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Mongtec BBT collet chucks and milling chucks

79 article numbers on BBT40 · BBT50 · BBT30. ER, SKS high-speed, precision screw and power milling chucks on the BBT dual-contact taper. Mongtec Precision is a Taiwanese brand, designed and engineered in Taichung, Taiwan.

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What BBT changes

A standard BT holder locates on the taper alone. Under load the spindle bore opens slightly, the holder pulls in, and the gauge length moves. BBT (dual contact, or "big-plus" style) adds face contact: the flange touches the spindle nose at the same time the taper seats. The holder is then located on two surfaces at once, so it cannot pull in, and the bending stiffness at the joint goes up sharply.

Two practical consequences. First, Z-axis repeatability: with the face constrained, the tool tip stays where it was set as spindle speed and cutting load change. Second, chatter resistance on long tools — the extra stiffness is at the joint, which is exactly where a long holder wants to flex.

BBT holders require a spindle machined for dual contact. Fitting one to a plain BT spindle will seat on the taper only and gains nothing; fitting a plain BT holder into a dual-contact spindle is fine and simply behaves as ordinary BT.

What is on this page

ER collet chucks in UM-nut, standard and mini-nut versions, clamping Ø1–34 mm depending on the collet. SKS high-speed collet chucks for high-rpm finishing. NDC precision screw collet chucks for small-diameter, long-reach work. HC power milling chucks for heavy stock removal, where the clamping mechanism grips over a long length and takes side load rather than pulling the tool.

Article numbers — dimensions in mm

Dimension symbols are the catalogue's own and refer to the dimension drawing printed for each product. A dash means the catalogue does not print a value for that cell; those are confirmed in writing at RFQ. Where a table's printed header disagrees with its drawing, a note above the table says so.

ER Collet Chuck — 55 article numbers

Article no.	D	D1	L	Capacity
BBT40QER16UMQ70	28	32	70	1-10
BBT40QER20UMQ70	34	35	70	1-13
BBT40QER25Q70	42	42	70	2-16
BBT40QER32Q70	50	50	70	2-20
BBT40QER40Q80	50	63	80	3-26
BBT40QER16UMQ100	28	32	100	1-10
BBT40QER20UMQ100	34	35	100	1-13
BBT40QER25Q100	42	42	100	2-16
BBT40QER32Q100	50	50	100	2-20
BBT40QER40Q100	50	63	100	3-26
BBT40QER16UMQ160	28	32	160	1-10
BBT40QER20UMQ160	34	35	160	1-13
BBT40QER25Q160	42	42	160	2-16
BBT40QER32Q160	50	50	160	2-20
BBT40QER40Q160	50	63	160	3-26
BBT50QER16UMQ70	28	32	70	1-10
BBT50QER20UMQ70	34	35	70	1-13
BBT50QER25Q70	42	42	70	2-16
BBT50QER32Q70	40	50	70	2-20
BBT50QER40Q80	63	63	80	3-26
BBT50QER50Q100	64	78	100	6-34
BBT50QER16UMQ100	28	32	100	1-10
BBT50QER20UMQ100	34	35	100	1-13
BBT50QER25Q100	42	42	100	2-16
BBT50QER32Q100	50	50	100	2-20
BBT50QER40Q100	63	63	100	3-26
BBT50QER16UMQ160	28	32	160	1-10
BBT50QER20UMQ160	34	35	160	1-13
BBT50QER25Q160	42	42	160	2-16
BBT50QER32Q160	50	50	160	2-20
BBT50QER40Q160	63	63	160	3-26
BBT40QER16Q70	28	28	70	1-10
BBT40QER20Q70	34	34	70	1-13
BBT40QER16Q100	28	28	100	1-10
BBT40QER20Q100	34	34	100	1-13
BBT40QER16Q160	28	28	160	1-10
BBT40QER20Q160	34	34	160	1-13
BBT50QER16Q70	28	28	70	1-10
BBT50QER20Q70	34	34	70	1-13
BBT50QER16Q100	28	28	100	1-10
BBT50QER20Q100	34	34	100	1-13
BBT50QER16Q160	28	28	160	1-10
BBT50QER20Q160	34	34	160	1-13
BBT40QER11MQ70	16	16	70	1-7
BBT40QER16MQ70	22	22	70	1-10
BBT40QER20MQ70	28	28	70	1-13
BBT40QER25MQ70	35	35	70	2-16
BBT40QER11MQ100	16	16	100	1-7
BBT40QER16MQ100	22	22	100	1-10
BBT40QER20MQ100	28	28	100	1-13
BBT40QER25MQ100	35	35	100	2-16
BBT40QER11MQ160T	16	16	160	1-7
BBT40QER16MQ160T	22	22	160	1-10
BBT40QER20MQ160	28	28	160	1-13
BBT40QER25MQ160	35	35	160	2-16

High Speed SKS Collet Chuck — 8 article numbers

Article no.	D	D1	L	Capacity	M
BBT40QSKS10Q90	27.5	27.1	90	2-10	M21.5*1
BBT40QSKS16Q90	40.6	40	90	3-16	M32*1.5
BBT40QSKS20Q90	48.5	48	90	2-20	M40*1
BBT40QSKS25Q90	55.6	55	90	6-25	M45*1.5
BBT40QSKS10Q120	27.5	27.1	120	2-10	M21.5*1
BBT40QSKS16Q120	40.6	40	120	3-16	M32*1.5
BBT40QSKS20Q120	48.5	48	120	2-20	M40*1
BBT40QSKS25Q120	55.6	55	120	6-25	M45*1.5

High Speed SKS Collet Chuck — 10 article numbers

Article no.	D	D1	D2	D3	L	L1	L2	L3	L4	Capacity
BBT30QNDC14Q80	30	50	53	-	80	56	43	26	11	4-14
BBT30QNDC14Q130	24	30	53	-	130	105	78	60	-	4-14
BBT30QNDC20Q80	40	53	-	-	80	56	28	19	-	4-20
BBT40QNDC20Q70	40	63	-	-	70	38	18	-	-	4-20
BBT40QNDC20Q120	40	63	-	-	120	89	68	-	-	4-20
BBT40QNDC14Q70	30	50	-	-	70	43	28	11	-	4-14
BBT40QNDC14Q120	24	30	53	-	120	93	78	61	-	4-14
BBT40QNDC32Q110	53	63	-	-	110	14	-	-	-	12-32
BBT50QNDC20Q130	34	55	70	-	130	93	81	73	24	4-20
BBT50QNDC32Q145	60	70	-	-	145	108	14	-	-	12-32

Power Milling Chuck — 6 article numbers

Article no.	d	D	L	Capacity
BBT40QHC20Q90	20	50	90	3-16 / 20
BBT40QHC25Q100	25	59	100	3-20 / 25
BBT40QHC32Q105	32	72	105	3-25 / 32
BBT50QHC20Q105	20	50	105	3-16 / 20
BBT50QHC25Q105	25	59	105	3-20 / 25
BBT50QHC32Q110	32	72	110	3-25 / 32

Source: Mongtec BT·BBT Tooling System catalogue, Ver 2026.

Check pull-stud thread and spindle standard before ordering. BT holders are supplied without pull studs, and the thread (M12, M16, M24) and stud form vary by machine builder and by region. Send Mongtec the machine make, model and the pull-stud drawing with the RFQ.

Frequently asked

Can I use a BBT holder in an ordinary BT spindle?

It will physically seat, but on the taper only — you get BT performance, not dual-contact performance, and you have paid for a feature you cannot use. The spindle nose has to be ground for face contact.

Is BBT the same as BIG-PLUS?

Dual contact is the engineering principle; BIG-PLUS is a specific licensed system. Mongtec BBT holders are built to the dual-contact geometry. Confirm compatibility with your specific spindle in writing at RFQ.

Which ER nut should I choose?

UM nut for general work — it is the strongest and easiest to torque correctly. Mini nut where the nut diameter would foul the workpiece. Standard hex nut where you already own the wrenches.