Ramped shooting boards - do they really work better?

[n0legs]

Someone needs to firmly define some parameters here.
What is the point of reference to decide whether the angle at which a cutting edge is presented to the material, is in fact a skew cut ?
Grain direction, longest dimension?

 

[MusicMan]

Neither. It's the angle of the blade edge relative to its direction of motion, as has been said several times. Anything other than 90 degrees is a skew cut. The material is immaterial!

Keith

 

[Tom K]

Neither. It's the angle of the blade edge relative to its direction of motion, as has been said several times. Anything other than 90 degrees is a skew cut. The material is immaterial!

Keith

Now you are just waving a plane around whats the point in that?

 

[n0legs]

Neither. It's the angle of the blade edge relative to its direction of motion, as has been said several times. Anything other than 90 degrees is a skew cut. The material is immaterial!

Keith

So it's accepted that a skew cut can be achieved without a skew plane, yes ?

I'm processing all of this :lol:

 

[MusicMan]

Yes. As we do when planing difficult material, rotate the plane by say 20 deg but keep the direction of the cut along the board.
Keith

 

[bugbear]

Yes. As we do when planing difficult material, rotate the plane by say 20 deg but keep the direction of the cut along the board.
Keith

Like this:

BugBear (who didn't keep the original vector version of the diagrams )

 

[MusicMan]

But yours is prettier!

 

[n0legs]

So, if we were to turn the piece of timber in BB's diagram 90 degrees, but leave the plane in the same position, would this still be a skew cut?

 

[bugbear]

So, if we were to turn the piece of timber in BB's diagram 90 degrees, but leave the plane in the same position, would this still be a skew cut?

Yes - the angle of the workpiece makes no difference - think about a super-squirly piece of burr; we
can still take a skew cut, even though the grain direction is so mixed up as to be meaningless.

While I'm on;

It's often useful to examine extreme cases when marginal cases
are hard to think about.

So here's a diagram of an extremely large amount of skew (around 80 degrees). This is very
nearly all "slice" and no "push".

Now we now consider trying to make a ramped shooting board to
do the same.

Whilst one can have a ramp at 80 degrees, all you're doing is "pushing"
in a different direction; the slicey-ness of a skew cut is missing.

BugBear

 

[Tom K]

So, if we were to turn the piece of timber in BB's diagram 90 degrees, but leave the plane in the same position, would this still be a skew cut?

Yes Nolegs even if you rotate so that the plane is horizontal its still skew provided the plane remains in the same position.

 

[Tom K]

So, if we were to turn the piece of timber in BB's diagram 90 degrees, but leave the plane in the same position, would this still be a skew cut?

Yes - the angle of the workpiece makes no difference - think about a super-squirly piece of burr; we
can still take a skew cut, even though the grain direction is so mixed up as to be meaningless.

While I'm on;

It's often useful to examine extreme cases when marginal cases
are hard to think about.

So here's a diagram of an extremely large amount of skew (around 80 degrees). This is very
nearly all "slice" and no "push".



Now we now consider trying to make a ramped shooting board to
do the same.

Whilst one can have a ramp at 80 degrees, all you're doing is "pushing"
in a different direction; the slicey-ness of a skew cut is missing.

BugBear

Does anyone ever use that sort of extreme angle? It looks like it may just put a gouge in workpiece.

 

[bugbear]

Does anyone ever use that sort of extreme angle? It looks like it may just put a gouge in workpiece.

No they don't; it is (as I noted) an extreme case to make the principles more evident.

BugBear

 

[Tom K]

Yeah more theoretical than anything I suppose. The reverse could be said of very shallow angles. I'd say 5 degrees often get's applied while doing straight planing without even thinking about it.

 

[woodbrains]

Hello,

I use a ramped shooting board, and they are very useful. Mine is ramped high towards the fence end, so it does not have a tendency to lift the stock off the board, and the ramp angle was decided on, by the maximum width of stock I anticipated planing. I figured about 8 in wide would be the max width of any drawer side I would make and 1/2 in max thickness. I made the ramp steep enough so (with a bit of leeway) a jack/try plane iron would have its entire width used planing such a board. I'm not sure why anyone would think it is a waste of time making such a board; continually using the bottom half inch of a plane iron and not touching any of the rest makes no sense to me at all. I do use a back fence that fits in a tapered housing. That way, any wear on the leading edge of the fence can be trued up and with a couple of shavings off the fence side, any shortening is compensated for. Mine has lasted a long time.

Regarding the skew issue, it is confusing thinking about angles! Instead, think about what happens at the blade tip, to clarify what is going on. Skew planing does two things; it narrows the effective width of the blade and lowers the effective pitch, both making the plane easier to push. A ramped shooting board does neither of these things. In fact a RSB actually increases (albeit ever so slightly) the width of the shaving, so you could argue it is harder to use! In practice I find it makes no practical difference, but the saving in sharpening is well worth the effort.

Just a comment on heavier planes; they have more momentum, so do help with this sort of work. Yes, they require more energy to push, but more momentum is easier to achieve with mass than speed. It is personal preference, of course, but I like a heavier plane for shooting, because of momentum.

Mike.

 

[n0legs]

:arrow: BB, Musicman, Tomk. Thanks for the explanation.
Mike (woodbrains) that's a great insight, thanks

 

[Jacob]

.....
Just a comment on heavier planes; they have more momentum, so do help with this sort of work. Yes, they require more energy to push, but more momentum is easier to achieve with mass than speed. It is personal preference, of course, but I like a heavier plane for shooting, because of momentum.

Mike.

You would soon change your mind if you had a lot to do as in the old days where somebody might be doing the same repetitive operation for a long time.

 

[woodbrains]

.....
Just a comment on heavier planes; they have more momentum, so do help with this sort of work. Yes, they require more energy to push, but more momentum is easier to achieve with mass than speed. It is personal preference, of course, but I like a heavier plane for shooting, because of momentum.

Mike.

You would soon change your mind if you had a lot to do as in the old days where somebody might be doing the same repetitive operation for a long time.

Hello,

The momentum required to make the cut is the same no matter what plane is used and who is pushing it, otherwise it will stall. Momentum can be achieved with speed in a light plane, but since the action of cutting wood acts against the plane, there is only so fast a plane can go. Mass is not affected by the opposing force of the cut, so momentum is easier to achieve with mass than speed.

I suppose if you have a lot to plane, you develop the physique to do it. Or are you saying old timers wimped out and modern woodworkers with a lot to plane are fitter and stronger than their ancestors? :lol:

Mike.

 

[Jacob]

.....
Just a comment on heavier planes; they have more momentum, so do help with this sort of work. Yes, they require more energy to push, but more momentum is easier to achieve with mass than speed. It is personal preference, of course, but I like a heavier plane for shooting, because of momentum.

Mike.

You would soon change your mind if you had a lot to do as in the old days where somebody might be doing the same repetitive operation for a long time.

Hello,

The momentum required to make the cut is the same no matter what plane is used and who is pushing it, otherwise it will stall. Momentum can be achieved with speed in a light plane, but since the action of cutting wood acts against the plane, there is only so fast a plane can go. Mass is not affected by the opposing force of the cut, so momentum is easier to achieve with mass than speed.

I suppose if you have a lot to plane, you develop the physique to do it. Or are you saying old timers wimped out and modern woodworkers with a lot to plane are fitter and stronger than their ancestors? :lol:

Mike.

Your physics is so confused I can hardly begin to untangle it!
Hypothetically you could plane quite well with a plane of zero mass (and hence zero momentum at any velocity).
In fact you can plane quite well with a light plane (low momentum at a given velocity compared to a heavier plane) - ask all the woody users.
A heavy plane moving will have momentum behind the cut - but only to the extent that you have accelerated the plane beforehand - you don't get something for nothing - you have to put the force in.
But you also have to pull the plane back and start it off again- which will take more effort with a heavy plane. So you gain nothing (but may lose nothing) on the cut stroke but you lose on all the other movements of the plane.
Momentum comes into play with tools like hammers where an accelerated heavy object imparts all its energy in a short impact, but this isn't much like planing.

 

[custard]

The momentum required to make the cut is the same no matter what plane is used and who is pushing it, otherwise it will stall. Momentum can be achieved with speed in a light plane, but since the action of cutting wood acts against the plane, there is only so fast a plane can go. Mass is not affected by the opposing force of the cut, so momentum is easier to achieve with mass than speed.

That's pretty smart. I've been planing wood for forty years but never thought of it in quite those terms before. Although what about the return stroke, surely then it's just dead weight?

The workshop where I trained didn't get electricity until the 1960's, and has a tradition of only ever using one bench plane, a number 7 or 8. When I spoke to the old boys who were around in those days they always claimed a big plane netted out as easier to use, but the older I get and the worse becomes the tennis elbow I find a light bevel up jack becomes the plane I reach for in the majority of cases!

 

[matt_southward]

If we are talking about the physics, then we first have to state our underlying assumptions with regard to the operation. Mike is correct in that the momentum can be the same for a given, defined cut (we would have to measure the actual speed and mass of the relative planes to be able to equalise the momentum - who is going to do that?! So equality of momentum is theoretical at best. This assumes an equal number of strokes (not a given).

However Jacob is absolutely correct in that far more work is done when shifting a heavier mass (work in the physics sense of energy expenditure). That forward and backward momentum of a higher mass comes at a pretty high price energetically, (and don't forget the higher losses due to increased friction with the higher mass), so it's likely a user preference as to which method they prefer, rather than absolute. If you were doing a lot of it, then you would pay the price in extra shredded wheat in the mornings!
I haven't done enough shooting with a woodie to be able to compare, but I can see the attraction for this use.

Another interesting thread!