Mitutoyo 154-107 Small Hole Gage 0.3 to 0.4 Inch Half Ball

Product Description

The MITUTOYO 154-107 is a small hole gage used to measure the inside diameter of holes, slots, and bores in the 0.3 to 0.4 inch range. It uses a half ball contact style that seats evenly inside the bore, allowing the technician to lock the gage and transfer the measurement to an outside micrometer for a precise reading. At 4 inches in overall length, it fits comfortably in hand for controlled feel during measurement. This tool is used by machinists, millwrights, and precision tradespeople who need accurate inside-diameter readings in tight spaces where a standard bore gage will not reach.

This gage is well suited for measuring small holes in machined components, valve seats, hydraulic fittings, and similar precision parts encountered in HVAC, plumbing, and industrial maintenance work. The 0.3 to 0.4 inch measurement range covers a common set of small-bore diameters found in fluid handling and mechanical assemblies. It is a hand-transfer gage, meaning the locked dimension is read by measuring across the ball with an outside micrometer after withdrawal from the bore.

Key Features

• Measurement range: 0.3 to 0.4 inches for small inside-diameter work
• Half ball contact style for consistent seating in round bores
• 4 inch overall length provides controlled reach into shallow holes
• Lock mechanism holds the expanded diameter for transfer measurement to an outside micrometer
• Compact size allows use in tight spaces where larger bore gages cannot fit

Compatibility

Designed as a standard small hole gage for use with any outside micrometer capable of reading in the 0.3 to 0.4 inch range.

Installation Notes

Small hole gages are used by machinists and precision maintenance technicians and require no fastening or wiring. Insert the gage into the bore, expand the ball until light drag is felt, lock the setting, and withdraw the gage without disturbing the set diameter. Read the locked dimension using a calibrated outside micrometer. Avoid overtightening the lock, as this can distort the ball and introduce measurement error.