A couple of new shooting boards

[Jake]

I'm failing to see the difference from normal skew planing, except in this the wood is the bit which is presented at a skew, not the plane - same effect, surely?

No different from having a vice which was angled, and pushing the plane in a straight line.

 

[Steve Maskery]

Well that's the point, Jake, I think it is different.

In skew planing, one end of the blade edge is ahead in travel of the other. The edge is not perpendicular to the direction of travel.

With a ramp SB the edge is still perpendicular to the direction of travel. If I get a mo I'll post a diagram.

S

 

[dennis]

Steve

Even though the blade is perpendicular the bottom of the blade is traveling along the wood ahead of the top,as the plane reaches the end of the board note that as the wood is sloping the bottom of the blade reaches the end of the wood first.

Dennis

 

[Steve Maskery]

Yes, but that is not skew.

Take the extreme example of shooting the end of a cylinder (let's not get sidetracked about breakout difficulties). On a normal SB the cut is straight across, and on a ramped SB the cut is still straight across, albeit in a different direction. Changing the shape of the workpiece does not change a straight cut into a skew cut.

A skew cut cuts more cleanly because it reduces the effective cutting angle, a ramped SB does not change that, it only changes the direction from which you attack the workpiece. It's not the same at all.

Take the ramp to the extreme of having it ramped at 90 degrees. It would still work, but skewing a plane to 90 degrees would result in a score line down the workpiece and no shavings at all.

S

 

[Jake]

I still don't see it - the only way I can envisage it is that instead of skewing the plane wrt to the wood, you are skewing the wood wrt to the plane. How does the edge know the difference?

edit: Oh, OK, the scoring a line point is a good illustration - hmmm.

 

[Jake]

OK, with you now, I think. So to get a skewed effect, you'd need the plane on a wedge-shaped carriage.

 

[dennis]

Well you havent convinced me steve,I still think that it is skewed.




Dennis

 

[Steve Maskery]

It's the difference between driving a car from one pavement to another over, say 100 yards and skidding the car from one to t'other over the same difference. It makes a difference which way the car, or plane, is facing, because that affects the effective cutting angle.

I've taken my eyes out now but it will post a pic tomorrow, I think I know how I can draw it..

I'll win you all over, yet!


Goodnight all
S

 

[Chris Knight]

Derek,
Thanks very much.

 

[dennis]

Steve

Gave it a little thought whilst having brew today and realised as you say that you are actually drifting the plane across the wood and also that because of the gradual slope of the ramp there will be very little skew.So I would call it a drift cut with minimal skew.Thanks for your explanation it made me think about it and it is always good to learn something.

Cheers

Dennis