Fixed-jaw machine vises

In an ideal fixed-jaw vise example, 10 kN of compression gives 10 MPa average pressure at each 100 × 10 mm contact. At 100 × 5 mm, pressure doubles to 20 MPa with the same force. A separate 500 N horizontal cut load 40 mm above the supports creates 20 N·m overturning moment. Contact uniformity is assumed, and real edge loads, jaw deflection and support spacing govern actual capacity.

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

Fixed location and moving clamp

Carr Lane assigns cutting reactions to stationary locators. The moving jaw seats the part against them. Carr Lane locating and clamping principles

A fixed locating jaw may be replaceable or adjustable between setups.

A support plane, a fixed-jaw face and an end stop locate different directions. Check the actual contact on rough or tapered faces.

Jaw lift and pull-down mechanisms

Kurt's DX4 manual describes its AngLock geometry as inducing a downward component equal to half the forward force, to reduce movable-jaw lift. This is a mechanism description for that vise, not an additional guaranteed downward force on every workpiece. The same manual identifies high or one-sided clamping as a possible source of jaw lift and accuracy loss. Kurt DX4 manual, pp. 3 and 5

Gerardi's standard-vise page describes a different pull-down arrangement: angled jaw plates drag the workpiece toward the vise base during tightening. It also identifies fixed-jaw perpendicularity, base parallelism and longitudinal key alignment as important to matching vises. These are features of the cited product system, not generic accuracy specifications. Gerardi standard vises

A pull-down mechanism can reduce jaw lift. Check separately for workpiece bending, debris at supports and uneven contact.

Actuation and rated force

The DX4 manual supplies these torque-to-clamping-force pairs:

Its torque-wrench limit is 70 ft·lbf. These values apply to the DX4, not every vise with the same nominal jaw width. They also do not make input torque and clamping force interchangeable units. Kurt DX4 manual, pp. 4–5

Hydraulic actuation is another option. ROEMHELD's I 4.112 sheet, issue 11-24 E, describes double-acting exterior-clamping vises with a fixed jaw and integrated cylinder. Its size 1 lists a 40 mm jaw, 30 mm stroke and 9.5 kN maximum force; size 2 has a 65 mm jaw and 15 kN maximum force. Maximum operating pressure is 250 bar. ROEMHELD I 4.112, p. 1

The same sheet treats jaw height as a constraint on the permissible operating conditions and supplies a height-versus-pressure chart for custom jaws. Its overall maxima therefore do not establish the same available force for every tall-jaw configuration. Hydraulic pressure, cylinder force and force delivered through the actual jaw assembly remain distinct. ROEMHELD custom-jaw conditions, pp. 3 and 5

Supports, contact and deformation

Carr Lane relates clamp placement to support locations and warns that excessive or poorly directed force can deform the workpiece. The fixed jaw and base can react loads directly, while loads along an unsupported direction may depend more heavily on friction and additional locators. Carr Lane support and force discussion

Engineering interpretation: machinable soft jaws and steps change contact area, seating and access. A thin wall can distort while firmly gripped and recover after release. Increasing force can therefore reduce motion while worsening the unloaded shape. A jaw face that locates one operation may not locate the next operation from the same manufacturing datum.

The mounting interface also participates in stiffness. A vise attached to a machine table, pallet or fixture plate forms a load path through its base and fasteners. Nominal jaw capacity does not describe the capacity of that entire connection, nor clearance for the cutter, holder, spindle and moving machine components.

Worked example: contact area and moment

Original hypothetical model: assume a vise applies a 10 kN compressive force through two opposed, flat jaw contacts. Each side carries the same 10 kN reaction. If each actual contact area is 100 × 10 mm:

Average pressure at each contact = 10,000 / 1,000
                                 = 10 N/mm² = 10 MPa

If grip height falls to 5 mm with all else unchanged, each area becomes 500 mm² and its average pressure doubles to 20 MPa. This assumes uniform contact; real edge loading and jaw deflection can produce higher local stress. The two opposed forces are not summed into a 20 kN force through the part.

For a separate assumed 500 N horizontal cutting force acting 40 mm above the support plane, the overturning moment is 500 × 0.040 = 20 N·m. A clamp-force rating alone does not resolve that moment: jaw contact, support span and force direction also enter equilibrium. Neither example establishes an allowable cutting load or production force.

Coverage and source dates

The DX4 manual explicitly prints Manual Revision: 10.06.2016. ROEMHELD's sheet prints Issue 11-24 E. No issue dates were established for the Gerardi or Carr Lane pages; upload and crawl dates are not revisions.

This reference covers stationary machine vises with a fixed locating jaw. It does not establish universal torque, pressure, jaw lift, grip depth, accuracy, workpiece distortion or mounting capacity. Product ratings and geometric examples do not establish a particular shop's installed vise, jaw preparation or approved machining setup.

Related reference

Workholding and fixture references