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. 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 ..



Close up of one ..



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.



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



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



I have a very comprehensive article on my website on "setting up and using a shooting board": http://www.inthewoodshop.com/ShopMad...%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!



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/...nd+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. 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.