Sunday, May 31, 2009

A Pentel-Based Mechanical Pencil - Start to Finish

I've enjoyed making these Pentel mechanical pencils so much I figured it's time to share the process. I'm using sappy walnut for this walkthrough.

The tools are:
  • Lathe- A Turncrafter Pro 5-speed lathe from PSI
  • Drill Chuck- MT2 drill chuck from Harbor Freight
  • Dead Center- Generic MT2 dead center
  • Live Center- 60* live center from Woodcraft
  • Step Drill Bit- Step drill bit from rherrel on
  • Step Mandrel- Step mandrel with steel and delrin bushings from rherrel on
  • Scroll Chuck- Generic scroll chuck came with the lathe
  • Your chosen sharp pointy things- I generally use a roughing gouge and a skew for these
I first choose the material. Here I used some interesting sappy walnut. For a lighter color, I use air-dried wood. If I want it darker, I will either stain the air-dried wood, or buy steamed walnut.

Square the end then measure it against the step bit. From experience I've found that I like the length from where I mounted the stop on the bit to about halfway down the small end.

Cut the blank at the mark using the same tools you used to square the end. Mark the centers of the blank and drill a small shallow hole to guide your centers. Mount the blank on the lathe between centers and rough it round.

Take the blank out and remove the centers. Mount the scroll chuck on the headstock and loosely mount the blank in it. Mount your drill chuck with the step drill bit in the tailstock and line the bit up with the hole in the blank from the center. Assuming your drillstop is set up correctly, you can now drill the pen's hole.

Drill as you would any other blank, 1/4" at a time, backing out to clear chips and keep from overheating the bit or the material. I like to rest the drill stop against the blank's end to burn it square. I usually get it pretty good off the table saw, but this also helps define the click end nicely.

When it's drilled, remove the blank from the chuck. Remove the drill chuck and bit, and mount your live center. Mount the mandrel on the scroll chuck (or a collet chuck if you have one) loosely and bring the live center up to the mandrel. When you tighten the scroll chuck, the mandrel will be perfectly aligned with the tailstock.

With many woods, particularly softer woods such as this sappy walnut, stabilization is needed. I prefer CA glue.

Pour thin CA glue into the hole, making sure the wood is fully saturated at the nib end where it is thinnest. I will also saturate the click end because that gets some abuse as well. The center of the barrel won't generally need to be stabilized unless it is a burl or spalted wood. Then you may need to saturate the entire blank.

I am using Titebond's CA glue here because I was out and that's what Woodcraft (I think) sells. Use what is most cost-effective or available to you.

When you're done soaking the wood in CA, let it cure for a few hours minimum. While the outside may be dry, the CA inside the tube might still be sticky or even really wet.

At this point you will need to re-drill the hole. I just hold the drill chuck in my hand with the bit still mounted. Gentle turning by hand will smooth the hole and remove any runs or blobs without removing any more wood.

When you're done, mount the blank on your step mandrel with the steel bushings. Loosely tighten the nut then bring the tailstock up snug enough for the live center to turn when you spin the mandrel. Tighten the nut on the mandrel finger tight, bring up the tool rest and go!

Turn the shape you want for your pen, but larger than the final diameter. I like to rough it big, then pare it down to size with the skew. Final sanding will take it a bit undersized, the difference to be made up with my CA/BLO finish. If you want a different finish or don't want to build it that much, make sure your sanding takes it to the final diameter.

As mentioned, I use a CA/BLO finish on my pens. The BLO will darken most woods, but more importantly it acts as a lubricant and accelerator for the CA. Using this method, I can put 10 very thin coats on in 15 minutes. Makes for an extremely durable and beautiful finish that can be done in a few minutes instead of days.

This pencil I made "beefy", a more masculine shape than is usually found in pencils. In the final photos, you can see it compared to a more typical pencil, in this case one made from curly jatoba.

I hope this walkthrough helped you decide to start making some Pentel-based pencils. The Pentel Sharp mechanism is miles better than any pencil available as a "kit" from the usual penturning suppliers. And it's available in 0.5, 0.7 and 0.9mm sized leads.