I've seen a few Instructables as well as videos from all over the internet on how to turn wooden pens, but not very many on turning acrylic. Since acrylic is very different than wood to turn, it took me a while to come up with a good method. However now, after some experimenting, I've come up with a good and reliable method for turning this difficult material. You can find acrylic blanks like the one I used here. The hardware used was the Round Top European style. If you are in the US then woodcraft would probably have these supplies. Whatever blank or hardware you use, you'll surely have a unique pen. As well, I've also made a series of videos to go along with each step since it's import to see the cutting techniques in action. The best part is that the cutting techniques used can be applied to wooden pens to achieve an incredibly smooth finish before sanding.
Step 1: Marking and Cutting the Blank
Step 2: Drilling
Using a 7 mm drill bit mounted in a drill press, I drill a hole in the center of the barrel blank that goes all the way through. It's important that the drill bit is bought out frequently to clear the flute. This will also prevent the blank from being damaged. A "Quick-Grip" clamp is used to help hold the blank steady during the drilling process. If you have a vice for your drill press, I recommend using it (like the diagram shows).
Step 3: Gluing the Tubes Into the Barrel Blanks
Once the hole is drilled, grab the brass tubes that came with the pack. using relatively rough sandpaper, scuff up the tubes until they're no longer shiny. Once that's done, put a dab of gorilla glue on a scrap gluing surface (a paper plate works great) and a few drops of water on the brass tube (water helps the gorilla glue expand). Roll the tube in the glue and insert it in the barrel with a twisting motion. This is done for both tubes. Insert the tube into the corresponding barrel blank (long tube in bottom barrel, short tube in top barrel). Gorilla Glue is ideal because it expands 3-4 times with moisture, holding the tube securely in place.
Step 4: Flush-Trimming the Tubes
A "Barrel Trimmer" or "Pen Mill" is mounted in the chuck of my drill-press. I then turn the drill press on and slowly feeding the cutter into the blank, like my video shows. This done to each end of every blank.
Step 5: Mounting the Blanks for Turning
The picture shows the order of how the blanks are mounted. This will vary for different hardware styles but usually instructions for mounting the blanks are provided. There is one free-spinning ring used for sizing up the tennon for the center band. This ring is "noted" in the picture. The order for the Round Top European goes as follows: second-largest busing first, top barrel second, stepped bushing (with largest ring slipped over smaller half) third (with smaller half up against the top barrel), bottom barrel fourth and smallest bushing fifth. Or, you can just watch the video.
Step 6: Roughing Out the Blanks
To get the best idea of how I roughed the blanks down, watch the video as well as read the following sentences. I use a small spindle gouge the take light passes so the acrylic doesn't shatter. It's important to know the proper cutting method to use with a gouge. Lean the tool into your cuts. Make sure that the tool rest is close up to the work piece. As well make sure that the edge that's cutting has an adequate amount of support. If the tool isn't supported enough as it cuts, you will experience a catch. A catch will usually scar wood. I've never had one on acrylic, but I imagine it could compromise the blank.
Step 7: Final Turning - Top Barrel
Now the the pen has been rounded a bit you can start on finishing the barrels up. I start with the top one. To achieve the smooth finish on the acrylic necessary for a scratch-free finish, you will need to know how to bevel a skew chisel to make fine sheering cuts. The video I made shows the proper method for making these cuts. Hold the tool so it has a substantial amount of support. Then touch the bevel to the work-piece and lean it into the material and begin shearing off fine shavings. A tennon is also cut (to accept the center-ring) using a parting tool and the sizing ring (the largest of the bushings). When the sizing ring fits over the tennon snugly that means the center-ring will fit well too. The rest of the Barrel is shaved down until it's just about flush with the sizing ring. Remember not to make this too close of a fit since sanding needs to be done.
Step 8: Final Turning - Bottom Barrel
The bottom Barrel is shaped using the same cutting method as the top one except there is no tennon. The video shows how it's shaped. It tapers down to the smallest bushing with a neat contour. Make this Barrel any shape you want as long as it fits into the 1/16" of the center-ring that over-laps. Also make sure that it's comfortable to write with.
Step 9: Sanding and Polishing
One of the most difficult parts of turning acrylic is achieving a smooth, scratch free finish. During the sanding process, I start with 150 grit and finish with 12000 grit. The order of how I sanded goes like this: 150, 200, 400, 600, 1500, 1800, When I get up to 1500 grit I start using Micro Mesh sheets. The Micro-mesh sheets I used can be found here. The most important part about polishing is to not apply a ton of pressure. Sand very, very lightly. Back the micro mesh sheet up with a paper towel if necessary.
Step 10: Assembly
Assembling the pen is relatively straight-forward. Assembling this pen is no different from assembling any other turned pen (If you are using the Round Top European hardware). As my video shows, the threaded insert is first pressed into the top end of the top barrel, then comes the clip and clip screw, after that the nib is then pressed into the bottom end of the bottom barrel, then the twist mechanism is pressed into the opposite end of the bottom barrel, then the center-ring is glued onto the tennon and then the ink cartridge screws into the end of the twist mechanism. Finally, this pen is ready for use! These pens are very unique whether your using Slimline or Round-Top European hardware and when all these steps are followed, the results are remarkable. They could also be engraved if you had a method for doing so. I'm still trying to figure out a way to accomplish that using a Dremel.