Testing hardness with pencils
I've been reading all the various posts about methods and devices for testing alloy hardness. One post by Molly recommended using pencils of varying hardness to compare against the surface hardness of bullets and ingots. This is widely used in labs to test hardness of metal coatings by scratching the surface in a particular way to see if the pencil digs into the surface or glides over it.
After some searching, I found that Office Depot, a large chain of stationary stores here in the US, carries just what I needed - the Staedtler Mars Lumograph set of pencils for artists. Cost is $10 for the set of 12 wooden pencils in a flat metal case, already sharpened, ranging from 6B to 4H.
Molly said 6B pencils are same hardness as pure lead and H equal to linotype. Can anyone provide an approximate BHN number for the other pencils in between? These are 6B, 5B, 4B, 3B, 2B, B, HB, F, and H. The set continues on up to 2H, 3H and 4H, but if H is lino, I won't be using alloys any harder than that. BTW, I tried out the pencils on the base of a fresh bullet cast from what I believe to be Lyman no 2. F scratched the surface, but HB just left a trail of graphite on the shiny surface, as predicted.
I really like this method. Its quick, cheap and repeatable. No spring loaded devices, no ball bearings, no measuring indents with a digital caliper. Just apply the pencil and see immediately if it scratches or writes. You assistance in converting the pencil numbers to BHN is appreciated. thx - CW
Got pencil set at A.C Moore
went to local A.C Moore today Pencil set (see pic) was listed at $19.99 not $9.99 as was Office Depot.I got the manager and showed him the print out from Office Depot. He had no explaination. I told him I would buy the set at the Office Depot price or shop elsewhere. He say "Ok" Point is "My Mama said" You better shop around"Oh by the way I tested some 20-1 alloy i bought from a vender. It was 20-1 although I cant get it to mushroom when i use drilled out hollow points