Steep cone

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Steep taper with tool holder

The steep taper is the standardized form of a tool taper for clamping various tools in the main spindle of a machine tool. The steep taper is standardized in DIN ISO 7388 Part 1.

The main areas of application are milling machines .

Steep taper shafts have the following advantages:

  • No self-locking (in contrast to the Morse taper , which has a simple taper angle of only about 1 ° 26 'to about 1 ° 30') due to a sufficiently large taper angle, thus a simple tool change without jamming. This is particularly important for automatic tool changes.
  • Small clamping path, therefore relatively short clamping time and relatively precise tool position.
  • High bending stiffness due to the short distance between the cutting edge and the spindle bearing (short overall length).

Common sizes are SK10, SK15, SK20, SK25, SK30, SK35, SK40, SK45, SK50 and SK60.

As a nominal dimension, these size specifications only roughly correspond to the largest inside diameter of the cone of the receptacle, for example in the milling machine. According to DIN 2080 this is in mm:

SK10 15.875

SK15 19.050

SK20 22.225

SK25 25,400 (= 1 inch )

SK30 31.750

SK35 38,100

SK40 44,450

SK45 57.150

SK50 69.850

SK55 88,900

SK60 107.950

The (simple) cone angle is 8.297 ° (= 8 ° 17´ 50´´).

Steep cones as tool holders are typically made of case- hardening steel with a tensile strength (in the core) of 900 N / mm 2 . Case hardening takes place with little warpage down to a depth of 0.6–0.8 mm to a hardness of 58 ± 2 HRC . The steep taper with close tolerances is precision ground (outside) down to Ra ≤ 0.2.

More cones

A further development of the steep taper is the hollow shank taper .

Drill chuck taper DIN 238 is available in the following nominal sizes with the largest taper opening (inner diameter) on the drill chuck in mm:

B 6 6.35 (= 1/4 inch)

B 10 10.095 / 10.094

B 12 12.065

B 16 15.733

B 18 17.780

B 18 Albrecht 17,431 (cone shortened by 7 mm compared to DIN ISO 239)

B 22 21.793

B 24 23.825

J 0 6.350

J 1 9.754

J 2 14,199 (Jacobs DIN ISO 239)

J 3 20.60 (Jacobs DIN ISO 239)

J 33 15.850

J 6 17.170

Individual evidence

  1. ↑ http://www.herbertwirz.ch/files/Katalog_DIN2080.pdf p. 6.
  2. ↑ https://nirschl-gmbh.de/wzhalter.htm
  3. ↑ http://www.herbertwirz.ch/files/Katalog_DIN2080.pdf p. 5.
  4. ↑ http://www.herbertwirz.ch/files/Katalog_DIN2080.pdf p. 39.
  5. ↑ https://ch.roehm.biz/fileadmin/products/media/de/DC0000165.PDF p. 1015.
  6. ↑ https://www.ifanger.com/files/content/dokumente/pdf/produkte/bohrfutter/ncbf.pdf