A couple quick questions:
1: What tool is best for adjusting the calibration screws of a tribrach bubble level? (Also, what are those screws called?)
2: What is the proper technique used to adjust the bubble level while maintaining proper tension on the 3 calibration screws?
Thank you!
MP,
There's usually a little tool kit inside your total station case that will have the right gizmo to adjust the screws.
Dave
> A couple quick questions:
>
> 1: What tool is best for adjusting the calibration screws of a tribrach bubble level? (Also, what are those screws called?)
>
> 2: What is the proper technique used to adjust the bubble level while maintaining proper tension on the 3 calibration screws?
>
> Thank you!
I use one of these...
Instruction video pretty much explains it...
Matt
That's what we used.
We called them doughnuts.
> A couple quick questions:
>
> 1: What tool is best for adjusting the calibration screws of a tribrach bubble level? (Also, what are those screws called?)
>
The tool, I believe, is a capstan wrench. The screws are called capstan screws.
:good: :good:
The correct answer to the question as posted.
The question of how to maintain proper tension on the three screws is a good one; I've struggled a bit with this as well. Typically I'll snug them all up and then tighten the one(s) I need to in order to bring in the bubble.
and here I thought I was using an Allen wrench.
> and here I thought I was using an Allen wrench.
Don,
You may very well be. 🙂
> The question of how to maintain proper tension on the three screws is a good one; I've struggled a bit with this as well. Typically I'll snug them all up and then tighten the one(s) I need to in order to bring in the bubble.
I always press down slightly on the side of the vial when I'm done to see what the bubble does. It usually deflects a bit but I hope to see it gradually move back to centre. It often doesn't though - so it's definitely a skill to get it right.
> The question of how to maintain proper tension on the three screws is a good one; I've struggled a bit with this as well. Typically I'll snug them all up and then tighten the one(s) I need to in order to bring in the bubble.
I know the original post was about a bubble on a tribrach but a bubble I just replaced on a pole had a thin (I'd guess 1/16th inch) piece of rubber between the bottom of the bubble housing and the bubble cavity. I presume it was put there to keep tension on the screws to keep them from backing out. Yes, the bubble seems to hold adjustment well, even with the piece of rubber in there. This might be worth trying on a tribrach bubble.
The calibration screws on our rods have allen heads, however most of the tribrach bubbles I have seen have these:
I have noticed this as well, in fact I left that piece out on accident while replacing a bubble on one of our rods. It was nearly impossible to tension/adjust until I realized what I had done and replaced the little pad.
Perfect, thank you!
I've found they're usually in close adjustment to begin with, and the tiny bit of adjustment doesn't put undo strain on the bubble assembly.
If that isn't the case, backing the screws out, and then re-tightening them, once you're near level, incrementally with small adjustments applied evenly among the three screws, is the correct approach.
I put the instrument into the tribrach, fine level it, turn it 180 degrees and fine level halfway in, take the instrument out the tribrach and center the tribrach's bubble. Put the instrument back in and check it.