Commutator Bars

For commutator bars, mainly hot rolled or hot extruded material is cold drawn with good dimensional precision. Commutator bars has the longest history in our Cu products and evaluated highly also for the quality.

Commutator Bar Shapes and production size range

In specifying the length, short length, enlarged length and standard length can be selected.

  1. Short length is to be selected for use with no cutting.
  2. Enlarged length is selected for length for few cuts, including the length for cutting margin.
  3. Standard length is selected when the entire length is specified.

Standard Dimensional Tolerance

Tolerance of A, B and C is listed below. Please consult us for if more precise tolerances are necessary.

A B C※
10min 0.02min ±0.05 ±0.05 +0.4
10 less than ±0.04 ±0.04
0.02 less than ±0.035 ±0.035
remarks measured at marginal limit direct measurement


C Gap
Up to 50 Up to 0.03
Above 50 Up to 0.04

Length Tolerance(㎜)

Length Tolerance
Short Length +2
Enlarged Length +3
Standard Length +3

Warp, Twist and Camber(㎜)

Length Tolerance
over100 under 0.15% of length
up to 100 Please consult

Production Size Range and Properties

Material that can be applied id listed below conforming to JIS C2801 and besides TPC and 20Ag, 3Ag,8Ag is possible.
Please request us based on your application.
Mold commutators produced in recent years not only apply commutator bars but also formed bars, Cu tubes and strips and oxygen free Cu and AgOFC are also available.

Material Chemical Composition(%) Electrical Conductivity%
Cu Cu+Ag Ag
TPC 99.9%min 98min Equivalent to JIS2801 class1, general purpose with no requirements on Heat softening resistance.
99.9%min 0.15〜0.25 97min Equivalent to JIS C2810 class2, mainly for rolling stock with requirements on heat softening resistance
8 ag
99.9%min 0.085〜0.102 97min Mainly for rolling stock with requirements on heat softening resistance and general industrial use.

Gauge for dimension               Cross Section Gauge


Basically, the gauge for dimension measurement is to be provided.

It is possible for us to prepare the gauge bared by customer under actual expense.
The gauge to be provided should have dimensions or shape similar to the figure.


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