Steady rests

With rolling contact and no slip, a 100 mm workpiece at 1,000 rpm runs against a 35 mm steady-rest roller at about 2,857 rpm. The contact speed is 314.2 m/min. Doubling workpiece diameter at the same spindle speed doubles the contact speed. Check the roller's speed and load limits as well as whether the part fits the centering range.

Use Choosing workholding to compare location, support and restraint across fixture types.

Support location and purpose

A steady rest supports a shaft along its outside diameter, limiting deflection under cutting load.

Grizzly's G0509/G0509G manual illustrates the bed-mounted steady, saddle-mounted follow rest and tailstock center. It describes the steady as an alternative for facing the end of long stock when tailstock support would obstruct the operation. Overtightening its bearing-tipped fingers can deflect the part. Accessories remain machine-specific. Grizzly manual, revised March 2018, printed pp. 32–33

Manual fingers and self-centering rollers

Manual adjustment and hydraulic actuation describe how the contacts close, whereas fixed and travelling describe where the assembly moves. They are separate classifications. H. Richter supplies travelling rests in sliding-contact and rolling-contact forms; its Type 4 mounts on the slide to support continuous turning or thread cutting near the tool. Thus travelling support does not inherently mean hydraulic or roller-only construction. H. Richter, steady-rest overview, undated

Atling's Rev-04 manual describes three rollers approximately 120° apart, operated by cam-controlled levers. Its AXE, ASE, ANE, AXI and ASI designs include hydraulic and pneumatic versions. The contact surface must be machined and centered on the machine axis. Self-centering of the mechanism does not eliminate the need to align the complete rest and its bracket to the spindle. The manual also specifies cambered rollers when the rest travels along the workpiece. Atling operator's manual, Rev-04, pp. 1, 10–11; issue date not stated

Diameter range is not stroke or loading clearance

A centering range identifies the supported workpiece diameters for a specified configuration. Cylinder stroke is actuator travel; arm geometry converts that motion into contact movement. Neither number alone specifies the opening through which a part can be loaded, and a proximity switch indicating an end position is not a continuous diameter measurement.

For example, SMW-AUTOBLOK's SR 2 table distinguishes a 20–101 mm centering range with coolant chip guard from a 106 mm maximum axial clearing diameter. Its footnote separately limits radial loading with the chip guard to 92 mm, versus 101 mm without it. The table also lists 8–70 bar operating pressure, 450 daN maximum clamping force per roller, and 800 m/min maximum roller surface speed. These are SR 2 entries, not limits for the whole SR family, and maximum force is not a workpiece-weight rating. SMW-AUTOBLOK SR catalog extract, printed pp. 378–379, undated

Contact, force and thin walls

Atling warns that excessive pressure can leave roller marks and shorten roller life. Its working-pressure selection depends on cutting force, speed and workpiece quality; the supported surface's accuracy limits the machining result. The manual describes oil or grease lubrication configurations rather than a single common arrangement. Atling Rev-04, pp. 6, 11–12

Engineering synthesis: support force is a contact load, not free rigidity. A thin tube can ovalize locally even when its diameter fits the centering range. Roller width, profile, wall thickness, material, surface condition and force therefore affect distortion and marking. A catalog's maximum force does not establish an acceptable force for that tube; these sources provide no universal minimum wall thickness.

SMW-AUTOBLOK distinguishes cylindrical standard rollers from spherical rollers for travelling applications. Its options include synthetic rollers for polished or chrome-plated surfaces and carbide rollers for hardened surfaces. The same catalog differentiates oil, oil-plus-air and manual grease systems and ties lubrication to working conditions. It identifies the bracket as important to function and precision. Roller material, lubrication system and mounting are consequently part of the specified support configuration. SMW-AUTOBLOK selection and accessories extract, printed pp. 394–395, undated

Surface speed and roller speed

Original kinematic example: assume rolling contact without slip, a 100 mm workpiece at 1,000 rpm and a 35 mm roller. Workpiece surface speed is

v = π × 100 × 1,000 / 1,000 = 314.2 m/min.

The roller turns at 1,000 × 100 / 35 ≈ 2,857 rpm. At the same spindle speed a 200 mm workpiece doubles the contact speed to 628.3 m/min. A roller therefore does not rotate at spindle rpm, and a diameter range does not establish an rpm limit. These assumed dimensions illustrate the relationship; they do not approve a roller, lubrication system or machining setup. Bearing capability, load, temperature, workpiece dynamics and the machine's own limits remain separate constraints.

Scope and related reference

The examples cover turning support and named manufacturer configurations. They do not establish a universal slenderness ratio, support spacing, hydraulic pressure, tube-wall limit or permissible spindle speed. Contact alignment, bracket stiffness, cutting loads and loading paths remain specific to the machine and workpiece.

See Workholding and fixture references for the broader distinction between locating, supporting and restraining a part.