question regarding tear out !

[charles mathieu]

After avoiding yellow birch for the last year because of constant tear out with handplanes, I got a deal this afternoon on some cheap 8/4 birch that will be used for my upcoming roubo bench build. Well I did have again some nasty tear out when I pulled out my veritas low angle jack and low angle jointer. The jack blade has a microbevel of about 30 degres for a total of 42 and the jointer is probably the same. That's eyeballing as I sharpen freehanded. What I don't understand is that I got no tear out when I dimensioned the wood with my dewalt 13" planer. Why can't I achieve the same result with handplanes on that fricking birch ? I'm done with birch otherwise, it's a real pain to deal with and it sucks because it's quite beautiful and cheap around here.

[DERRECK BRYANS]

Bump up your microbevel to about 40 degrees to start.

[charles mathieu]

so 52 degres total ? Isn't that too hard to push ?

[Andrew Hughes]

Charles one reason your planer will cut without tearing up your birch is because it’s cutting the wood like a bevel down plane.
That’s my guess if your planer has straight knifes.


Good Luck

[David Eisenhauer]

Charles, some folks go even higher than a total of 52* with the LA planes. It does get harder to push, but very doable, especially if you don't try for thick shavings. Derrick Cohen has provided some good info on the creation and use of various low angle iron sharpening angles and I'm betting it could be found on his own website - inthewoodshopdotcom. Maybe he will chime in soon during his Euro train trip and help you out.

[Jim Koepke]

Birch is not a wood that works well with hand tools.

Mine didn't turn well either.

jtk

[Derek Cohen]

After avoiding yellow birch for the last year because of constant tear out with handplanes, I got a deal this afternoon on some cheap 8/4 birch that will be used for my upcoming roubo bench build. Well I did have again some nasty tear out when I pulled out my veritas low angle jack and low angle jointer. The jack blade has a microbevel of about 30 degres for a total of 42 and the jointer is probably the same. That's eyeballing as I sharpen freehanded. What I don't understand is that I got no tear out when I dimensioned the wood with my dewalt 13" planer. Why can't I achieve the same result with handplanes on that fricking birch ? I'm done with birch otherwise, it's a real pain to deal with and it sucks because it's quite beautiful and cheap around here.

Hi Charles

Tearout occurs when a planed section splits ahead of the blade (Type I chip formation). This is more likely to occur when the wood grain is reversed (i.e. one is planning into the grain). It is less likely to occur when planing downhill and with straight-grained timber.

There are two ways to prevent tearout. The first is a high cutting angle (either BU or BD planes), and the second is a closed up chipbreaker (BD plane; chipbreaker around 0.3 -0.4mm from the edge). Both these create a Type II chip formation. Here the chip is forced to break at the edge of the blade, which does not give it an opportunity to tear (which is the tearout).

Note that the standard (common angle) Stanley BD plane has a 45 degree frog (= 45 degree cutting angle). In interlocked grain, this is not high enough (without the aid of the chipbreaker) to control tearout. The cutting angle on your LA Jack (BU) is 42 degrees (12 degree bed + 30 degree bevel). This is even lower than the basic Stanley! You do not stand a chance with interlocked grain as the blade is creating a low angle wedge and splitting the wood well ahead of the blade (Type I).

The solution with a BU plane is to increase the bevel angle to create a high cutting angle (for a Type II chip). I would recommend a 50 degree bevel for a 62 degree cutting angle.

The downside to high cutting angles is that they create more resistance = more effort to push. However there are two ways around this. The first is to wax the sole of the plane. This is usually sufficient. The second is that one ends up taking shallower cuts.

Note that a high cutting angle on a BU plane blade is created by adding a high secondary bevel if you wish to also camber the blade. I advise this since a non-cambered blade will leave tracks. There is too much steel to camber a high angle on a full face. Create the camber and the secondary bevel at the same time.

Regards from Munich

Derek

[Jim Matthews]

This is for a benchtop?

If the glue faces bond well, leave the "show" face proud and either run a toothing plane or floor scraper for a presentable finish.

Mine gets me out of jams, on larger areas. There's a modern version from Sandvik, but that has a carbide blade with sharp corners.

https://www.finewoodworking.com/2016/11/10/a-great-mistake

[Prashun Patel]

If you dimensioned with the dewalt, why are you even using the jack and jointer now? Can’t you go straight to the smoother? Light passes and plane in the direction of the grain.

[charles mathieu]

If you dimensioned with the dewalt, why are you even using the jack and jointer now? Can’t you go straight to the smoother? Light passes and plane in the direction of the grain.


because I don't have a powered jointer so I flatten one face quickly then the rest is done with the dewalt. I also joint one edge with the jointer before ripping the other side. Thanks for the help guys, I'll try a 45-50 microbevel !

[Doug Dawson]

After avoiding yellow birch for the last year because of constant tear out with handplanes, I got a deal this afternoon on some cheap 8/4 birch that will be used for my upcoming roubo bench build. Well I did have again some nasty tear out when I pulled out my veritas low angle jack and low angle jointer.

What does tearout matter on a workbench? It's like a scratch in the bed of a work truck. Just sayin'.

[charles mathieu]

better learn how to avoid tear out on a bench than on a fine furniture later on...