Forward/Reverse Switch on a Bench Mill: Replacement Guide

By Products for bench top machinists | LittleMachineShop.com | Published: 2026-11-02

Category: How-to Guides

Replace a forward/reverse switch on a bench mill safely. Follow the step-by-step process for removal, wiring, and testing, plus tips to avoid common mistakes.

Quick Answer

To replace a forward/reverse switch on a bench mill, disconnect power, label and remove the old switch, install the new switch, reconnect wires per the diagram, and test operation before use. Always verify the replacement switch matches your mill's voltage and current ratings.

Why the Switch Fails and When to Replace It

A forward/reverse switch on a bench mill typically fails due to worn contacts, loose connections, or mechanical damage. Symptoms include intermittent operation, difficulty changing direction, or a switch that feels loose or won't stay in position. Before replacing, check that the problem isn't elsewhere—such as a blown fuse or a loose wire at the motor—since these can mimic switch failure.

Safety First: Lockout and Verification

Always disconnect the mill from its power source before beginning any electrical work. If possible, lock out the power switch to prevent accidental reconnection. Use a multimeter to verify that no voltage is present at the switch terminals. Never rely solely on the mill's power switch being off.

Step-by-Step Replacement Process

Disconnect Power and Lock Out: Unplug the mill from the wall outlet. If hardwired, turn off the circuit breaker and lock it. Verify with a multimeter that the switch terminals are dead. Double-check that the multimeter is functioning correctly by testing a known live circuit before testing the mill.
Remove the Old Switch: Take clear photos of the wiring before disconnecting anything. Label each wire with its terminal designation. Unscrew the switch from the control box and gently pull it out. Avoid pulling on wires; use a screwdriver to gently pry if the switch is stuck.
Prepare the New Switch: Compare the new switch to the old one to ensure identical terminal layout and ratings. If the new switch has a different configuration, consult the wiring diagram. Never assume color codes match; always follow the diagram.
Mount and Connect the New Switch: Secure the new switch in the control box. Reconnect wires to the corresponding terminals, referring to your photos and labels. Tighten terminal screws firmly but do not overtighten. Give each wire a gentle tug to confirm it's secure.
Test the Installation: Restore power and turn on the mill. Test forward and reverse directions at low speed. Listen for unusual noises and check that the spindle changes direction smoothly. If the motor runs in the wrong direction, swap the two motor leads as instructed in your mill's manual.
Final Check and Cleanup: Turn off power and inspect all connections for tightness. Replace the control box cover. Dispose of old switch properly. Run the mill for a few minutes in each direction to ensure no overheating or intermittent operation.

Product Facts

Switch, F/R: This switch is designed for HiTorque Mini Lathes and can also add reverse capability to a HiTorque Mini Mill by mounting in the control box and plugging into the empty connector on the potentiometer circuit board. It provides a direct replacement or upgrade path for HiTorque owners, ensuring compatibility and easy installation.
Switch, F/R