bowers fowler bore mic how do you calibrate.

[graffian]

So there is a hex grub screw in the fat bit of black, it was loose and it seems to lock the thimble; there’s easy to use as my nan would have said. The thinner bit of black has a flat head screw init and loosening it doesn’t seem to do anything. there is a hex axialyin the end the knurled ratchet is on, no idea what that does. it came with a 1.2501 setting ring and it’s 1.25 thou out and while i know it over reads having it spot on would be nice.

 

[addjunkie]

You use the setting ring to calibrate

 

[graffian]

How do you rotate one of the parts of the bore gauge to zero it to the setting ring? at the moment it over-reads and as long as I remember that figure all is wonderful. I guess i am going to have to undo the axial aligned hex bolt and see if the thimble is rotatable.

 

[oldbikedavey]

Bearing inner races can make reasonable setting rings, but need to be etched with their 'actual' dimension....

 

[graffian]

I generally dig in my old bearing draw for such things, but I got a setting ring with this, and as it turns out I don't have a bearing with a 32mm id[I checked]
but this came with 2 sets of anvils, one for 1-1.25" and one for 1.25-1.5inch and a 1.25" setting ring.
I have just unscrewed the socket head out that retains the thimble/ratchet. Now it's 67[a guess] thou out!
And I really am guessing the numbers of 25 thous as the line that coincides with the outer barrel marks doesn't.
So I have altered it, I am getting warmer.

The instructions on swapping the anvils would say how to zero it, and probably say: 'under no circumstances
remove the screw retaining the ratchet'

i am going to have to make a bit for my two points gauge so it works for 32mm.

 

[RichardM]

Have you tried Fowler tech support?

 

[graffian]

Have you tried Fowler tech support?

"Thank you for the question. I have handed it to the old git who should have retired years ago, he will get back to you pronto".
That was more or less their reply to my message about five years ago, and still he hasn't contacted me. Maybe I spelled my
email address wrong, or he retired?
Anyway I mailed them again a few days ago and got pretty much the same response.

So I took it apart slightly more than I had. It was much like I was expecting.
Much like I was expecting, and thought it can't be that simple, it would be to much of pain to assemble right.
And yes it took me a good few goes to get it right[ish], it underreads by half a thou.
It's probably best left alone now.

I must remember to paint the standard with the Ambersil waxy anticorossion goo before I put it away.