Comtorgage Purchasing Information

We will be happy to assist you with your Comtorgage needs. You can send us a print for a quote, or, for simple bores, follow the guidelines below:

Guidelines for Specifying a Comtorgage for Measuring Bores:

  • The first step is to determine the appropriate model of amplifier or coupler. The amplifier or coupler should have at least twice as much total range as the total bore diameter (MAX minus MIN). This will determine the amplifier model.
  • If the above process determines that you can use either a 1CM1 or CM1 amplifier (the metric equivalent is 1CM1M or CM1M), using the 1CM1 (or 1CM1M) amplifier is the better choice because it will result in slightly better gage R&R performance. If you are using a coupler, a CEM-420 is a better choice than a CEM-410 for the same reason. If you find this is confusing, please contact us.
  • The bore length must be longer than the expansion plug head length, or else a standard expansion plug should not be used. Contact us for additional options.
  • Once the amplifier or coupler has been determined, the expansion plug is specified by the mean bore size, and the model amplifier or coupler that it is to be used with.
  • Expansion plugs have specific tolerance ranges, and they should always be used with the proper amplifier or coupler. Otherwise, the size readout will not be linear. The mean size and the proper amplifier or coupler is always marked on each expansion plug.
  • A mean size master ring is required to master a Comtorgage.

Comtorgage Manufacturing Times:

Standard expansion plugs:

  • .1250" to 4.9999" (3.174mm to 126.999mm) - Approximately 3 Weeks
  • 5.0000" to 12.9999" (127.000mm to 330.198mm) - Approximately 5-6 Weeks


  • Usually in stock


  • Approximately 1 Week


  • Slatersville, Rhode Island


  • We will ship by UPS ground unless other shipping is requested


  • Marking of the mean bore diameter and the proper amplifier or coupler is standard.
  • Marking of tool numbers or part numbers on expansion plugs is an additional $8.00 per gage.
  • Marking of tool numbers or part numbers on amplifiers or couplers is an additional $8.00 per15-character line.

Ordering information:

Either send us a print for any Comtorgage application (section views are especially helpful), or provide the following information for each Comtorgage bore diameter application:

  • MIN/MAX Bore Diameter (this determines the amplifier or coupler model, the mean bore size, and the required master ring class)
  • Bore Length
  • Any unusual access requirements
  • Whether you want an amplifier or a coupler
  • Any additional marking
  • Any specific master requirements such as marking or certification

Send your purchase orders to

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