wrTie has begun!
To start off my titanium mechanical pencil build, called wrTie, I decided to teardown a number of different mechanical pencils for inspiration and design ideas. I find the mechanisms in mechanical pencils very interesting. I also find the manufacturing processes that are used exceptionally interesting.
Here is a teardown video of my favourite mass produced mechanical pencil: the Pentel P209 (0.9 mm version). The Pentel P20x series (there are 0.3, 0.5, 0.7 and 0.9 mm models) has been around for a long time. It is exceptionally well made given the price point it is hitting and the parts involved. There are 12 parts in total, including 5 fully machined parts. A number of the parts require plating. There are 2 parts that are molded out of plastic. And then it has to be assembled! You can buy a Pentel P209 for less than $5 in the United States and less than $7 in Canada. That’s actually pretty crazy considering this pencil contains machined parts and even more so once you consider that Pentel is probably selling it to it’s retailers for less than half of what they are retailed for.
The heart of the Pentel 200 series is a removable fully contained feeding cartridge. The cartridge features a number of machined components in the feeding mechanism. The components are probably massed produced on swiss style screw machines (a lathe but instead of the carriage moving the spindle moves in the Z direction – often called sliding headstock machines). These machines could be cam actuated screw machines or they could be CNC controlled units. CNC swiss style machines, like the ones produced by Star or Citizen, are really interesting machines. Here is a video of a Citizen L20, one of the more popular CNC swiss machine that you will find today:
The Pentel P209 cartridge has been used in a number of titanium mechanical pencil builds on Kickstarter. I can’t confirm it directly as I haven’t purchased one, but check out this project (you have to scroll about half way down and you’ll see a picture of what looks to be the Pentel cartridge: https://www.kickstarter.com/projects/cogent/titanium-mechanical-pencil-and-titanium-pen. Given the Pentel’s design, you could easily make a new mechanical pencil by machining a new outside body for the Pentel. I won’t be doing that because I think it is too easy!
thecogwheel 
I have exclusively used the Pentel P205/P207/P209 over my 34 year career in mechanical engineering. I have tried others but never found one I liked better. I used the 0.5mm for many years but have found as I get older that I like the 0.7mm and 0.9mm better….probably because I now require more pressure on the lead in order to write neatly. I do also have a P203, but only use it for special situations. It has a sliding lead barrel to maintain full support the fragile 0.3mm lead.
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