The fastest way to identify a BMT turret is to measure it. Four numbers decide the size: the centre bore, the distance between the mounting screws, the screw thread and the width of the key slot. This guide gives the standard values for BMT45 to BMT85 and the builder patterns that look like them but are not.
BMT is not an ISO or DIN standard, but the five common sizes are built to the same pattern by most turret makers. These are the dimensions for each size:
| Size | Centre bore | Bolt spacing A × B | Mounting screws | Key slot width | Locating pin hole |
|---|---|---|---|---|---|
| BMT45 | ø45 mm | 58 × 58 mm (29 + 29) | 4 × M8 | 15 mm | ø8 mm |
| BMT55 | ø55 mm | 64 × 64 mm (32 + 32) | 4 × M10 | 15 mm | ø8.3 mm |
| BMT65 | ø65 mm | 70 × 73 mm (35 + 35 × 36.5 + 36.5) | 4 × M12 | 18 mm | ø8.3 mm |
| BMT75 | ø75 mm | 90 × 90 mm (45 + 45) | 4 × M12 | 25 mm | ø11 mm |
| BMT85 | ø85 mm | 100 × 100 mm (50 + 50) | 4 × M12 | 25 mm | ø10 mm |
Bolt spacing is a physical property of the machine turret. These are the common values for each size; builder-specific turrets differ, so confirm against the turret drawing for your machine.
Note that BMT65 is the only one of the five that is not square: the screws are 70 mm apart in one direction and 73 mm in the other.
Each drawing shows the turret face as you see it when you stand in front of the station: the four mounting screws, the cross-shaped key slots, the centre bore and the locating pin hole. All dimensions are in millimetres, measured from the turret centre.
If all four numbers match one row of the table, you have a standard BMT turret. If the bore matches but the bolt spacing does not, you almost certainly have a builder-specific pattern — read on.
Several machine builders use their own turret patterns, and these are often given BMT numbers anyway. The bolt spacings are close enough to the standard sizes to cause wrong orders:
| You measured | Standard size it looks like | What it may actually be |
|---|---|---|
| 62 × 70 mm, ø40 bore | BMT55 (64 × 64) or BMT65 (70 × 73) | DMG MORI / Mori Seiki BMT40 — NL/NLX 20-station turrets, NZ, NTX 1000–3200, Duraturn, ALX, CLX 450 (BMT version) |
| 65 × 73 mm, ø60 bore | BMT65 (70 × 73) | Okuma BMT60 — LB/LU 2000–3000 EX M/MY/MW, GENOS L300 MW |
| 78 × 80 mm, ø60 bore | BMT75 (90 × 90) | Okuma LB/LU 4000 EX M/MY |
| 84 × 94 mm, ø60 bore | BMT85 (100 × 100) | DMG MORI / Mori Seiki BMT60 — NL/NLX 12-station turrets, NLX 4000, NT 4200–5400 |
| 50 × 50 mm | BMT45 (58 × 58) | Biglia BMT40 — B436, B438 |
| 40 × 55, 50 × 60 or 69 × 71 mm | Nakamura-Tome BMT44, BMT55 or BMT65 | Nakamura-Tome BMT44 (40 × 55), BMT55 (50 × 60) or BMT65 (69 × 71) — WT, WY, SC, NTY3, NTJ, TW, AS-200. These do not match the standard BMT55 and BMT65 of the same name |
| 68 × 110 mm, ø68 bore | none | Mazak BMT68 (QT, QTC, QTE, QTS, QTU M/MY/MS/MSY) |
These builders use their own turret patterns instead of, or alongside, the standard BMT sizes. The drawings below show the screw pattern, centre bore, key slots and locating holes for the most common ones. Dimensions are in millimetres from the turret centre. The same machine model can be built with a different turret, so check the station count and confirm against the turret drawing for your machine.
The full list of 38 builder-specific bolt patterns is on BMT bolt patterns by machine builder.
The nameplate on the machine is not enough. Several popular lathes are built with two different interfaces:
| Machine | Interfaces published for it | What decides it |
|---|---|---|
| Doosan / DN Solutions Puma 2100, 2600 | BMT55 and BMT65 | turret version fitted to the individual machine — both are listed for the same models |
| Hwacheon Hi-Tech 230 | BMT45 and BMT65 | BMT45 on the 20-station turret |
| Hwacheon Cutex 180 | BMT45 and BMT55 | BMT45 on the 16-station turret |
| Hardinge T-51 | BMT45 and BMT55 | turret version fitted to the individual machine |
| DMG MORI NL / NLX 1500–2500 | BMT40 and BMT60 (Mori Seiki patterns) | BMT40 on 20-station turrets, BMT60 on 12-station turrets |
| Nakamura-Tome TW-20 | two different Nakamura patterns | 12-station or 16-station turret |
This is why Mongtec asks for the station count and a photograph of the turret face before quoting a BMT holder, even when the machine model is known.
Standard BMT55 has four M10 mounting screws on a 64 × 64 mm square (32 mm either side of the centre), a ø55 mm centre bore and a 15 mm key slot.
BMT65 is larger in every dimension: ø65 mm bore instead of ø55, M12 screws instead of M10, an 18 mm key slot instead of 15, and a 70 × 73 mm screw pattern instead of 64 × 64. Holders are not interchangeable between the two.
No. The Okuma LB/LU EX pattern has a ø60 mm bore and 65 × 73 mm screw spacing. It shares the 73 mm dimension with standard BMT65 but not the 70 mm one, so a standard BMT65 holder will not bolt on.
No. Nakamura-Tome BMT44, BMT55 and BMT65 use their own screw patterns — 40 × 55, 50 × 60 and 69 × 71 mm. Nakamura-Tome BMT55 and BMT65 do not fit standard BMT55 (64 × 64) or BMT65 (70 × 73) holders.
Yes. Mongtec supplies driven and static holders for the standard BMT sizes and for builder-specific patterns, confirmed against the turret drawing for your machine before quoting.
Mongtec confirms fit and quotes from four details. Email them to info@mongtec.com or use the quote form — we reply within one working day.