leadlock

[buckley plumb]

hi can anyone spread any light on leadlocks fitted a few but some seem very loose or very tight.the one i did today the nut slid on but i had to stretch the split grab ring so the gap in the ring was 4mm - when fitted what should the gap be approx (this was a 9lbs lock ) the 7lbs locks seem loose the gap on the grab ring is about 1mm or loose but never had one blow off.

ant

 

[JCplumb]

If you get the right size they do seem to be too loose before you nip them up, but that's just how they are. I wouldn't worry about it.
Due to the nature of lead and it's differing sizes/weights etc. I think they make them with a good bit of room for varying pipe sizes, 4mm seems a bit high, I'd say it's usually 2mm ish. You know when it's tightened up though if it's a good grab.
I do always mention to customers that a leadloc is not ideal but are fitted as common practice and that lead replacement is the real solution. Cover your back with an advice notice mentioned on the invoice.
Like you though, I've not had one blow off.