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Mongtec BBT end mill holders

61 article numbers on BBT40 · BBT50. Weldon side-lock holders and coolant-channel holders on the BBT dual-contact taper. Mongtec Precision is a Taiwanese brand, designed and engineered in Taichung, Taiwan.

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Side lock, and when to use it

A Weldon holder clamps a flat on the tool shank with a set screw. It is the most positive drive there is — the tool cannot spin in the holder no matter what the cut does — and that is why roughing end mills and any tool taking a heavy radial bite are held this way.

The cost is concentricity. The screw pushes the shank sideways against the opposite bore wall, so a Weldon holder runs out more than a collet or a shrink chuck by design. For a roughing cutter that does not matter; for a finishing pass or a small-diameter tool at high rpm it does. Rough in Weldon, finish in a collet or shrink fit.

Coolant channels

The SEMC holders carry coolant channels that deliver flood coolant along the outside of the tool to the cutting zone, rather than relying on the machine's external nozzles. On a deep pocket or a long-flute cutter that is often the difference between evacuating chips and recutting them.

All of these are on the BBT dual-contact taper — taper and face seat together, so the holder cannot pull in under load and the gauge length holds.

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.

End Mill Holder (Weldon) — 31 article numbers

Article no.	d	D	L	M	Screw Quantity
BBT40QSLA06Q50	6	25	50	M6	1
BBT40QSLA08Q50	8	28	50	M8	1
BBT40QSLA10Q63	10	35	63	M10	1
BBT40QSLA12Q63	12	42	63	M12	1
BBT40QSLA14Q63	14	44	63	M12	1
BBT40QSLA16Q63	16	48	63	M14	1
BBT40QSLA18Q63	18	50	63	M14	1
BBT40QSLA20Q63	20	52	63	M16	1
BBT40QSLA25Q90	25	65	90	M18*2	2
BBT40QSLA32Q100	32	72	100	M20*2	2
BBT40QSLA40Q120	40	80	120	M20*2	2
BBT40QSLA06Q100	6	25	100	M6	1
BBT40QSLA08Q100	8	28	100	M8	1
BBT40QSLA10Q100	10	35	100	M10	1
BBT40QSLA12Q100	12	42	100	M12	1
BBT40QSLA14Q100	14	44	100	M12	1
BBT40QSLA16Q100	16	48	100	M14	1
BBT40QSLA18Q100	18	50	100	M14	1
BBT40QSLA20Q100	20	52	100	M16	1
BBT50QSLA06Q63	6	25	63	M6	1
BBT50QSLA08Q63	8	28	63	M8	1
BBT50QSLA10Q63	10	35	63	M10	1
BBT50QSLA12Q80	12	42	80	M12	1
BBT50QSLA14Q80	14	44	80	M12	1
BBT50QSLA16Q80	16	48	80	M14	1
BBT50QSLA18Q80	18	50	80	M14	1
BBT50QSLA20Q80	20	52	80	M16	1
BBT50QSLA25Q100	25	65	100	M18*2	2
BBT50QSLA32Q105	32	72	105	M20*2	2
BBT50QSLA40Q110	40	80	110	M20*2	2
BBT50QSLA50Q125	50	98	125	M24*2	2

End Mill Holder with Coolant Channels — 30 article numbers

Article no.	d	D	H	L
BBT40QSEMC16Q55	16	32	17	55
BBT40QSEMC22Q55	22	40	19	55
BBT40QSEMC27Q55	27	48	21	55
BBT40QSEMC32Q60	32	58	24	60
BBT40QSEMC40Q60	40	70	27	60
BBT40QSEMC16Q100	16	32	17	100
BBT40QSEMC22Q100	22	40	19	100
BBT40QSEMC27Q100	27	48	21	100
BBT40QSEMC32Q100	32	58	24	100
BBT40QSEMC40Q100	40	70	27	100
BBT40QSEMC16Q160	16	32	17	160
BBT40QSEMC22Q160	22	40	19	160
BBT40QSEMC27Q160	27	48	21	160
BBT40QSEMC32Q160	32	58	24	160
BBT40QSEMC40Q160	40	70	27	160
BBT50QSEMC16Q70	16	32	17	70
BBT50QSEMC22Q70	22	40	19	70
BBT50QSEMC27Q70	27	48	21	70
BBT50QSEMC32Q70	32	58	24	70
BBT50QSEMC40Q70	40	70	27	70
BBT50QSEMC16Q100	16	32	17	100
BBT50QSEMC22Q100	22	40	19	100
BBT50QSEMC27Q100	27	48	21	100
BBT50QSEMC32Q100	32	58	24	100
BBT50QSEMC40Q100	40	70	27	100
BBT50QSEMC16Q160	16	32	17	160
BBT50QSEMC22Q160	22	40	19	160
BBT50QSEMC27Q160	27	48	21	160
BBT50QSEMC32Q160	32	58	24	160
BBT50QSEMC40Q160	40	70	27	160

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

Weldon or Whistle Notch?

Weldon locks against a flat and resists rotation. Whistle Notch locks against an angled notch that also pulls the tool back against the holder face, adding axial location. Weldon is more common; use whichever your cutters are shanked for.

How much run-out does a Weldon holder have?

More than a collet — the set screw displaces the shank by design. Mongtec does not publish a single figure because it depends on tool shank tolerance. If run-out matters for the operation, use a collet, hydraulic or shrink-fit holder instead.

Do I need coolant-channel holders if my machine has through-spindle coolant?

Not necessarily. Through-spindle coolant with a coolant-through tool delivers to the tip directly. The SEMC channels are for tools without internal coolant, where the flow has to be guided down the outside.