Mahr Marameter M301P Series Snap Gage

Mahr Marameter M301P Series Snap Gage

The Mahr Marameter M301P Series is the industry benchmark for indicating snap gages, combining a patented Channel Lock frame design with large-format tungsten carbide anvils to deliver the flat, parallel measuring surfaces and long-term dimensional stability that high-production O.D. inspection demands. Purpose-built for rapid, repeatable measurement of cylindrical parts such as shafts, bolts, spindles, and stepped diameters as well as thickness and length checks, the M301P is the preferred comparative measurement platform across precision machining, automotive, aerospace, and general manufacturing inspection environments where throughput and accuracy cannot be traded off against each other.

The defining structural innovation of the M301P is its patented Channel Lock design, in which a single hex wrench controls the full adjustment and positive locking of the lower reference anvil anywhere within the 25mm (1") continuous adjustment range. Unlike competing designs that rely on multiple-point clamping or friction-based retention, the Channel Lock mechanism guarantees precise parallelism between the upper and lower anvil surfaces throughout the entire adjustment sweep eliminating the parallelism error that accumulates in conventional snap gages when anvils are repositioned to a new nominal. This makes the M301P equally reliable whether it is being set to a new part dimension in the morning or rechecked against a setting master at the end of a production shift.

The upper anvil travels 0.50mm (0.020") and connects to the mounted indicating instrument, which translates that travel into a direct comparative readout. The standard M301P is supplied without a lifting lever, for applications where direct part entry between the anvils is practical. The 301P variant adds an integrated lifting lever that retracts the upper anvil for easier loading of parts with shoulders, flanges, or non-uniform geometries that cannot be slid in from the open end of the frame. The indicator can be rotated to read from either the front or rear of the gage, allowing the M301P to be used hand-held or bench-mounted without repositioning the indicator to suit the operator's sightline.

Nine frame sizes cover measurement ranges from 0–25mm (0–1") through 203–229mm (8–9"), with each size sharing the same 29–30mm (1.16–1.2") frame beam dimension and increasing only in overall frame height as range increases. Blade anvil variants (300P-3x/301P-3x series) are available through the 76–100mm (3–4") range for groove diameter, narrow feature, and thread root measurement applications. All M301P frames accept a wide range of indicating instrument configurations: standard 12I/22I dial indicators at .0001" graduation, metric O1I/P1I comparators at 0.002mm graduation, Maxµm®III digital indicators with selectable resolution down to 0.5µm/0.00002", EDI-10102 electronic indicators, and Mahr air probes giving the M301P a resolution range from .0001" up through sub-micron capability depending on indicator choice. The EMD-301P variant adds digital data output, and the EDI-301P variant integrates a high-resolution µMaxµm electronic indicator with direct digital output for SPC-connected gaging stations.

Key Features

• Patented Channel Lock Design - The M301P's exclusive Channel Lock mechanism uses a single hex wrench to simultaneously adjust and positively lock the lower reference anvil at any point within the 25mm (1") adjustment span, maintaining precise parallel anvil surfaces throughout the entire range eliminating the parallelism errors inherent in conventional friction-based or multi-point clamping snap gage designs and ensuring the same measurement integrity whether the gage is freshly set or re-ranged after a production changeover.
• Large 15.5mm / 0.61" Square Tungsten Carbide Anvils - Both reference and sensitive anvils feature large 15.5mm × 15.5mm square tungsten carbide working surfaces that provide the flat, parallel contact geometry required for accurate diameter and thickness comparisons on cylindrical, prismatic, and flat parts; the carbide material delivers exceptional wear resistance in high-cycle production gaging environments, maintaining flatness and parallelism specifications far longer than hardened steel alternatives.
• Nine Frame Sizes 0 to 229mm / 0 to 9" Capacity - The M301P series scales from 0–25mm (0–1") through 203–229mm (8–9") across nine progressively sized frames, with all frames sharing the same 29mm (1.16") beam width and increasing only in height as range grows; blade anvil variants (300P-3x/301P-3x) extend groove diameter, narrow-feature, and thread root measurement capability through the 76–100mm (3–4") range using standard AL-110 hardened steel blade inserts as the default, with a full range of alternative insert widths available.
• Indicator Rotation Front-to-Rear and Lifting Lever Option for Flexible Deployment - The indicating instrument can be rotated to display from the front or rear of the gage frame without tools, supporting both hand-held and bench-mounted use without requiring the operator to reorient their sightline or the gage; the 301P variant adds an integrated lifting lever that retracts the sensitive contact to accommodate flanged, shouldered, or irregular parts that cannot be slid into the open jaw, a critical ergonomic advantage in high-volume gaging stations.
• Compatible with the Full Mahr Indicator Ecosystem - The M301P accepts all standard Mahr indicating instruments on an 8mm or 3/8" shank: 12I/22I dial indicators (.0001" / 0.002mm), O1I/P1I comparators, Maxµm®III digital indicators with user-selectable resolution (0.001mm / 0.005mm / 0.0005mm / .0001" / .0005" / .00002"), EDI-10102 electronic indicators, and Mahr air probes — with EMD-301P and EDI-301P variants providing integrated digital output for SPC data collection; metric suffixed "M" models available for all sizes.
• Single Hex Wrench Setup - Every adjustment on the M301P including anvil positioning, locking, and indicator mounting is accomplished with a single hex wrench that ships with the gage, eliminating the multi-tool setup overhead of conventional snap gages; this single-tool philosophy reduces changeover time on production floors where gages are frequently re-ranged, and ensures that all required tooling is always co-located with the gage itself when it is retrieved from a bench stand or carrying case.

Specifications

Items Included

• Mahr Marameter M301P snap gage frame
• Tungsten carbide anvils (plain) or hardened steel AL-110 blade anvils (blade variant)
• Single hex wrench for all adjustments

Mahr Marameter M301P Series Snap Gage Data Sheet