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Many years ago I was purchasing the Pentel P200 series of mechanical drafting pencils. They worked great until I started using them in construction while building my daughter's house. I was breaking the plastic sleeve regularly enough that I decided to fix the problem. I machined an aluminum sleeve to replace the plastic one and haven't broken one since.
I also made a mandrel to hold the sleeve while machining the surface. This speeds the operation and achieves better accuracy.
I fill the grooves in the sleeve with an acrylic paint that is color coded to the lead size in the pencil. Yellow is for 0.9mm, blue is for 0.7mm and black is for 0.5mm. These are the colors of the plastic sleeves on the original pencils. I also have one that is filled with red lead, therefore the grooves are red.
After the sleeve is complete, I polish it and then coat it with a clear sealer to prevent oxidation.
Starting with 3/8" aluminum stock, turn the end 0.236 x 0.052
Drill a #21 bit 1" deep. Turn approx. 2 1/2 degree taper.
Cut grooves for a better grip or just for looks. I used a 60 degree threading tool spaced every 0.080" x 0.020" deep.
Reverse the sleeve and trim to length (4.440"). Drill 1/4" x 3.75", then drill #15 x 4.27" and finish with a 17/64" x 0.8" deep.
Mandrel I built from 12L14 to hold pencil sleeve while finishing the outside.
Turn down sleeve surface to 0.361 to eliminate imperfections in the surface. Turn pocket clip recess 0.80" from end, 0.015 deep by 1/4" long.
The top yellow pencil survived building a house, the bottom two blues ones are brand new. I build them now to give as gifts.
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