Starrett ratchet stop tension

[francist]

Hi guys.
Is there a way to adjust the ratchet stop tension on a Starrett mic? I just picked up a 449B depth mic at a local pawn shop and the ratchet tension feels overly tight to me. I know how to adjust for backlash and calibrate the rods but can't find anything on adjusting ratchet tension -- is it possible to do that or is that a factory preset that can't be tweaked?

Thanks for any help.

-frank

 

[JimDawson]

There must be a spring in there, so see what you can do to weaken it a bit.

I just drag my finger across the spindle to feel the tension, I never use the ratchet. It seems to be more repeatable that way. Using the ratchet is kind of like using an impact wrench IMHO.

 

[mikey]

On my Starrett mics there is no provision for adjusting tension of the knob. A tight knob usually means dirt or varnish from old dried oil is in there so I just take the screw in the cap off, clean it and lube it. Works for me.

 

[Bill C.]

There must be a spring in there, so see what you can do to weaken it a bit.

I just drag my finger across the spindle to feel the tension, I never use the ratchet. It seems to be more repeatable that way. Using the ratchet is kind of like using an impact wrench IMHO.

True, it takes practice to get the feel.

 

[Bill C.]

Hi guys.
Is there a way to adjust the ratchet stop tension on a Starrett mic? I just picked up a 449B depth mic at a local pawn shop and the ratchet tension feels overly tight to me. I know how to adjust for backlash and calibrate the rods but can't find anything on adjusting ratchet tension -- is it possible to do that or is that a factory preset that can't be tweaked?

Thanks for any help.

-frank

I have used both the finger method and the ratchet. Some models have a slip fit type tension barrel as well. It is there as a production aide. These micrometers are used by everyone from master machinist to production machine operators. It gives the novice equal footing to a experience machinist. You can over-tighten the barrel and get a wrong dimension.

Remove the ratchet and clean it then if it is still to tight then try weakening the spring. Don't forget to put a drop of oil on the screw when you put it back together. You can always remove it if you want to.

 

[francist]

Great, thanks for the input. I don't always use the ratchet method either but sometimes I just want to double check or don't trust my feel. I'll try cleaning and see what happens.

-frank

 

[francist]

Well that worked nice, here's what I did:

First I ground a driver bit to fit the narrow-slot screws Starrett likes to use and then removed the screw in the end of the speeder. I could see the ratchet detents on the end cap, and a tiny little pin sticking out of the other part.

The pin dropped out freely, but I could see a wee spring still inside the hole which refused to come out. So, bit of carb cleaner for a couple minutes and suddenly it was loose enough to fish out with a dental pick. That being all the pieces, I cleaned them all, put a drop of oil on each as I put them back together.

Perfect! And the best part was with the parts all cleaned and oiled I discovered that there was enough resistance on the end screw as I turned it in so as to be able to set the ratchet tension just where I wanted it. The knob turns on the ratchet freely, but the screw stays put. So I don't know if that's the way you're supposed to do it, but it's working for me. Here's a couple pics if anyone is interested.

-frank

 

[benmychree]

A comment was made that the ratchet was like using a impact wrench; I think that I read that one is supposed to use only three clicks of the ratchet in taking a measurement. Personally, all my micrometers (0 - 6") have ratchets, I bought them all new that way because that is what the local dealer had in stock; I have been using them now for about 50 years, and go strictly by feel, never use the ratchets.