Warning!!! This is not for beginners/novices. For professional users only.   So.... Image 1   Image 2   I'm having a long conversation with stihl about dropping a file size when the chain is about halfway done. As the side plate angle goes to 90degrees, or you file into the tie strap if you use the same size file. Either is not good.   My boss (a very knowledgeable and a decent bloke) totally disagrees. Same size file all the way.   Stihl GB have been very thoughtful, this is their email.