251SI Gas fitting change

I'm getting tired of changing these fittings. I have many welders and NEVER have broke another but on my 3rd from Everlast. I'd like to just put a long nipple and another standard gas fitting I can get in any welding supply. Yes I realize it will be just hanging there but I can deal with that. I just can't deal with cheap parts that throw the whole project timeline off.
I believe i measured the inner small pipe as 3/8-24 fine thread and the gas connection as 5/8. Most 5/8 i see have 1/4 inch mpt on the inside and I think i need a reducing nipple but not seeing npt to fine thread. Can anyone confirm or point me in the right direction?

Attachment 14238

They break from over tightening. Very rare problem unless you put excessive force on it. Are you holding one side when you tighten the other as well? (using 2 wrenches)