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Spindle Tapers and Tool Holder Shanks

Standards that connect a machining center spindle to the tool holder. Dimensions such as gauge diameter, flange diameter, and pull stud thread are taken from tooling manufacturers' technical documents and public information on standards; values that differ between manufacturers are shown side by side.

How the spindle and holder make contact (schematic)
GapBT (7/24 taper)Contact on the taper onlyDual contact (BBT, etc.)Taper + flange faceHSK (hollow, 1/10 taper)Short taper + face, pulled in from inside

Red lines = surfaces that contact the spindle; yellow arrows = pull-in force (pull stud for BT and BBT, internal clamping segments for HSK). Spindle on top, holder below. For dual contact, the spindle must also be designed for it.

▦7/24 taper quick reference (BT, SK, CAT)

DesignationGauge diameterFlange diameterL1Pull stud thread
BT3031.75[1][8]46[1][8]48.4[1][8]M12[1][8][9]
BT4044.45[1][8]63[1][8]65.4[1][8]M16[1][8][9][10]
BT5069.85[1][8]100[1][8]101.8[1][8]M24[1][8][11]
SK3031.75[6][13]50[6][13]47.8[6][13]M12[6][13][14]
SK4044.45[6][13]63.55[6][13]68.4[6][13]M16[6][13][15][16]
SK5069.85[6][13]97.5[6][13]101.75[6][13]M24[6][13][17]
CAT301.250 in[18]1 source · reference1.812 in[18]1 source · reference1.875 in[18]1 source · reference1/2-13 UNC[18]1 source · reference
CAT401.750 in (44.45 mm)[7][18]2.500 in[7][18]2.687 in[7][18]5/8-11 UNC[7][18]
CAT502.750 in (69.85 mm)[7][18]3.875 in[7][18]4.000 in[7][18]1-8 UNC[7][18]

Units are mm (for CAT, some values follow sources that give inches). Even with the same gauge diameter, the flange, length, and pull stud differ, so BT, SK, and CAT holders cannot be swapped as they are (see "Compatibility" below).

Printed from Kezuriba (kezuriba.net/en/tooling/spindle/)

BT

BT30

Standard
JIS B 6339-2, MAS 403 (formerly a Japan Machine Tool Builders' Association standard), ISO 7388-2 (types J, JD, JF)[1][2][3]HAIMER states that JIS B 6339-2 is also called MAS 403. ISO 7388-2 forms J/JD/JF are the BT type (Meusburger)
Taper
7/24[2][4][5]The names of the ISO 7388, JIS B 6339, and ASME B5.50 standards themselves contain "7/24 taper"
Taper half-angle
8°17′50″ +4″ (half angle)[1][6][7]1 source · referenceThe same statement appears on three HAIMER pages (same publisher). The taper tolerance is AT3 on the same page. The value of around 16°35′40″ for the included angle is unconfirmed in other sources
Gauge diameter (mm)
31.75[1][8]HAIMER table D1, TAC table D1
Flange diameter (mm)
46[1][8]HAIMER table D3, TAC table D6. Symbols differ by source
L1 (mm)
48.4[1][8]L1 in both tables (same symbol, same value). Check the definitions on the drawings in each source's figures
b (mm)
16.1[1][8]HAIMER table B1, TAC table B (H12). Appears to be the drive keyway width, but this was not confirmed in the drawings
Pull stud thread
M12[1][8][9]
Coolant type
J (none), JD (through-spindle), JF (from the flange side)[1][3]
Dual contact
None[1][3]Standard BT centers by the taper only (the end face does not contact)
Approx. speed
  • HAIMER:Primarily suitable up to 12,000 min⁻¹ (primarily suitable … up to 12,000 rpm)[1]
1 source · referenceMaker's guideline. Varies with spindle, holder, and balance. Not a standard value
Main machines
—Not confirmed in public sourcesNo primary source was found that explicitly states a correspondence such as "No.30 = small machines, No.40 = medium, No.50 = large / heavy cutting" between taper number and machine size
Size
BT30

BT40

Standard
JIS B 6339-2, MAS 403 (formerly a Japan Machine Tool Builders' Association standard), ISO 7388-2 (types J, JD, JF)[1][2][3]HAIMER states that JIS B 6339-2 is also called MAS 403. ISO 7388-2 forms J/JD/JF are the BT type (Meusburger)
Taper
7/24[2][4][5]The names of the ISO 7388, JIS B 6339, and ASME B5.50 standards themselves contain "7/24 taper"
Taper half-angle
8°17′50″ +4″ (half angle)[1][6][7]1 source · referenceThe same statement appears on three HAIMER pages (same publisher). The taper tolerance is AT3 on the same page. The value of around 16°35′40″ for the included angle is unconfirmed in other sources
Gauge diameter (mm)
44.45[1][8]HAIMER table D1, TAC table D1
Flange diameter (mm)
63[1][8]HAIMER table D3, TAC table D6. Symbols differ by source
L1 (mm)
65.4[1][8]L1 in both tables (same symbol, same value). Check the definitions on the drawings in each source's figures
b (mm)
16.1[1][8]HAIMER table B1, TAC table B (H12). Appears to be the drive keyway width, but this was not confirmed in the drawings
Pull stud thread
M16[1][8][9][10]
Coolant type
J (none), JD (through-spindle), JF (from the flange side)[1][3]
Dual contact
None[1][3]Standard BT centers by the taper only (the end face does not contact)
Approx. speed
  • HAIMER:Primarily suitable up to 12,000 min⁻¹ (primarily suitable … up to 12,000 rpm)[1]
1 source · referenceMaker's guideline. Varies with spindle, holder, and balance. Not a standard value
Main machines
—Not confirmed in public sourcesNo primary source was found that explicitly states a correspondence such as "No.30 = small machines, No.40 = medium, No.50 = large / heavy cutting" between taper number and machine size
Size
BT40

BT50

Standard
JIS B 6339-2, MAS 403 (formerly a Japan Machine Tool Builders' Association standard), ISO 7388-2 (types J, JD, JF)[1][2][3]HAIMER states that JIS B 6339-2 is also called MAS 403. ISO 7388-2 forms J/JD/JF are the BT type (Meusburger)
Taper
7/24[2][4][5]The names of the ISO 7388, JIS B 6339, and ASME B5.50 standards themselves contain "7/24 taper"
Taper half-angle
8°17′50″ +4″ (half angle)[1][6][7]1 source · referenceThe same statement appears on three HAIMER pages (same publisher). The taper tolerance is AT3 on the same page. The value of around 16°35′40″ for the included angle is unconfirmed in other sources
Gauge diameter (mm)
69.85[1][8]HAIMER table D1, TAC table D1
Flange diameter (mm)
100[1][8]HAIMER table D3, TAC table D6. Symbols differ by source
L1 (mm)
101.8[1][8]L1 in both tables (same symbol, same value). Check the definitions on the drawings in each source's figures
b (mm)
25.7[1][8]HAIMER table B1, TAC table B (H12). Appears to be the drive keyway width, but this was not confirmed in the drawings
Pull stud thread
M24[1][8][11]
Coolant type
J (none), JD (through-spindle), JF (from the flange side)[1][3]
Dual contact
None[1][3]Standard BT centers by the taper only (the end face does not contact)
Approx. speed
  • HAIMER:Primarily suitable up to 12,000 min⁻¹ (primarily suitable … up to 12,000 rpm)[1]
1 source · referenceMaker's guideline. Varies with spindle, holder, and balance. Not a standard value
Main machines
—Not confirmed in public sourcesNo primary source was found that explicitly states a correspondence such as "No.30 = small machines, No.40 = medium, No.50 = large / heavy cutting" between taper number and machine size
Size
BT50

SK (DIN 69871 / ISO 7388-1)

SK30

Standard
  • DIN ISO 7388-1 (former DIN 69871)
  • ISO 7388-1:2007 (forms A, AD, AF, U, UD, UF)
  • JIS B 6339-1
[6][12][2][4]DIN ISO 7388-1:2014-07 replaces DIN 69871-1:1995-10 (DIN Media). JIS B 6339-1 corresponds to ISO 7388-1:2007 (AFNOR)
Aliases
DIN 30, ISO 30 (type A)
Taper
7/24[2][4][5]The names of the ISO 7388, JIS B 6339, and ASME B5.50 standards themselves contain "7/24 taper"
Taper half-angle
8°17′50″ +4″ (half angle)[1][6][7]1 source · referenceThe same statement appears on three HAIMER pages (same publisher). The taper tolerance is AT3 on the same page. The value of around 16°35′40″ for the included angle is unconfirmed in other sources
Gauge diameter (mm)
31.75[6][13]HAIMER table D1, TAC table D1
Flange diameter (mm)
50[6][13]HAIMER table D4, TAC table D6
L1 (mm)
47.8[6][13]L1 in both tables
b (mm)
16.1[6][13]HAIMER table B1, TAC table B (H12)
Pull stud thread
M12[6][13][14]
Coolant type
A (none), AD (through-spindle via pull stud), AF (from the flange side; formerly type B), AD/AF (formerly type ADB)[6][3]
Dual contact
None[6][3]Centered by the taper only (Meusburger: centred without flat contact)
Approx. speed
  • HAIMER:Primarily suitable up to 12,000 min⁻¹[6]
1 source · referenceMaker's guideline. Not a standard value
Main machines
—Not confirmed in public sourcesNo primary source was found that explicitly states a correspondence such as "No.30 = small machines, No.40 = medium, No.50 = large / heavy cutting" between taper number and machine size
Size
SK30

SK40

Standard
  • DIN ISO 7388-1 (former DIN 69871)
  • ISO 7388-1:2007 (forms A, AD, AF, U, UD, UF)
  • JIS B 6339-1
[6][12][2][4]DIN ISO 7388-1:2014-07 replaces DIN 69871-1:1995-10 (DIN Media). JIS B 6339-1 corresponds to ISO 7388-1:2007 (AFNOR)
Aliases
DIN 40, ISO 40 (type A)
Taper
7/24[2][4][5]The names of the ISO 7388, JIS B 6339, and ASME B5.50 standards themselves contain "7/24 taper"
Taper half-angle
8°17′50″ +4″ (half angle)[1][6][7]1 source · referenceThe same statement appears on three HAIMER pages (same publisher). The taper tolerance is AT3 on the same page. The value of around 16°35′40″ for the included angle is unconfirmed in other sources
Gauge diameter (mm)
44.45[6][13]HAIMER table D1, TAC table D1
Flange diameter (mm)
63.55[6][13]HAIMER table D4, TAC table D6
L1 (mm)
68.4[6][13]L1 in both tables
b (mm)
16.1[6][13]HAIMER table B1, TAC table B (H12)
Pull stud thread
M16[6][13][15][16]
Coolant type
A (none), AD (through-spindle via pull stud), AF (from the flange side; formerly type B), AD/AF (formerly type ADB)[6][3]
Dual contact
None[6][3]Centered by the taper only (Meusburger: centred without flat contact)
Approx. speed
  • HAIMER:Primarily suitable up to 12,000 min⁻¹[6]
1 source · referenceMaker's guideline. Not a standard value
Main machines
—Not confirmed in public sourcesNo primary source was found that explicitly states a correspondence such as "No.30 = small machines, No.40 = medium, No.50 = large / heavy cutting" between taper number and machine size
Size
SK40

SK50

Standard
  • DIN ISO 7388-1 (former DIN 69871)
  • ISO 7388-1:2007 (forms A, AD, AF, U, UD, UF)
  • JIS B 6339-1
[6][12][2][4]DIN ISO 7388-1:2014-07 replaces DIN 69871-1:1995-10 (DIN Media). JIS B 6339-1 corresponds to ISO 7388-1:2007 (AFNOR)
Aliases
DIN 50, ISO 50 (type A)
Taper
7/24[2][4][5]The names of the ISO 7388, JIS B 6339, and ASME B5.50 standards themselves contain "7/24 taper"
Taper half-angle
8°17′50″ +4″ (half angle)[1][6][7]1 source · referenceThe same statement appears on three HAIMER pages (same publisher). The taper tolerance is AT3 on the same page. The value of around 16°35′40″ for the included angle is unconfirmed in other sources
Gauge diameter (mm)
69.85[6][13]HAIMER table D1, TAC table D1
Flange diameter (mm)
97.5[6][13]HAIMER table D4, TAC table D6
L1 (mm)
101.75[6][13]L1 in both tables
b (mm)
25.7[6][13]HAIMER table B1, TAC table B (H12)
Pull stud thread
M24[6][13][17]
Coolant type
A (none), AD (through-spindle via pull stud), AF (from the flange side; formerly type B), AD/AF (formerly type ADB)[6][3]
Dual contact
None[6][3]Centered by the taper only (Meusburger: centred without flat contact)
Approx. speed
  • HAIMER:Primarily suitable up to 12,000 min⁻¹[6]
1 source · referenceMaker's guideline. Not a standard value
Main machines
—Not confirmed in public sourcesNo primary source was found that explicitly states a correspondence such as "No.30 = small machines, No.40 = medium, No.50 = large / heavy cutting" between taper number and machine size
Size
SK50

CAT (ASME B5.50)

CAT30

Standard
ASME B5.50-2015 (reaffirmed 2025)[5][7]The ASME title is "7/24 Taper Tool to Spindle Connection for Automatic Tool Change". The relationship with ISO 7388-1 form U is unconfirmed
Aliases
CV30、ANSI 30
Taper
7/24[2][4][5]The names of the ISO 7388, JIS B 6339, and ASME B5.50 standards themselves contain "7/24 taper"
Taper half-angle
8°17′50″ +4″ (half angle)[1][6][7]1 source · referenceThe same statement appears on three HAIMER pages (same publisher). The taper tolerance is AT3 on the same page. The value of around 16°35′40″ for the included angle is unconfirmed in other sources
Gauge diameter
1.250 in[18]1 source · referenceHAIMER table D1, TAC table A (gage dia.). Shown in inches
Flange diameter
1.812 in[18]1 source · referenceHAIMER table D4, TAC table H
L1
1.875 in[18]1 source · referenceHAIMER table L1, TAC table B
Pull stud thread
1/2-13 UNC[18]1 source · referenceTAC writes 0.500-13 / 0.625-11 / 1.000-8, HAIMER writes 5/8"-11 / 1"-8. The UNC designation is based on the TAC column heading (UNC-2B)
Coolant type
AD (through-spindle), AF (from the flange), B[7]1 source · referenceHAIMER states it is made as ADB, usable as both AD and B
Dual contact
None[7]1 source · reference
Approx. speed
—Not confirmed in public sourcesNo maker guideline for CAT30 was confirmed
Main machines
—Not confirmed in public sourcesNo primary source was found that explicitly states a correspondence such as "No.30 = small machines, No.40 = medium, No.50 = large / heavy cutting" between taper number and machine size
Size
CAT30
CAT30 was confirmed only in TAC Rockford's table (one source)

CAT40

Standard
ASME B5.50-2015 (reaffirmed 2025)[5][7]The ASME title is "7/24 Taper Tool to Spindle Connection for Automatic Tool Change". The relationship with ISO 7388-1 form U is unconfirmed
Aliases
CV40、ANSI 40
Taper
7/24[2][4][5]The names of the ISO 7388, JIS B 6339, and ASME B5.50 standards themselves contain "7/24 taper"
Taper half-angle
8°17′50″ +4″ (half angle)[1][6][7]1 source · referenceThe same statement appears on three HAIMER pages (same publisher). The taper tolerance is AT3 on the same page. The value of around 16°35′40″ for the included angle is unconfirmed in other sources
Gauge diameter
1.750 in (44.45 mm)[7][18]HAIMER table D1, TAC table A (gage dia.). Shown in inches
Flange diameter
2.500 in[7][18]HAIMER table D4, TAC table H
L1
2.687 in[7][18]HAIMER table L1, TAC table B
Pull stud thread
5/8-11 UNC[7][18]TAC writes 0.500-13 / 0.625-11 / 1.000-8, HAIMER writes 5/8"-11 / 1"-8. The UNC designation is based on the TAC column heading (UNC-2B)
Coolant type
AD (through-spindle), AF (from the flange), B[7]1 source · referenceHAIMER states it is made as ADB, usable as both AD and B
Dual contact
None[7]1 source · reference
Approx. speed
  • HAIMER:Primarily suitable up to 25,000 min⁻¹ (primarily suitable … up to 25,000 rpm)[7]
1 source · referenceEven from the same HAIMER, the BT and SK pages say 12,000 and the CAT page says 25,000 (see the discrepancy in the README)
Main machines
—Not confirmed in public sourcesNo primary source was found that explicitly states a correspondence such as "No.30 = small machines, No.40 = medium, No.50 = large / heavy cutting" between taper number and machine size
Size
CAT40

CAT50

Standard
ASME B5.50-2015 (reaffirmed 2025)[5][7]The ASME title is "7/24 Taper Tool to Spindle Connection for Automatic Tool Change". The relationship with ISO 7388-1 form U is unconfirmed
Aliases
CV50、ANSI 50
Taper
7/24[2][4][5]The names of the ISO 7388, JIS B 6339, and ASME B5.50 standards themselves contain "7/24 taper"
Taper half-angle
8°17′50″ +4″ (half angle)[1][6][7]1 source · referenceThe same statement appears on three HAIMER pages (same publisher). The taper tolerance is AT3 on the same page. The value of around 16°35′40″ for the included angle is unconfirmed in other sources
Gauge diameter
2.750 in (69.85 mm)[7][18]HAIMER table D1, TAC table A (gage dia.). Shown in inches
Flange diameter
3.875 in[7][18]HAIMER table D4, TAC table H
L1
4.000 in[7][18]HAIMER table L1, TAC table B
Pull stud thread
1-8 UNC[7][18]TAC writes 0.500-13 / 0.625-11 / 1.000-8, HAIMER writes 5/8"-11 / 1"-8. The UNC designation is based on the TAC column heading (UNC-2B)
Coolant type
AD (through-spindle), AF (from the flange), B[7]1 source · referenceHAIMER states it is made as ADB, usable as both AD and B
Dual contact
None[7]1 source · reference
Approx. speed
  • HAIMER:Primarily suitable up to 25,000 min⁻¹ (primarily suitable … up to 25,000 rpm)[7]
1 source · referenceEven from the same HAIMER, the BT and SK pages say 12,000 and the CAT page says 25,000 (see the discrepancy in the README)
Main machines
—Not confirmed in public sourcesNo primary source was found that explicitly states a correspondence such as "No.30 = small machines, No.40 = medium, No.50 = large / heavy cutting" between taper number and machine size
Size
CAT50

Two-face contact (BIG-PLUS)

BBT30 / BBT40 / BBT50 (CAT and DIN types also exist)

Standardization
Not a standard of ISO, DIN, JIS, ASME, etc. (BIG DAISHOWA's proprietary system. BIG holds the grand master gauge, and only licensees have traceable master gauges)[21]1 source · reference
Trademark
BIG-PLUS® Spindle System (registered trademark of BIG DAISHOWA). Marked "BIG-PLUS® Spindle System" and "License BIG Daishowa Seiki"[19]1 source · referenceCompany name notation: BIG DAISHOWA (Daishowa Seiki Co., Ltd. / BIG Daishowa Seiki Co., Ltd.). The catalog says "Original Development of BIG DAISHOWA Seiki Co., Ltd."
Dual contact
Yes[19]1 source · reference
How it works
Two-face contact in which the holder's taper and flange face seat simultaneously against the spindle taper and spindle end face[19][20]1 source · reference
End-face gap (mm)
—Not confirmed in public sourcesThe numerical gap between the spindle end face and the flange (before clamping) could not be confirmed in public materials
Key dimension
The distance between the taper gauge line and the flange face is what decides two-face contact (value not disclosed)[22]1 source · reference
Contact diameter comparison
    • Size BT30
    • Conventional wheels ø1.250 in
    • BIG-PLUS ø1.811 in
    • Size CV40
    • Conventional wheels ø1.750 in
    • BIG-PLUS ø2.500 in
    • Size CV50
    • Conventional wheels ø2.750 in
    • BIG-PLUS ø3.875 in
[19]1 source · referenceComparison of "contact diameter" on the BIG page (taper only vs. when the end face also contacts)
Approx. speed
—Not confirmed in public sourcesNo published value from BIG DAISHOWA could be confirmed
Adoption
More than 100 machine tool makers have adopted it (BIG DAISHOWA's announcement)[21][22]1 source · referenceMedium, since these are two pages from the same publisher
Licensees
  • BIG DAISHOWA INC
  • REGO-FIX
  • SHOWA TOOL CO., LTD
  • BIG KAISER PRECISION TOOLING LTD
  • SUMITOMO
  • SANDVIK COROMANT
  • YUKIWA SEIKO USA, INC
[19]1 source · referenceLicensees listed on the BIG DAISHOWA page (manufacture, sale, use). The Japanese name does not appear on the BIG page; it is a name supplied here
Compatibility
BIG-PLUS holders can be used on standard spindles, and standard holders can be used on BIG-PLUS spindles (but two-face contact occurs only when both are BIG-PLUS)[19][20]1 source · reference
Caution on unlicensed products
Unlicensed two-face contact tools from other makers are on the market, and BIG warns that those without the marking "BIG-PLUS Spindle System-License BIG DAISHOWA SEIKI" risk poor performance or spindle damage[21][22]1 source · reference
Size
BBT30 / BBT40 / BBT50 (CAT and DIN types also exist)

Two-face contact (NIKKEN 2LOCK / 3LOCK)

NBT (2LOCK) / MBT (3LOCK)

Trademark
2LOCK and 3LOCK are Nikken Kosakusho product names (both described as "BT two-face contact"). 2LOCK tools are NBT, 3LOCK tools are MBT[23][24][25]1 source · referenceThe 2LOCK page says "2LOCK tool (NBT), born from the technology of the 3LOCK tool (MBT)". Whether it is a registered trademark is unconfirmed
Dual contact
Yes[23][24]1 source · reference
How it works
Two-face contact for BT. 3LOCK is marketed as countering thermal expansion at high rotation speed and spindle taper expansion[23]1 source · reference
Compatibility
—Not confirmed in public sourcesStatements such as "2LOCK can be used on standard BT spindles / 3LOCK requires a two-face contact spindle" and "taper:end face = 90:10" appear only in search summaries derived from dealer pages and are unconfirmed in NIKKEN's primary sources
Manufacturer's claim
3 to 5 times tool life (manufacturer's claim); less Z-direction change at high rotation speed and improved ATC repeatability (2LOCK)[23][24]1 source · reference
Other NIKKEN systems
There is also a separate line, the NC5 Tooling System (1/10 short taper, two-face contact)[23]1 source · reference
Size
NBT (2LOCK) / MBT (3LOCK)

Two-face contact (HAIMER's BT/CAT with face contact)

BT30/40/50, CAT40/50 with face contact

Dual contact
Yes[1][7]1 source · reference
How it works
A form that adds end-face contact to the BT and CAT taper. HAIMER states "fully compatible with Big-Plus spindles"[1][7]1 source · referenceHAIMER is not on BIG DAISHOWA's licensee list. Recorded in the README together with BIG's warning to "use only registered-trademark BIG-PLUS holders" (search summary)
Size
BT30/40/50, CAT40/50 with face contact

HSK

HSK-A32 (form C is the same size. Form E is 25–50)

Standard
  • DIN 69893-1 (A, C)
  • DIN 69893-2 (B, D)
  • DIN 69893-5 (E)
  • DIN 69893-6 (F)
  • ISO 12164-1:2023 (A, AB, C, CB, EB)
  • ISO 12164-3:2023 (T, TA, U = for lathes)
[26][3][2][29]The forms in ISO 12164-1:2023 are A, AB, C, CB, EB. Form F is only in DIN 69893-6 and does not appear in the ISO 12164 titles
Taper
1/10[30]1 source · referenceThe Sumitomo Electric catalog describes HSK as "1/10 Taper". A second primary source is unconfirmed
Taper diameter (mm)
24[26][27]
  • TAC Rockford:24
  • HAIMER:24.007
TAC table D1 is 24, HAIMER table D3 is 24.007 (appears to be the upper limit including tolerance)
Flange diameter (mm)
32[26][27]Nominal size = flange diameter (HAIMER table D1, TAC table D)
L1 (mm)
16[26][27]L1 in both tables
Pull studs
Not required (clamped from inside)[3][31]Meusburger: No pull stud necessary
Coolant tube thread
M10×1[26]1 source · referenceHAIMER table G (appears to be the thread of the coolant tube)
Type
A、C、E[26][27][28]HAIMER stock sizes: A32–A125, E25–E50, F63 and F80. TAC's Form C table covers 32–100, with the same flange diameter, taper diameter, and L1 as form A
Dual contact
Yes[26][30][3]Constrained by the taper and flange end face
Approx. speed
—Not confirmed in public sourcesNo numerical HSK speed guideline could be confirmed in maker publications. HAIMER and Meusburger say only "for high-speed machining"
Size
HSK-A32 (form C is the same size. Form E is 25–50)

HSK-A40 (form C is the same size. Form E is 25–50)

Standard
  • DIN 69893-1 (A, C)
  • DIN 69893-2 (B, D)
  • DIN 69893-5 (E)
  • DIN 69893-6 (F)
  • ISO 12164-1:2023 (A, AB, C, CB, EB)
  • ISO 12164-3:2023 (T, TA, U = for lathes)
[26][3][2][29]The forms in ISO 12164-1:2023 are A, AB, C, CB, EB. Form F is only in DIN 69893-6 and does not appear in the ISO 12164 titles
Taper
1/10[30]1 source · referenceThe Sumitomo Electric catalog describes HSK as "1/10 Taper". A second primary source is unconfirmed
Taper diameter (mm)
30[26][27]
  • TAC Rockford:30
  • HAIMER:30.007
TAC table D1 is 30, HAIMER table D3 is 30.007 (appears to be the upper limit including tolerance)
Flange diameter (mm)
40[26][27]Nominal size = flange diameter (HAIMER table D1, TAC table D)
L1 (mm)
20[26][27]L1 in both tables
Pull studs
Not required (clamped from inside)[3][31]Meusburger: No pull stud necessary
Coolant tube thread
M12×1[26]1 source · referenceHAIMER table G (appears to be the thread of the coolant tube)
Type
A、C、E[26][27][28]HAIMER stock sizes: A32–A125, E25–E50, F63 and F80. TAC's Form C table covers 32–100, with the same flange diameter, taper diameter, and L1 as form A
Dual contact
Yes[26][30][3]Constrained by the taper and flange end face
Approx. speed
—Not confirmed in public sourcesNo numerical HSK speed guideline could be confirmed in maker publications. HAIMER and Meusburger say only "for high-speed machining"
Size
HSK-A40 (form C is the same size. Form E is 25–50)

HSK-A50 (form C is the same size. Form E is 25–50)

Standard
  • DIN 69893-1 (A, C)
  • DIN 69893-2 (B, D)
  • DIN 69893-5 (E)
  • DIN 69893-6 (F)
  • ISO 12164-1:2023 (A, AB, C, CB, EB)
  • ISO 12164-3:2023 (T, TA, U = for lathes)
[26][3][2][29]The forms in ISO 12164-1:2023 are A, AB, C, CB, EB. Form F is only in DIN 69893-6 and does not appear in the ISO 12164 titles
Taper
1/10[30]1 source · referenceThe Sumitomo Electric catalog describes HSK as "1/10 Taper". A second primary source is unconfirmed
Taper diameter (mm)
38[26][27]
  • TAC Rockford:38
  • HAIMER:38.009
TAC table D1 is 38, HAIMER table D3 is 38.009 (appears to be the upper limit including tolerance)
Flange diameter (mm)
50[26][27]Nominal size = flange diameter (HAIMER table D1, TAC table D)
L1 (mm)
25[26][27]L1 in both tables
Pull studs
Not required (clamped from inside)[3][31]Meusburger: No pull stud necessary
Coolant tube thread
M16×1[26]1 source · referenceHAIMER table G (appears to be the thread of the coolant tube)
Type
A、C、E[26][27][28]HAIMER stock sizes: A32–A125, E25–E50, F63 and F80. TAC's Form C table covers 32–100, with the same flange diameter, taper diameter, and L1 as form A
Dual contact
Yes[26][30][3]Constrained by the taper and flange end face
Approx. speed
—Not confirmed in public sourcesNo numerical HSK speed guideline could be confirmed in maker publications. HAIMER and Meusburger say only "for high-speed machining"
Size
HSK-A50 (form C is the same size. Form E is 25–50)

HSK-A63 (form C is the same size. Form E is 25–50)

Standard
  • DIN 69893-1 (A, C)
  • DIN 69893-2 (B, D)
  • DIN 69893-5 (E)
  • DIN 69893-6 (F)
  • ISO 12164-1:2023 (A, AB, C, CB, EB)
  • ISO 12164-3:2023 (T, TA, U = for lathes)
[26][3][2][29]The forms in ISO 12164-1:2023 are A, AB, C, CB, EB. Form F is only in DIN 69893-6 and does not appear in the ISO 12164 titles
Taper
1/10[30]1 source · referenceThe Sumitomo Electric catalog describes HSK as "1/10 Taper". A second primary source is unconfirmed
Taper diameter (mm)
48[26][27]
  • TAC Rockford:48
  • HAIMER:48.010
TAC table D1 is 48, HAIMER table D3 is 48.010 (appears to be the upper limit including tolerance)
Flange diameter (mm)
63[26][27]Nominal size = flange diameter (HAIMER table D1, TAC table D)
L1 (mm)
32[26][27]L1 in both tables
Pull studs
Not required (clamped from inside)[3][31]Meusburger: No pull stud necessary
Coolant tube thread
M18×1[26]1 source · referenceHAIMER table G (appears to be the thread of the coolant tube)
Type
A、C[26][27][28]HAIMER stock sizes: A32–A125, E25–E50, F63 and F80. TAC's Form C table covers 32–100, with the same flange diameter, taper diameter, and L1 as form A
Dual contact
Yes[26][30][3]Constrained by the taper and flange end face
Approx. speed
—Not confirmed in public sourcesNo numerical HSK speed guideline could be confirmed in maker publications. HAIMER and Meusburger say only "for high-speed machining"
Size
HSK-A63 (form C is the same size. Form E is 25–50)

HSK-A80 (form C is the same size. Form E is 25–50)

Standard
  • DIN 69893-1 (A, C)
  • DIN 69893-2 (B, D)
  • DIN 69893-5 (E)
  • DIN 69893-6 (F)
  • ISO 12164-1:2023 (A, AB, C, CB, EB)
  • ISO 12164-3:2023 (T, TA, U = for lathes)
[26][3][2][29]The forms in ISO 12164-1:2023 are A, AB, C, CB, EB. Form F is only in DIN 69893-6 and does not appear in the ISO 12164 titles
Taper
1/10[30]1 source · referenceThe Sumitomo Electric catalog describes HSK as "1/10 Taper". A second primary source is unconfirmed
Taper diameter (mm)
60[26][27]
  • TAC Rockford:60
  • HAIMER:60.012
TAC table D1 is 60, HAIMER table D3 is 60.012 (appears to be the upper limit including tolerance)
Flange diameter (mm)
80[26][27]Nominal size = flange diameter (HAIMER table D1, TAC table D)
L1 (mm)
40[26][27]L1 in both tables
Pull studs
Not required (clamped from inside)[3][31]Meusburger: No pull stud necessary
Coolant tube thread
M20×1.5[26]1 source · referenceHAIMER table G (appears to be the thread of the coolant tube)
Type
A、C[26][27][28]HAIMER stock sizes: A32–A125, E25–E50, F63 and F80. TAC's Form C table covers 32–100, with the same flange diameter, taper diameter, and L1 as form A
Dual contact
Yes[26][30][3]Constrained by the taper and flange end face
Approx. speed
—Not confirmed in public sourcesNo numerical HSK speed guideline could be confirmed in maker publications. HAIMER and Meusburger say only "for high-speed machining"
Size
HSK-A80 (form C is the same size. Form E is 25–50)

HSK-A100 (form C is the same size. Form E is 25–50)

Standard
  • DIN 69893-1 (A, C)
  • DIN 69893-2 (B, D)
  • DIN 69893-5 (E)
  • DIN 69893-6 (F)
  • ISO 12164-1:2023 (A, AB, C, CB, EB)
  • ISO 12164-3:2023 (T, TA, U = for lathes)
[26][3][2][29]The forms in ISO 12164-1:2023 are A, AB, C, CB, EB. Form F is only in DIN 69893-6 and does not appear in the ISO 12164 titles
Taper
1/10[30]1 source · referenceThe Sumitomo Electric catalog describes HSK as "1/10 Taper". A second primary source is unconfirmed
Taper diameter (mm)
75[26][27]
  • TAC Rockford:75
  • HAIMER:75.013
TAC table D1 is 75, HAIMER table D3 is 75.013 (appears to be the upper limit including tolerance)
Flange diameter (mm)
100[26][27]Nominal size = flange diameter (HAIMER table D1, TAC table D)
L1 (mm)
50[26][27]L1 in both tables
Pull studs
Not required (clamped from inside)[3][31]Meusburger: No pull stud necessary
Coolant tube thread
M24×1.5[26]1 source · referenceHAIMER table G (appears to be the thread of the coolant tube)
Type
A、C[26][27][28]HAIMER stock sizes: A32–A125, E25–E50, F63 and F80. TAC's Form C table covers 32–100, with the same flange diameter, taper diameter, and L1 as form A
Dual contact
Yes[26][30][3]Constrained by the taper and flange end face
Approx. speed
—Not confirmed in public sourcesNo numerical HSK speed guideline could be confirmed in maker publications. HAIMER and Meusburger say only "for high-speed machining"
Size
HSK-A100 (form C is the same size. Form E is 25–50)

HSK-A125 (form C is the same size. Form E is 25–50)

Standard
  • DIN 69893-1 (A, C)
  • DIN 69893-2 (B, D)
  • DIN 69893-5 (E)
  • DIN 69893-6 (F)
  • ISO 12164-1:2023 (A, AB, C, CB, EB)
  • ISO 12164-3:2023 (T, TA, U = for lathes)
[26][3][2][29]The forms in ISO 12164-1:2023 are A, AB, C, CB, EB. Form F is only in DIN 69893-6 and does not appear in the ISO 12164 titles
Taper
1/10[30]1 source · referenceThe Sumitomo Electric catalog describes HSK as "1/10 Taper". A second primary source is unconfirmed
Taper diameter (mm)
95[26][27]
  • TAC Rockford:95
  • HAIMER:95.016
TAC table D1 is 95, HAIMER table D3 is 95.016 (appears to be the upper limit including tolerance)
Flange diameter (mm)
125[26][27]Nominal size = flange diameter (HAIMER table D1, TAC table D)
L1 (mm)
63[26][27]L1 in both tables
Pull studs
Not required (clamped from inside)[3][31]Meusburger: No pull stud necessary
Coolant tube thread
M30×1.5[26]1 source · referenceHAIMER table G (appears to be the thread of the coolant tube)
Type
A[26][27]HAIMER stock sizes: A32–A125, E25–E50, F63 and F80. TAC's Form C table covers 32–100, with the same flange diameter, taper diameter, and L1 as form A
Dual contact
Yes[26][30][3]Constrained by the taper and flange end face
Approx. speed
—Not confirmed in public sourcesNo numerical HSK speed guideline could be confirmed in maker publications. HAIMER and Meusburger say only "for high-speed machining"
Size
HSK-A125 (form C is the same size. Form E is 25–50)

HSK-A160

Standard
  • DIN 69893-1 (A, C)
  • DIN 69893-2 (B, D)
  • DIN 69893-5 (E)
  • DIN 69893-6 (F)
  • ISO 12164-1:2023 (A, AB, C, CB, EB)
  • ISO 12164-3:2023 (T, TA, U = for lathes)
[26][3][2][29]The forms in ISO 12164-1:2023 are A, AB, C, CB, EB. Form F is only in DIN 69893-6 and does not appear in the ISO 12164 titles
Taper
1/10[30]1 source · referenceThe Sumitomo Electric catalog describes HSK as "1/10 Taper". A second primary source is unconfirmed
Taper diameter (mm)
120[27]1 source · reference
Flange diameter (mm)
160[27]1 source · reference
L1 (mm)
80[27]1 source · reference
Size
HSK-A160

HSK-E25

Standard
DIN 69893-5[26]1 source · reference
Taper diameter (mm)
19.006[26]1 source · referenceHAIMER table D3
Flange diameter (mm)
25[26]1 source · reference
L1 (mm)
13[26]1 source · reference
Coolant tube thread
M8×1[26]1 source · reference
Torque transmission
Friction only (not driven through a keyway)[3]1 source · referenceE and F forms transmit torque purely by friction (Meusburger)
Applications
High-frequency spindles (graphite machining, etc.), woodworking machines[3]1 source · reference
Size
HSK-E25

HSK-F63

Standard
DIN 69893-6[26][3]
Taper diameter (mm)
38[26][32]HAIMER 38.009, TAC 38 +0.009/+0.006. Same taper diameter as HSK-A50, only the flange is 63 (Meusburger: reduced taper and thus large collar)
Flange diameter (mm)
63[26][32]
L1 (mm)
25[26][32]
Applications
Woodworking, dry machining only[3]1 source · reference
Size
HSK-F63

HSK-F80

Taper diameter (mm)
48.010[26]1 source · reference
Flange diameter (mm)
80[26]1 source · reference
L1 (mm)
32[26]1 source · reference
Size
HSK-F80
HAIMER's table writes "HSK-F80 Makino", so it may be intended for a specific machine maker (unconfirmed)

Coromant Capto (ISO 26623)

C3

Standard
ISO 26623-1:2020 (shank), ISO 26623-2:2014 (receiver)[2][31]The ISO title is "Polygonal taper interface with flange contact surface"
Trademark
Coromant Capto® is a registered trademark of Sandvik Coromant. Other makers' compatible products come under names such as "PSC (Polygon Shank Cone)" (e.g., HAIMER PSC: Compatible with Capto)[33][31]
Taper
—Not confirmed in public sourcesThe polygon taper gradient (e.g., 1:20) could not be confirmed in maker publications
Coupling diameter (mm)
32[33][31]Sandvik: six sizes C3–C10, diameters 32, 40, 50, 63, 80, 100. HAIMER PSC table D1 is 32–80
Pull studs
Not required[31]1 source · reference
Dual contact
Yes[31][3]Polygon taper plus flange end-face contact
Applications
Multitasking machines (turn-mill), quick change on lathes and machining centers, modular extensions[33][31][3]
Size
C3

C4

Standard
ISO 26623-1:2020 (shank), ISO 26623-2:2014 (receiver)[2][31]The ISO title is "Polygonal taper interface with flange contact surface"
Trademark
Coromant Capto® is a registered trademark of Sandvik Coromant. Other makers' compatible products come under names such as "PSC (Polygon Shank Cone)" (e.g., HAIMER PSC: Compatible with Capto)[33][31]
Taper
—Not confirmed in public sourcesThe polygon taper gradient (e.g., 1:20) could not be confirmed in maker publications
Coupling diameter (mm)
40[33][31]Sandvik: six sizes C3–C10, diameters 32, 40, 50, 63, 80, 100. HAIMER PSC table D1 is 32–80
Pull studs
Not required[31]1 source · reference
Dual contact
Yes[31][3]Polygon taper plus flange end-face contact
Applications
Multitasking machines (turn-mill), quick change on lathes and machining centers, modular extensions[33][31][3]
Size
C4

C5

Standard
ISO 26623-1:2020 (shank), ISO 26623-2:2014 (receiver)[2][31]The ISO title is "Polygonal taper interface with flange contact surface"
Trademark
Coromant Capto® is a registered trademark of Sandvik Coromant. Other makers' compatible products come under names such as "PSC (Polygon Shank Cone)" (e.g., HAIMER PSC: Compatible with Capto)[33][31]
Taper
—Not confirmed in public sourcesThe polygon taper gradient (e.g., 1:20) could not be confirmed in maker publications
Coupling diameter (mm)
50[33][31]Sandvik: six sizes C3–C10, diameters 32, 40, 50, 63, 80, 100. HAIMER PSC table D1 is 32–80
Pull studs
Not required[31]1 source · reference
Dual contact
Yes[31][3]Polygon taper plus flange end-face contact
Applications
Multitasking machines (turn-mill), quick change on lathes and machining centers, modular extensions[33][31][3]
Size
C5

C6

Standard
ISO 26623-1:2020 (shank), ISO 26623-2:2014 (receiver)[2][31]The ISO title is "Polygonal taper interface with flange contact surface"
Trademark
Coromant Capto® is a registered trademark of Sandvik Coromant. Other makers' compatible products come under names such as "PSC (Polygon Shank Cone)" (e.g., HAIMER PSC: Compatible with Capto)[33][31]
Taper
—Not confirmed in public sourcesThe polygon taper gradient (e.g., 1:20) could not be confirmed in maker publications
Coupling diameter (mm)
63[33][31]Sandvik: six sizes C3–C10, diameters 32, 40, 50, 63, 80, 100. HAIMER PSC table D1 is 32–80
Pull studs
Not required[31]1 source · reference
Dual contact
Yes[31][3]Polygon taper plus flange end-face contact
Applications
Multitasking machines (turn-mill), quick change on lathes and machining centers, modular extensions[33][31][3]
Size
C6

C8

Standard
ISO 26623-1:2020 (shank), ISO 26623-2:2014 (receiver)[2][31]The ISO title is "Polygonal taper interface with flange contact surface"
Trademark
Coromant Capto® is a registered trademark of Sandvik Coromant. Other makers' compatible products come under names such as "PSC (Polygon Shank Cone)" (e.g., HAIMER PSC: Compatible with Capto)[33][31]
Taper
—Not confirmed in public sourcesThe polygon taper gradient (e.g., 1:20) could not be confirmed in maker publications
Coupling diameter (mm)
80[33][31]Sandvik: six sizes C3–C10, diameters 32, 40, 50, 63, 80, 100. HAIMER PSC table D1 is 32–80
Pull studs
Not required[31]1 source · reference
Dual contact
Yes[31][3]Polygon taper plus flange end-face contact
Applications
Multitasking machines (turn-mill), quick change on lathes and machining centers, modular extensions[33][31][3]
Size
C8

C10

Standard
ISO 26623-1:2020 (shank), ISO 26623-2:2014 (receiver)[2][31]The ISO title is "Polygonal taper interface with flange contact surface"
Trademark
Coromant Capto® is a registered trademark of Sandvik Coromant. Other makers' compatible products come under names such as "PSC (Polygon Shank Cone)" (e.g., HAIMER PSC: Compatible with Capto)[33][31]
Taper
—Not confirmed in public sourcesThe polygon taper gradient (e.g., 1:20) could not be confirmed in maker publications
Coupling diameter (mm)
100[33]1 source · referenceSandvik: six sizes C3–C10, diameters 32, 40, 50, 63, 80, 100. HAIMER PSC table D1 is 32–80
Pull studs
Not required[31]1 source · reference
Dual contact
Yes[31][3]Polygon taper plus flange end-face contact
Applications
Multitasking machines (turn-mill), quick change on lathes and machining centers, modular extensions[33][31][3]
Size
C10

KM (ISO 26622)

KM32 (Sumitomo Electric designation TS32)

Standard
  • ISO 26622-1:2017 (shank)
  • ISO 26622-2:2008 (receiver)
  • ISO 26622-3/-4:2026 (form with four locking elements)
[2]1 source · referenceThe ISO title is "Modular taper interface with ball track system"
Trademark
—Not confirmed in public sourcesIt could not be confirmed in Kennametal's primary sources that KM is a Kennametal registered trademark (the Kennametal site is rendered by JS and the body text could not be retrieved)
Taper
1/10[30]1 source · reference1/10 Taper appears in the table of Sumitomo Electric's Modular Taper Shank (stated to conform to ISO 26622-1)
Flange diameter (mm)
32[30]1 source · referenceSumitomo Electric Mounting Dia., TAC Rockford gauge table Dg. TAC explains "size = tool change flange diameter"
Dual contact
Yes[30]1 source · referenceLocated by two faces: the taper and the flange
Size
KM32 (Sumitomo Electric designation TS32)

KM40 (Sumitomo Electric designation TS40)

Standard
  • ISO 26622-1:2017 (shank)
  • ISO 26622-2:2008 (receiver)
  • ISO 26622-3/-4:2026 (form with four locking elements)
[2]1 source · referenceThe ISO title is "Modular taper interface with ball track system"
Trademark
—Not confirmed in public sourcesIt could not be confirmed in Kennametal's primary sources that KM is a Kennametal registered trademark (the Kennametal site is rendered by JS and the body text could not be retrieved)
Taper
1/10[30]1 source · reference1/10 Taper appears in the table of Sumitomo Electric's Modular Taper Shank (stated to conform to ISO 26622-1)
Flange diameter (mm)
40[30][34]Sumitomo Electric Mounting Dia., TAC Rockford gauge table Dg. TAC explains "size = tool change flange diameter"
Dual contact
Yes[30]1 source · referenceLocated by two faces: the taper and the flange
Size
KM40 (Sumitomo Electric designation TS40)

KM50 (Sumitomo Electric designation TS50)

Standard
  • ISO 26622-1:2017 (shank)
  • ISO 26622-2:2008 (receiver)
  • ISO 26622-3/-4:2026 (form with four locking elements)
[2]1 source · referenceThe ISO title is "Modular taper interface with ball track system"
Trademark
—Not confirmed in public sourcesIt could not be confirmed in Kennametal's primary sources that KM is a Kennametal registered trademark (the Kennametal site is rendered by JS and the body text could not be retrieved)
Taper
1/10[30]1 source · reference1/10 Taper appears in the table of Sumitomo Electric's Modular Taper Shank (stated to conform to ISO 26622-1)
Flange diameter (mm)
50[30][34]Sumitomo Electric Mounting Dia., TAC Rockford gauge table Dg. TAC explains "size = tool change flange diameter"
Dual contact
Yes[30]1 source · referenceLocated by two faces: the taper and the flange
Size
KM50 (Sumitomo Electric designation TS50)

KM63 (Sumitomo Electric designation TS63)

Standard
  • ISO 26622-1:2017 (shank)
  • ISO 26622-2:2008 (receiver)
  • ISO 26622-3/-4:2026 (form with four locking elements)
[2]1 source · referenceThe ISO title is "Modular taper interface with ball track system"
Trademark
—Not confirmed in public sourcesIt could not be confirmed in Kennametal's primary sources that KM is a Kennametal registered trademark (the Kennametal site is rendered by JS and the body text could not be retrieved)
Taper
1/10[30]1 source · reference1/10 Taper appears in the table of Sumitomo Electric's Modular Taper Shank (stated to conform to ISO 26622-1)
Flange diameter (mm)
63[30][34]Sumitomo Electric Mounting Dia., TAC Rockford gauge table Dg. TAC explains "size = tool change flange diameter"
Dual contact
Yes[30]1 source · referenceLocated by two faces: the taper and the flange
Size
KM63 (Sumitomo Electric designation TS63)

KM80 (Sumitomo Electric designation TS80)

Standard
  • ISO 26622-1:2017 (shank)
  • ISO 26622-2:2008 (receiver)
  • ISO 26622-3/-4:2026 (form with four locking elements)
[2]1 source · referenceThe ISO title is "Modular taper interface with ball track system"
Trademark
—Not confirmed in public sourcesIt could not be confirmed in Kennametal's primary sources that KM is a Kennametal registered trademark (the Kennametal site is rendered by JS and the body text could not be retrieved)
Taper
1/10[30]1 source · reference1/10 Taper appears in the table of Sumitomo Electric's Modular Taper Shank (stated to conform to ISO 26622-1)
Flange diameter (mm)
80[30][34]Sumitomo Electric Mounting Dia., TAC Rockford gauge table Dg. TAC explains "size = tool change flange diameter"
Dual contact
Yes[30]1 source · referenceLocated by two faces: the taper and the flange
Size
KM80 (Sumitomo Electric designation TS80)
TAC Rockford's gauge table has no KM100. The existence of KM100 is unconfirmed in primary sources

⇄Compatibility (BT, SK, CAT, dual contact)

BT (ISO 7388-2) and SK/DIN (ISO 7388-1)

  • Same 7/24 taper and gauge diameters (No.30 31.75, No.40 44.45, No.50 69.85 mm)
  • Flange diameters differ (No.40: BT 63 mm / SK 63.55 mm; No.50: BT 100 / SK 97.5)
  • L1 in the table differs (No.40: BT 65.4 / SK 68.4 mm)
  • Meusburger explains that ISO 7388-2 differs from ISO 7388-1 in taper length, collar width, gripper groove, and keyway
[1][6][8][13][3]

BT40 and CAT40

  • Same gauge diameter, 44.45 mm (=1.750 in)
  • Pull stud threads differ (BT40 is M16, CAT40 is 5/8-11)
  • Flange diameter: BT40 63 mm, CAT40 2.500 in (63.5 mm)
[1][7][8][18]

BIG-PLUS and standard BT

BIG-PLUS holders can be used in standard spindles, and standard holders in BIG-PLUS spindles (without two-face contact)[19][20]1 source · reference

No primary source that clearly states compatibility was found, so only the fact that the dimensions differ is given. For combinations of a dual-contact spindle and holder, follow the specifications of the spindle manufacturer and the holder manufacturer.

⊥Pull studs (pull bolts, retention knobs)

Pull studs of different shape and length are used by each machine maker, and using the wrong one leads to accidents or machine damage[9]1 source · reference

ISO 7388-3 types:AD、AF、UD、UF、JD、JF[2]1 source · referenceISO 7388-3:2016, title "Retention knobs of forms AD, AF, UD, UF, JD and JF". A series = ISO 7388-1 form A (DIN/SK), J series = ISO 7388-2 (BT), U series = ISO 7388-1 form U

BT30

Standard
JIS B 6339-3 (continuation of MAS 403), ISO 7388-3 types JD/JF[2][9]
Angle
  • BIG DAISHOWA:MAS-I 45° / MAS-II 60°[9]
1 source · referenceAngles are expressed differently by source (BIG gives MAS-I 45° and MAS-II 60°, SCHUNK writes MAS 403 as 30°/45°). Whether these are different notations of the same shape or different things is unconfirmed
Thread
M12[9][1][8]

BT40

Standard
ISO 7388-3 form JF (SCHUNK notation: former MAS 403 30°/45°)[10][2]
Angle
  • BIG DAISHOWA:MAS-I 45° / MAS-II 60°[9]
  • SCHUNK:Two types: 45° and 30°[35]
1 source · referenceAngles are expressed differently by source (BIG gives MAS-I 45° and MAS-II 60°, SCHUNK writes MAS 403 as 30°/45°). Whether these are different notations of the same shape or different things is unconfirmed
Thread
M16[10][9][1][8]
Dimensions (mm)
  • SCHUNK(AZB JIS-BT 40 45°/30°):—[10][35]
1 source · referenceThe dimension table values are the same for 45° and 30° (SCHUNK)

BT50

Standard
ISO 7388-3 form JF[11]1 source · reference
Angle
1 source · referenceAngles are expressed differently by source (BIG gives MAS-I 45° and MAS-II 60°, SCHUNK writes MAS 403 as 30°/45°). Whether these are different notations of the same shape or different things is unconfirmed
Thread
M24[11][1][8]
Dimensions (mm)
  • SCHUNK(AZB JIS-BT 50 45°):—[11]
1 source · reference

SK30

Standard
  • ISO 7388-3 form AD (through-coolant, former DIN 69872 form A)
  • ISO 7388-3 form AF (no hole, former DIN 69872 form B)
[14][2]
Angle
15°[14]1 source · referencea in the SCHUNK table
Thread
M12[14][6][13]
Dimensions (mm)
1 source · reference

SK40

Standard
  • ISO 7388-3 form AD (through-coolant, former DIN 69872 form A)
  • ISO 7388-3 form AF (no hole, former DIN 69872 form B)
[15][16][2]
Angle
15°[15][16]1 source · referencea in the SCHUNK table
Thread
M16[15][16][6][13]
Dimensions (mm)
1 source · reference

SK50

Standard
  • ISO 7388-3 form AD (through-coolant, former DIN 69872 form A)
  • ISO 7388-3 form AF (no hole, former DIN 69872 form B)
[17][2]
Angle
15°[17]1 source · referencea in the SCHUNK table
Thread
M24[17][6][13]
Dimensions (mm)
1 source · reference

ISO 7388-1 form U No.40 (SCHUNK product name SK 40 45° UD)

Standard
ISO 7388-3 form UD (SCHUNK notation: former ISO 7388-2 form B)[36]1 source · reference
Angle
45°[36]1 source · reference
Thread
M16[36]1 source · reference
Dimensions (mm)
1 source · reference
The relationship between form U and ASME B5.50 (CAT) is unconfirmed in primary sources. Note that the thread is metric M16

CAT40 (ASME B5.50)

Standard
ASME B5.50[5]1 source · referenceASME B5.50 covers both the shank and the retention knob (pull stud)
Angle
  • WIDIA (Kennametal):45° (half taper angle)[37]Search summary only (the page is rendered by JS and the body text was not confirmed)
Not confirmed in public sources
Thread
5/8-11[7][18][37]WIDIA figures from search summary only. High confidence from the two companies HAIMER and TAC

CAT50 (ASME B5.50)

Standard
ASME B5.50[5]1 source · reference
Angle
  • WIDIA (Kennametal):45°[38]Search summary only
Not confirmed in public sources
Thread
1-8[7][18][38]WIDIA figures from search summary only

CAT40 (for MAZAK machines, metric thread)

Standard
Machine maker proprietary (non-standard)[39]1 source · reference
Angle
45°[39]1 source · reference
Thread
M16[39]1 source · reference
Dimensions (mm)
1 source · reference
An example of a machine with CAT40 but a metric thread. BIG DAISHOWA's table also has machine-maker-specific forms such as MAZAK 45° and DMG MORI Form B 90°

📚Sources

Values with no mark agree across two or more independent publishers. BIG-PLUS® is a registered trademark of BIG DAISHOWA, which states explicitly that it is not a standard of a standards body.

  1. HAIMER GmbH「Steep taper JIS (MAS 403) BT30/BT40/BT50 – Technical specifications JIS B 6339-2」
  2. ISO, "ICS 25.060.20 Dividing and tool-workpiece holding devices" (list of standards)
  3. Meusburger Georg GmbH & Co KG「Tool holders – overview of the most important connections」
  4. AFNOR Editions「JIS B 6339-1:2011 Tool shanks with 7/24 taper for automatic tool changers – Part 1」
  5. ASME「B5.50 – 7/24 Taper Tool to Spindle Connection for Automatic Tool Change」
  6. HAIMER GmbH「Steep taper DIN ISO 7388-1 (formerly DIN 69871) SK30/SK40/SK50」
  7. HAIMER GmbH「Steep taper ASME B5.50 CAT40/CAT50 – Technical specifications」
  8. TAC Rockford「BT Tool Holder Specifications (100.226)」
  9. BIG DAISHOWA, "High Performance Tooling Solutions Vol 3 – Pullstud bolts (p.178)"
  10. SCHUNK SE & Co. KG, "AZB JIS-BT 40 45° MAS 403 (Ident.-Nr. 9150122)"
  11. SCHUNK SE & Co. KG, "AZB JIS-BT 50 45° MAS 403 (Ident.-Nr. 9938226)"
  12. DIN Media, "DIN ISO 7388-1:2014-07" (replaces DIN 69871-1:1995-10)
  13. TAC Rockford「DIN Tool Holder Specifications (100.224)」
  14. SCHUNK SE & Co. KG, "AZB SK 30 15° ISO 7388-3 AF (Ident.-Nr. 9150106)"
  15. SCHUNK SE & Co. KG, "AZB SK 40 15° ISO 7388-3 AD (Ident.-Nr. 9938210)"
  16. SCHUNK SE & Co. KG, "AZB SK 40 15° ISO 7388-3 AF (Ident.-Nr. 9150117)"
  17. SCHUNK SE & Co. KG, "AZB SK 50 15° ISO 7388-3 AD (Ident.-Nr. 9938211)"
  18. TAC Rockford「CAT/ANSI Tool Holder Specifications (100.221)」
  19. BIG DAISHOWA「BIG-PLUS Dual Contact Spindle System」
  20. BIG DAISHOWA, "BIG-PLUS Dual Contact" (catalog p.3)
  21. BIG DAISHOWA「Is BIG-PLUS An International Standard?」
  22. BIG DAISHOWA「BIG-PLUS Licensed vs Unlicensed」
  23. Nikken Kosakusho (NIKKEN), "3LOCK Tooling System (BT dual contact)"
  24. Nikken Kosakusho (NIKKEN), "2LOCK Tooling System (BT dual contact)"
  25. Nikken Kosakusho (NIKKEN), "3LOCK Milling Chuck (standard specification) catalog PDF"
  26. HAIMER GmbH「Hollow taper shank DIN 69893 HSK-A, HSK-E, HSK-F」
  27. TAC Rockford「HSK Form A Specifications (100.141)」
  28. TAC Rockford「HSK Form C Specifications (100.143)」
  29. BSI「BS ISO 12164-1:2023 Hollow taper interface with flange contact surface – Part 1」
  30. Sumitomo Electric Industries (Sumitomo Electric Hardmetal), "Sumitomo General Catalog 2025-2026 p.476 (Modular Taper Shank / HSK)"
  31. HAIMER GmbH「Spindle interface ISO 26623 HAIMER PSC tool holders」
  32. TAC Rockford「HSK Form F Specifications (100.146)」
  33. Sandvik Coromant「Coromant Capto® – Three systems in one」
  34. TAC Rockford「KM Master Setting Gauges (455.K00)」
  35. SCHUNK SE & Co. KG, "AZB JIS-BT 40 30° MAS 403 (Ident.-Nr. 9938229)"
  36. SCHUNK SE & Co. KG, "AZB SK 40 45° ISO 7388-3 UD (Ident.-Nr. 9938218)"
  37. WIDIA (Kennametal Group), "Retention knob IDRK40CV" (part no. 1026590)
  38. WIDIA (Kennametal Group), "Retention knob IDRK50CV" (part no. 1026690)
  39. SCHUNK SE & Co. KG, "AZB MAZAK CAT 40 45° L1=41,3 (Ident.-Nr. 9938222)"