Spi 91-378-0 Feeler Gage 0.025 in Parallel Leaf Steel

Product Description

The SPI 91-378-0 is a parallel-leaf feeler gage used to measure narrow gaps, clearances, and tolerances in mechanical assemblies. The blade measures 0.025 inches thick, 0.5 inches wide, and 12 inches long, giving technicians a consistent, full-length contact surface for accurate readings. Constructed from high carbon steel, the leaf resists wear and holds its dimension under repeated use. This type of gage is a standard hand tool for HVAC, engine, and general mechanical service where precise gap measurement is required before or after adjustment.

Feeler gages like the 91-378-0 are used across residential and commercial HVAC service, engine valve adjustment, compressor assembly, and general precision maintenance. The 12-inch parallel leaf design suits applications where a straight, consistent blade profile is necessary from tip to handle. Technicians reach for this gage when checking spark plug gaps, valve clearances, bearing fits, and similar close-tolerance specifications during installation or preventive maintenance.

Key Features

• 0.025-inch blade thickness for measuring close-tolerance gaps
• Parallel leaf style provides a consistent cross-section along the full 12-inch length
• High carbon steel construction for durability and dimensional stability
• 0.5-inch blade width offers stable surface contact during measurement
• Single-leaf format allows direct use without disassembly from a set

Compatibility

Designed as a general-purpose parallel-leaf feeler gage suitable for any application requiring a 0.025-inch gap measurement with a 12-inch blade length.

Installation Notes

Feeler gages are hand tools requiring no installation; however, they should be kept clean and lightly oiled to prevent corrosion and maintain accuracy. When measuring gaps, insert the blade without forcing it — the correct gage thickness produces light drag with no bending of the leaf. Store flat and away from moisture to prevent warping of the high carbon steel blade.