Adjust Bowers bore mic

[jlw™]

So I've got this Bowers bore mic that has served me well for about a decade. I check it on the ring every use. Well, last week I let some one borrow and now its off 5 tenths on the ring gage.

 

Can any one enlighten me on adjusting it? I've never had to and can't find anything with Google. My newer bore mics have wrenches and such but this one does not.

 

[Guest]

Zero it to the gage.....typically, there is a screw in the end of the barrel.........loosen it slightly and adjust it to zero, the retighten

[Sticky]

Time to buy some digimatic Holtests

 

You would think there should be an obvious adjustment screw?

[jlw™]

Time to buy some digimatic Holtests

 

You would think there should be an obvious adjustment screw?

 

 

I'll buy a full set on your dollar!  These are my personal gages.

 

The newer ones I have do have a very obvious adjustment as well as provided wrenches and instructions (never had to adjust them either tho).  These however seem to be hidden.  The Only obvious screws are the lock, the thimble (only loosens the thimble), and two on the "cover" there.  I figure the cover needs to come off but it's an odd size.  Not a 2mm or a 2.5mm and also not a 5/64.  I figure it's by design to be difficult.

[The Cathedral]

Hard to tell, but judging by the old school design there is two jam nuts inside the thimble riding on the plunger; you'd have to adjust the jam nuts to move the plunger. Not hard, just trial and error. 

[Sticky]

I'm surprised you've never had to adjust them. Is there a ratchet on the end or is it thimble only?

[jlw™]

Ratchet.

 

I have 6 of them.  4 of them I've had for 10+ years.  Never had to adjust a single one, always perfectly on ZERO.  I'm very peculiar about my tools.  The guy I loaned them to is a caveman.  No doubt he twisted the thimble instead of the ratchet while I always use the ratchet and never twist it hard.  Guess I should have explained that it's a gage and not a hole spreader.

[THEE THAINZ™]

Hole spreader    Good old school yard humor.......Oh what I would say if it were not for Daniel.....