Shooting board question

[Mike Henderson]

Now that I'm asking shooting board related questions, let me ask one more:

"What's the advantage of a ramped shooting board?"

The only advantage I see is that the whole plane blade might be used instead of just the lower part of the plane blade. But how much of an advantage is that? On a ramped shooting board you risk having the end of the board closest to you being so high so that the plane won't cut the top of it (for a thick board).

All comments welcome.

Mike

[Billy Chambless]

One advantage I see is that the ramp, in effect, skews the blade of the plane, thereby lowering the angle of cut. This can be a big advantage when shooting end grain with a standard angle plane.

[Don C Peterson]

...except that the effective skew angle is pretty small to the point of being insignificant it seems to me. The greater the angle of the ramp the more likely that you won't be able to shoot the entire width of the board and a higher angle would make holding the lumber against the shooting board more difficult too.

Another point against ramped boards is that it precludes the use of a cambered iron in the plane. Most folks probably don't use a cambered iron in their shooting planes, but some might and to me it just puts another limit on what you can do...

The last thing is that it complicates the making of the shooting board. A flat shooting board is very simple to make, it's the kind of thing that can be made in under an hour. The ramped shooting board is more of a project. So, when I was considering making one, the cons easily outweighed the pros as far as I could tell.

[Mike Henderson]

One advantage I see is that the ramp, in effect, skews the blade of the plane, thereby lowering the angle of cut. This can be a big advantage when shooting end grain with a standard angle plane.
The ramped shooting board I'm thinking of has the plane moving on the flat, and the board on a slope (higher towards the user and lower towards the stop) - like this (http://www.hntgordon.com.au/shootingboards.htm). In this case, you do not get any skew advantage.

To gain any skew advantage, the plane has to have motion sidewards as well as forward. Think about when you skew a plane when smoothing a board - your don't push is forward, you push it with the plane held at an angle to the direction you're pushing it.

On a ramped shooting board, the plane is pushed forward only - no sideways motion - so there's no skewing of the blade.

The board is angled so as you push the plane forward, the top of the blade engages the board first, then as you push forward more, the contact moves to the lower part of the blade. But this is not a skew action. The contact of the blade with the wood is always directly forward with no "slicing" action at all.

Mike

[harry strasil]

like the website stated its for shooting small thin boards. The tool has to match what you are working. If you want to shoot thick boards, use one of those ones that has a screw to hold the work while you shoot the end. You can skew the plane at whatever angle you want. Memory fails me as to what they are called.

[Wilbur Pan]

Hi Mike,

If I imagine the shooting board/board/plane assembly rotated 90 degrees so that the board to be planed is now vertical, and if you stand so that the board is now sticking straight in front of you and the plane is now angled relative to your position, it certainly looks like the plane goes through a skewing motion, since the angle of travel is not in line with the axis of the plane. Maybe I'm missing something.

In any case, the amount of skew with this shooting board would be minimal. The effect of skewing on the effective angle of the plane is described by this formula:

tan (effective angle) = cos (skew angle) x tan (bedding angle)

Just eyeballing the picture, it looks like the skew angle would be about 25° at most. For a standard 45° bedded plane, the effective angle would be 42°.

I think that the main benefit of these ramped boards is that you get even wear across the plane blade. One disadvantage is that this feature would limit the thickness of the board that you can shoot to some extent.

[Mike Henderson]

Hi Mike,

If I imagine the shooting board/board/plane assembly rotated 90 degrees so that the board to be planed is now vertical, and if you stand so that the board is now sticking straight in front of you and the plane is now angled relative to your position, it certainly looks like the plane goes through a skewing motion, since the angle of travel is not in line with the axis of the plane. Maybe I'm missing something.

In any case, the amount of skew with this shooting board would be minimal. The effect of skewing on the effective angle of the plane is described by this formula:

tan (effective angle) = cos (skew angle) x tan (bedding angle)

Just eyeballing the picture, it looks like the skew angle would be about 25° at most. For a standard 45° bedded plane, the effective angle would be 42°.

I think that the main benefit of these ramped boards is that you get even wear across the plane blade. One disadvantage is that this feature would limit the thickness of the board that you can shoot to some extent.
Wilbur - I think as long as the plane moves directly forward you don't get any skewing action.

Let me take two examples to extremes. Let's look first at skewing a smoothing plane when smoothing a panel. The extreme is to continue to skew the plane as you push it. The blade will be at more and more of an angle to the wood fibers. At the absolute extreme, the blade will be parallel to the motion of the plane and will no longer cut anything - you'll be pushing the plane sideways.

Now, let's look at the ramped shooting board. If there's some skew action, as we raise the angle of the wood relative to the direction of the plane we'd expect to get more skew angle, as we did with the smoothing plane. When we raised the wood to 90* to the direction of motion of the plane we'd expect no cutting to take place.

However, on the ramped shooting board, the cutting action is exactly the same at 90* as it was at 0* - the blade is hitting the wood fibers head on.

Another way to think of it is to consider a regular shooting board where the platform for the wood is parallel to the direction of travel of the plane. No skewing there. Now, suppose we put a piece of wood that was cut in the shape of a triangle on the platform. Would you expect to get any skewing on that cut?

I can't see any skewing on a ramped shooting board (like the one in the picture). The only advantage I can see is that you use more of the blade for the cut so maybe you don't have to sharpen so often.

Mike

[Andrew Homan]

Mike,
I don't think that picturing a triangular board gives you an accurate picture of what is going on, but that doesn't matter.

I use a ramped shooting board at home and a flat board at my school's workshop. Both work fine. The advantage of the ramped board is, like others said, that you get to use a greater portion of your edge. If you are planing end-grain, this means that you get a somewhat longer shooting "session" before needing to hone.

For most tasks, the ramped board is not limiting. It is not for large boards. Whether or not this is inconvenient depends on your practices. I have found that shooting really comes into its own for smaller pieces, including the end grain of rails and stiles. If I am truing the end grain of a larger piece, I clamp it vertically and plane as usual, without a shooting board.

Cheers,
Andy

[Wilbur Pan]

Wilbur - I think as long as the plane moves directly forward you don't get any skewing action.

You're right. I was trying to visualize this in my head, but when I went to my shop and checked this out with a board and a plane, what you say is correct.

[Derek Cohen]

I have made, and use, a number of shooting boards.

I have a shooting board plane with a skew blade (Stanley #51/52), and flat- and ramped shooting boards with square blades, the latter generally used with a LA Jack.

The ramp angle (4-5 degrees) in the ramped shooting board is toolow to create a skewed cut. That is not what it is about. What you will notice when you use ramped and non-ramped (flat) shooting boards side by side is that the ramped board is smoother in the cut. By smoother I mean that it is less jarring as the blade contacts the wood in a progressive slice. Again I emphasize that this slicing action is not great, but it is enough to have this effect.

Certainly, wear is spread a little more with the ramped board, but the down side is that you also lose a little thickness of cut on wide boards.

Here are a couple of ramped shooting boards I recently completed for others ..

http://i13.photobucket.com/albums/a262/Derek50/Tools%20that%20I%20have%20made/Shooting%20board/Shooting%20board%20for%20Judy/Chuteboardsx2.jpg

Close up of one ..

http://i13.photobucket.com/albums/a262/Derek50/Tools%20that%20I%20have%20made/Shooting%20board/Shooting%20board%20for%20Judy/Judy-main1.jpg

These have a few new features.

The fence is micro-adjustable (by 1/8" fore and back) and then extendable for wear.

The rear end of the fence is rounded off to prevent breakout.

http://i13.photobucket.com/albums/a262/Derek50/Tools%20that%20I%20have%20made/Shooting%20board/Shooting%20board%20for%20Judy/Fence-brokendown1.jpg

The mitre fence is attached at the rear with a bolt. Standard hex key needed - same as for square fence sub fence.

http://i13.photobucket.com/albums/a262/Derek50/Tools%20that%20I%20have%20made/Shooting%20board/Shooting%20board%20for%20Judy/Judy-mitre2.jpg

This method allows you to use the fine adjustment on the mitre fence as well as the main fence.

http://i13.photobucket.com/albums/a262/Derek50/Tools%20that%20I%20have%20made/Shooting%20board/Shooting%20board%20for%20Judy/Judy-combinedmitre.jpg

I have a very comprehensive article on my website on "setting up and using a shooting board": http://www.inthewoodshop.com/ShopMadeTools/Setting%20Up%20and%20Using%20a%20Shooting%20Board4 .html This contains flat- and ramped boards, mitre- and donkeys ear attachments, tuning, and techniques of use.

One last pic - I always wanted to post this one .. a shooting board shooting a shooting board! :)

http://i13.photobucket.com/albums/a262/Derek50/Tools%20that%20I%20have%20made/Shooting%20board/Shooting%20board%20for%20Judy/Chutebeingshot.jpg

Regards from Perth

Derek

[Ganthan Rhodes]

Wilbur - I think as long as the plane moves directly forward you don't get any skewing action.

Let me take two examples to extremes. Let's look first at skewing a smoothing plane when smoothing a panel. The extreme is to continue to skew the plane as you push it. The blade will be at more and more of an angle to the wood fibers. At the absolute extreme, the blade will be parallel to the motion of the plane and will no longer cut anything - you'll be pushing the plane sideways.

Now, let's look at the ramped shooting board. If there's some skew action, as we raise the angle of the wood relative to the direction of the plane we'd expect to get more skew angle, as we did with the smoothing plane. When we raised the wood to 90* to the direction of motion of the plane we'd expect no cutting to take place.

However, on the ramped shooting board, the cutting action is exactly the same at 90* as it was at 0* - the blade is hitting the wood fibers head on.

Another way to think of it is to consider a regular shooting board where the platform for the wood is parallel to the direction of travel of the plane. No skewing there. Now, suppose we put a piece of wood that was cut in the shape of a triangle on the platform. Would you expect to get any skewing on that cut?

I can't see any skewing on a ramped shooting board (like the one in the picture). The only advantage I can see is that you use more of the blade for the cut so maybe you don't have to sharpen so often.

Mike

Mike ...

I believe that a ramped shooting board creates a skewed cut on edge or end grain, just like a plane with a skewed blade does on a flat shooting board.

In both case the blade is tilted in relation to the edge/end grain creating a shearing action (by spreading the cut over a wider area), plus it also lowers the effective pitch of the blade compared to a straight cut.

He's what Chris Schwarz had to say when reviewing a ramped shooting board.

"The shooting board shown here is made by Micheal Connor in Australia from New Guinea Rosewood, a dense and stable material. This shooting board is unusual in that the area that holds the work is ramped about 4° along its length. This ramping does two things: It spreads out the wear on your plane's iron a little. For example, a 3/4" x 6"-wide piece of stock will wear an area of your iron that's 1-3/32" instead of a 3/4"-wide area of your iron. Plus, the ramp makes the plane a bit easier to push through the end grain because the ramp creates a shearing cut.

Having the ramp is nice, but I wouldn't call it a do-or-die feature. My shop-made shooting board is flat and made from plywood. It's fine. I just have to push a little harder and sharpen more often."

You can see the whole article here.

http://www.woodworking-magazine.com/blog/Shooting+Board+A+Review+And+Primer.aspx


GR

[Mike Henderson]

Derek - thank you for the pictures and the pointer. I'm going to use some of those ideas on the next shooting board I make.

Ganthan - As stated earlier, as long as the blade edge is contacting the wood at 90* to the motion of the plane, there is no shearing (or skewing) action. You can verify this for yourself in a variety of ways. Think again of a smoothing plane being used to smooth a panel. You stand on one side of the panel and push the plane directly forward. No skewing.

Now, walk one quarter around the panel so you're making a cut at 90* to your previous cut, but push the plane directly forward. No skewing. The position of the wood does not make any difference when determining skewing, only the angle of the blade edge to the direction of motion.

You do get skewing with a skew chisel. You push it forward and the edge is at an agle to the direction of motion so you do get skewing action there.

The only way to get a skewing action on a shooting board (like the one I posted a picture of) is to use a plane with a skewed blade in the plane.

Mike

[Mike Henderson]

Let me give another way to visualize the cutting of a board on a ramped shooting board.

Put a board on the ramp. Now, use a square with one edge on the plane ramp (the place where the plane slides) and draw lines upward on the board. Draw a lot of lines close to each other.

Visualize the plane blade moving through the wood. When the plane initially contacts the board, it only contacts the bottom of the board so the cut is quite small. But as soon as it's into the wood, the cut is the full width of the board (actually just a bit more than the width of the board).

Think of cutting each slice of the board along those lines - let's say a 1 mm slice, just for example. The blade contacts that slice square on, and cuts the whole 1 mm thick when the plane moves forward 1 mm.

Now, consider a plane with a skewed blade cutting through the same board, with the same marks, and the same 1mm visualized slices. The blade does not cut through the entire 1mm as the plane moves forward 1mm. The blade "slices" through that 1mm section because the blade is at an angle to the direction of motion.

And as shown in several books (see Leonard Lee's book on sharpening), the skewed blade has a lower effective angle of cut.

Mike

Added comment: One might argue that you could draw the slices in any direction - and could choose to draw them such that the blade cuts the slice over time, and not within the width of the slice. But if you do that, then the blade is cutting many slices at the same time and when you analyze the situation, you have to analyze all of the slices being cut at any one time and sum them. The reason you select the slice to be parallel to the cutting edge is so that you only have to analyze one slice. Then to get the effort for the whole board, you just have to multiply by the number of slices in the board.

So if you were analyzing the effect of using a skewed blade in a plane, you'd choose slices parallel to the edge of the blade and thick enough so that you fully cut one slice when moving the plane forward by some distance (say 1 mm). So the choice of the slice is not arbitrary but is chosen to minimize the analysis.

I hope that's a clear explanation.

[Ganthan Rhodes]

Well Mike, I'm afraid we'll have to agree to disagree. :)

The analogy you're using does not describe how my ramped shooting board works. Mine creates a skewed cut by tilting the edge of the board in relation the plane blade so the width of the blade is not perpendicular to the board edge. This spreads the cut over a wider area of the blade and lowers the effective pitch of the blade -- which is the outcome of skewing as I understand it.

Page 41 of Hack's "The Hand Plane Book" provides a pretty clear explanation of the physics of skewing a cut, if you have it.

GR

[Billy Chambless]

The ramped shooting board I'm thinking of has the plane moving on the flat, and the board on a slope (higher towards the user and lower towards the stop) - like this (http://www.hntgordon.com.au/shootingboards.htm). In this case, you do not get any skew advantage.



Yep.

I had the geometry screwed ("skewed"?) up. As you say below, the motion of the plane is still at 90 degrees to the edge of the blade. Thanks for the explanation.

[Mike Henderson]

Well Mike, I'm afraid we'll have to agree to disagree. :)

The analogy you're using does not describe how my ramped shooting board works. Mine creates a skewed cut by tilting the edge of the board in relation the plane blade so the width of the blade is not perpendicular to the board edge. This spreads the cut over a wider area of the blade and lowers the effective pitch of the blade -- which is the outcome of skewing as I understand it.

Page 41 of Hack's "The Hand Plane Book" provides a pretty clear explanation of the physics of skewing a cut, if you have it.

GR
Well, Ganthan, I've given several examples to demonstrate that there's no skewing when the blade edge is 90* to the direction of motion. Perhaps you could give some examples, or pictures, to illustrate your contention that skewing is taking place in that situation.

Or even an argument that my examples are not correct or realistic.

I think I have a good understanding of the geometry of skewing and why you get a lower effective blade angle when you skew, but skewing only occurs when the blade edge is not at 90* to the motion of the blade. If you can refute that proposition, please post here.

But perhaps your ramped shooting board is different in some way from the picture I posted earlier in this thread - different in that the plane does not move straight forward. If so, please post a picture so we can all understand.

Mike

[Mike K Wenzloff]

Ganthan is correct, Mike.

Whether the wood is ramped, the plane is ramped, or a skewed cutter on a plane which is pushed in-line with the board, all produce a skewed cut.

However, a 4 degree ramp for the plane is only moderately useful for keeping the slight fuzz which can be produced on the top of a board with a non-skewed plane pushing in-line with the wood.

I believe we've had this discussion before (iirc). At least it was discussed on one of the boards. Draw out the cutting action. There is a skew however slight.

Take care, Mike

[Mike K Wenzloff]

Just in the interest of 4 people not having to produce a drawing, here is one--sorry for the size.

http://www.wenzloffandsons.com/temp/shootboard_skew.jpg

Starting at the top left, going down and then the image on the right:

(1) Straight-bladed plane. Plane and wood in the same plane.
(2) 25 degree skew-bladed plane. Plane and wood in same plane.
(3) Straight-bladed plane. Wood ramped at 4 degrees.
(4) Straight-bladed plane. Plane ramped at 4 degrees.
(5) 4 degree skew-bladed plane. Plane and wood in same plane.

Comments. Drawing 3, 4 and 5 all produce the same exact skewed cutting action. Drawing 3 has the leading edge of the cutter at the bottom of the board, training edge on the top.

Drawing 4 and drawing 5 have the leading edge of the cutter on the top of the board and the trailing edge on the bottom.

A ramped board (whether the wood or plane is ramped) produces the exact same skewed cutting action as a plane with a skewed cutter pushed straight through the wood *if* the skew of the cutter is the same (4 degree) angle as per the illustrations above.

Which, as I wrote, 4 degrees is not much and so the efficacy is equally and or proportionally less than a noticeably (15/20/25 degree) skewed cutter in a plane.

Have fun picking it apart.

Take care, Mike

[Mike Henderson]

Ganthan is correct, Mike.

Whether the wood is ramped, the plane is ramped, or a skewed cutter on a plane which is pushed in-line with the board, all produce a skewed cut.

However, a 4 degree ramp for the plane is only moderately useful for keeping the slight fuzz which can be produced on the top of a board with a non-skewed plane pushing in-line with the wood.

I believe we've had this discussion before (iirc). At least it was discussed on one of the boards. Draw out the cutting action. There is a skew however slight.

Take care, Mike
I don't think you're correct, Mike, for the reasons given in my earlier posts. If you can refute any of my examples, I'll be happy to review your arguments.

Mike

[Mike K Wenzloff]

I don't think you're correct, Mike, for the reasons given in my earlier posts. If you can refute any of my examples, I'll be happy to review your arguments.

Mike
How about refuting the drawing?

Take care, Mike

[Tristan Raymond]

There's skew and then there's skew. You can skew the blade to the direction of the plane's motion or skew the blade to the geometric plane of the wood. I think this is where the confusion lies (or is that lays).

[Mike Henderson]

How about refuting the drawing?

Take care, Mike
I don't know what drawing you're talking about, but go ahead and refute it (but show the drawing).

Here's another thought example. Suppose I had a plane that had two inches of blade exposed on the shooting edge (so I can cut a board two inches wide) and I had a shooting board that was not ramped.

Now, take square piece of wood that has a diagonal of two inches. We can all agree that when I just lay it on the shooting board, no skewing takes place. Now, let's elevate the edge closest to us by some amount. According to you, skewing now takes place.

But, let's keep elevating that edge. If skewing is taking place, we should reach a point where the blade no longer cuts the wood because the skew angle is 90*.

But as I keep turning the board, eventually I'll turn it 90* and lo and behold, the geometry is exactly what I started with, and the force to push the plane is exactly the same as when I started.

I'm sure many other examples are possible. The thing you have to do is take the example to the conclusion. If skewing is occurring at 4*, then it must also be occurring at 45* and at 90*. This is easy to show with a plane or a chisel but it doesn't occur as long as the blade is 90* to the direction of motion.

I await your counter arguments or refutation of my arguments.

Mike

Another easy example is shooting a round piece of stock.

[Ganthan Rhodes]

Mike W - Thanks for providing the drawings. I was thinking of throwing something together, but dreading the work required to attempt to support my anal point of view. I've participated in similar discussions before and always find them interesting.

Mike H - The more I read, the more I feel the debate is one of definitions. I think you believe that skewing only occurs when a plane blade is not 90* to the forward direction of the plane. In the case of a ramped shooting board, I feel skewing occurs when the blade edge is not 90* to the (typically) parallel sides of the board being planed, creating the following outcomes:

* More of the blade is cutting the same width of wood (due to the tilt); and

* The effective pitch of the blade is lowered.

I think these outcomes accurately define "skew" and, as Mike W said, can be the result of many configurations between plane blade and wood.

Are you sold, yet. :)

GR

[Mike K Wenzloff]

The drawing is a couple posts up...(post #18).

Mike

Edit to add a link to the picture in case your bwoser/security of the browser is blocking the image:
http://www.wenzloffandsons.com/temp/shootboard_skew.jpg

[Mike Henderson]

As long at the blade is moving directly forward - at 90* to the direction of motion of the plane, no skewing takes place. It is only when the blade edge has some sideways motion that skewing takes place.

The position of the wood is immaterial which you can prove by using a smoothing plane and planing from different angles. As long as you push the plane directly forward, no skewing takes place.

To maintain that skewing takes place you have to show what occurs when the angle is taken to 90*. If the plane stops cutting, then you had skewing. If not, no skewing.

Mike

[Mike K Wenzloff]

As long at the blade is moving directly forward - at 90* to the direction of motion of the plane, no skewing takes place. It is only when the blade edge has some sideways motion that skewing takes place...
I believe you are confusing skewed cutting action with a slicing cutting action.

At least that's what you are describing above (a slicing action). These are two different types of cutting action. Look it up.

In the image (post #18) the skew-bladed plane (4 degree skew) and the image to its left (the plane riding on a 4 degree downsloping ramp) produce an identical cut: one that is skewed.

Take care, Mike

[Mike Henderson]

I believe you are confusing skewed cutting action with a slicing cutting action.

At least that's what you are describing above (a slicing action). These are two different types of cutting action. Look it up.

In the image (post #18) the skew-bladed plane (4 degree skew) and the image to its left (the plane riding on a 4 degree downsloping ramp) produce an identical cut: one that is skewed.

Take care, Mike
No, I'm not confusing that. The fact that the wood is angled is immaterial to the skew action. The skew action and the advantage occuring from the skew action results from the blade edge beign at an angle to the direction of motion. If the blade edge is not angled to the direction of motion then no skewing takes place. I've given many examples to illustrate this.

Take your picture and gradually raise the angle of the wood to 45* then to maybe 75*, and finally to 90*. If your argument was correct, the skewing would increase, gradually moving to no cutting at all.

But that doesn't happen. You can't have skewing at 4* and then have it dissappear as the angle gets larger.

Mike

[Randy Klein]

Just to throw in my 2 cents and yet another analogy, but I don't see any skew cutting in a ramped board.

And the promised alternate analogy:

If you took the wood off the shooting board and clamped it in a vice (for better visualization):

1. A non-ramped board would be as if you planed from end to end, with the plane's travel most inline with end mid points.
2. A ramped board would be if you planed from end to end but the plane's travel was more inline with the corners (along the diagonal).

Skewing the plane to the direction of travel in either of the above scenarios is the only way to have a skew cut, but this is difficult to do on a shooting board, but not when its clamped in a vice.

A skew cut is when the iron is at an angle to the direction of travel, regardless of how the wood is oriented to your plane.

Orienting the wood differently (as in scenario #2 above) is analogous to planing diagonally across the grain.

To have a skew cut for end grain on a shooting board, you would need a skewed iron and again, the orientation of the wood is unimportant, so ramped vs unramped wouldn't matter.

You could engineer an overly complicated shooting board to impart a skew cut, but it's not something I'd want to do.

[Mike K Wenzloff]

Ok, let's try this one image at a time.

Looking at the image in post #18. The bottom right drawing. 4 degree skewed cutter. Plane moves in a horizontal motion, in the same plane as the wood.

Is this a skewed cut?

Mike

[Randy Klein]

Ok, let's try this one image at a time.

Looking at the image in post #18. The bottom right drawing. 4 degree skewed cutter. Plane moves in a horizontal motion, in the same plane as the wood.

Is this a skewed cut?

Mike


Yes, since your iron is skewed at angle to the direction of the plane's travel, you will have a skewed cut.

[Mike Henderson]

Except we know the blade edge is not skewed to the direction of travel, so you will not have a skewed cut.

If your thesis is correct, you should have no trouble pointing out the errors in the many examples I've given.

Mike

[Mike K Wenzloff]

But we know the blade edge is not skewed to the direction of travel, so you will not have a skewed cut.
...
In the lower right drawing, the blade is skewed. Direction of travel is forward, plane and wood in the same horizontal plane. Though it is small, it is a 4 degree skewed cutter. Therefor the cutter edge is skewed to the direction of travel--at 4 degrees.

Or have I misunderstood your statement above?

Mike

[Joel Goodman]

Another 2 cents. The argument for angled ramp not being the same as the skewed blade this: the line of force is perpendicular to the blade's edge with a "skewed" ramp; with a skewed blade it is at some angle. In practical terms I think the very slight angle in the ramped shooting board is the more important factor -- skewed planes aren't made with a 4 degree skew. I am interested that Derek feels that the ramped version makes a better cut. Has anyone else used both types of shooting board? Sometimes the results defy the theory!

[Mike Henderson]

In the lower right drawing, the blade is skewed. Direction of travel is forward, plane and wood in the same horizontal plane. Though it is small, it is a 4 degree skewed cutter. Therefor the cutter edge is skewed to the direction of travel--at 4 degrees.

Or have I misunderstood your statement above?

Mike
As Randy said, the way you've drawn it, you would have a skewed cut because the blade edge is at an angle to the direction of travel. But that's not what's really happening. In the real world, the blade in the plane is at 90* to the direction of travel. You can't change that fact.

Randy's posting in #28 is the same position I hold.

Mike

[Mike K Wenzloff]

...A skew cut is when the iron is at an angle to the direction of travel, regardless of how the wood is oriented to your plane. ....
Really?

Ok. Here's is the same plane with a 4 degree skewed cutter. The plane is moving forward on a ramp sloped upward in relation to the wood. The ramp is 4 degrees.

Is this a skewed cut?

http://www.wenzloffandsons.com/temp/shootboard_skew2.jpg

It meets your and Mike's criteria of a skewed cutter and also challenges the statement that wood orientation doesn't matter--something you both have claimed.

Well, this has been a fun diversion from a really long work week. Only it doesn't accomplish a darn thing. So it's back to work for me.

Take care, Mike

[Mike Henderson]

Really?

Ok. Here's is the same plane with a 4 degree skewed cutter. The plane is moving forward on a ramp sloped upward in relation to the wood. The ramp is 4 degrees.

Is this a skewed cut?

http://www.wenzloffandsons.com/temp/shootboard_skew2.jpg

It meets your and Mike's criteria of a skewed cutter and also challenges the statement that wood orientation doesn't matter--something you both have claimed.

Well, this has been a fun diversion from a really long work week. Only it doesn't accomplish a darn thing. So it's back to work for me.

Take care, Mike
I'm not sure I understand the picture, but if the blade is skewed at an angle to the direction of travel of the plane, then it's a skew cut. If the blade edge is 90* to the direction of travel of the plane, then it's not a skew cut. The criteria is pretty straightforward.

The position of the wood is immaterial.

Mike

[Ganthan Rhodes]

Well, Ganthan, I've given several examples to demonstrate that there's no skewing when the blade edge is 90* to the direction of motion. Perhaps you could give some examples, or pictures, to illustrate your contention that skewing is taking place in that situation.

Or even an argument that my examples are not correct or realistic.

I think I have a good understanding of the geometry of skewing and why you get a lower effective blade angle when you skew, but skewing only occurs when the blade edge is not at 90* to the motion of the blade. If you can refute that proposition, please post here.

But perhaps your ramped shooting board is different in some way from the picture I posted earlier in this thread - different in that the plane does not move straight forward. If so, please post a picture so we can all understand.

Mike

In order to do what you ask, I cann't start by assuming your definition of a skew cut is correct. If I do, it's a tautology and there's no point in debate. I agree that it's one way of achieving a skew cut, but not the only way. If you can support your current definition, great. Just post your source(s) and I'll read them with an open mind.

In the meantime, here's Hack's take on skewing a cut. Before going any further, please let me know if you agree with it or not.

http://books.google.ca/books?id=Zq2M06PRxvEC&pg=PA41&lpg=PA41&dq=plane+%22skew+cut%22&source=web&ots=XLOzsOvAjD&sig=SMhhNweo00wr6M1nlr4_6iND0DE&hl=en&sa=X&oi=book_result&resnum=2&ct=result


If you have other resources you'd like me to see, please let me know.

Thanks.

GR

[Mike Henderson]

The pictures seem to agree with what I've been saying. If you do not agree with the definition I gave, what definition would you use?

Let me suggest that you just state your thesis rather than asking me questions. If there are assumptions you need to make, state the assumptions and proceed from there.

Mike

Leonard Lee has a discussion of skewing in his book "The Complete Guide to Sharpening" - his discussion agrees with what I've been posting.

[Ganthan Rhodes]

The pictures seem to agree with what I've been saying. If you do not agree with the definition I gave, what definition would you use?

Mike

Leonard Lee has a discussion of skewing in his book "The Complete Guide to Sharpening" - his discussion agrees with what I've been posting.

I'm using the definition I've mentioned to in two previous posts. Here's the gist:

"I feel skewing occurs when the blade edge and wood are configured to achieve the following outcomes:

* More of the plane blade is cutting the same width of wood (due to the tilt); and

* The effective pitch of the blade is lowered.

I think these outcomes accurately define "skew" and, as Mike W said, can be the result of many configurations between plane blade and board."

Do you disagree with anything in that statement? Also, would you mind restating your definition so there's no confusion.

I have Leonard Lee's book in front of me. There's lots on skew cuts in Chapter 2. I too feel that what he says is consistent with my definition of skew cutting. However, I can't find anything that restricts it as narrowly as you have previously defined it. Maybe I missed it. Please point me to the passage and I'll read it right away.

Thanks.

GR

[Mike Henderson]

My definition is that there is no skewing when the blade edge is at an angle of 90* to the motion of the plane.

If you can demonstrate skewing in that situation, I'd appreciate your explanation.

Mike

[Randy Klein]

I imagine many here have Leonard Lee's book. So if you look at page 10, in the upper right, it shows a comparison between a straight and skew cut.

Notice how it demonstrates this comparison with a circle (standing in for a single fiber). A circle is rotation invariant, so no matter how you rotate the image, the skew and straight cut comparison will remain.

Now bundle a bunch of those circle fibers together and you have the end grain of the board. Since each single fiber is invariant to rotation, then the sum of those fibers are also rotation invariant since cutting is a linear operation (pun intended for those math geeks out there).

The conclusion being that the orientation of the board has no bearing on skew vs straight since the cut is defined as the orientation of the cutting edge to a single, circular, rotation-invariant fiber.

[Andrew Homan]

* More of the blade is cutting the same width of wood (due to the tilt); and



Hi Ganthan,
I visualized this, and then double-checked it for real on my ramped shooting board -- that is exactly what is going on.
-Andy

[Ganthan Rhodes]

My definition is that there is no skewing when the blade edge is at an angle of 90* to the motion of the plane.

If you can demonstrate skewing in that situation, I'd appreciate your explanation.

Mike

That is not a definition, Mike.:) (That's the same as saying your definition is that a ramped shooting board can't make a skew cut). I disagree with your definition, but that's how this all got started. I can't find any support for it and it doesn't seem you can provide any either. It seems it's just your opinion and I respect that.

However, if you agree with my definition of a skew cut, I can prove that a ramped shooting board creates one, albiet small.

GR

[Ganthan Rhodes]

Hi Ganthan,
I visualized this, and then double-checked it for real on my ramped shooting board -- that is exactly what is going on.
-Andy

That's been my experience, Andy. Plus the effective pitch of the blade is lowered. That's a bit harder to visualize, but Lord help me (and everyone) if I have to draw a picture. :)

GR

[Randy Klein]

Hi Ganthan,
I visualized this, and then double-checked it for real on my ramped shooting board -- that is exactly what is going on.
-Andy

More blade is cutting because you are essentially going from corner to corner which gives a larger cross section. But each individual fiber is still being cut at 90 degrees to the iron.

[Mike Henderson]

That is not a definition, Mike.:) (That's the same as saying your definition is that a ramped shooting board can't make a skew cut). I disagree with your definition, but that's how this all got started. I can't find any support for it and it doesn't seem you can provide any either. It seems it's just your opinion and I respect that.

However, if you agree with my definition of a skew cut, I can prove that a ramped shooting board creates one, albiet small.

GR
Skewing, as a definition, is when the blade edge is angled relative to the direction of motion. This configuration gives a lower effective edge angle.

But the lower effective angle comes from the blade edge being angled relative to the motion of the plane. So using the lower effective blade angle is just another way of saying what I gave as a definition.

Likewise, your comment that "more of the plane blade is cutting the same width of wood" can only occur if the blade is angled relative to the motion of the plane. So again, your comment is just another way of saying what I gave as a definition.

But I suppose if we cannot agree on the definition, we're not going to agree on much else.

I'm going to stop responding to this thread unless you can give some example of how you can get a skewed cut from a blade that is 90* to the direction of motion. This back and forth is not going anywhere.

Mike

[Ganthan Rhodes]

I'm going to stop responding to this thread unless you can give some example of how you can get a skewed cut from a blade that is 90* to the direction of motion. This back and forth is not going anywhere.

Mike

OK, Mike. I feel the same way.

If I get ambitious early next week I may draw a couple of diagrams to show why I believe a ramped shooting board imparts a slight skew with a blade that is 90* to the direction of motion. Or, maybe not. Life is short and I didn't come to SC to make enemies. :)

GR

[Matt Bickford]

I know Mike Henderson to be correct. The plane is moving perpendicularly to the iron's edge. There is no reduction in cutting angle. If the plane was pushed on an angled carriage (ie the ramp moved along with the plane) the cutting angle would change. (Using a plane with a skewed iron is an angled carriage.)

If you think this "sheering" cut is easier than you also thing it's easier to push a plane diagonally across a piece than straight down it. It may be slightly easier, I don't know. I do know that it definitely doesn't reduce the effective cutting angle of the iron no matter how you correctly look at it or who states that it does.

I've never used a ramped shooting board, but I'd have to imagine that it's actually more difficult to use because more of the iron is engaged at each instant with the same cutting angle.

[Matt Bickford]

As a side note. A poster at FWW's knots posted drawings of this that, if linked, were so clear that this thread wouldn't have lasted past 10 replies. I wish it was worth locating...

[Derek Cohen]

Gad, what a thread to read first thing in the morning! The headache I have already is worse than a hangover!

I skimmed the last two pages so I may have missed something. It just seems to me as if everyone is going around in circles. Here is my take ..

The first question to ask is not whether there is skew, but to ask why one would want to have skew.

The answer is to lower the effective cutting angle, so as to obtain a cleaner cut in endgrain (note end grain - this can be detrimental when shooting interlinked edge grain, such as in drawer sides). In modern times we do not need to do this as we now have good bevel up planes, such as the LV or LN LA Jacks, planes which cut as well - or even better (I know this from experience) - than the yesteryear skew-bladed mitre planes.

So why then would one persevere with a skewed cut (yes there is one - just don't go there. It is not the point here), particularly one at 4 degrees, which is not a significant angle if attempting to create a skew cut to lower the effective cutting angle? And the answer folks - wait for it (insert drum roll here :) - is to soften the impact of the blade hitting the board. That is all. There is really not enough spreading of the wear on a blade to do it for that reason. Anyway, if shooting end grain you want to be using a S-S-Sharp blade, and by the time you are wanting to benefit from spreading the wear, the blade will be useless.

The question is whether it is worth the effort to build a ramped shooting board? Take my word that they require a considerable extra effort. I sell mine for a small fortune and lose heavily on the deal. I really only do them as a special favour. But - yes - they are worth it. I cannot say that the cut they produce is better - it just feels that way since they work with less effort and, by comparison to a flat board, are smooth in use. Definitely worth making one if you are prepared to give the time.

Regards from Perth

Derek

[Robert Rozaieski]

I have to agree with Mike. All a ramped shooting board does is change the orientation of the stock to the plane. It seems easier to use because at the start of the cut, you are not cutting the entire edge, just easing into the piece from the corner. Remove less material (at the start of the cut) and the cut is easier.

[Phillip Pattee]

I agree with Mike Henderson as long as the motion of the plane is perpendicular to the cutting edge you don't achieve any skew cutting. Imagine cutting the end of a round dowel rod--this should take the confusion of the woods angle out of it. To achieve a skew cut the direction of motion of the plane and the angle of the cutting edge relative to that motion are all that matter.

I suppose that you could build a jig similar to a donkeys ear that rode where the plane normally does and clamp the plane to it. This would achieve a skew cut. You would probably also have to elevate your wood as well to get it up where the blade would be due to the plane's angle. You might want to do this so that you could skip the purchase of a LA jack plane and use the plane you already have.:rolleyes:

[Ray Gardiner]

I agree with Mike Henderson as long as the motion of the plane is perpendicular to the cutting edge you don't achieve any skew cutting. Imagine cutting the end of a round dowel rod--this should take the confusion of the woods angle out of it. To achieve a skew cut the direction of motion of the plane and the angle of the cutting edge relative to that motion are all that matter.



Yes agreed, the motion of the plane is at right angles to the blade, but relative to the wood (on an ramped shooting board) it is skewing,

Imagine keeping the plane still and sliding the wood across at an angle. Refer to Garret Hacks description(below).

By ramping the shooting board, you introduce a sideways component to the motion. (at an angle to the blade).


http://www.sawmillcreek.org/attachment.php?attachmentid=93302&stc=1&d=1217142359

Think in terms of the motion of the wood relative to the blade.

Regards
Ray
PS: Nothing like a good shooting war. (...sorry I couldn't resist)

In the extreme (impossible) case of a 90 degree ramp you would be going parallel to the blade, and no cutting would take place. Since it would be all
sideways motion and no forward motion.

[Wilbur Pan]

Picture = 1K words.

The white rectangle is the plane. (It's rectangular because it's a Japanese plane. ;) )

The brown rectangle is a board.

The first diagram is what I think we all agree is clearly a skewed cut.

The second diagram is what I think we all agree is clearly a non-skewed cut.

The third diagram is what happens on a ramped shooting board.

In the fourth diagram, I've made the shooting board invisible. This is what I thought was a skewed cut when I imagined it in my head. It is clear that the stock is at an angle relative to the orientation of the plane. But if you magically expanded the stock to a larger board (dotted line rectangle), it would match the diagram of a non-skewed cut. If this really was a skewed cut, that would mean that the effective cutting angle of a plane would be dependent on the outside dimensions of the board, which of course is silly.

(BTW, I'm up at this hour because I'm on call tonight, and waiting for an ER to call me back. What's Ray's excuse? ;) )

[Ray Gardiner]

Picture = 1K words.
(BTW, I'm up at this hour because I'm on call tonight, and waiting for an ER to call me back. What's Ray's excuse? ;) )

Hi Wilbur,
It's late afternoon here in Australia! (GMT+10) Just finished cleaning up the workshop, and waiting for dinner..

I'm still trying to figure out your diagram... I still think the key is the motion of the blade **relative** to the wood.

Regards
Ray.

[Randy Klein]

Good pics wilbur, I think that illustrates it perfectly.

[Ray Gardiner]

Hi Wilbur,

Ok, you win. A ramped shooting board is not a skew cut. More of an
angled slicing cut.

Your diagram number 4 convinced me.

Regards
Ray

[Mike K Wenzloff]

At the most simple, a skew cut presents a leading and trailing edge through the cut. By its nature, it is a slicing cut in practice.

A ramped plane chute presents a leading and trailing edge in relation to the cut and produces a slicing cut.

Me thinks some people need to stop conceptualizing, build one--doesn't need to be as uptown as Derek's--a watch how both the plane actually moves in relation to the board as well as the chip formation.

It really is as simple as that. If one uses a short piece of stock and planes the long grain it is easy to see that the greater the plane chute's drop (4 degrees or higher) the shaving will not be a simple tight roll. It is the same type of curled shavng that is produced with a skew bladed plane shoved straight in-line. Which due to its leading/trailing edge, produces a different curled shaving than a straigt-bladed plane.

So, just build a junk board. It is simple.

Take care, Mike
who's also now done.

[Mike Henderson]

At the most simple, a skew cut presents a leading and trailing edge through the cut. By its nature, it is a slicing cut in practice.

A ramped plane chute presents a leading and trailing edge in relation to the cut and produces a slicing cut.

Take care, Mike
who's also now done.
Mike - see my post #13 which shows (in words) that there is no leading and trailing edge once the blade is into the wood (for a blade that is 90* to the direction of motion).

Wilbur's pictures (above) show visually what I was saying in that post.

Thanks, Wilbur for creating that. Your picture is much more effective than my words.

Mike

[Mike K Wenzloff]

Make a ramped shooting board. Actually observe the long-grain shaving. It isn't the shaving of a straight through cut with a non-skewed plane.

It only takes a few minutes to knock out a perfectly usable (but perhaps ugly) ramped shooting board. Shave a sort piece of long-grain.

Do a little emperical testing rather than theorizing or logical deduction. Might learn a difference between real-world cutting action and, well, whatever this all has been.

Take care, Mike
Ok. Now I won't post on this anymore...

[Mike Henderson]

Make a ramped shooting board. Actually observe the long-grain shaving. It isn't the shaving of a straight through cut with a non-skewed plane.

It only takes a few minutes to knock out a perfectly usable (but perhaps ugly) ramped shooting board. Shave a sort piece of long-grain.

Do a little emperical testing rather than theorizing or logical deduction. Might learn a difference between real-world cutting action and, well, whatever this all has been.

Take care, Mike
Ok. Now I won't post on this anymore...
Actually, I used one but didn't find any difference between it and my flat shooting board (for equal boards). That led me to analyze what was happening.

Mike

[Ray Gardiner]

Make a ramped shooting board. Actually observe the long-grain shaving. It isn't the shaving of a straight through cut with a non-skewed plane.


Ok, did that, and it certainly looks like a skewed cut, so what is wrong with Wilbur's diagram..

I think the thing that fooled me was the sleight of hand making the ramp dissapear. No ramp == No skewing. (See wilbur's figure 4)

I have redrawn Wilburs Diagram, ( the vital missing part of Wilbur's drawing being the blade)

And added an example of what happens if the board moves instead of the plane, which I hope shows clearly that it is in fact a skew cut.


http://www.sawmillcreek.org/attachment.php?attachmentid=93327&stc=1&d=1217178059

Ok, folks blaze away, I'm ready to be convince otherwise.

Oh, and diagrams not showing blades or ramps will be analysed more carefully next time.

Regards
Ray

[Mike Henderson]

I can't see your picture, Ray, but it doesn't matter which object "moves" since the only thing that matters is the relative motion between the two objects. You can analyze either assumption since they are equal.

The only way I can see a skew cut occurring is if you consider the board moving along it's long axis. But, of course, that's not the correct movement. The board moves along the axis of the plane and 90* to the edge of the blade.

Wilbur's diagram is correct. You can visualize the board moving in Wilbur's drawing if you wish, but it doesn't change the geometry.

Mike

[Ray Gardiner]

I can't see your picture, Ray, but it doesn't matter which object "moves" since the only thing that matters is the relative motion between the two objects. You can analyze either assumption since they are equal.

Mike

Hi Mike,
Here is the direct url, your browser may be blocking in-line images for some reason.

http://www.sawmillcreek.org/attachment.php?attachmentid=93327&stc=1&d=1217178059

Take a look, see what you think. I will catch up with the discussion tomorrow. (it's getting late here, and the ebay auction I was watching has gone over my limit!)

Regards
Ray

[Matt Bickford]

Mike W, why do you sell saws made with different pitches? Can I not simply change the pitch by entering the cut at a different angle?: 8 degrees follow picture #1, 6 degrees follow #2, 10 degrees follow #3. I mean, I'm cutting at an angle. It must change the effective pitch. (please note the extraordinarily high level of sarcasm.) Derek must agree simply because it's easier to start. Derek, you should offer people their money back if that's part of your advertising, it's false.

I think there are a handful of people that don't understand why Wilbur's Diagram #1 actually reduces the effective cutting angle.

[Pedro Reyes]

I don't know what skew means to everyone anymore, or slicing cut for that matter.

Just like Mike H. said, an angled shooting board, DOES NOT change the effective cutting angle.

Instead of diagrams, imagine a board with an infinte end grain area (or forget about edges in your board, or imagine a butcher block), put it in your angled shooting board, shoot... are you changing the angle? Unless the edge of the blade is moving in a direction which is not perpendicular to it, then you are not changing the effective cutting angle.

Saying that a ramped shooting board changes the cutting angle is like saying that planing a board's face at 45 degrees (just like scrub lanes are used) is changing the cutting angle, and I think we all agree with this one. This is changing the way the cut is presented to the grain, but not the cutting angle of the blade.

None of this says ramped shooting boards don't have advantages, there is the obvious use of more of the blade.

peace

/p

[John Schreiber]

I am certain that all of you are better craftsmen than I, and I am coming into this thread late, but I do understand geometry and physics. An angled shooting board does not introduce a skew. There are two issues which might make this clearer. First,


Imagine planing the end of a dowel without a shooting board. Whatever angle you come at the surface, so long as you move the plane perpendicular to the edge of the blade, you are not making a skew cut. Now imagine that dowel in a regular and an angled shooting board. That is the same as changing the angle which you approach the end, but still keeping the direction of travel the same.

If instead you come at the end of the dowel with the blade at an angle, the blade will have a lower effective pitch and it will plane more easily. That is a skewed cut.


Second, Ganthan wrote that skewing creates

the following outcomes:

* More of the blade is cutting the same width of wood (due to the tilt);When skewing, if the wood is wider than the blade, the same amount of blade is in fact cutting a smaller width of wood. If the wood is narrower than the blade as in a shooting board, more of the blade is cutting more of the wood. An angled shooting board does not create either of those circumstances; in that case, more of the blade is cutting more of the wood.


and

* The effective pitch of the blade is lowered.Because the plane is traveling perpendicular to the blade, the effective pitch is not lowered. Imagine the dowel above.

All that being said, an angled shooting board may still work better than a flat one. When using an angled shooting board on a rectangular piece of wood, the blade first hits a corner, then it eases into the whole width of the board. That would slightly decrease the shock to the plane and the user and might lead to a smoother cut.

[Wilbur Pan]

Hi Mike,
Here is the direct url, your browser may be blocking in-line images for some reason.

http://www.sawmillcreek.org/attachment.php?attachmentid=93327&stc=1&d=1217178059

Take a look, see what you think. I will catch up with the discussion tomorrow. (it's getting late here, and the ebay auction I was watching has gone over my limit!)

Regards
Ray

Hi Ray,

I can't see your diagrams either, and the URL you gave gives me a "Invalid Attachment specified. If you followed a valid link, please notify the administrator" error message from SMC.

I wasn't hiding anything by omitting the blade. You can use the front end of the plane as a representation of what the blade is doing, since the blade is parallel to the front and back edges of the body of the plane.

[Wilbur Pan]

At the most simple, a skew cut presents a leading and trailing edge through the cut. By its nature, it is a slicing cut in practice.

A ramped plane chute presents a leading and trailing edge in relation to the cut and produces a slicing cut.

Me thinks some people need to stop conceptualizing, build one--doesn't need to be as uptown as Derek's--a watch how both the plane actually moves in relation to the board as well as the chip formation.

It really is as simple as that. If one uses a short piece of stock and planes the long grain it is easy to see that the greater the plane chute's drop (4 degrees or higher) the shaving will not be a simple tight roll. It is the same type of curled shavng that is produced with a skew bladed plane shoved straight in-line. Which due to its leading/trailing edge, produces a different curled shaving than a straigt-bladed plane.

So, just build a junk board. It is simple.

Take care, Mike
who's also now done.


Mike - see my post #13 which shows (in words) that there is no leading and trailing edge once the blade is into the wood (for a blade that is 90* to the direction of motion).

Wilbur's pictures (above) show visually what I was saying in that post.


Hi Mikes,

(How often does one get to use a salutation like that?)

I think that there is a little bit of talking past each other going on here. I think that what Mike H. refers to as a skew cut is a skewed presentation of the plane in order to change the effective cutting angle of the plane blade, and that what Mike W. refers to as a skew cut is a skewed presentation of the plane such that the blade edge is not perpendicular to the grain direction irregardless of what happens to the effective cutting angle.

If I'm right in my assessment above, and there is a big chance that I might be way off base, you could revise my diagram with these labels instead. (I also added in a line for the plane blade itself for Ray.)

It is clear that neither definition results in the same sort of shaving as when you plane a board with the plane lined up with the grain direction of the board. But one of them will change the effective cutting angle of the blade, and the other won't.

FWIW, when I think of a skew cut with a plane, I am thinking about planing in such a way that I am lowering the effective cutting angle of the blade (first diagram). When I think about what's going on with a ramped shooting board, I think about it more as planing diagonally across the grain (fourth diagram). But here it's really just getting into semantics, and doesn't change the mechanics of what's going on.

So probably the best thing to say is, "A ramped shooting board does not change the effective cutting angle of the plane."

[Ganthan Rhodes]

Mike.

Just checking back in on the fray.

I sat down late last night with pencil, paper, and reference books to prove my belief that a ramped shooting board produced a skewed cut. Well, that didn't go so well, since all I did was prove myself wrong.

I came up with drawings similar to Wilbur's, but not as elegant and concluded that a ramped shooting board does not:

* Create the slicing cut associated with a skewing cut; or

* Lower the effective pitch of the blade when cutting.

Oh well ... I guess I'm still trainable. I'll go put on the pointy hat.

GR

[Ray Gardiner]

I wonder where the file I uploaded went? Here it is again, I'll use an external link this time.

1. We all agree is a skewed cut
2. We all agree is NOT.
3. We all disagree... (I will call it a slicing cut, since there is a sideways component to the cutting action)
4. I hope is obvious is a skewed cut.

So, go figure, when the board moves it's a skewed cut. when the plane moves it's not skewed, but not a straight cut either, the sideways action would be difficult the replicate free-hand.


http://www.backsaw.net/pics/ramped%20shooting%20board_2.jpg

[Mike Henderson]

Ray - one thing that I do when analyzing something like picture #3 is to take it to extremes. If some effect is occurring, it should get more pronounced at the extremes.

So suppose we were to put the piece of wood at a much greater angle. If a slicing cut is taking place, the slicing should be even more pronounced at that higher angle.

So think about that piece of wood moving toward 90* - not all the way to 90* but getting close. Is the slicing action increasing? Now, what happens when we get to the extreme of 90*? Does it act like a saw now?

My analysis is that no slicing occurs. The plane simply moves into the wood, and as it get further in a different part of the plane blade is used to cut the wood. No real movement occurs of the wood - as the plane blade moves into the wood, wood "appears" at a lower part of the blade and disappears at the higher part of the blade. But no physical movement of the wood occurs - it's all forward motion so no "slicing" occurs.

For some reason I always try to explain things in words, and that's not always the best way. Wilbur really helped everyone understand how things work with his pictures. I'll give some thought to see if there's a picture I can produce to illustrate what I've said above.

Mike

[Ray Gardiner]

Hi Mike,
Many years ago a pure maths professor taught me "reductio ad absurdum" is a valid logical process for mathematical proofs. However here we have real world constraints and shades of grey to factor into any logical proof. The fact that an argument fails at an extreme case doesn't mean there aren't intermediate instances where it is true.

Anyway back to shooting boards, as the ramp angle approaches 90 degrees the blade would need to become infinitely wide, and the side ways movement exaggerated to the point where the blade would just be moving straight up
since no forward motion would be possible. (also no cutting would be taking place).

Now moving back to a shallow angled ramp, the wood fibres are moving sideways across the blade, as the plane moves forward. This is what I am calling slicing. (ok it might be different to skewing).

The other thing that is confusing me, is that logically it shouldn't matter if the board moves or the plane moves. (it should be all relative). But it seems to me that if the board moves it sure looks like skewing.


Regards
Ray

[Mike Henderson]

Now moving back to a shallow angled ramp, the wood fibres are moving sideways across the blade, as the plane moves forward. This is what I am calling slicing. (ok it might be different to skewing).

The other thing that is confusing me, is that logically it shouldn't matter if the board moves or the plane moves. (it should be all relative). But it seems to me that if the board moves it sure looks like skewing.


Regards
Ray
I think if you consider it more, you'll see that the wood fibers are not moving sidewards across the blade. The only movement is the forward movement of the blade which cuts the fibers with that forward movement. I think what might be confusing you is that the cutting point on the blade changes as you push the plane into the wood. But that is not due to any movement of the wood. In fact, we know the wood doesn't move - it is usually clamped to the shooting board (maybe only with hand pressure).

Regarding the movement of the board, the difference is that when you show the board moving, you move it along it's long axis. But to duplicate the situation where the plane is moving, you need to show it moving along the long axis of the plane. [added note: You can do that by showing the ramp and the board moving to the left (with the board fixed to the ramp). That will move the board along the long axis of the plane.]

Mike

[Johnny Kleso]

Derek those are some nice looking shooting boards..
Are they Jarrah?

I think the skewing pushed the work down as well as back giving a stable cut..

Think if you had a un-square back cut and no skew you work might want to lift to be flush to the fence/Stop.. With a skewed cut it helps lock work in two directions..

[Ray Gardiner]

Hi Mike,

Well argued, and you've withstood the onslaught of (my feeble) counter arguments.

Thanks for an interesting discussion. I think I'll let it sink in for a bit.

Got to get some woodworking done before it gets dark (chopping firewood)

Regards
Ray

[John Schreiber]

Oh well ... I guess I'm still trainable. I'll go put on the pointy hat.
No pointy hat for you Ganthan. Pointy hats only go to those who keep pushing the wrong path out of habit and don't take the time to understand.
:):p:D

[Mike K Wenzloff]

No pointy hat for you Ganthan. Pointy hats only go to those who keep pushing the wrong path out of habit and don't take the time to understand.
Nice condencension there, John. Smiley faces or no.

Take care, Mike

[John Schreiber]

Nice condencension there, John. Smiley faces or no.

Take care, Mike
I'm sorry Mike.

[Ganthan Rhodes]

No pointy hat for you Ganthan. Pointy hats only go to those who keep pushing the wrong path out of habit and don't take the time to understand.
:):p:D

Thanks, John. It was rather traumatic for me ... my first time being wrong and all.
:eek::(;):D

GR

[Billy Chambless]

Thanks, John. It was rather traumatic for me ... my first time being wrong and all.
:eek::(;):D

GR

The trauma lessens with repeated wrongness.


DAMHIKT.

[Ray Gardiner]

Here's an idea, for a new design ramped shooting board.

Put an angled block under the plane, that way you get a ramped AND skewed shooting board.

Regards
Ray

[Ray Gardiner]

Firstly, let me apologise for the lingering death that this thread has suffered.
There are just a few loose ends to tidy up.

For those who have followed the discussion so far, Mike Henderson argued successfully that since the motion was at right angles to the blade no skewing (by definition) was taking place. Obvious, really once you define skewing in that manner. That means of course that no reduction in effective angle takes place either.

However, there is **something** happening on a ramped shooting board, that I have mistaken for skewing. I suspect it has to do with the angle the blade intersects the top edge of the board, but it most certainly doesn't feel like a straight cut, and shavings don't look like it either.

Here is an example of what I mean,

http://www.backsaw.net/pics/Shavings.jpg

1. Straight Cut No 5 wide mouth
2. Ramped Cut No 5.
3. Skewed Cut No 5.

4. Straight Cut LN 4 narrow mouth ( well, a lot narrower than the Stanley 5)
5. Ramped Cut LN 4
6. Skewed Cut LN 4

You will notice the characteristic tight spiral a straight cut produces and Also note the spread out spiral produced by a skewed cut, more pronounced on a wider mouth opening. Finally notice the ramped cut is somewhere between the two.


Ok, I conclude that ramped cutting isn't quite like a straight cut, it has to do with the cut moving across the blade as the stroke proceeds, in particular the angle the blade intersects the top edge of the board. It might not be skewing within the strict definition of skewing as such. But it definitely looks like it. ( and feels like it, well to me anyway).

Apologies again, to all who have had enough of the thread. (I'll go and get my pointy hat now..)

Regards
Ray

[Joel Goodman]

It would seem from the shavings that everybody can claim some degree of "rightness" in this discussion. The shavings tell an interesting story.

[Mike Henderson]

Ray, this is hard to describe in words, but when you cut a shaving off of a board at an angle to the blade, you will get a shaving that is not rolled tightly in one plane - each spot on the shaving will coincide with the place on the wood where it was removed.

This won't be exact, but if you held the shaving alongside the board on the ramp, and rotated it as you moved it along the board, the coil would unwind so that the shaving followed the board.

Couple of things to remember. 1. The outside of the coil is the end of the board. 2. The coil may coil up tighter or looser than the forward motion.

But that doesn't change the cutting action into a skew cut or a slicing cut. It's just an artifact of cutting a sloped board with a straight blade edge.

Mike

Here's a "backwards" way of showing what's happening. Take a strip of paper and wrap it around a pencil. You can wrap it in any way you want to begin - in a single wrap on top of each previous wrap, or in a spiral along the pencil. Now, hold the end of the paper down, and push the pencil directly forward (that is, at 90* to the long axis of the pencil) until the paper is almost unwrapped. What you'll find is either a straight line (relative to the direction of the pencil) - if you wrapped it on top of the previous wrap - or an angled line - if you wrapped it in a spiral along the pencil. The shaving works the same way.

To beat this example to death, let me suggest another way to look at the pencil and strip of paper. Lay out the strip of paper - tape the far end down. Now, put your pencil on the other end at some angle to the strip (90* is valid, also). Imagine you have a magic blade below your pencil, but in line with your pencil, which is cutting the strip from the table. Roll your pencil forward and observe the configuration of the resuting roll. If you laid the strip at an angle of a few degrees to the motion of the pencil, you should get a spiral wound on the pencil.