Hi all,
I am looking for a mechanical pencil that uses all the lead stick. All mech. pencils I have used waste one-third of it. Any suggesstions?
Dr Whom
Welcome to the boards. 
You don’t say where you’re posting from.
Here in the UK a plastic propelling pencil costs about £0.50 ($0.90).
For that I only want it to work reasonably well. (I have about 4 sitting on my desk as we speak, because there was an offer on them…)
I think the problem with a mechanical pencil using all the lead would that the lead advancer would have to be very close to the pencil’s tip, making the tip of the pencil considerably thicker and more difficult to use.
Either way, each piece of lead would only cost about 5-8 cents anyway and there’s probably other areas you could focus on waste management much more effectively…
Bic used to make a refillable (cheap) mechanical pencil that used all the lead. I don’t recall precisely how it advanced the lead, but you clicked the top like a pen in order to push the lead out. If you were careful, and didn’t break the lead, it would use all of it if I recall correctly. You were also able to push the lead in a bit by clicking the eraser and gently pushing the lead back until it was the length you desired. I am not sure if that version is still available or not, or it you would be able to find it. Perhaps online? Good luck.
Adding, the barrel of the Bic mechanical pencil (they were yellow, with erasers on the top that pulled off to put lead in, it could hold more than one stick too I think) was of a uniform diameter. I remember there were springs in the pencil top mechanism, but I don’t recall the contraption that pushed the lead out. It’s been too long since I used one, they were part of my school supplies.
I´m in love with my Faber Castell 2mm clutch pencil ever since I first held it in my hand, even more when I removed the metal clip on it´s tail; it´s a great mechanical pencil and the thick lead makes sketching a pleasure.
Also there are colour leads available!
And yes, it uses the whole lead.
My trusty mechanical pencil used to be a Pilot, a wonderful instrument, but I’ve switched to the more available Pentel PS535 in the last few years. It has a sliding sleeve that fully retracts into the instrument. I do estimate that I lose about a fifth (not a third) of each piece of lead. Each piece costs about 8 cents, which comes to less than 2 cents thrown away per lead. That’s tolerable for me. What’s more costly to me is a replacement erase!
Thanks for the great responses. I’m the suburbs of Chicago, IL. While I know the price is cheap for lead, waste in any for is wasteful. Price is irrelavant.
Dr WHom
I used Rotring mechanical pencils all through Architectural school. Once the lead was to a point where it wouldn’t advance I usually just put in a new piece of lead behind it. It would push the smaller piece down the shaft. Zero waste.
Modern mp’s mechanism is for convenience of clicking the eraser to feed a bit of lead, has and internal rubber clutch, if any. Find one using long lead.
I have several older pencils using short lead, and a screw feed, clutch at tip that holds all but the last 1/8" of lead. I have a double ended, two color pencil, in front of me now, intended for red and blue lead for marking up anything you want to make distinct notations on.
So the Latest is not always the Greatest 
If US/CAN send email.
I used to have a mechanical pencil that instead of clicking you turned the end. That turned a corkscrew inside the pencil that had a metal pin with a prong in that spiral, as you turned it it moved the pin up or down, that pin pushed on the lead, and would run the lead till the end.
That’s the old fashioned one made by “Skillcraft” and others. Hard to find if at all.
That is what DRWhom is looking for. Maybe he’ll call back.
The modern ones use longer lead, feed one stick after the other at the click of the eraser top and waste lead.
Ah yes, think of all the poor starving children in Africa who could be saved by the graphite we carelessly throw away every day… 
My Rotring 600 allows you to advance the next piece of lead while the previous one is still in the tube, making for essentially no waste.
Go to drafting or engineering supply. Quality and cost are much higher.They use all the lead. PS .2 mm is really easy to snap the lead. I prefer a 7 or 9