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Mongtec BT collet chucks

183 article numbers on BT30 · BT40 · BT50. ER, GER, OZ, TG, SKS high-speed, pull-back and precision screw collet chucks on the BT taper — Ø1 to Ø34 mm. Mongtec Precision is a Taiwanese brand, designed and engineered in Taichung, Taiwan.

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Six clamping systems, one taper

A collet chuck grips a plain cylindrical shank by squeezing a slit sleeve around it. Which sleeve you use decides the clamping range, the run-out and the grip. Mongtec catalogues six on the BT taper.

ER is the workhorse — DIN 6499, the most widely stocked collet in the world, Ø1–34 mm across ER11 to ER50. Each collet covers a 1 mm range, so a full set is a real investment, but every tool shop already has one. The nut decides the rest: the UM nut is the strong general-purpose choice, the mini nut (M) reduces the nose diameter where it would foul the part, and the GER nut is the sealed version for coolant-through work.

OZ and TG collets take heavier cuts than ER at the same nominal size: fewer slits, more contact area, more torque before the shank spins. Choose them for roughing where you would otherwise reach for a Weldon holder but need concentricity too.

SKS is the high-speed system — a shorter, stiffer body with a balanced nut, made for spindles that actually turn at the speeds their nameplate claims.

Pull back (DC) collets draw the tool into the holder as they close instead of only squeezing it. That removes axial float and is why they are the choice for small-diameter, long-reach work: Ø1–12 mm bores in bodies down to Ø14 mm, in lengths to 200 mm.

NDC precision screw collet chucks are the slimmest of the lot, with a stepped nose that clears the part on deep, narrow features.

Choosing between them

Start with what the job needs at the tip. If it is reach and a small tool, pull-back or NDC. If it is speed and finish, SKS. If it is torque, OZ or TG. If it is none of those in particular, ER — and the collets will already be in the drawer.

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 usable 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 — 96 article numbers

Catalogue page 4 prints this table’s headers as D / d1 / d2 / d3. The values are the same D / D1 / L / Capacity set that pages 5 and 6 print correctly for the identical article numbers, and the last figure in each article number matches the L column — so the symbols are shown corrected here, with the discrepancy recorded rather than hidden.

Article no.	D	D1	L	Capacity
BT30QER16UMQ70	28	32	70	1-10
BT30QER20UMQ70	34	35	70	1-13
BT30QER25Q70	42	42	70	2-16
BT30QER32Q70	40	50	70	2-20
BT30QER40Q70	50	63	70	3-26
BT30QER16UMQ100	28	32	100	1-10
BT30QER20UMQ100	34	35	100	1-13
BT30QER25Q100	42	42	100	2-16
BT30QER32Q100	40	50	100	2-20
BT40QER16UMQ70	28	32	70	1-10
BT40QER20UMQ70	34	35	70	1-13
BT40QER25Q70	42	42	70	2-16
BT40QER32Q70	50	50	70	2-20
BT40QER40Q80	50	63	80	3-26
BT40QER16UMQ100	28	32	100	1-10
BT40QER20UMQ100	34	35	100	1-13
BT40QER25Q100	42	42	100	2-16
BT40QER32Q100	50	50	100	2-20
BT40QER40Q100	50	63	100	3-26
BT40QER16UMQ160	28	32	160	1-10
BT40QER20UMQ160	34	35	160	1-13
BT40QER25Q160	42	42	160	2-16
BT40QER32Q160	50	50	160	2-20
BT40QER40Q160	50	63	160	3-26
BT40QER16UMQ200	28	32	200	1-10
BT40QER20UMQ200	34	35	200	1-13
BT40QER25Q200	42	42	200	2-16
BT40QER32Q200	50	50	200	2-20
BT40QER40Q200	50	63	200	3-26
BT50QER16UMQ70	28	32	70	1-10
BT50QER20UMQ70	34	35	70	1-13
BT50QER25Q70	42	42	70	2-16
BT50QER32Q70	40	50	70	2-20
BT50QER40Q80	63	63	80	3-26
BT50QER50Q100	64	78	100	6-34
BT50QER16UMQ100	28	32	100	1-10
BT50QER20UMQ100	34	35	100	1-13
BT50QER25Q100	42	42	100	2-16
BT50QER32Q100	50	50	100	2-20
BT50QER40Q100	63	63	100	3-26
BT50QER16UMQ160	28	32	160	1-10
BT50QER20UMQ160	34	35	160	1-13
BT50QER25Q160	42	42	160	2-16
BT50QER32Q160	50	50	160	2-20
BT50QER40Q160	63	63	160	3-26
BT50QER16UMQ200	28	32	200	1-10
BT50QER20UMQ200	34	35	200	1-13
BT50QER25Q200	42	42	200	2-16
BT50QER32Q200	50	50	200	2-20
BT50QER40Q200	63	63	200	3-26
BT50QER25Q250	42	42	250	2-16
BT50QER32Q250	50	50	250	2-20
BT50QER40Q250	63	63	250	3-26
BT50QER25Q300	42	42	300	2-16
BT50QER32Q300	50	50	300	2-20
BT50QER40Q300	63	63	300	3-26
BT30QER16Q70	28	28	70	1-10
BT30QER20Q70	34	34	70	1-13
BT30QER16Q100	28	28	100	1-10
BT30QER20Q100	34	34	100	1-13
BT40QER16Q70	28	28	70	1-10
BT40QER20Q70	34	34	70	1-13
BT40QER16Q100	28	28	100	1-10
BT40QER20Q100	34	34	100	1-13
BT40QER16Q160	28	28	160	1-10
BT40QER20Q160	34	34	160	1-13
BT40QER16Q200T	28	28	200	1-10
BT40QER20Q200	34	34	200	1-13
BT50QER16Q70	28	28	70	1-10
BT50QER20Q70	34	34	70	1-13
BT50QER16Q100	28	28	100	1-10
BT50QER20Q100	34	34	100	1-13
BT50QER16Q160	28	28	160	1-10
BT50QER20Q160	34	34	160	1-13
BT50QER16Q200T	28	28	200	1-10
BT50QER20Q200	34	34	200	1-13
BT30QER11MQ70	16	16	70	1-7
BT30QER16MQ70	22	22	70	1-10
BT40QER11MQ70	16	16	70	1-7
BT40QER16MQ70	22	22	70	1-10
BT40QER20MQ70	28	28	70	1-13
BT40QER25MQ70	35	35	70	2-16
BT40QER11MQ100	16	16	100	1-7
BT40QER16MQ100	22	22	100	1-10
BT40QER20MQ100	28	28	100	1-13
BT40QER25MQ100	35	35	100	2-16
BT40QER11MQ160T	16	16	160	1-7
BT40QER16MQ160T	22	22	160	1-10
BT40QER20MQ160	28	28	160	1-13
BT40QER25MQ160	35	35	160	2-16
BT50QER16MQ100	22	22	100	1-10
BT50QER20MQ100	28	28	100	1-13
BT50QER25MQ100	35	35	100	2-16
BT50QER16MQ160T	22	22	160	1-10
BT50QER20MQ160	28	28	160	1-13
BT50QER25MQ160	35	35	160	2-16

ER Collet Chuck — 2 article numbers

Article no.	D	L	L1
BT40QER25Q36	29.5	36	9
BT40QER32Q36	37.5	36	9

GER Nut Collet Chuck — 16 article numbers

Article no.	D1	L	Capacity
BT30QGER16Q70	30	70	1-10
BT30QGER20Q70	35	70	1-13
BT30QGER25Q70	40	70	2-16
BT30QGER32Q70	48	70	2-20
BT40QGER16Q70	30	70	1-10
BT40QGER20Q70	35	70	1-13
BT40QGER25Q70	40	70	2-16
BT40QGER32Q70	48	70	2-20
BT40QGER16Q100	30	100	1-10
BT40QGER20Q100	35	100	1-13
BT40QGER25Q100	40	100	2-16
BT40QGER32Q100	48	100	2-20
BT50QGER16Q100	30	100	1-10
BT50QGER20Q100	35	100	1-13
BT50QGER25Q100	40	100	2-16
BT50QGER32Q100	48	100	2-20

OZ Collet Chuck — 7 article numbers

Article no.	D	L	Capacity
BT30QOZ16Q70	43	70	3-16
BT30QOZ25Q80	60	80	3-25
BT40QOZ16Q70	43	70	3-16
BT40QOZ25Q70	60	70	3-25
BT40QOZ32Q80	72	80	6-32
BT50QOZ25Q85	60	85	3-25
BT50QOZ32Q90	72	90	6-32

TG Collet Chuck — 6 article numbers

Article no.	D	L	Collet	Capacity
BT40QTG75Q70	50	70	TG75	2-20
BT40QTG100Q80	60	80	TG100	3-25
BT40QTG100Q100	60	100	TG100	3-25
BT40QTG100Q150	60	150	TG100	3-25
BT50QTG100Q90	60	90	TG100	3-25
BT50QTG100Q150	60	150	TG100	—

High Speed SKS Collet Chuck — 18 article numbers

Article no.	D	D1	L	Capacity	M
BT30QSKS10Q60	27.5	27.1	60	2-10	M21.5*1
BT30QSKS16Q60	40.6	40	60	3-16	M32*1.5
BT30QSKS10Q90	27.5	27.1	90	2-10	M21.5*1
BT30QSKS16Q90	40.6	40	90	3-16	M32*1.5
BT40QSKS10Q60	27.5	27.1	60	2-10	M21.5*1
BT40QSKS16Q70	40.6	40	70	3-16	M32*1.5
BT40QSKS10Q90	27.5	27.1	90	2-10	M21.5*1
BT40QSKS16Q90	40.6	40	90	3-16	M32*1.5
BT40QSKS20Q90	48.5	48	90	2-20	M40*1
BT40QSKS25Q90	55.6	55	90	6-25	M45*1.5
BT40QSKS10Q120	27.5	27.1	120	2-10	M21.5*1
BT40QSKS16Q120	40.6	40	120	3-16	M32*1.5
BT40QSKS20Q120	48.5	48	120	2-20	M40*1
BT40QSKS25Q120	55.6	55	120	6-25	M45*1.5
BT50QSKS10Q120	27.5	27.1	120	2-10	M21.5*1
BT50QSKS16Q120	40.6	40	120	3-16	M32*1.5
BT50QSKS10Q165	27.5	27.1	165	2-10	M21.5*1
BT50QSKS16Q165	40.6	40	165	3-16	M32*1.5

Pull Back Collet Chuck — 28 article numbers

Article no.	L	D	Capacity
BT30QDC06Q60	60	14	1-6
BT30QDC06Q90	90	14	1-6
BT30QDC06Q120	120	14	1-6
BT30QDC08Q60	60	22	1-10
BT30QDC08Q90	90	22	1-10
BT30QDC08Q120	120	22	1-10
BT30QDC12Q80	80	34	1-12
BT40QDC06Q60	60	14	1-6
BT40QDC06Q90	90	14	1-6
BT40QDC06Q120	120	14	1-6
BT40QDC06Q150	150	14	1-6
BT40QDC08Q60	60	22	1-10
BT40QDC08Q90	90	22	1-10
BT40QDC08Q120	120	22	1-10
BT40QDC08Q150	150	22	1-10
BT40QDC08Q200	200	22	1-10
BT40QDC12Q90	90	34	1-12
BT40QDC12Q120	120	34	1-12
BT40QDC12Q150	150	34	1-12
BT40QDC12Q200	200	34	1-12
BT50QDC06Q120	120	14	1-6
BT50QDC06Q150	150	14	1-6
BT50QDC08Q120	120	22	1-10
BT50QDC08Q150	150	22	1-10
BT50QDC08Q200	200	22	1-10
BT50QDC12Q120	120	34	1-12
BT50QDC12Q150	150	34	1-12
BT50QDC12Q200	200	34	1-12

Precision Screw Collet Chuck — 10 article numbers

The BT table prints its first two headers as L / D. The values match the D / D1 columns printed on the BBT page for the same dimensions, so the symbols are shown corrected here. Confirm at RFQ if the distinction matters to your fixture.

Article no.	D	D1	D2	D3	L	L1	L2	L3	L4	Capacity
BT30QNDC14Q80	30	50	53	—	80	56	43	26	11	4-14
BT30QNDC14Q130	24	30	53	—	130	105	78	60	—	4-14
BT30QNDC20Q80	40	53	—	—	80	56	28	19	—	4-20
BT40QNDC20Q70	40	63	—	—	70	38	18	—	—	4-20
BT40QNDC20Q120	40	63	—	—	120	89	68	—	—	4-20
BT40QNDC14Q70	30	50	—	—	70	43	28	11	—	4-14
BT40QNDC14Q120	24	30	53	—	120	93	78	61	—	4-14
BT40QNDC32Q110	53	63	—	—	110	14	—	—	—	12-32
BT50QNDC20Q130	34	55	70	—	130	93	81	73	24	4-20
BT50QNDC32Q145	60	70	—	—	145	108	14	—	—	12-32

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

What run-out should I expect from an ER collet chuck?

It is set by the collet and the shank together, not by the holder alone. A worn or dirty collet is the commonest cause of run-out in a tool crib. Clean the taper and the collet seat, and replace collets that have been over-torqued — they take a set.

Can I clamp a shank smaller than the collet size?

Only within the collet’s own range — an ER32 collet marked 20 mm closes to about 19 mm and no further. Clamping below the range distorts the collet and grips on three points instead of all round.

ER or milling chuck for heavy cuts?

A power milling chuck (the HC and CT series) grips over a much longer length and is built for side load; ER is built for general purpose. For sustained heavy roughing, use the milling chuck.