I haven’t gotten to the mine yet, but don’t workers take tools straight from the resource storage if there is none in their station chest? If it’s not working for your mine they may have a proximity on how close they need to be for this to work. In that case just build a resource storage near your mine and you should be set. You could make a worker at the smithy produce pickaxes for them too and you wouldn’t have to touch them at all after that.