I have filed a groove into needles like that in the past so that it can be adjusted with a flat precision screwdriver. I just unscrewed the outer brass bit so the needle comes out with it and then you can hold the outer bit in one hand and wind the needle out so you can file a groove in the end. Some needles are glued in and need to be warmed with a lighter until the glue melts before you can unscrew them.