Editorial Technical Reference

Linear rail clamp (clamping and braking element that holds a carriage on a profile linear rail)

Clamping and braking elements that ride on a profile linear rail · normally closed (spring-applied) or normally open, pneumatic or hydraulic, holding force against carriage load, opening and closing times, rated clamping cycles and fit to the rail make and size

A rail clamp is a small block mounted next to the carriage on a profile linear guide: jaws press on the free faces of the rail to hold the axis in position, or to brake it. The key choice is whether it clamps when pressure is applied (normally open) or when pressure is lost (normally closed, spring-applied), which decides what happens to a vertical axis or a loaded table when air or power fails. Then size the holding force, pick pneumatic or hydraulic, and match it to the rail make, type and size.

Clamping and braking elements for profile rail linear guides: pneumatic and hydraulic, normally open and normally closed (spring-applied) designs, holding force, response times, rated cycles and rail compatibility. Profile rail guides and their load ratings are covered on the Precision linear guide rail page; long and butt-jointed rails on the Linear guideways for long axes page; roller guides on the Linear guide system with rollers page; carriage blocks on the Linear guideway carriage block page; fixture clamping on the Hydraulic clamping system for machining fixtures page.

CNFX editorial research · Sources checked October 12, 2026 · 4 sources

Normally closed or normally open Holding force and fit

Profile rail with carriage blocks on a machine base

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Normally closed or normally openWhat happens when air fails. Holding force and fitN, pressure, rail make and size.

Normally closed or normally open: what happens when air fails

Zimmer's MKS series is "Energize to open (NC) through spring-loaded energy storage" and is described as a "Safety element" with "Safe clamping in case of energy failure"; a pneumatic piston drives a wedge-type gear that presses the jaws on the free surfaces of the rail, and the spring closes the unit without pressure. [1] Its MK series is the opposite, "Energize to close (NO)", closing with pressure and open without it. [2]

Holymech's rail clamp page describes air pushing a piston and wedge to press friction blocks against the rail, with the spring returning the wedge to release "When the air is broken", which reads as normally open; but its parameter table lists a "Release Pressure" of 0.55-0.8 MPa (standard series) or 0.2-0.45 MPa (low-pressure series), which reads as normally closed. The two descriptions conflict; ask Holymech which action each model has. [4]

For vertical axes, gravity-loaded tables or any axis that must not move on loss of air or power, ask for a normally closed (spring-applied) clamp and the supplier's statement of its safety function.

Holding force, pressure, timing and fit to the rail

Zimmer's product pages give the figures to compare for a size-25 rail. [1] [2] [3]

Zimmer lists for each clamp the rail makers, rail types, sizes and carriage types it fits (for the KBH2505AS1, for example, Bosch Rexroth and Ewellix size-25 rails) and gives positioning accuracy of ±0.02 mm; the MKS and MK clamps are rated for ISO 14644-1 class 6 clean rooms. [3] [1] [2]

Clamp	Action	Holding force	Pressure	Open / close time	Rated cycles	Source
Zimmer MKS2501N	Pneumatic, NC (spring)	750 N; 1,400 N with PLUS connection	5.5-6.5 bar (6 nominal)	0.02 / 0.015 s	B10d 5,000,000	[1]
Zimmer MK2512F	Pneumatic, NO	1,200 N	2-6.5 bar (6 nominal)	0.025 / 0.01 s	B10d 5,000,000	[2]
Zimmer KBH2505AS1	Hydraulic, NO	2,200 N	5-110 bar (100 nominal)	0.05 / 0.1 s	B10d 10,000,000	[3]
Holymech standard series	See conflict above	15 kN @ 0.6 MPa	0.55-0.8 MPa release	≤ 60 ms response	Not stated	[4]

Give the rail make, type and size, the force to hold (axis load, cutting or process force, and a safety factor), the air or oil pressure available, and whether the clamp must also brake a moving axis.

Rail clamp details

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Rail: [make; type; size; carriage type]
Action: [normally closed spring-applied; normally open]
Medium: [pneumatic; hydraulic; pressure available]
Force: [holding force needed; safety factor]
Function: [clamp only; clamp and brake]
Timing: [open and close time]
Life: [cycles]
Environment: [clean room; stainless; temperature]

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Rail clamp makers

1 company lists this product among what they make. Company figures are quoted from each company's own website; every card states where the relationship came from.

Changzhou Heli Automation Technology Co., Ltd.

Manufacturing site to be confirmed for the order

Lists pneumatic linear rail clamps in standard and low-pressure series with holding force and response time figures.

Product scope checked 2026-10-12

Current product source ↗

Linear rail clamp product page · profile compiled by CNFX from public sources

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Compiled and source-reviewed by the CNFX editorial team. Each manufacturer above links to the page on that company's own website where the product is listed, with the date we checked it. How we source and review · Page last updated 13 October 2026

Buyer questions

What clamp holds a vertical axis if air fails?

A normally closed, spring-applied type such as Zimmer's MKS, which clamps safely in case of energy failure. [1]

How much force do rail clamps hold?

Zimmer's size-25 clamps range from 750 N (pneumatic NC) to 2,200 N (hydraulic); Holymech lists up to 15 kN. [1] [3] [4]

Does one clamp fit every rail?

No; Zimmer lists the rail makers, types, sizes and carriages each clamp fits. [3]

How fast do they act?

Zimmer's MKS2501N opens in 0.02 s and closes in 0.015 s. [1]

Sources and what still needs a direct check

Sources checked 2026-10-12. Zimmer Group publishes product pages for its MKS, MK and KBH clamping elements; Holymech publishes its linear rail clamp page.

Zimmer Group — MKS2501N clamping element (pneumatic, NC) ↗ Maker product page Return to text ↑
Zimmer Group — MK2512F clamping element (pneumatic, NO) ↗ Maker product page Return to text ↑
Zimmer Group — KBH2505AS1 clamping element (hydraulic) ↗ Maker product page Return to text ↑
Holymech (Changzhou Heli Automation) — Linear rail clamp ↗ Maker product page Return to text ↑

Still to check yourself

Choose NC or NO action.
Size holding force with safety factor.
Match rail make, type and size.
Check pressure and timing.
Confirm brake duty if needed.
Verify the legal supplier and factory.

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