Pencil shape in regards to lead hardness testing

[Ramson222]

I bought a set of pencils to test hardness with and would like to know how to sharpen them.
Should I just trim them back, until the wood part is no longer tapered. Or should I grind off the point until I get a full sized lead that is flat.
Is there some sort of sharpener I need to get which makes flat points.

[kevin c]

See post #53 in the stickies thread on pencil testing.

[Ramson222]

Read that already all 12 pages. Nothing was specified, other than full lead width and flat tipped.

[KenH]

You most likely got overwhelmed with all 12 pages, but post #53 gives detailed info on shaping the lead pencil. Too sum up,

#1, expose the round lead of pencil by removing the wood covering without damaging the lead itself. This should give a nice round "rod" of lead.

#2. Sand the lead end so it's exactly square with rest of exposed lead.

#3. Hold pencil at a 45⁰ angle so just the edge is cutting into the lead.

That procedure will give exact and very accurate results. If you just sharpen the pencil in a sharpener, then sand the tip flat while holding pencil vertical you'll still get "pretty good" results.

And do purchase the exact set of pencils mentioned in the thread. If I remember correctly it's Staedtler Mars Lumograph set of pencils for artists. Here ya' go: put this item number in the Amazon search bar and the correct set should show up. B0014E2S0Q

I've been using that method for a couple yrs now, works good. I did rig up a 1/2" steel ball penetrator for my Rc tester so I could put 150 KG pressure for 60 seconds. Measuring the diameter of the impression, doing the calculation gives very accurate results - this is the way they do hardness testing in a lab. The results of lead pencil agrees very close to the impression test.

Ken H

[kevin c]

My hard earned experience also taught me to not expose too much lead (the wood braces the rod against inadvertent side pressure and the breakage that comes with that), and to push on the end of the pencil, down its long axis, and not press down from the sides as I usually do when writing (same result - broken lead and cussing).

[Grmps]

http://castboolits.gunloads.com/show...rdness-testing

[kevin c]

Nice little trick, there, gramps!

[KenH]

Grmps, that's a perfect thread! Thanks for the info.

[Ramson222]

Yes thank you very much.

[DougGuy]

I actually use a vintage pencil sharpener that puts a real precision point on the pencil, and I sharpen the end of it not square to the center of the pencil, but at a slight angle like a chisel so that when I lay the pencil at an angle, the sharpened part is at 90 degrees to the surface of the lead I want to test. To each his own, this way works good for me.