I'm still inexperienced having turned pens for only 6 months though I've sold more than 60 pens in the last few months and whilst none have been returned (yet).
I couldn't tell the difference between a good and poor plating but have been surprised at the lack of accuracy in the manufacturing tollerances.
I've had tubes that won't fit on the mandrel with others distinctly sloppy and this clearly applies also to the other components as I sometimes need to try fit several before I find something suitable. Failing that I have to glue in the part or file out the tube - crazy and annoying.
I've had a broken sierra mechanism and slimlines that will hardly turn without using ptfe spray whilst a couple of others are so slack that if you push hard when writing the point retracts. Needless to say, none of these were sold on.
I've bought kits from numerous places now (except the USA) but like the dork I am, can't always remember where so when it happens I sometimes can't remember who sold me the kit. Why doesn't everyone put labels on the packets?
I'd like to buy kits from America but the costs put me off as I don't think I can sell for enough of a premium.
Favourite pens for me so far are the stratus and vertex click pens which feel solid and have a lovely smooth mechanism. I've given up on pencils and won't buy any more after using what I've got as they seem just too fragile for my liking.
Bob