Is it new? If its new its perfectly normal: its probably not thread but just a collection of metal which has been scraped + scratched off another surface to create the shite your'e seeing. Heres a quick cleaning/checking guide for you to tick off and follow: CHECKING THE HUB SHELL If its jammed, pull the driver out and give it a good ol clean, remove any grime, oil and grit and see if everythings ok. the ratchet ring (bit with teeth, inside the hub shell) should be fixed solidly and not move. Check that the wheel spins nicely without the driver inside by picking the wheel up by the axle and give it a spin. To be honest its very rare that theres a problem with the hubshell, more often than not I found (actually come to think of it I only ever had 1 problem with my profile... :confused: ) that the driver would be the issue CHECKING THE DRIVER OK first off play with the pawls, make sure the springs are all present + ok and all the pawls are there too lol. They may not feel super smooth when you press them in but so long as they move with little force and return without assisstance, they're all good. Next give the flat bit of the driver a clean and remove any shards of metal from there. You may need to clean the .5mm or so gap between the driver + the driver bearings too. Other than that, check the sprocket is fixed and tight and the bearings are smoothish otherwise thats it I know its stating the obvious really, but its worth checking those anyway. Hope it helps, sorry if it doesn't but add more info and id love to help out