# Tailstock centers

Live and dead centers, center-hole contact and taper mounting, combined loads, and axial thermal-growth compensation.

Reviewed: 2026-11-02

Tags: tooling, workholding, turning, tailstocks, centers

A freely expanding **500 mm** workpiece with assumed coefficient **12×10⁻⁶/K** grows **0.120 mm** under a uniform **20 K** rise. With a tailstock center, force and displacement also depend on preload and machine and part stiffness. Riten's spring-loaded live centers specify axial travel and thrust limits separately. Check how much travel remains at the starting preload. [Riten catalog, Concentric spring-loaded centers, printed page 31](https://www.riten.com/wp-content/uploads/2023/02/Riten-Catalog-0223a.pdf#page=31).

Use [Choosing workholding](../workholding-and-fixtures.md) to compare location, support and restraint across fixture types.

A tailstock center locates and supports the workpiece at a prepared hole. Its mounting shank mates separately with the machine.

## Live, revolving and dead centers

Riten distinguishes bearing-supported **live centers** from solid **dead centers**. A dead center can rotate in a bearing-supported live tailstock; the name describes center construction, not necessarily its motion. [Riten, Live Centers technical support](https://www.riten.com/technical-support/live-centers/1000/)

In the usual bearing-type live or revolving center, the rotating contact follows the workpiece while the mounting shank remains seated in the tailstock. With a stationary dead center, relative rotation occurs at the workpiece/point interface instead. These contact arrangements have different friction, heating and lubrication requirements; the name alone does not establish a permissible speed or lubricant.

## Center hole and mounting taper

Riten identifies **60° included point angle** as a common United States convention and lists Morse, Jarno and Brown & Sharpe among mounting tapers. It associates malformed or off-center holes with workholding problems. An extended point improves tool clearance while sacrificing rigidity relative to a shorter point. [Riten, center geometry and application selection](https://www.riten.com/technical-support/live-centers/1000/)

The following distinctions are geometric explanations:

| Interface or dimension | Function | Separate constraint |
| --- | --- | --- |
| Point and center-hole cone | Support the workpiece through mating contact | Included angle, contact diameter and depth |
| Mounting shank and socket | Locate and retain the center in the tailstock | Taper family, size and seating condition |
| Point projection | Provides access around the workpiece end | Stiffness and interference |
| Tailstock alignment | Relates support to the spindle axis | Cannot be inferred from matching point angles |

**Engineering synthesis:** a conical point should contact the intended conical seat, rather than merely bottoming in a pilot hole. An oversize entrance chamfer or a damaged contact cone changes that support. Matching “60°” labels does not establish adequate contact diameter, alignment or load capacity. A Morse-taper number likewise does not describe the working point's shape.

## Product limits depend on the center design

Riten's catalog gives these **Multi-Use live-center** examples:

| Model | Mounting taper | Listed maximum speed | Listed workpiece weight | Drawing angles V/V2 |
| --- | --- | --- | --- | --- |
| 60223 | MT3 | 5,000 rpm | 330 lb | 60°/60° |
| 60263 | MT3 | 4,000 rpm | 685 lb | 60°/60° |

The same mounting taper and contact angles therefore do not imply equal speed or weight ratings. These entries describe named products, not any MT3 center. [Riten catalog, Multi-Use Live Center, printed page 30](https://www.riten.com/wp-content/uploads/2023/02/Riten-Catalog-0223a.pdf#page=30)

Riten's technical page treats radial load, axial load and speed together in bearing-life calculations. It states a weight-rating basis of **100 rpm, 2,000 hours and L10 life**. Maximum-speed and full-weight entries do not establish simultaneous operation without combined-load conditions. [Riten, load and life basis](https://www.riten.com/technical-support/live-centers/1000/)

Radial support load, axial tailstock thrust and cutting force are different quantities. As engineering interpretation, the center's share of workpiece weight depends on support positions and mass distribution. Cutting forces and overhang can change that reaction. A weight figure is neither a universal radial cutting-force allowance nor an axial preload setting.

## Axial contact force and thermal growth

Axial force seats the workpiece against the center. Too little restraint can allow movement; excessive force can deform a slender part or overload the contact and bearings. Temperature changes can alter this force if the support system restrains axial growth. These are mechanical relationships, not a universal pressure recommendation.

Riten's **Concentric spring-loaded live centers** use a spring-loaded spindle to accommodate thermal expansion. Their catalog separately specifies spring travel and thrust-load limits. This is an intentional compensating design; an ordinary bearing-type live center does not acquire axial compliance merely because its point rotates. [Riten catalog, Concentric spring-loaded centers, printed page 31](https://www.riten.com/wp-content/uploads/2023/02/Riten-Catalog-0223a.pdf#page=31)

Actuator area, mechanism and control determine thrust from hydraulic pressure. Check point travel under starting preload and verify bearing capacity and alignment.

## Worked example: free thermal growth

**Original hypothetical model:** assume a 500 mm workpiece, constant linear expansion coefficient α = 12×10⁻⁶/K and uniform temperature increase of 20 K:

```text
Free length increase = α × L × ΔT
                     = 12×10⁻⁶/K × 500 mm × 20 K
                     = 0.120 mm
```

The assumed coefficient is not certified material data for a cited workpiece. The result is free growth, not the displacement of a constrained part or a preload increase. Predicting force would additionally require stiffness, initial contact force and thermal behavior of the machine and workpiece. It does not establish that any particular spring center has adequate remaining travel.

## Coverage and source dates

No technical issue date was established for the cited Riten page or catalog. The catalog filename and download-directory year are not assigned as edition dates. Sources were inspected on November 2, 2026.

These examples do not establish universal point size, center-hole geometry, speed, weight capacity, thrust, tailstock pressure or bearing life. Tool clearance, mounting, workpiece geometry, alignment and combined loads remain application-specific. Product references do not establish a shop's installed center or approved operating conditions.

## Related reference

[Workholding and fixture references](index.md)