Mahr Micromar 844 A Measuring Pistol

Mahr Micromar 844 A Measuring Pistol

The Mahr Micromar 844 A is a self-centering 3-point inside measuring pistol designed for precise, repeatable internal diameter measurement of through holes, blind holes, and centering shoulders across a measuring range of 6mm to 200mm (0.25" to 7.9"). Available in seventeen individual head-size configurations and three basic unit-only options, the 844 A is the indicator-gage platform of choice for production machining, inspection, and tool room applications where the self-centering geometry of a 3-point measuring system must be combined with the ergonomics and constant measuring force of a pistol-grip handle without the cost or form factor of a fully digital integrated instrument.

The 844 A's measurement principle centers on the 44 Ak interchangeable measuring head: three laterally positioned anvils, each offset at 120° intervals around the bore circumference, that automatically center the measuring head on the bore axis regardless of how the pistol is inserted. Anvils from 12mm are carbide-tipped, and from 12mm the anvils can be used to measure the bottom of a bore. Below 12mm, chrome-plated steel anvils provide corrosion resistance while maintaining the geometry needed for small-bore measurement. From 40mm, all measuring heads are made from aluminum to reduce weight, keeping the instrument comfortable for sustained use at larger diameters where steel head construction would add meaningful mass at the end of the pistol. The measuring head attaches to the 844 Ag basic unit via a threaded connection that allows heads to be swapped between the same basic unit as part diameter requirements change, meaning a single 844 Ag handle body can serve multiple bore dimensions across its compatible range, with only the 44 Ak head requiring replacement.

The pistol grip incorporates a constant measuring pressure for locking onto the bore diameter with no operator influence. This is the critical structural difference between the 844 A and a conventional 2-point dial bore gage: the spring-loaded constant force mechanism in the pistol body applies a defined, repeatable contact force to the measuring head anvils every time the trigger is operated, independent of how firmly or lightly the operator grips the handle. The result is cycle-to-cycle measuring force consistency that would require significant operator training to achieve manually with a lever-actuated gage.

The 844 A is a body-only instrument: the indicating instrument is not included and is selected separately. Measuring value indication is always easy to read when using an electronic dial indicator with a rotatable display. Any Mahr indicator on an 8mm mounting shank is compatible from the 1086 R digital indicator (0.0005mm resolution) to the 1086 Ri (Integrated Wireless) and the 1086 R-HR (0.0001mm high-resolution) allowing the 844 A body to be upgraded as data collection and resolution requirements evolve without replacing the measuring system. For applications requiring deeper bore access than the standard measuring depth provides, the 44 Av threaded extension (available in four sizes for 6–200mm ranges) adds 75mm or 150mm of additional reach, with all measuring depth specifications published in the complete ordering table below.

Key Features

• 3-Anvil Self-Centering at 120° with Constant Pistol-Grip Measuring Force - Three 44 Ak measuring head anvils positioned at 120° intervals automatically center on the bore axis at insertion, while the pistol body's constant-force spring mechanism applies a fixed, repeatable contact pressure with each trigger operation eliminates both the centering skill required by 2-point dial bore gages and the measuring force variability that makes handheld comparative bore gaging operator-dependent; the result is consistent, reproducible readings from the first cycle regardless of operator technique or grip force.
• Threaded Interchangeable Measuring Heads - The 44 Ak measuring heads attach to the 844 Ag basic unit via a standard threaded connection, allowing a single pistol handle to serve any diameter within its compatible range by swapping only the head; the 844 Ag basic unit is available in three range configurations (6–100mm, 20–100mm, and 100–200mm) and accepts all seventeen 44 Ak head sizes within that range, making head-only replacement significantly more economical than purchasing a complete new measuring system for each diameter change.
• Carbide-Tipped Anvils from 12mm - Measuring heads from 12mm use carbide-tipped anvils for superior wear resistance in high-cycle production gaging environments, and the carbide tip geometry is configured to allow measurement directly at the bottom of a blind bore eliminating the standoff distance that prevents chrome-tip and ball-tip gages from reaching the full depth of a blind hole; below 12mm, chrome-plated steel anvils provide the corrosion resistance and dimensional stability required for small-bore precision measurement in coolant and cutting fluid environments.
• 44 Av Extension Adds Up to 150mm of Bore Depth - Four 44 Av threaded extension sizes (75mm for 6–12mm and 12–20mm ranges; 150mm for 20–30mm and 30–200mm ranges) thread between the 844 Ag basic unit and the 44 Ak measuring head to extend the standard measuring depth by up to 150mm enabling blind hole and deep groove measurement at full bore depth where the standard pistol body alone cannot reach the measurement plane, without requiring a separate extended-reach instrument.
• Any 8mm Shank Indicator, Including Digital, Wireless, and High-Resolution - The 844 A accepts any Mahr indicator on an 8mm mounting shank as the readout device, including the 1086 R digital indicator (0.0005mm resolution, USB/RS-232/Digimatic output), the 1086 Ri (Integrated Wireless ANT+ to i-Stick receiver), and the 1086 R-HR (0.0001mm / 0.1µm high-resolution) allowing the same bore measurement platform to serve applications ranging from production floor pass/fail inspection to laboratory-grade SPC data collection without replacing the 844 A body or measuring head; the indicator is selected, purchased, and upgraded independently.
• Seventeen Head Sizes from 6–200mm - The complete 844 A range covers seventeen measuring spans from 6–8mm through 175–200mm, with error limits of 3µm for heads through 40mm, 4µm for 40–100mm, 5µm for 100–150mm, and 6µm for 150–200mm, reflecting the relationship between bore diameter, anvil contact geometry, and achievable measurement uncertainty across the full size range, and enabling customers to specify the appropriate error limit for each bore diameter in their measurement plan rather than accepting a single blanket specification across all sizes.

Specifications

Items Included

• Mahr Micromar 844 Ag basic unit / measuring pistol (range as specified)
• 44 Ak measuring head (range as specified)
• Instruction manual
• Carrying case

Mahr Micromar 844 A Measuring Pistol 4487700 Datasheet

Mahr Micromar 844 A Measuring Pistol 4487612 Datasheet