Spi 91-391-3 Feeler Gage Parallel Leaf High Carbon Steel

Product Description

The SPI 91-391-3 is a single-leaf feeler gage designed for precise gap and clearance measurements in mechanical and HVAC service applications. The parallel leaf measures 0.04 millimeters (approximately 0.0016 inches) thick, 0.5 inches wide, and 12 inches long, providing reach into tight clearance areas. Constructed from high carbon steel, the leaf resists flex and maintains a flat, consistent surface across its full length. Licensed mechanics, HVAC technicians, and precision maintenance professionals use this tool when checking valve clearances, burner orifice gaps, bearing fits, and other close-tolerance specs requiring a reliable feeler standard.

This feeler gage is suited for both residential and light commercial service work where single-leaf precision measurements are required. The 12-inch parallel leaf length allows access to recessed components in furnace heat exchangers, compressor housings, pump assemblies, and mechanical equipment panels. Its compact 0.5-inch blade width fits into narrow slots without disturbing adjacent components. The straight parallel profile makes it easy to read contact feel consistently from one technician to the next.

Key Features

• Parallel leaf profile delivers uniform thickness across the full 12-inch length
• High carbon steel construction for rigidity and long service life
• 0.04 mm nominal thickness for fine-tolerance gap checking
• 0.5-inch blade width fits narrow clearance slots
• 12-inch length provides reach into deep or recessed measurement points

Compatibility

Designed as a general-purpose single-leaf feeler gage for use in HVAC, mechanical, and precision maintenance applications requiring 0.04 mm gap measurements.

Installation Notes

No power disconnection is required for gage use alone, but always follow appropriate lockout/tagout procedures when measuring clearances on energized or pressurized equipment. Insert the leaf parallel to the mating surfaces without forcing to avoid bending the blade. Clean the leaf before and after use to prevent contamination of precision surfaces. Store flat to preserve calibration accuracy.