Press fitting pen parts requires a deft touch, but you don't need a special clamp or vise to do the job: I use my lathe and a pair of 1-1/2-in.-thick hardwood blocks. Each block has a 1-in.-deep hole drilled in it, sized to fit snugly over the lathe’s headstock and tailstock spindles. Remove both lathe centers and slip on the blocks. Mark the center of each block so you can precisely align the pen parts. Hold each part in place and carefully advance the tailstock.