Bore Gages
Bore Gages
A bore gets measured at the machine, and then someone writes the number down and types it in somewhere else. Fowler's bore gages cover the measurement and the handoff: electronic Holemikes and pistol grips send the reading out over Bluetooth, USB, or proximity output, while dial bore gages and mechanical Holemikes need no battery or screen at all. Sizes run from 0.037″ (0.95 mm) with MicroGage to 12.2″ (310 mm) with Ultima heads. Pick a type below, then narrow by bore size.
Enter the bore size you want to measure
Enter your bore diameter to see the gages that cover it.
...or pick a bore size range
On Sale
Price
Fowler-Bowers BLUETOOTH 0.375" - 0.750"/10 - 20mm XTH3 Holematic Pistol Grip Set
$3,550.00 $3,195.00
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How to choose
Choosing a type
Five families, each built for a different bore job
Dial bore gages read on a mechanical dial with no battery, in sets from 0.7″ to 12″ for general shop work. Holemikes are 2-point and 3-point bore micrometers with fixed anvils and extended travel, mechanical or electronic with Bluetooth. Pistol grips add a trigger handle with constant measuring pressure, so the reading doesn't depend on the operator's feel. Ultima reads to 0.00001″ (0.0001 mm) across 2 to 310 mm bores, and MicroGage is the 2-point system for the smallest holes.
Resolution
Match the reading to the tolerance on the print
Dial bore gages read in 0.0005″ divisions, with 0.0001″ on the X-Tender (0.01 mm on the metric one). Mechanical Holemikes read in 0.00025″ graduations, and electronic Holemikes and pistol grips resolve to 0.00005″ (0.001 mm). Start from the tolerance, then choose the family whose smallest division sits comfortably inside it.
Setting
Every reading is set against a ring or a master
Holemikes, pistol grips, Ultima, and MicroGage are set in rings that carry UKAS certificates. Dial bore gages are zeroed against a setting master, and Fowler's kits set any bore gage up to 6″ (150 mm) to 0.0001″ (0.003 mm). Extensions reach deeper bores when matched to the measuring range of the head they're used with.
Common questions
A dial bore gage shows the difference from a setting master on a dial. A Holemike is a bore micrometer with a graduated scale or electronic display, fixed anvils, and extended travel, so one head covers a wider span. Mechanical Holemikes read in 0.00025″ graduations, against 0.0005″ on a standard dial bore gage.
It's a bore gage head on a trigger-style handle that applies constant measuring pressure, so the reading doesn't depend on how hard the operator squeezes. Fowler-Bowers XTH3 pistol grips have self centering heads, adjustable trigger travel to reduce hand fatigue, and Bluetooth, proximity, and USB output across 0.080″ to 12″ (2 to 300 mm).
MicroGage is the 2-point system for small bores, with models from 0.037″ to 0.407″ (0.95 to 10.35 mm). XTD3 Holemikes and XTH3 pistol grips start at 0.080″ (2 mm), and Ultima heads start at 0.078″ (2 mm).
Ultima is a modular system of FASTFIT measuring heads, setting rings, and a handle, covering bores from 0.078″ to 12.2″ (2 to 310 mm) at a resolution of 0.00001″ (0.0001 mm). Several probe holders can connect to one readout, so different bore sizes can be measured at one station. The readout is sold separately.
Yes. A bore gage reads against a known diameter, so it's set before use. Dial bore gages use a setting master, and Holemikes, pistol grips, Ultima, and MicroGage use setting rings, which come with UKAS certificates.
XT Series replacement heads with standard anvils are sold individually from 3/8″ to 12″. Heads with special anvils for threads, splines, and slots are available through the Fowler Technical Department.