Control Knobs - 70 Series Round Knob Locks Details

Durable Push-to-Turn Control Knobs, from the EHC Knob Lock 70 Series & available with custom options.

The EHC 70 Control Knobs transmit rotary motions, disengaging automatically when released.

• Round Knob Lock Controls
• Coupling Design
• Custom Options

EHC Round Knob Locks are perfect for use with MS91528 Knobs & EH71 Knobs, freely rotating in unengaged mode.


The EHC Push-to-Turn Knob design utilizes sprag-type clutch mechanism, offering security against shock, vibration and inadvertent change. The EHC 70 Series provides ease of operation, accurate positioning and positive locking.


• Positive lock of control setting
• Ease of setting; one-hand operation
• Locked in the unengaged mode
• Infinite setting’s locks positively on release
• Prevents movement from shock or vibration or accidental movement
• Zero backlash
• Must be fully depressed before movement
• Mounting hardware supplied with knob
• Designed for the EHC  MS91528 style series
• Engineered to meet military specifications

Installation Instructions

Use the special lockwasher for mounting behind the panel and the special mounting nut with tabs for mounting in front of the panel.* When attaching the control knob to the shaft, engage the tabs in the tabs slot. Surface“L” , in the control knob, and Surface“K” , on the special mounting nut must be mounted flush against each other.


On ring skirted knobs, screws loosened out of tapped holes may fall into assembly. On dial skirted knobs, disassembled screws would allow outer shell to dis-engage from knob assembly. Loosen set screws enough to permit entry of shaft into shaft hole. Secure tightly. Knob is now in LOCKED position. In order to rotate it, the knob must be fully depressed. This UNLOCKS it permitting free rotation of the shaft. RELEASE again to LOCK. * If necessary, use the mounting nut of the device to be controlled as a checknut behind special lockwasher to orient threaded bushing flush with special mounting nut at Surface K.

Part Number: PT70

Diam:   Height + 0.30    Shaft Min:   Screw:   Dial Diam:    Style:    Hole:   Finish:

 .730          .830                  .62            .390            -                2           1        None
 .730          .950                  .62            .390         1.150            3           2          G
Ordering Guide

Cap Design & Diam:
                   Style:             Shaft Hole Diameter:     Finish (Black):

Indicate Part No from above       2 - Ring Skirt             1 - 1/8" Round             None - Gloss
                                               3 - Dial w.Arrow           2 - 1/4" Round               G - Matte
                                            3NP– Dial No Arrow

Code Example: PT70-3NP-1G

Cap Design:
          Style:              Shaft Hole:      Finish:
Series                Dial-no-Arrow            .125"            Matte
PT70-                     3NP-                       1                 G