That seems correct to me in every respect, though I would expect pencils that use other, more premium materials to last longer than that. I also was not aware that later iterations of the TK-matic had plastic chucks. The three I have (Al, green, and black) seem to be first gen.
2 Likes
similar images here.
2 Likes
Well, clearly for me thereās no performance difference. I donāt experience any lead slippage. Maybe I have an early model with brass chuck. Iām not going to disassemble it to find out, as the process can often result in an unusable pencil.
I have one mid-tier mechanical pencil with a plastic chuck that I had to clean due to lead slippage. Iād been using a soft lead which contributed to that. But after the cleaning, it was fine. Iāve never experienced that with brass chuck pencils using soft lead. If anything, what tends to happen is lead dust build-up coats the channel and possibly the chuck, making lead advancement difficult. And then I have to clean it out with metal wire.
3 Likes
Outside of abuse (including things like lab exposure to corrosive chemical vapors) Iāve yet to ever encounter any complete mechanical failure of plastic chucks in a typical pencil. And regarding slippage, Iāve run into cases, albeit infrequently, where it was variations in the diameter of the lead I was using. A .01mm variation can be enough to cause slippage if the bore is right at the margin. I havenāt checked many manufacturers but I do recall that Pentel hi-polymer lead is usually somewhere between .06mm and .08mm larger in diameter than the official size, at least for .5mm and up.
Automatic designs are a lot more complex, of course, and that just seems like the wrong place to me to be trying to economize.
4 Likes