Optical Encoder Assembly


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  • NOTE: The MASSO Optical Encoder will not work with the Sherline/Acorn CNC Controller.

About the Optical Encoder

The optical encoder was designed by MASSO to work with Sherline machines in conjunction with the MASSO controller. They designed a compact optical encoder for us that fits perfectly with our machines and our accessories. The optical encoder, speed control wiring, and the MASSO software let you control your spindle speed with g-code.

The optical encoder comes with the MASSO controller, but if you already have an optical encoder for your mill, you can add another optical encoder for your lathe without having to purchase another controller.

You can also order limit switches for your other machine. CLICK HERE.

What’s Included:

  • Optical encoder kit (optical encoder, mounting hardware, and gap setter)
  • Main Encoder speed control cable and ground cable
  • Speed control cable
  • Tach spindle pulley RPM sticker
  • Mill headstock cable support* (ball screw mills only)
    *NOTE: The headstock cable support ships only with P/N 8769. It is not included with any lathes or leadscrew mills.

Select Your Headstock Option

Be sure to select your headstock option above. The bracket mounts for the standard headstocks are different than the ones that ship with a 3C collet headstock. The standard headstocks included the #1 Morse taper with 3/4 x 14 threads, the 9/16″ headstock, and the ER-16 headstock.

The improper use of machine tools and their accessories can result in serious injury. Before using this tool, thoroughly read the instructions and make sure you understand its proper and safe use.


Always wear safety glasses when operating machine tools.

Download PDF Sherline/MASSO CNC Controller Initial Start Instructions

Instructions PDF Download

Download PDF Threading and Spindle Speeds/MASSO Conversational Threading Program

Instructions PDF Download

Download PDF Optical Encoder Mounting Instructions

Instructions PDF Download

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Installing the Optical Encoder

Setting up the Optical Encoder

NOTE: The MASSO optical Encoder is designed to work with the MASSO controller. This encoder may not work with other controllers or control boards. If you intend to use this encoder with a different control or control board, send the information below to the controller manufacturer so they can verify whether this encoder will work with their product.

Optical Encoder Specifications

Below is the information for the MASSO optical encoder, which comes from the MASSO website:

As stated in the MASSO manual, the MASSO encoder is an optical quadrature encoder.

MASSO Encoder Voltage Range: 12 to 24VDC

Output signals: 0v for LOW signal, 10v for HIGH signal.

An incremental encoder is used to monitor spindle RPM and also for synchronized threading on lathes.

Pin No. Description Type
Pin 1 Signal A Opto input (5 to 24v)
Pin 2 Signal B Opto input (5 to 24v)
Pin 3 Signal Z – Index Opto input (5 to 24v)


Spindle Encoder Signal

The A & B signals are Quadrature signals, i.e. 90 degrees out of phase with one another. MASSO can use these signals to determine the speed and direction the spindle is turning.
The A, B signal sequence runs as follows.

  • A – High, B – Low
  • A – High, B – High
  • A – Low, B – High
  • A – Low, B – Low

The sequence repeats. The sequence will reverse if the spindle is run in the opposite direction.

Upgrading the Spindle Encoder on MASSO G2 (https://docs.masso.com.au/wiring-and-setup/setup-and-calibration/upgrading-the-spindle-encoder-G2)

The maximum pulse frequency on encoder inputs for MASSO G2 controllers is 8 kHz. The MASSO G2 can be upgraded to 20Khz by replacing the Encoder Optocouplers. For more information on this, please click on the “Ordering the SFH615A Optocouplers” link below.

Part No. Description Quantity
40340 10-32 x 1″ SHCS and 40660 #10 washers for 3C headstock spacer 2
40530 5-40 x 3/8″ SHCS 2
40720 10-32 x 1-1/2″ SHCS and 40660 #10 washers for standard headstock spacers 2
67124 Zip ties 4
68002 5-40 x 3/8″ SHCS 1
68060 Tach spindle pulley RPM sticker 1
87810 Optical encoder 1
87812 Optical encoder cover 1
87813 .129 optical encoder gauge 1
87814 Optical encoder bracket 1
87816 Optical encoder spacer for standard headstock (standard headstocks only) 1
87817 Optical encoder spacer for 3C headstock (3C headstock only) 1
87820 Main Encoder speed control cable and ground cable 1
87830 Speed control cable 1
87840 Mill headstock cable support* (ball screw mills only) 1

*NOTE: The cable support ships only with P/N 8769. It is not included with any lathes or leadscrew mills.