Self-centering vises
Opposed jaw motion, center versus fixed-jaw datums, centering specifications, shallow gripping and product-specific force and torque limits.
Tags: tooling, workholding, vises, five-axis
On this page
In the ideal width example, stock grows from 50.0 to 50.4 mm. With symmetric motion and parallel contacts, the self-centering jaws move from ±25.0 to ±25.2 mm and the midpoint stays fixed. With one stationary contact face, the midpoint moves 0.2 mm. Actual workpiece location also depends on seating, jaw error and the vise's position in machine coordinates.
Use Choosing workholding to compare location, support and restraint across fixture types.
5th Axis describes opposing jaws driven by a left- and right-hand leadscrew. 5th Axis, Self-Centering Explained
Center datum versus fixed-jaw datum
| Arrangement | Ideal reference when stock width changes | What still needs definition |
|---|---|---|
| Opposed centering jaws | Midpoint between the two jaw-contact positions | Actual contact geometry and the vise center relative to machine coordinates |
| Fixed jaw and moving jaw | Contact plane at the fixed jaw | Workpiece midpoint shifts with width |
| Shaped soft jaws | Machined locating surfaces | Their relationship to the desired part datums |
Symmetric motion locates the midpoint of the actual contact faces. Roughness and unequal contact can shift it.
Provide a longitudinal stop and vertical seating independently of the centering screw.
A bounded force and range example
The 5th Axis V510X product page lists:
| Property | Published value |
|---|---|
| Jaw width | 125.7 mm |
| Clamping force | 25.0 kN at 75 N·m |
| Maximum leadscrew torque | 75 N·m |
| Maximum jaw-bolt / mounting-bolt torque | 47 / 47 N·m |
| Jaw-forward range | 8.3–184.7 mm |
| Jaw-reversed range | 60.3–234.7 mm |
Reversing the jaws changes the range; the leadscrew and fastening bolts also have distinct torque limits. These values concern the named product, not every self-centering vise. 5th Axis, V510X specifications
The page's FAQ states self-centering repeatability better than ±0.0005 inch (±0.0127 mm) and distinguishes standard serrated roughing jaws from machinable soft jaws for finished surfaces. It also acknowledges jaw lift. A repeatability claim therefore does not eliminate contact, seating or jaw-deflection effects. 5th Axis, V510X FAQ
A clamping-force value is not an allowable cutting force in every direction. As engineering interpretation, friction, positive gripping geometry, cutter-force direction, part height and support determine the restraint needed. Screw torque does not transfer directly into a guaranteed pullout resistance without the rest of that system.
Grip depth and five-axis access
LANG's Makro•Grip / Makro•Grip FS instructions, version 2024/02, specify 3 mm standard support/clamping depth, with customer-specific heights available. Its technical table gives centering accuracy ±0.02 mm and maximum tightening torque 30/60/100 N·m for base-body widths 46/77/125 mm respectively. The same manual separately states <0.005 mm repeat accuracy for the Quick•Point mounting interface. Those two accuracy statements describe different interfaces. LANG Technik, operating instructions, printed pp. 7–9
The manual's serrated-clamping section addresses pre-stamped workpieces, clean contacts and controlled torque for repeatable force and avoiding deformation. Its 3 mm grip is part of that designed arrangement; it is not permission to grip any material or jaw type by 3 mm. LANG Technik, workpiece clamping, printed p. 10
Engineering synthesis: shallow contact exposes more of the workpiece for machining. However, tool and holder clearance depend on jaw height, part shape, spindle approach and machine motion. Tall parts also increase the moment produced by a lateral cutting force. Five-side accessibility and adequate restraint remain separate requirements.
Centering repeatability is not finished-part accuracy
A vise can return consistently to a biased position. The assembly may also repeat at its mounting interface while presenting a different center because jaws, contact surfaces or stock geometry changed. Centering accuracy, centering repeatability and remounting repeatability should therefore retain their stated definitions and conditions.
These are engineering distinctions. They do not assign a combined error by simply adding unrelated catalog figures. Finished-feature location additionally depends on machine calibration, tool geometry, work offsets, cutting deflection and deformation of the workpiece. A thin wall can move under clamp load and recover after release even when the jaw mechanism repeats closely.
Worked example: stock-width change
Original idealized arithmetic: assume planar parallel contact faces, perfectly symmetric jaw motion and a vise center at x = 0. For a 50.0 mm-wide blank, contact positions are −25.0 and +25.0 mm. For a 50.4 mm blank:
Half width = 50.4 / 2 = 25.2 mm
Contact positions = −25.2 and +25.2 mm
Midpoint = (−25.2 + 25.2) / 2 = 0 mm
With a fixed contact plane at x = 0 instead, the nominal centers are 25.0 and 25.2 mm: a 0.2 mm shift. The example explains the datum difference. It does not model jaw errors, nonparallel stock, tooth penetration, deformation or actual centering tolerance.
Coverage and source dates
LANG's manual cover prints version 2024/02. No technical issue date was established for the cited 5th Axis pages. Sources were inspected on November 2, 2026; copyright and search dates are not revisions.
This reference does not establish universal jaw travel, grip depth, holding force, screw torque, repeatability, stock hardness or cutting capacity. Jaw selection, workpiece material and shape, mounting and machining forces remain specific to the actual assembly. Product examples do not establish a shop's installed workholding or approved loads.