I found a decent scrapyard lately and bought a 2000 mm of spirit level. It has a broken vertical vial.
The precision of this level is one millimeter per meter (0.057 degree.)
The vial was glued on two plastic plates. I destroyed one of the plastic plates before I removed it.
Two days ago I went to the scrapyard again to buy few stuff. One worker was to offer the poor spirit level for 2,000 KRW to me. When I heard it, I chuckled to myself ‘Is she serious? Maybe there are customers who buy such out of shape levels.’ I told to the worker.
“The condition of the body is so battered, it’s a useless level except the vials.”
There was a moment of silence. Then suddenly the worker said
“I’ll give it to you for free.”
My response was “Are you sure?”
because I know that sellers hardly give any product for free to customer.
“Yes, take it.”
“Thanks a lot.”
When I came to my workshop, I immediately started removing the vertical vial. It took about 10 minutes.
Checking alignment of the vertical vial so that it indicates true vertical line. I drew two straight lines in parallel using the two spirit levels as guide. Right side one is done by the 300 mm spirit level.
Two parallel lines have equal distance between any pair of points that lies on a line that crosses the parallel lines with right angle. I measured distances between the lines along few positions using a straight edge. All the measurements were close to 53 mm.