I did my first closed-end pen last weekend. Most of what I did was 'ad hoc'.
I was doing a slim with a 7mm tube, so I drilled the blanks using a 7mm bit. I left the blank that was to be closed longer than the tube, and only drilled deep enough for the tube to bottom out, leaving about 1/2" of wood at the end of the blank with no hole. When I glued the tubes in (I used polyurethane glue), I made sure to not use too much glue - I didn't want it to fill the hole and work its way back up inside the tube. Finally, I glued a small scrap of wood on the closed end to serve as a waste block that I would later part off.
I used a piece of 1/4" all-thread clamped in a Jacobs chuck mounted into the morse taper of the headstock on my lathe as the mandrel. I could have used a real mandrel, but since I was experimenting, I opted to use a piece of all-thread rather than an expensive mandrel. I loaded the rod/mandrel in this order:
- a short piece of HDPE next to the Jacobs chuck
- a 7mm slim bushing
- the first blank (the one with the hole all the way through)
- a 7mm slim bushing
- the second blank (the one with the closed end)
The, I used the live center in the tail stock to apply pressure on the closed end of the blank. The purpose of that scrap of HDPE was twofold - to protect the jaws of the Jacobs chuck from tool slips, and also to have something slightly resiliant on the shaft to absorb the axial pressure from the tail stock.
I turned the double-ended blank normally. I turned the closed-end blank all the way into the small waste block, with a cove centered on the glue seam between the blank and the waste block. After sanding both blanks, and I applied two coats of thin CA/BLO followed by four coats of medium CA, then smoothed the finish through 12000 MM, and finally polished them with plastic polish.
The final step was to part off the waste block, back the tailstock away from the workpiece, smooth the end, sand, apply a small dab of medium CA, and then polish the end with plastic polish.
I was actually practicing for doing something similar with a 10mm kit. In that case, everything will be the same except that I will use bushings for a 10mm kit. 10mm bushings are different in that they are stepped, and the tube actually slips over the bushing. This presents a problem at the closed end - the 1/4" rod/mandrel will be smaller than the ID of the tube. To solve this problem, I have another small cylinder of HDPE that has a 1/4x20 threaded hole so that it screws onto the rod/mandrel, and that I've machined to have a OD that just fits inside the 10mm tube. So just before sliding the closed-end blank onto the rod/mandrel, I will thread this onto the end of the rod/mandrel where it will act as an internal spacer to keep the blank centered around the rod.
The only other thing that I would do differently in the future is that after parting off the end of the closed end blank, I would dismount everything, and then load the closed end blank alone onto a different, shorter rod/mandrel. I think that working that unsupported end would be easier because there would be less runout.
