Morse Tapers and Other Tapers

Dimensions of tapers used in lathe tailstocks, drill press spindles, drill chucks, etc. Cross-checked against the official ISO standard samples, the full public text of the Indian standards, and tool manufacturers' documents.

▦Morse taper quick reference

Number	Taper	Gauge diameter (mm)	Small end diameter, reference (mm)	Draw screw
MT0	1:19.212^[1][2][3]	9.045^[1][2][4]	6.4^[1][2]	—^[1]1 source · reference
MT1	1:20.047^[1][2]	12.065^[1][2][5]	9.4^[1][2]	M6 (inch products: UNC 1/4)^[1][2][5]
MT2	1:20.020^[1][2][3]	17.78^[1][2][5]	14.6^[1][2]	M10 (inch products: UNC 3/8)^[1][2][5]
MT3	1:19.922^[1][2][3]	23.825^[1][2][5]	19.8^[1][2]	M12 (inch products: UNC 1/2)^[1][2][5]
MT4	1:19.254^[1][2][3]	31.267^[1][2][5]	25.9^[1][2]	M16 (inch products: UNC 5/8)^[1][2][5]
MT5	1:19.002^[1][2][3]	44.399^[1][2][5]	37.6^[1][2]	M20 (inch products: UNC 5/8)^[1][2][5]
MT6	1:19.180^[1][2][3]	63.348^[1][2][5]	53.9^[1][2]	M24 (inch products: UNC 1)^[1][2][5]
MT7	—Not confirmed in public sources	—Not confirmed in public sources	—	—Not confirmed in public sources

The taper ratio differs slightly for each Morse taper number (about 1/20). MT7 is not included in ISO 296.

Taper shape and taper ratio (cross-sections at the same scale)

Both are drawn at the same scale, with the taper angles per the standard values (L of MT3 is the maximum l1 of 81 mm; the length of the 7/24 taper section is a rough guide above the drawing). Taper ratio is expressed as the difference in diameters ÷ length, using diameters rather than the half-angle.

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

Morse taper (MT)

MT0ISO 296, IS 1715, DIN 228

Taper: 1:19.212^[1][2][3]= 0.6246:12 (0.05205). The ISO 1119 taper angle (included angle) is 2°58′53.8″
Taper half-angle: 1°29′27″^[2]1 source · reference
Gauge diameter (mm): 9.045^[1][2][4]TAC's MT0 column says Contact us, with no value
Small end diameter, reference (mm): 6.4^[1][2]d (reference value)
Length: l1 max 50 / l3 56.5 (symbols as in the ISO 296 table)^[1][2]
Draw screw: —^[1]1 source · referenceIn ISO 296, the thread column for MT0 is "—" (not specified)
Tang: Tang thickness b(h13) = 3.9, e max 10.5^[1]1 source · reference
Size: MT0

There is no MT0 in the inch table (ISO 296 Table 3)

MT1ISO 296, IS 1715, DIN 228, ASME B5.10

Taper: 1:20.047^[1][2]=0.59858:12 (0.04988)
Taper half-angle: 1°25′43″^[2]1 source · reference
Gauge diameter (mm): 12.065^[1][2][5]Inch notation D = 0.475 in (ISO 296 Table 3)
Small end diameter, reference (mm): 9.4^[1][2]
Length: l1 max 53.5 / l3 62^[1][2][5]
Draw screw: M6 (inch products: UNC 1/4)^[1][2][5]TAC gives M6x1
Tang: b=5.2, e max 13.5^[1]1 source · reference
Size: MT1

MT2ISO 296, IS 1715, DIN 228, ASME B5.10

Taper: 1:20.020^[1][2][3]ISO 296 writes "1:20,02". Included angle 2°51′40.8″ (ISO 1119)
Taper half-angle: 1°25′50″^[2]1 source · reference
Gauge diameter (mm): 17.78^[1][2][5]0.700 in
Small end diameter, reference (mm): 14.6^[1][2]
Length: l1 max 64 / l3 75^[1][2][5]
Draw screw: M10 (inch products: UNC 3/8)^[1][2][5]
Tang: b=6.3, e max 16^[1]1 source · reference
Size: MT2

MT3ISO 296, IS 1715, DIN 228, ASME B5.10

Taper: 1:19.922^[1][2][3]Included angle 2°52′31.4″
Taper half-angle: 1°26′16″^[2]1 source · reference
Gauge diameter (mm): 23.825^[1][2][5]0.938 in
Small end diameter, reference (mm): 19.8^[1][2]
Length: l1 max 81 / l3 94^[1][2][5]
Draw screw: M12 (inch products: UNC 1/2)^[1][2][5]
Tang: b=7.9, e max 20^[1]1 source · reference
Size: MT3

MT4ISO 296, IS 1715, DIN 228, ASME B5.10

Taper: 1:19.254^[1][2][3]Included angle 2°58′30.4″
Taper half-angle: 1°29′15″^[2]1 source · reference
Gauge diameter (mm): 31.267^[1][2][5]1.231 in
Small end diameter, reference (mm): 25.9^[1][2]
Length: l1 max 102.5 / l3 117.5^[1][2][5]
Draw screw: M16 (inch products: UNC 5/8)^[1][2][5]
Tang: b=11.9, e max 24^[1]1 source · reference
Size: MT4

MT5ISO 296, IS 1715, DIN 228, ASME B5.10

Taper: 1:19.002^[1][2][3]Included angle 3°0′52.4″
Taper half-angle: 1°30′26″^[2]1 source · reference
Gauge diameter (mm): 44.399^[1][2][5]1.748 in
Small end diameter, reference (mm): 37.6^[1][2]
Length: l1 max 129.5 / l3 149.5^[1][2][5]
Draw screw: M20 (inch products: UNC 5/8)^[1][2][5]Inch products use the same UNC 5/8 as MT4
Tang: b=15.9, e max 29^[1]1 source · reference
Size: MT5

MT6ISO 296, IS 1715, DIN 228, ASME B5.10

Taper: 1:19.180^[1][2][3]Included angle 2°59′11.7″
Taper half-angle: 1°29′36″^[2]1 source · reference
Gauge diameter (mm): 63.348^[1][2][5]2.494 in
Small end diameter, reference (mm): 53.9^[1][2]
Length: l1 max 182 / l3 210^[1][2][5]
Draw screw: M24 (inch products: UNC 1)^[1][2][5]
Tang: b=19, e max 40^[1]1 source · reference
Size: MT6

MT7ASME B5.10 (reportedly)

Taper: —Not confirmed in public sourcesISO 296 and IS 1715 cover only MT0–6. The values 1:19.231 and D = 83.058 mm were found only on shop and aggregator sites and in search summaries, which cannot be cited as sources
Gauge diameter (mm): —Not confirmed in public sourcesSame as above
Draw screw: —Not confirmed in public sources
Size: MT7

The text of ASME B5.10 could not be obtained

Metric taper (ME)

ME4ISO 296, IS 1715, DIN 228

Taper: 1:20^[1][2]Half angle 1°25′56″ (IS 1715)
Gauge diameter (mm): 4^[1][2]d≈2.9, l1 max 23, l2 max 25
Draw screw: —^[1]1 source · referenceThread and tang not specified (—)
Size: ME4

ME6ISO 296, IS 1715, DIN 228

Taper: 1:20^[1][2]
Gauge diameter (mm): 6^[1][2]d≈4.4, l1 max 32, l2 max 35
Draw screw: —^[1]1 source · referenceNot specified
Size: ME6

ME80ISO 296, IS 1715, DIN 228

Taper: 1:20^[1][2]
Gauge diameter (mm): 80^[1][2]d≈70.2, l1 max 196, l3 220
Draw screw: M30^[1][2]
Tang: b=26, e max 48^[1]1 source · reference
Size: ME80

ME100ISO 296, IS 1715, DIN 228

Taper: 1:20^[1][2]
Gauge diameter (mm): 100^[1][2]d≈88.4, l1 max 232, l3 260
Draw screw: M36^[1][2]
Tang: b=32, e max 58^[1]1 source · reference
Size: ME100

ME120ISO 296, IS 1715, DIN 228

Taper: 1:20^[1][2]
Gauge diameter (mm): 120^[1][2]d≈106.6, l1 max 268, l3 300
Draw screw: M36^[1][2]
Tang: b=38, e max 68^[1]1 source · reference
Size: ME120

ME160ISO 296, IS 1715, DIN 228

Taper: 1:20^[1][2]
Gauge diameter (mm): 160^[1][2]d≈143, l1 max 340, l3 380
Draw screw: M48^[1][2]
Tang: b=50, e max 88^[1]1 source · reference
Size: ME160

ME200ISO 296, IS 1715, DIN 228

Taper: 1:20^[1][2]
Gauge diameter (mm): 200^[1][2]d≈179.4, l1 max 412, l3 460
Draw screw: M48^[1][2]
Tang: b=62, e max 108^[1]1 source · reference
Size: ME200

Brown & Sharpe taper (B&S)

B&S 1ISO 296 Table 3

Taper: 1:23.904 (=0.502:12, approx. 0.502 in/ft)^[1]1 source · referenceCorresponds to the commonly cited "approx. 0.5 in/ft". Only B&S No.1–3 appear in ISO 296
Gauge diameter (inch): 0.23922^[1]1 source · referencemm conversion 6.076 (calculated). D1≈0.24314, d≈0.2, l1 max 15/16 in
Size: B&S 1

B&S 2ISO 296 Table 3

Taper: 1:23.904^[1]1 source · reference
Gauge diameter (inch): 0.29968^[1]1 source · reference≈7.612 mm (calculated). d≈0.25, l1 max 1 3/16 in
Size: B&S 2

B&S 3ISO 296 Table 3

Taper: 1:23.904^[1]1 source · reference
Gauge diameter (inch): 0.37525^[1]1 source · reference≈9.531 mm (calculated). d≈0.3125, l1 max 1 1/2 in
Size: B&S 3

No source that can be cited was found for No.4 and above

Jacobs taper (JT)

JT0ISO 239, IS 2243

Large end diameter (mm)

6.35^[6][7]

Small end diameter (mm)

5.802^[6][7]Calculated value (reference)

Length (mm)

11.112^[6][7]IS 2243 gives 11.11

Diametral taper

ISO 239:1999:0.04929^[6]
IS 2243:1971:0.04928^[7]

1 source · referenceDiffers at the 5th digit

Size

JT0

JT1ISO 239, IS 2243

Large end diameter (mm): 9.754^[6][7]
Small end diameter (mm): 8.469^[6][7]
Length (mm): 16.669^[6][7]IS gives 16.67
Diametral taper: 0.07709 (=1:12.972, included angle 4°24′52.9″)^[6][7][3]
Size: JT1

JT2SISO 239 (J2s), IS 2243 (2 short)

Large end diameter (mm): 13.94^[6][7]
Small end diameter (mm): 12.386^[6][7]
Length (mm): 19.05^[6][7]
Diametral taper: 0.08155 (same as JT2)^[6][7]
Size: JT2S

ISO 239 calls it "J2s"

JT2ISO 239, IS 2243

Large end diameter (mm): 14.199^[6][7]
Small end diameter (mm): 12.386^[6][7]
Length (mm): 22.225^[6][7]IS gives 22.22
Diametral taper: 0.08155 (=1:12.262, included angle 4°40′12.2″)^[6][7][3]
Size: JT2

JT33ISO 239, IS 2243

Large end diameter (mm): 15.85^[6][7]
Small end diameter (mm): 14.237^[6][7]
Length (mm): 25.4^[6][7]
Diametral taper: 0.0635 (=1:15.748, included angle 3°38′13.4″)^[6][7][3]IS 2243 gives 0.06349. Only a rounding difference
Size: JT33

JT6ISO 239, IS 2243

Large end diameter (mm): 17.17^[6][7]
Small end diameter (mm): 15.852^[6][7]
Length (mm): 25.4^[6][7]
Diametral taper: 0.05191 (=1:19.264, included angle 2°58′24.9″)^[6][7][3]
Size: JT6

JT3ISO 239, IS 2243

Large end diameter (mm): 20.599^[6][7]
Small end diameter (mm): 18.951^[6][7]
Length (mm): 30.956^[6][7]IS gives 30.96
Diametral taper: 0.05325 (=1:18.779, included angle 3°3′1.2″)^[6][7][3]
Size: JT3

Shown in parentheses in ISO 239 (size to be avoided where possible)

JT4ISO 239, IS 2243

Large end diameter (mm): 28.55^[6][7]
Small end diameter (mm): 26.346^[6][7]
Length (mm): 42.069^[6][7]
Diametral taper: 0.0524^[6][7]
Size: JT4

Both standards say "avoid where possible"

JT5ISO 239, IS 2243

Large end diameter (mm): 35.89^[6][7]
Small end diameter (mm): 33.422^[6][7]
Length (mm): 47.625^[6][7]IS gives 47.62
Diametral taper: 0.05183^[6][7]
Size: JT5

Size to be avoided where possible

7/24 (National / NT)

CommonISO 297, ISO 1119

Taper: 7:24 (=1:3.4285714, taper on diameter 0.29167)^[8][3]1 source · referenceMedium, since both are published by ISO
Taper half-angle: 8°17′49.7″ (rounded to 8°17′50″)^[3]1 source · referenceIncluded angle divided by 2. Agrees with HAIMER's 8°17′50″
Included angle (full angle): 16°35′39.4443″ (=16.594290°)^[3]1 source · referenceAlso agrees with the calculation atan(7/48)×2
Size: Common

As its title says, ISO 297 is for "manual change". It lists a method of pulling in with a draw bolt (draw bar) screwed in from the rear, and a method of holding the collar from the front

NT30 (ISO 297 No.30)ISO 297

Gauge diameter (mm): 31.75^[8]1 source · referenceD1 = reference diameter at the gauge plane. The table has length columns of 68.4 and 48.4
Draw screw: M12 (UN products: 0.500-13)^[8]1 source · reference
Size: NT30 (ISO 297 No.30)

Treating NT30 as ISO 297 No.30 was the researcher's judgment

NT40 (ISO 297 No.40)ISO 297

Gauge diameter (mm): 44.45^[8]1 source · referenceThe table has length columns of 93.4 and 65.4
Draw screw: M16 (UN products: 0.625-11)^[8]1 source · reference
Size: NT40 (ISO 297 No.40)

No.45ISO 297

Gauge diameter (mm): 57.15^[8]1 source · reference
Draw screw: M20 (UN products: 0.75-10)^[8]1 source · reference
Size: No.45

NT50 (ISO 297 No.50)ISO 297

Gauge diameter (mm): 69.85^[8]1 source · reference
Draw screw: M24 (UN products: 1.000-8)^[8]1 source · reference
Size: NT50 (ISO 297 No.50)

No.55–80 also exist: D1 is 88.9/107.95/133.35/165.1/203.2/254, threads M24/M30/M36/M36/M48/M48

Relationship between NT and BT

Size: Relationship between NT and BT
Relationship: Mitsubishi Materials explains that "NT has the same taper angle and dimensions as BT, but is mounted with a draw bar"^[9]1 source · referenceGauge diameters (31.75/44.45/69.85) and threads (M12/M16/M24) agree between ISO 297 and BT (spindle-tapers.json), but in the taper length column, ISO 297 No.40 has 93.4, and a column with the same value as BT40's L1 of 65.4 also appears. Whether the dimensions are completely identical is unconfirmed

📚Sources

Values with no mark agree across two or more independent publishers. ISO values were checked against the sample PDFs that ISO publishes, and the Indian Standards (IS) against their publicly available full text.