MITUTOYO SERIES 331 SPLINE MICROMETER

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▪The anvil and spindle are of small diameter for measuring splined shafts, slots, and keyways.
▪IP65 water/dust protection (series 331).
▪Measuring faces: Carbide.
▪Equipped with Ratchet Stop for constant measuring force.

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MITUTOYO SERIES 331 SPLINE MICROMETER

Product Overview

The Mitutoyo Series 331 Spline Micrometer is a digital Digimatic precision measuring instrument featuring a small-diameter anvil and spindle specifically designed for measuring splined shafts, slots, and keyways. Equipped with IP65 water and dust protection, carbide-tipped measuring faces, and a ratchet stop for consistent measuring force, this instrument delivers reliable performance in demanding industrial measurement environments.

Key Features & Capabilities

Small-diameter anvil and spindle engineered for measuring splined shafts, slots, and keyways
IP65 water and dust protection rating
Carbide-tipped measuring faces for enhanced durability and wear resistance
Ratchet Stop mechanism for constant, repeatable measuring force
Electromagnetic rotary sensor position detection method
Built-in Digimatic output functionality compatible with optional connection cables and U-WAVE wireless data systems
Approximately 2.4 years of battery life under normal use (powered by a single SR44 battery)

Technical Specifications

Metric Models (Digimatic)

Code No.	Range (mm)	Resolution (mm)	Maximum Permissible Error $JMPE$ (µm)	Flatness (µm)	Parallelism (µm)	Measuring Face
331-251-30	0 - 25	0.001	±2	0.3	2	Type A ($\varnothing$3 mm)
331-252-30	25 - 50	0.001	±2	0.3	2	Type A ($\varnothing$3 mm)
331-253-30	50 - 75	0.001	±2	0.3	2	Type A ($\varnothing$3 mm)
331-254-30\*	75 - 100	0.001	±3	0.3	3	Type A ($\varnothing$3 mm)
331-261-30	0 - 25	0.001	±2	0.3	2	Type B ($\varnothing$2 mm)
331-262-30	25 - 50	0.001	±2	0.3	2	Type B ($\varnothing$2 mm)
331-263-30	50 - 75	0.001	±2	0.3	2	Type B ($\varnothing$2 mm)
331-264-30\*	75 - 100	0.001	±3	0.3	3	Type B ($\varnothing$2 mm)

\Made to order.*

Inch/Metric Models (Digimatic)

Code No.	Range (in)	Resolution	Maximum Permissible Error $JMPE$ (in)	Flatness (in)	Parallelism (in)	Measuring Face
331-351-30	0 - 1	0.00005 in / 0.001 mm	±0.0001	0.000012	0.00008	Type A
331-352-30	1 - 2	0.00005 in / 0.001 mm	±0.0001	0.000012	0.00008	Type A
331-353-30	2 - 3	0.00005 in / 0.001 mm	±0.0001	0.000012	0.00008	Type A
331-354-30	3 - 4	0.00005 in / 0.001 mm	±0.00015	0.00012	0.00008	Type A
331-361-30	0 - 1	0.00005 in / 0.001 mm	±0.0001	0.000012	0.00008	Type B
331-362-30	1 - 2	0.00005 in / 0.001 mm	±0.0001	0.000012	0.00008	Type B
331-363-30	2 - 3	0.00005 in / 0.001 mm	±0.0001	0.000012	0.00008	Type B
331-364-30	3 - 4	0.00005 in / 0.001 mm	±0.00015	0.00012	0.00008	Type B

Dimensional Specifications (Metric Models)

Code No.	L (mm)	a (mm)	b (mm)	c (mm)
331-251-30 / 331-261-30	0	7.3	32.5	17.5
331-252-30 / 331-262-30	25	10.1	47	17.5
331-253-30 / 331-263-30	50	11.5	60	17.5
331-254-30 / 331-264-30	75	16.7	76	20.3

Standard Accessories

SR44 Battery (1 pc., Code No. 938882 included for operational checks)
Setting Standard (1 pc., included for models with measuring range > 0–25 mm / 0–1 in)
Spanner (1 pc., Code No. 301336)