I have a gas lens setup. I've been using some new no-name nozzles I got on eBay with my 200A air cooled #26 torch. In the middle of a weld the top third of the nozzle cracks off right at the shoulder. At first I thought the ceramic or the manufacturing of the nozzle was defective but then I realized that the collet body is pressing up against the inside of the nozzle and putting it in tension leading to the crack. I compared the new nozzle to some of my old ones that have never been a problem. It turns out that the new ones neck down about an 1/8th of a inch sooner than the old ones. (Probably nothing, but I notice too that the new ones are a much deeper pink color than the old.)
More specifically I'm using a 45v26 collet body with a 54n16 nozzle which I'm pretty sure are supposed to work togather. I have a #26 weldcraft flex-head 200A torch. I'm using both the nozzle gasket and the gas lens insulator one after the other just like mom taught me. The combination of the two still don't make the nozzle seat forward enough.
If I could find a spacer washer made of whatever those white plastic is (delrin?) that would probably fix it-- or better yet one insulator that's just thicker.
Help I can't weld until I solve this problem!