BNI Interchangeable Point Live Center — Overview & Specifications
A complete reference for the BNI live center whose point (insert shaft) swaps quickly on a 1/10 taper — working principle, accuracy, full dimension tables, and a six-point selection guide.
Overview
▲ Product appearance (POINTTECH catalog)
The BNI is a live (rotating) center mounted in the tailstock of a lathe or CNC lathe: it supports the workpiece on a built-in bearing set and rotates with it. Whereas a dead (fixed) center rubs against the workpiece and generates heat and wear, a live center lets the internal bearings absorb the rotation, dramatically reducing friction damage and heat at the center hole during high-speed or heavy-load turning.
What sets the BNI apart is that its point is coupled to the body through a 1/10 (degree) mounting taper. The operator simply swaps the insert shaft, so a single body can run six point shapes — from 60°/75°/90° standard cones to cup and pipe-supporting points — making it ideal for high-mix production and frequent setup changes where minimizing tooling-change time matters.
Key Features
- Accuracy of the center inner diameter (point seat) guaranteed to 0.003 mm — concentricity is preserved across swaps.
- Accuracy after point locking guaranteed to 0.005 mm — interchangeable, yet delivering run-out close to a one-piece design.
- Excellent for versatile production by changing insert shafts quickly.
- Point heat-treated to HRc 60 ± 2 for wear resistance and shape retention.
- Six standard point types (H, I, J, K, L, M) supplied.
- Because of the insert-shaft construction, the admissible workpiece weight is limited.
- Point mounting taper is 1/10 degree.
- Order-made special-shape points are available.
Because the design is interchangeable, the insert-shaft taper seat must be kept clean and the point firmly locked to guarantee the 0.005 mm accuracy. The insert-shaft stiffness limit also means that, at the same MT, the admissible workpiece weight is lower than a one-piece live center — always observe the Workpiece Weight and Max RPM limits in the table below.
Specifications (Body)
Unit: mm, kg. The point mounting taper is 1/10 degree and the maximum run-out of every model is 0.005 mm. A 'SET' order includes the body plus all 6 insert shafts and the disassemble kit.
MODEL | MT | A | B | C | L | Workpiece Weight | Max RPM | Weight |
|---|---|---|---|---|---|---|---|---|
051002 | 2 | 50 | 25 | 68 | 116.5 | 80 | 5,000 | 0.6 |
051003 | 3 | 50 | 25 | 85 | 133.5 | 150 | 5,000 | 0.8 |
051004 | 4 | 69 | 32 | 108 | 168 | 250 | 3,800 | 1.7 |
051005 | 5 | 88 | 40 | 136 | 212 | 650 | 3,000 | 3.9 |
Interchangeable Points (Insert Shafts)
A BNI set includes six insert shafts (H, I, J, K, L, M) and a disassemble kit. H is a 60° cone, I a 75° cone, and J a 90° cone point; K is a 30°/60° compound cone, L a cup (recessed) point, and M a bull point for supporting pipe/tube outside diameters. Each dimension (a = OD/height, b = overall length, c = cone length, d = bore) varies by MT. Unit: mm.
MODEL | MT | Dim | H(60°) | I(75°) | J(90°) | K | L | M |
|---|---|---|---|---|---|---|---|---|
051002 | 2 | a | 24 | 24 | 24 | 18 | 45 | 22 |
051002 | 2 | b | 51.5 | 46.5 | 43 | 55.5 | 51 | 40 |
051002 | 2 | c | 20 | 15 | 11.5 | 25 | 17.5 | 18 |
051002 | 2 | d | - | - | - | 8 | 25 | 6.5 |
051004 | 4 | a | 28 | 28 | 28 | 26 | 55 | 40 |
051004 | 4 | b | 61.5 | 55.5 | 51.5 | 73 | 61.5 | 55 |
051004 | 4 | c | 23.5 | 17.5 | 13.5 | 36 | 21.5 | 35 |
051004 | 4 | d | - | - | - | 12 | 30.2 | 16.5 |
051005 | 5 | a | 38 | 38 | 38 | 32 | 70 | 52 |
051005 | 5 | b | 78 | 70 | 64 | 90 | 74 | 65 |
051005 | 5 | c | 32 | 24 | 18.5 | 46 | 26 | 45 |
051005 | 5 | d | - | - | - | 13 | 40 | 25.4 |
Order examples: '051004 Body' = MT4 BNI body only (without an insert shaft); '051004 SET' = MT4 BNI body and 6 insert shafts included; '051004H' = MT4 BNI insert shaft type H. (051003 is the MT3 variant: only the body dimensions differ — its point dimensions are identical to 051002.)
Selection Guide
First match the body model (051002–051005) to your tailstock-sleeve Morse taper (MT2–MT5). Then compare the workpiece weight and target spindle speed against the table's Workpiece Weight and Max RPM. As RPM rises, the permissible bearing load and axial load fall, so for high-speed work it is safer to keep a margin below the rated figures.
- Standard round bar / shaft with a center hole: H (60°) — the most common cone point.
- Wide center angle / chamfered work: I (75°) or J (90°).
- Hollow parts needing bore support: K (30°/60° compound cone) or L (cup point).
- Supporting pipe / tube OD: M (bull point) for outside-diameter clamping.
- Shops that change shapes often: order the 'SET' to stock all 6 points plus the disassemble kit.
Applications
The BNI suits high-mix low-volume production, prototype and die work, training lathes, and general machining where round bars, pipes, and flanges are processed on a single tailstock. Because the insert shaft has a weight limit, however, large heavy-duty continuous turning is better served by a one-piece heavy-cutting live center (e.g. the TN family).