Before I start on this repair, I will give you a little history lesson about me and this 6" engineers level.
Many years ago, I did a short stint in a metrology lab, a time I didn't really enjoy, but it has helped me now. These levels were the type we used in the factory, and it was one of my jobs to repair and calibrate them (much finer than I am doing here, because we had specialist setting equipment).
A few months ago, Stew asked to borrow my level to set up his machines, no problems normally, and I thought the 6" would be easier for doing the job. After getting it out of my instrument cupboard, I noticed that the vial was empty of liquid, so Stew went away with the 12" one, and I was left with a level with no bubble.
Last week I bought a replacement vial @ 16 squid each (a new level is well over 100 squid), anyway, the company had a min order of 50 squid, so I bought 3 spare vials and a few spare mini vials that are fitted to these levels. No worries, I am sure that another will be broken at some time, or if anyone needs a new vial, I can let them have one without going to the company.
So here is the faulty level, and the very fragile glass vial. The vials aren't too bad, it is the tiny heat sealed tube at the end that is the real problem bit.
The two end holes are where the screws are that keeps everything together, and once removed, everything just comes apart.
The end plugs come out once the retaining screws are manouvered to sitting inside the plugs, and the vial protective sleeve slides off.
If you look into the end, you will notice that the vial is retained in position by a layer of plaster of paris.
The plaster breaks up very easily, and soon the whole lot comes apart. As I suspected, the small sealing tube had snapped off and the liquid had gently drained and evaporated away. I must have at one time, rough handled the level, and caused this to happen. The coloured card is there just to give a background colour to the vial, and you could put almost any colour you want in there.
So now to the assembly.
First off, the backing card is put in and gently followed by the vial. Until the vial is stuck in, it is very fragile because of what was mentioned earlier.
I then centred the vial up in the aperture. This isn't critical, close enough is good enough, but it is better if you can get it very close or spot on.
Once centralised, masking tape was used to hold it in position.
I got to this point yesterday, and when I went into my storeroom to get the sealing plaster, it wasn't there. I must have thrown it out sometime.
So at first light, I was on the trail to get something to stick it in with. We don't have any hobby or craft shops in town, so plaster of paris was out of the question, and I decided to use fast setting, non shrink, crack repair, that is used on plaster walls. That should be perfectly good enough.
It was mixed up to a consistency where it would stand up in a peak and not collapse, just like when making meringue.
This was then put into the tube to a depth of about 3/16" on each end of the vial, taking great care not to damage the glass seal.
After an hour, it was set enough to clean up the overspill and assemble the unit back up.
The bubble length in each individual vial is a different length normally, so each level has to be set up to that bubble length, getting it spot on central.
But unless you are in a metrology lab, you will be hard pushed to find something that is perfectly level. If you can find somewhere that is a nice flat surface, and somewhere close to level, you can use that for your setup.
I used an area on my mill table to do it, and marked up an area that was to be used, so that the level is set up on the same position each time it is turned around. As you can see, my table isn't level, it is maybe six thou out over the 3ft table length.
You use a combination of slackening and tightening all four screws to end up with, when the level is turned thru 180 degrees, the same reading.
This is the first side.
Turned around, and this is the second reading. Very, very close, and this will do for now. I will let the plaster set for another day or so, then recheck and fine tune it if needed. As you can see, the table is one division out of level on both ways.
I popped the 12" onto the table in the same sort of position, and again, that shows one division out.
So I am now happy that the repaired level will be plenty good enough to be used in my shop.