Technique: Tear-out control with hand planes

We all have to plane different types of wood and some of them could be highly figured and cause tear-out.

Here are some known methods that are effective at reducing those tear-out.

For a standard plane with a 45 degree bed:
1. A sharp iron
2. A reduced mouth opening
3. Moving the chipbreaker closer to the cutting edge
4. Adding a 5 or 10 degree back-bevel
5. Reducing the depth of cut
6. Increasing the chipbreaker angle

In details now.

Point 1. If your iron is dull you have to take a heavier cut and this may easily cause tear-out.  Sharpening your iron is the first thing to do.

Point 2. This is more controversial.  In order to work properly, the mouth should be the width of the shaving plus a few thousands.  It's difficult to measure and also very difficult to set.  On top of this, if you want to take a heavier shaving you have to readjust the mouth.
In the picture below, the mouth is approximately 0.0015", the chip is 0.001" and the chipbreaker is set à 0.0015" from the edge.  This is a close to impossible setting.

This sketch comes from Steve Elliot website

A 0.010" mouth with a depth of cut of 0.002" is almost useless.  The idea is that the mouth opening should be small enough so that the chip if forced to bend without tearing out.

In order to achieve this level of precision with the mouth opening, the seat will have to be adjust continuously, for every depth of cut.  I believe that it is just not possible or practible.  I my case, my planes mouths are set between 0.01" to 0.02".  I find it easier to adjust the chipbreaker, see point 3 and 6.

Point 3.  Moving the chipbreaker close to the edge.  This is what I do all the time with all my planes.  It's not that easy but it seems that I can manage to achieve it properly and with this I totally control all tear-outs.

I use a small hammer to slowly push the chipbreaker closer to the edge.  I'm trying to be very close to the edge but not "that" close.  It's hard to measure something like this.

Here is a picture showing how close the chipbreaker should be to the edge.

Seen with a Celestron microscope

A 0.1mm calibration line.  It means that the distance between the chipbreaker and the edge is around0.004".

This blade/chipbreaker set-up has been tested in difficult wood and intentionally against the grain and it works.  It's not that difficult to set.

Point 4. A back bevel could be a solution.  If you do that expect a more difficult plane to push and a somewhat not so nice surface finish.

With my sharpening technique I have a tiny 3 or 4 degree back bevel and I just don't see any difference with a standard 45 degree blade.
The higher the back bevel, the better tear-out control you will have.  A dedicated blade is something to keep in mind.
If you use a 10 or 15 degree back bevel, you will have to adjust your chipbreaker accordingly.  This angle may cause a bad fit between the back of your blade and the chipbreaker.

Point 5. Oh yeah!  Reducing the depth of cut is always a solution but removing shaving 0.001" at the time can take a lot of time.

Point 6. A very good study has been made by professor Chutaro Kato from Japan.  There use to be a video but the link doesn't seem to work anymore.  Professor Kato clearly demontrate how close the chipbreaker should be to the edge and what angle should the chipbreaker have.

He demonstrate that the chip breaker should have an angle between 50 to 80 degree and the distance to the edge should be around 0.008".  An angle of 80 degree plus a frog at 45 degree gives you an increadible 125 degree.

As a side note, professor Kato uses an infinite mouth opening.  There is nothing that can act as a mouth in his study.

Now, low-angle planes tear-out control.

1. A sharp iron
2. A reduced mouth opening
3. Increasing the sharpening angle
4. Reducing the depth of cut

In details now.

Point 1, Point 2 and Point 4.  I have the same comments as for a standard 45 degree bed plane.  See above.

Point 3. This is your best method of controlling tear-out.  A 12 degree bedded blade with a 25 or 30 degree bevel gives you 37 or 42 degree.  This is a perfect receipe to get tear-out.

A total angle (bed + bevel) under 50 degree will cause problems.  Between 50 and 60 tear out are under control.

But, even if high angles are a solution for a low-angle plane, I see three problems:
- Your plane will be much more difficult to push then a regular plane.
- Those high angle can not be achieve with a free hand sharpening technique and that means that it will take more time to sharpen with a guide.
- The surface finish is not as nice as what you could get with a standard plane properly set.

I hope it will help you.
Normand