I suspect there isn't a simple rule of thumb - a lot would depend in the size and geometry of the crimp and the relative size of the tool. For small lugs (e.g. for ≤4mm²) even a cheap ratchet crimper will likely compress pretty much the whole tube in one go - and subsequent attempts may do more to disturb the first go than provide any improvement. Bigger stuff and relatively thin jaws on the tool I could see might take a few goes to compress a decent length of the tube.

   - Andy.

If you use Cembre (I think its pronounce Shum Bray) then they have a guide on what kind and size of lug for what kind and size of cable.  It also advises what type of crimp machine and the crimp head with the recommended amount of crimps required per lug.  Probably the biggest thing to consider is the application of the lug.  Eg 4mm2 CSA CPC for a domestic CU vs and 50mm2 CSA for a distribution unit or if the lug is for an ATX eviroment

Thanks. I am aware of Cembre's instructions - but it is worth noting that for the same size and nominal spec it does vary from manufacturer to manufacturer no doubt due to die width, barrel thickness, assumed tooling and other details.

I was more wondering if there was a generic table or rule of thumb, perhaps one that gets taught in college, that contractors might fall back on.

Reason for asking is that I have a situation where the manufacturer's guidance clearly hasn't been followed and before embarking on a crusade I thought I'd make sure I wasn't missing something obvious.