Dial Test Indicator- what’s a clutch for?

[StevSmar]

I’m looking at Dial Test Indicators and the websites for the Mitutoyo True Test indicators in the 531 series generally have this in the description “No-clutch structure for automatic reversal of measuring direction.”

What is this?

I’ve read that some dial test indicators can have their point moved past the end stops without loosening a screw (which implies a clutch?), but this wording has got me scratching my head.

 

[RJSakowski]

My dial test indicators have an overide mechanism which permits adjustment of the angle of the probe. It is basically a friction mechanism adjusted with the pivot screw. I guess you could call it a clutch.

 

[StevSmar]

My textbook Machine Tool Practices” by Kibbe et. al. says that dial test indicators can be “equipped with a movement reversing lever. This means the indicator can be actuated by pressure from either side of the tip”

I still find the Mitutoyo wording strange. There was no mention of what this feature does in their new online catalogues.

 

[Liljoebrshooter]

My 513-504 indicators have a lever you have to move to change the direction you want to indicate from. I believe the dial turns the same direction either pushing up or down on the tip.
Some turn both directions.
Joe
Found a picture.

 

[682bear]

I think Joe is correct... I had a peacock indicator that had the lever on the side to reverse the movement of the tip... I think that is what they are calling a 'clutch'.

-Bear

 

[mksj]

Dial test indicators need to be at a specific angle to the work piece for accuracy and the change is not linear as in a dial indicator. A clutch allows you to se the proper angle and also is a safety feature should you push past the maximum range. Some indicators allow multiple revolutions so have a longer range, the clutch will kick in if you exceed that. Older test indicators were unidirectional so you need to flip a level to measure in the opposite directions, newer ones automatically flip in the reverse direction, and the needles always moves clockwise.

 

[StevSmar]

Thankyou @RJSakowski , @Liljoebrshooter , @682bear , @mksj for your responses!

I didn’t know that the dial test indicators needle always moved in the same direction. Interesting that some have a lever too.

I guess I’ll just have to purchase one to see for myself what it means…

 

[Canuck75]

Just to add to the conversation.
I bought a Verdict DTI many years ago which incorporates a reversing lever and a ratcheting stylus (clutch?). The styli can be changed out by simply rotating a spring retention clip on the outside freeing the styli. All styli have a serrated surface on the one side and to change position (ratcheting) you simply move it against the serrations under the pressure of the spring clip. Very handy in all respects. It came with several styli, the smallest one gives a direct reading while the others give a relative reading. In other words a .001" change in reading is not an actual .001" except when using the smallest styli.

 

[T Bredehoft]

No-clutch structure for automatic reversal of measuring direction.”

The Mitotoyu indicator I have automatically reverses direction, without the need to reverse a lever, also includes the ability to adjust the position of the pointer, (as suggested 'a clutch')