Shooting Boards

[gregbois]

Derek,

Would my math -- or is it geometry? -- be wrong in assuming that the donkey's ear placed on the 5 degree slope of the shooting board will yield a compound mitre, not at 90 degrees?

Greg

[Derek Cohen]

Hi Greg

No compound angle. The ramp allows the blade to enter the work at a 5 degree skew, cuts with this slight skew. Think of skewing a smoothing plane as you push it down a board.

The advantage of this slight skew is to reduce the impact from a straight blade. It is not affecting the quality of the cut, per se. Also, a ramp does not "save" the blade in terms of widening the part of the blade use. Again, the skew is too little.

It a ramped board worth the effort to build? In my experience it is ... if using a straight blade. I began making these boards about 20 years ago. However I mostly use a Stanley #52 shooting board with a Veritas shooting plane.

Regards from Perth

Derek

[Large Wooden Badger]

Thanks Derek that is helpful, I do not yet have a 51 so I should incorporate a ramp.

[gregbois]

Yes, thanks Derek.  I was picturing it all wrong.  My shooting board has the ramp tilted, too, and I saw in my mind's eye the creation of a compound angle rather than a meeting at 90 degrees.  For many years I've used the shooting plane I built while studying with Krenov.  We also built the shooting boards in class, of plywood with lignum vitae ramps.  I recently splurged and got the Veritas shooting plane.  The pure heft of that beast produces nice fish scale shavings.  I am thinking that the keeper on your ramp might make the use of any plane on the shooting board run more true.

Anyway, thanks for sharing your infinite knowledge and experience.

Greg

[imapseudonym]

No compound angle. The ramp allows the blade to enter the work at a 5 degree skew, cuts with this slight skew. Think of skewing a smoothing plane as you push it down a board.

The advantage of this slight skew is to reduce the impact from a straight blade. It is not affecting the quality of the cut, per se. Also, a ramp does not "save" the blade in terms of widening the part of the blade use. Again, the skew is too little.

Skewing a smoothing plane as you push it down a board does (at least) two things: it reduces the impact of the blade's initial contact with the wood (as you note), but it also changes the effective angle of the blade by causing the blade to move at an angle relative to the slope of the bevel. Think of this latter effect as causing the wood to drive up a slight swithcback instead of straight up the steeper slope. 

A ramp on a shooting board has only the first benefit (lessening the impact from the blade making initial contact with the full thickness of the board at once), it does not reduce the effective cutting angle since the motion of the blade is still parallel to the slope of the bevel. The ramped shooting board would be more like changing the orientation of the board while still using the smoothing plane in a straight-ahead orientation. A skewed blade in a shooting board has both benefits.

Whether there is any real-world benefit to the skew over the ramp I can't say.

[KyleD]

As a counter to Hank’s flat board, there is a 5 degree ramped board (in Jarrah and quartersawn Tasmanian Oak) ..

Derek, with the angle of that shooting board I am imagining the cutting force is pushing the work piece up as well as into the fence. would reversing the angle so the plane blade travels down and forward help hold the work piece in place? Or is this just not a problem?

[Derek Cohen]

Kyle, if there is any up force, it is either theoretical or so minor that it is irrelevant. Don't sweat it.

Regards from Perth

Derek

[Handplanesandmore]

The workpiece will never get lifted up as a hand is placed on the workpiece to keep it down and against the fence.

Simon

[KyleD]

Thanks guys for answering the question. I do know that moving the plane sideways a little as pushing it forward really helps on end grain. My experience comes from trimming end grain flush on box joints with my trusty LV block plane.