CDI 7502MRMH – 3/8" Drive Micrometer Torque Wrench

The CDI 7502MRMH is a 3/8-inch drive, dual-scale micrometer click-type torque wrench covering 100–750 in-lb (11.3–84.7 Nm) — the high-range inch-pound workhorse in the CDI metal handle family. At 16 inches long and 2.50 lb, it's built with the mechanical leverage the upper end of that range demands, and its coverage of the 360–420 in-lb spark plug installation band puts it at the center of piston engine A&P work.

The wrench that covers spark plug torque and everything above it

Spark plug installation on Continental and Lycoming engines is specified at 360–420 in-lb — right in the middle of the 7502MRMH's range, not at the edge where accuracy degrades. Cylinder base nut torque sequences on many Lycoming and Continental models fall in the 400–600 in-lb band. Heavy structural fasteners at the firewall and engine mount, crankcase through-bolt hardware, and prop flange hardware on heavier singles extend toward the 750 in-lb ceiling. One wrench, one documentation chain, the full upper band of piston engine fastener work.

Documentation-ready for certificated maintenance

Every 7502MRMH ships individually serialized with a NIST-traceable certificate of calibration, satisfying traceability requirements in FAA-accepted maintenance programs, Part 145 repair station QCMs, and ISO 9001 quality systems. Meets or exceeds ASME B107.14 and ISO 6789. Accuracy: ±4% CW, ±6% CCW of indicated value from 20–100% of full scale.

Built for high-range work without sacrificing portability

• 16" overall length provides the leverage arm needed for accurate torque application at 500–750 in-lb
• 5 in-lb graduation — appropriate resolution for hardware specified in 10–50 in-lb increments in aircraft maintenance manuals
• 2.50 lb knurled metal handle withstands sustained professional use on high-cycle engine maintenance tasks
• Spring-loaded pull-down lock ring locks the setting positively — essential when working through multi-fastener torque sequences
• Laser-marked dual scale reads in-lb and Nm simultaneously — no conversion chart needed
• Fixed ratcheting 3/8" drive head with quick-release button for fast socket changes between fastener types
• Audible click plus tactile impulse confirms torque in noisy hangar and flight line environments
• Rated to a minimum of 5,000 operating cycles
• Made in the USA by CDI Torque Products, a Snap-on Industrial Brands company

Where A&P mechanics reach for the 7502MRMH

• Spark plug installation on Continental O-200, O-300, IO-360, and TSIO series engines (360–420 in-lb)
• Spark plug installation on Lycoming O-320, O-360, IO-540, and TIO series engines (360–420 in-lb)
• Cylinder base nut torque sequences — Lycoming and Continental overhaul and top-end work
• Crankcase through-bolt hardware and main bearing cap fasteners
• Firewall and engine mount structural attach hardware
• Prop flange hardware on heavier light singles and light twins approaching the 750 in-lb ceiling

Why source aviation tooling from Pilot John International

Pilot John International is an aviation-specialist distributor — not a general industrial catalog. We serve Part 145 repair stations, FBOs, MRO operations, and flight schools across the U.S. We know that spark plug torque documentation is one of the most frequently audited items in a Part 145 QCM, and that the wrench used to set it needs a current NIST-traceable certificate — not just a receipt. Our on-site ISO 17025-accredited calibration laboratory recertifies the 7502MRMH and returns it with documentation your quality system can stand behind.

CDI 7502MRMH Torque Wrench Calibration

Click-type torque wrenches like the CDI 7502MRMH are precision instruments that require periodic recalibration to maintain the accuracy your maintenance program demands. ASME B107.14 and ISO 6789 both recommend recalibration at regular intervals — typically every 12 months or 5,000 cycles, whichever comes first — and immediately following any overload, impact, or drop event. While the 7502MRMH ships with an individual NIST-traceable calibration certificate from the factory, that certificate has a service life, and operating with an out-of-tolerance torque wrench on aircraft fasteners is a documented cause of under- and over-torque events with real airworthiness consequences. Pilot John International's ISO 17025-accredited calibration laboratory provides traceable torque wrench calibration services for the CDI 7502MRMH and a wide range of other precision torque tools, issuing a fully documented calibration certificate upon completion. Whether your QMS operates under FAA oversight, AS9100, or an internal calibration interval program, PJi's lab delivers the traceability and turnaround your operation requires. Learn more about PJi's ISO 17025 Calibration Services →