Reliable method to meaure metal thickness

[langy]

Nothing like over thinking a job is there

Just find an edge somewhere and measure that

 

[steviec_lj]

BMW body panels are usually 0.8mm.

Replaced enough over the years.

This is where I get all my car panels/steel from: http://www.carz2.co.uk/misc-steel-c-589.html

 

[500e]

http://2.imimg.com/data2/LR/MC/MY-908091/measuring-tools2-500x500.jpg

Still using my fathers
1 Brown & Carpenter Pennsylvania US
1 Roebuck
1 Starett All Must be 70 years old.

 

[Wedg1e]

mk - I guess you haven't seen the small handheld units. we have a couple at work, and they're used to tell pipe work and tank thicknesses. it'd happily do bodywork. but it wouldn't be worth purchasing yourself.

I could hire you one...

Actually, this reminds me of a demo I did to an inspection company at a fuel storage depot. The fuel is in those big tanks you see at such places; the tanks are ferrous and they rust, so the tank farm operators keep painting them.
Periodically they get someone with an ultrasonic thickness gauge to come along and check for loss of wall thickness. Obviously several hundred square yards of plate is going to take a while with one of those, plus the scaffolding that needs to be erected...
Anyway, we had a thing called Scorpion which was like a wire-guided model car. It had a humungous magnet in its belly that meant it would 'stick' to the vertical wall of the tank while you 'drove' it around. On-board was an ultrasonic probe that was 'coupled' to the tank wall by a ball made of a special rubber (normally you'd have to use a gel couplant, think pre-natal scans but of course you couldn't carry enough gel on the Scorpion, hence the ball).
So I stuck the Scorpion on the tank and we set about taking some measurements. Within minutes we had large areas of the tank looking like it was paper-thin and about to pop! A ladder and a hand-held gauge were produced and eventually we deduced that the paint was the problem: so many coats had been applied over the years that previously-delaminated rust was being held in place on the tank wall; the UT probe was measuring the thickness of the rust, not the wall!
Obviously the only solution was to clean the entire tank back to bare metal and then scan it, but that wasn't a cost-effective option either so they erected scaffolding and did it the old, slow way.

A few months later there was a bit of a bang and some smoke... it was Buncefield. I guess the tank wall corrosion was the least of their problems...