Multi-Sealing Live Center (UN / UNH) Complete Guide
A comprehensive document covering the standard UN and high-speed UNH series — their construction, sealing design, full dimension table, carbide-tipped point options and a selection guide.
Overview
▲ Product appearance (POINTTECH catalog)
A multi-sealing live center is a precision support tool mounted in the tailstock of a lathe or CNC turning machine. It supports one end of the workpiece while rotating together with it; an internal bearing absorbs the rotation, so — unlike a fixed dead center — there is no friction heat or wear between the workpiece and the center point, making it suitable for high-speed and continuous machining.
The POINTTECH Multi-Sealing family is an advanced development of the best-selling BN standard type, and its defining feature is the multi-sealing arrangement. A high-performance lip seal and a V-seal are placed in series to provide a double barrier against dust and coolant ingress into the bearing section. The family comprises the standard-speed UN and the high-speed UNH, each available with MT4 and MT5 Morse taper shanks.
The spindle is heat-treated to HRc60±2 to withstand press-fit loads and repeated use, and the body is also heat-treated for rigidity and durability. Point run-out (TIR) is guaranteed within 0.003mm (0.0001").
Key Features
- Advanced new product of the BN type — same mounting compatibility with improved sealing
- Accuracy guaranteed to 0.003mm TIR (0.0001") for concentric, precision turning and grinding
- Multi-sealing (high-performance lip seal + V-seal) protects against ingress of dust and coolant
- Longer product life shortens maintenance time on automated CNC installations
- Point heat-treated to HRc60±2 for wear resistance
- Heat-treated body for extra strength, rigidity and long life
- Carbide-tipped point available (UNC type for UN, UNHC type for UNH), point hardness HRa90±5
- UN: standard speed / UNH: high-speed rating
Specifications
Dimensions are in mm and weights in kg. The model number in parentheses denotes the carbide-tipped version. A is the head diameter, L the overall length, and C the body length.
MODEL (Carbide) | Type | MT | A | C | L | Workpiece Weight | Max R.P.M | Max Run-Out |
|---|---|---|---|---|---|---|---|---|
151004 (152004) | UN | 4 | 69 | 108 | 210.5 | 800 | 3,800 | 0.003 |
151005 (152005) | UN | 5 | 88 | 136 | 265.5 | 2,000 | 3,000 | 0.003 |
171004 (172004) | UNH | 4 | 69 | 108 | 210.5 | 800 | 6,000 | 0.003 |
171005 (172005) | UNH | 5 | 88 | 136 | 265.5 | 2,000 | 5,000 | 0.003 |
Detailed auxiliary dimensions (B·D·E·F·G): MT4 models — B30, D62.5, E40, F8, G14. MT5 models — B38, D79, E50.5, F8, G18. Tool weight: UN MT4 = 2kg, UN MT5 = 4.5kg, UNH MT4 = 2kg, UNH MT5 = 5kg.
The 0.003mm run-out guarantee and HRc60±2 heat treatment apply under normal operating conditions. The tabulated max RPM and workpiece weight are not simultaneous absolute limits — they follow an RPM-vs-load relationship in which the permissible workpiece weight decreases as speed rises. Run heavy workpieces at lower speed and high-speed work with lighter workpieces.
Carbide-Tipped Point
The standard point is heat-treated steel (HRc60±2), but for applications demanding higher wear resistance a carbide-tipped model can be selected. The carbide point has a hardness of HRa90±5 and slows tip wear and run-out growth when machining abrasive or hardened workpieces, or during long unattended runs.
- UN (UNC type): MT4 → 152004, MT5 → 152005
- UNH (UNHC type): MT4 → 172004, MT5 → 172005
Selection Guide
First choose MT4 or MT5 to match the Morse taper of your tailstock sleeve. MT4 supports workpieces up to about 800kg and MT5 up to about 2,000kg.
Then select the series by speed requirement. For general machining, UN (MT4 3,800 / MT5 3,000 rpm) is sufficient; for high-speed turning or shorter cycle times, choose UNH (MT4 6,000 / MT5 5,000 rpm). For abrasive or hardened materials, or long unattended machining, additionally specify the carbide-tipped model.
Applications
Suited to CNC turning in coolant-rich, chip- and dust-heavy environments, continuous operation on unattended automated lines, and precision turning and grinding support of shafts and axially symmetric parts. Thanks to the multi-sealing design, the life-extension benefit is especially marked in processes where coolant penetration previously caused frequent bearing damage.