Thanks for the inputs everyone. Not surprising that the #2 pencil is clearly the most widely preferred. The simple pencil just fails me too often: Short use before re-sharpening. Easily breaks in use or in your pocket. No indigenous pocket clip. Cheap ones don't sharpen reliably. Must have a separate sharpener. I'm in search of something "better" for the primary purpose of marking off turning partitions. Not impeaching the pencil users. Certainly a simple, cheap and workable solution. One I've used myself quite often.
I was hoping for some imaginative solutions I had not thought of. The mechanical carpenter's pencil is the only "new-to-me" thing I've seen suggested so far. I had seen the Irwin "carpenter tip" things, but I don't care for those for any kind of woodworking use. As I said I have been using a carpenter's pencil of late, but it is only slightly more durable than a #2.
I have some Staedtler 2mm lead holders. Will give those a try, but am skeptical it'll be much more durable than a #2. Maybe a little because it is thicker.
I have a Pica mark-on-everything deep hole ink marker. It does mark on everything nicely, but mine leaks and can make a mess. I haven't tried their lead version. Has some promise with the thick lead.
I also have 0.5, 0.7, and 0.9 pencils. None are tough enough IMO for turning. The 0.9 is OK though.
Someone suggested/uses chalk. I have some and some marking crayons too. I'm not real fond of chalk dust though. Maybe the marking crayons. But both fail the same areas as a pencil.
I had also picked up some disposable grade school mechanical pencils that use a lead I think is a little bigger than 0.9. My thought process was that these were cheap enough to use and throw away. What I found is the plastic housing just doesn't hold up and also tends to wander on the tool rest due to the convex shape.
As for the comment that the 5.6 will be 1/4" wide when dull, thus requiring sharpening just like a pencil: I expect the fat lead to break less frequently and require less sharpening than a #2 by a large margin. Unless you are doing identical replication work, a fairly wide line is also sufficient to mark for proportioning purposes. I may not be able to use until it is completely blunt, but it should go a long way before it reaches that point. Besides, because it's all lead you can probably rough sharpen in on a smooth rounded area of the work piece by simply laying it over on its side while spinning the wood. Further, the selected lead holder also has a built-in sharpener, always at hand if sharpening is called for; no separate sharpener to lose. The point is retracted and protected when in my pocket, while being secured by the pocket clip. The venerable pencil fails in all these areas. I'll report back on the 5.6 mm lead once I get it and use it a bit.
If anyone has something "new" to suggest, please post it. I'm looking to improve on the wheel......uh I mean pencil
