Why are there different knife angles

Grinding on a whetstone

Grinding on a whetstone? The right sharpening angle in three steps!

Step 1: Determine the sharpening angle for your knife

A knife edge can have different angles. The smaller the angle, the sharper the knife. With a very sharp knife, the cutting edge is therefore very narrow. Japanese knives are made of very hard steel (from 60 HRC) and can be ground very sharply with a very small angle. For other knives, for example German knives, somewhat softer types of steel (55-58 HRC) are often used; the cutting edge is therefore also ground at a larger angle.

With Japanese knives the angle of the knife edge is mostly 30 °, "normal" knives have an angle between 36 ° and 40 °. The sharpening angle of your knife is half of the cutting edge angle (after all, you are sharpening both sides). A Japanese knife (some examples below) is therefore sharpened at an angle of 15 ° (30 ° / 2), with other knives the angle is 18 ° to 20 °.

If you find that your knife is quickly dull or damaged, you may be sharpening your knife too thin. In this case, we recommend that you use a larger sharpening angle.

Examples of brands with knives made of hard steel (grinding angle 15 °) are Böker, Eden, Global, Kai Shun, Robert Herder, Sakai Takayuki, Zwilling Myabi.

To determine the sharpening angle of pocket knives, we recommend the following rule of thumb:

  • With intensive use of the knife = sharpening angle 46 °
  • With normal use of the knives = grinding angle 36-40 °
  • If the knife is rarely used = sharpening angle 30 °

Step 2: How steeply does the knife have to be held when sharpening

The desired sharpening angle is determined by the inclination of the knife in relation to the sharpening stone. The correct height or inclination can be easily calculated with a simple formula. After you have determined the desired sharpening angle, you measure the width of the knife. Then look in the table below to see how steeply you have to hold the knife against the whetstone.

Blade widthGrinding angle 12 °15 ° grinding angleGrinding angle 18 °Grinding angle 20 °Sharpening angle 23 °
10 mm2.08 mm2.59 mm3.09 mm3.42 mm3.91 mm
15 mm3.12 mm3.88 mm4.64 mm5.13 mm5.86 mm
20 mm4.16 mm5.18 mm6.18 mm6.84 mm7.82 mm
25 mm5.20 mm6.47 mm7.73 mm8.55 mm9.77 mm
30 mm6.24 mm7.77 mm9.27 mm10.26 mm11.72 mm
35 mm7.28 mm9.06 mm10.82 mm11.97 mm13.68 mm
40 mm8.32 mm10.35 mm12.36 mm13.68 mm15.63 mm
45 mm9.36 mm11.65 mm13.91 mm15.39 mm17.58 mm
50 mm10.40 mm12.94 mm15.45 mm17.10 mm19.54 mm
55 mm11.44 mm14.24 mm17 mm18.81 mm21.49 mm
60 mm12.47 mm15.53 mm18.54 mm20.52 mm23.44 mm

Step 3: Practical tools for the correct angle of inclination

If you don't want to use a ruler, there are two practical aids available: There are grinding aids available on the market that specify a fixed incline. Alternatively, you can set the desired height with a stack of euro coins. Both aids can be used to maintain the correct angle of inclination that is required for grinding.

Grinding aid

A grinding aid is clamped onto the back of the knife. Small grinding aids create a fixed height of 4.5 mm, with large ones it is 6.5 mm. With a grinding aid, however, you are less flexible when grinding hands-free. In the table below you will find possible heights:

Blade heightGrinding angle 12 °15 ° grinding angleGrinding angle 18 °Grinding angle 20 °Sharpening angle 23 °
10 mm2.08 mm2.59 mm3.09 mm3.42 mm3.91 mm
15 mm3.12 mm3.88 mm4.64 mm5.13 mm5.86 mm
20 mm4.16 mm5.18 mm6.18 mm6.84 mm7.82 mm
25 mm5.20 mm6.47 mm7.73 mm8.55 mm9.77 mm
30 mm6.24 mm7.77 mm9.27 mm10.26 mm11.72 mm

When using a sharpening aid, we recommend that you attach a strip of adhesive tape to the back of the knife beforehand. Any damage to the blade can thus be avoided.

Euro coins

If you want to set the correct height with the help of euro coins, you first determine the following points:

1) Determine the sharpening angle with which you want to sharpen the knife.
2) Read the height in the table at step 2.
3) Measure the blade thickness in mm.
4) Calculate: Height in mm minus half the blade thickness. This is the height that you set with the coins (the back of the knife has to be upright when grinding).

Example: You want to sharpen a Böker Saga chef's knife at an angle of 15 °. The blade has a width of 52 mm, the blade thickness is 2.4 mm, the height from the table in step 2 is approx. 13 mm. So you calculate: approx. 13 mm - 1.2 mm = 11.8 mm. This is the height that you can measure with the euro coins.

coinStrength
1 cent1.67 mm
2 cents1.67 mm
5 cents1.67 mm
10 cents1.93 mm
20 cents2.14 mm
50 cents2.38 mm
1 €2.33 mm
2 euros2.20 mm