from 20 on the ramp, starts increasing the width of cut.
Finally there is wear, which does not always follow width of cut, the effect of this is over time after a blade wears less quickly. To figure this out you can take one corner of your board and measure the vertical distance to the opposite corner, and that is your width of cut, on both straight and skew planes minimal is at flat maximum is at 90.
It is all a compromise between these things, if you have a lot of mass likely cutting angle (only affected by skew) is more important than jarring, if you don't jarring becomes increasingly more important.
/p
Contributor
There may also be the difference of a shearing cut and a slicing cut and where they diverge. My understanding of these could be totally wrong, but what the heck.Another aspect is width of cut, also influenced by both skew and ramp angle, more width more force needed.
In my view, a straight on cut is a shearing cut. A slicing cut comes about when the work piece, the blade or both are skewed away from a straight on attack. My presumption is a shearing cut requires more effort than a slicing cut.
We also have the bedding angles to consider. If the Veritas Shooting Plane was available a few years ago, it might have been my choice over the LN #62 for a shooting plane. As it is, if a little extra money comes my way the VSP may still find a place in my shop.
jtk
"A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
- Sir Winston Churchill (1874-1965)
Member
Jim, I'm not sure how to define them. But for the most part all end grain cuts are shearing cuts.
But I think what you mean is for example cutting a stalk of celery is easier if you pull your knife as you push it down, that simply pushing the knife down (slicing vs shearing).
This is influenced in our case by the skew only I believe, not the board angle, I am assuming fibers are round.
/p
Contributor
Yeah, I'm just going to step away because there's a break-down in communication here somewhere. I think I'm referencing definitions of words others are not (which could be a misunderstanding of the terms on my part), and the physics in my mind just are simply not adding up.
For example, in my mind, shearing is done with 2 blades. A plane is a single blade and slices, whereas scissors cut through a shearing action caused by two edges sliding past each other. A plane will *never* shear since it has a single blade. So nothing person to anyone. Perhaps I'll come back with a nice formula or something at some point to get across what I'm saying.
The Barefoot Woodworker.
Fueled by leather, chrome, and thunder.
Contributor
Maybe his should have its own thread, but am I the only one who noticed that the new Lee Valley woodworking catalog showed up in their ipad app a couple of days ago?
John
Contributor
I do see your point. I looked it up, and it turns out there are multiple definitions, so it could be used either way. Your definition: b : any of various cutting tools or machines operating by the action of opposed cutting edges of metal —usually used in pluralYeah, I'm just going to step away because there's a break-down in communication here somewhere. I think I'm referencing definitions of words others are not (which could be a misunderstanding of the terms on my part), and the physics in my mind just are simply not adding up.
For example, in my mind, shearing is done with 2 blades. A plane is a single blade and slices, whereas scissors cut through a shearing action caused by two edges sliding past each other. A plane will *never* shear since it has a single blade. So nothing person to anyone. Perhaps I'll come back with a nice formula or something at some point to get across what I'm saying.
however, it can also mean: a : internal force tangential to the section on which it acts —called also shearing forceb : an action or stress resulting from applied forces that causes or tends to cause two contiguous parts of a body to slide relatively to each other in a direction parallel to their plane of concontacting
As for the discussion on ramping the shooting board, there is no need to ramp the board with a skewed blade because it is already angled to the wood. In the case of the Veritas shooter, the angle would be negated on an upward ramp, and enhanced on a downward ramp, but I don't see the need for an angle greater than what the plane comes with, and enhancing the angle would also minimize the thickness of board that could be cut.
Contributor
Actually, you may be saying this clearer or more correct than my post, re: shear vs slice.For example, in my mind, shearing is done with 2 blades. A plane is a single blade and slices, whereas scissors cut through a shearing action caused by two edges sliding past each other. A plane will *never* shear since it has a single blade. So nothing person to anyone. Perhaps I'll come back with a nice formula or something at some point to get across what I'm saying.
Maybe it would be clearer comparing it to pushing a blade straight into the edge of a piece of paper as opposed to presenting one corner of the blade to the paper and sliding it to the opposite corner while it is being pushed through the paper.
Maybe it is just being up so late that has my mind trying to figure it out.
jtk
"A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
- Sir Winston Churchill (1874-1965)
Member
people keep saying this, and while I will not attach any qualitative adjectives (better, necessary or so) this is simply inaccurate.
a board at an angle is not the same as a skewed blade. Skewing the blade relative to direction of travel (as is on the LV plane used on a shooting board) among other things lowers the cutting angle, and this effect CAN NOT be enhanced or undone by ramping the board.
Wood is anisotropic, but end grain cuts at 90 degrees are isotropic (this means independent of direction), basically on faces and edges direction of travel matters, across the grain or along the grain (both with and against) make a difference. But on end grain direction does not matter, except if someone would argue the direction of rings on engrain (i.e. easier to cut flatsawn endgrain over quartersawn end grain)... if this is accepted, then the only other variables are cutting angle, cutting width and the initial shock or jarring effect. Angling the board has an effect on all but cutting angle.
Which one of all these is more important, may be subjective, not to mention influenced by the plane's mass in the case of jarring, the dimensions of the board in the case of width of cut, etc.
I am refraining from attaching qualitative arguments, just trying to explain the cutting physics
/p
[OP]
Contributor
There was a post today on Wood Central that raised the question of the ramped board and the skew of the #51 type plane. Of course I cannot link to that website, so I have copied part of my reply here:
First of all, the ramp angle of the shooting board is about 5 degrees, and the angle of the skew on the plane is 20 degrees.
The main advantage of the ramped board is to reduce the impact as the plane blade hits it. In a flat board with a square blade the impact would be square on. That produces maximum impact vibration. The ramping of the shooting board platform enables the blade to enter the wood progressively, that is, at an angle of 5 degrees, and this reduces the jarring from impact. A plane with a skewed blade, such as a #51-type, would enter the wood on a flat board at a progressive 20 degrees. On the ramped board this gets reduced to 15 degrees. For entry purposes this is insignificant. I would argue, nevertheless, that the main benefit from a ramped shooting board would be found for a shooting plane with a square blade.
The fact that there is a change of angle at impact does not mean that there is any change in the cutting performance of a skewed blade on a ramped shooting board. Once past the impact zone, the blade continues to cut as it always does. It is the shearing action of the skewed blade on the plane that is the strength of the #51-type shooter. The angle at which the work piece is held should not have any effect.
You may wish to read a comparison I made between three shooting planes (LN #51, LN #9 and LV LA Jack) on both flat and ramped shooting boards:http://www.inthewoodshop.com/Furnitu...sCompared.html
Scan down to "Cutting Angles and the Effect of Skew".
Regards from Perth
Derek
Contributor
Hello all,
Well it came! My new shooting plane is here! Of course the thing came while I was out of town so I didn't get to lay hands on it until Friday. By the way, thanks to air conditioned post office and humid, non-air conditioned shop, it already got its first bit of rust, but it knocked right off. I should have left it packaged and let it come to shop temperature but I couldn't wait, and it got a little condensation on it.
So certainly this is my new favorite plane. I am very pleased and I still feel it is one of the most innovative new planes in recent years. Certainly it does the job it is designed to do, but it's also very artistically rendered and so much sexier than a square miter plane. Kudos to the designers.
I love the adjustable mouth, the grub screws for maintaining blade adjustment, and the tapped holes for a miter track or a fence. Nice touch.
One negative, however, is the milling of the gap where the blade goes. It is very rough, and for me in the tropics that means harder to wax and easier to rust. Aside from that is has no effect on the use and/or accuracy of the plane.
certainly if my shop ever caught on fire it would be one of the first tools I grabbed, along with her brothers and sisters in the bevel up department.
image.jpg
Contributor
Nice Malcolm!
Is that the Jack you have there?
"If you have all your fingers, you can convert to Metric"
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