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BT40 MAS 403 CTSA precision power milling chuck Ø16–32 mm

Kortools

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€140.18

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BT40-CT16SA-90

BT40-CT20SA-90

BT40-CT25SA-90

BT40-CT32SA-90

BT40-CT25SA-105

BT40-CT32SA-105

BT40-CT32SA-135

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Product description

BT40 MAS 403 CTSA precision power milling chuck, Ø16–32 mm

Power milling chuck with a BT40 (MAS 403 BT / JIS B 6339) taper in the CTSA precision version. A tool with a cylindrical shank of diameter d is clamped directly in the chuck bore, smaller shanks through SC straight collets. The tightened nut clamps the chuck onto the shank with high force, so the clamping stays rigid in heavy milling, and the holder runout is ≤ 0.005 mm.

Available bore diameters: 16, 20, 25 and 32 mm. Length L = 90 mm (Ø16–32), and longer versions: Ø25: 105 mm; Ø32: 105 and 135 mm. Select the variant when purchasing.

Applications

roughing and heavy cutting with end mills with cylindrical shanks
machining of moulds and aerospace and energy equipment parts where high clamping force and rigidity are needed
precise work: runout ≤ 0.005 mm at a projection of 4 × d (standard HC power chuck: ≤ 0.008 mm)
smaller shank diameters through SC straight collets (collets not included)
CNC milling machines and machining centres with a BT40 spindle (MAS 403 BT)

Specification

Taper type	BT40 (MAS 403 BT / JIS B 6339)
Tool clamping	power clamping: clamping nut, bore for a cylindrical shank d
Bore diameter d	16, 20, 25 or 32 mm (depending on variant)
Smaller shank diameters	with SC straight collets: Ø16: 3–12 mm; Ø20: 3–16 mm; Ø25: 3–20 mm; Ø32: 3–25 mm (collets not included)
Holder runout	≤ 0.005 mm (at a projection of 4 × d)
Balance grade	at least G6.3 (if you need G2.5, ask before purchasing)
Coolant	AD version (central coolant supply)
Nut tightening	hook spanner or ball spanner for nut diameter D (dimension table)
Material	alloyed case-hardened steel (carburized depth 0.8 ± 0.2 mm)
Hardness	HRC 56–60
Taper	taper tolerance < AT3, surface roughness Ra < 0.2 µm
Standard	MAS 403 BT / JIS B 6339 (taper)

Balance grade: at least G6.3. If you need G2.5 for high spindle speeds, write to us before purchasing — we will check the specific piece before shipping.

Coolant: AD version (coolant through the spindle centre). If your spindle supplies coolant through the flange (form B), write to us before purchasing.

Dimension table

Dimension drawing – BT40 MAS 403 CTSA precision power milling chuck Ø16–32 mm

Variant	d [mm]	D [mm]	L [mm]	SC collets: shanks [mm]
BT40-CT16SA-90	16	45	90	3–12
BT40-CT20SA-90	20	52	90	3–16
BT40-CT25SA-90	25	61	90	3–20
BT40-CT25SA-105	25	61	105	3–20
BT40-CT32SA-90	32	73	90	3–25
BT40-CT32SA-105	32	73	105	3–25
BT40-CT32SA-135	32	73	135	3–25

d – bore diameter (tool shank), D – outer diameter of the clamping nut (select the spanner for it), L – length from the flange face (spindle side) to the holder front face, SC collets – range of smaller shanks clamped through straight collets. The drawing shows two versions: Type 1 (CT16, CT20, CT25) and Type 2 (CT32). Dimensions ℓ, ℓ1, ℓ2 and L0 describe the inside and the neck of the holder and are not needed for selection.

Read the complete designation of the selected variant. For example, BT40-CT20SA-90 means a BT40 taper, a CTSA power milling chuck with a Ø20 mm bore and length L = 90 mm.

How to select

Check that the spindle has a BT40 interface (MAS 403 BT), not SK40.
Bore d = tool shank diameter (e.g. an end mill with a Ø20 shank = CT20SA). A smaller shank can be clamped through an SC straight collet from the range in the table.
The tool shank must be cylindrical.
A hook spanner or ball spanner matching diameter D is needed to tighten the nut.

FAQ

Will it fit my machine?
The holder has a BT40 taper to MAS 403 BT (JIS B 6339). Before purchasing, confirm that the standard, size and pull stud match the machine spindle requirements. BT40 and SK40 are different tapers, so the designation “40” alone is not sufficient to confirm the selection.

How does it differ from an HC power chuck?
It is the precision version of the power milling chuck: runout ≤ 0.005 mm at a projection of 4 × d, compared with ≤ 0.008 mm for HC. Both are designed for heavy milling with high clamping force.

How does it differ from an ER collet chuck?
A power milling chuck clamps the shank with much higher force and rigidity than an ER chuck, so it is suitable for heavy roughing. An ER chuck covers a wider range of diameters by changing the collet.

Are SC collets included?
No. SC straight collets for smaller shanks are selected separately; ask about availability.