hardness tester question

[fast ronnie]

I want to build a hardness tester similar to the Cabin Tree. Does anyone know what the angle of the point is?

I also would like to know the size and pitch of the penetrator threads.

I would like to use the chart from a Cabin Tree so that I'm not out in left field as to the hardness compared to the indicator reading.

Any help would be appreciated.

Ron

[Crusty Deary Ol'Coot]

Ronnie,

It appears that the bolt on the penetrator is a 3/4" N.C. bolt. I can't tell you what the angle is on the penetrating point and considering the point barely penetrates the bullet during testing I'm not sure it is critical.

I think more important is the fact that during testing, the penetrating point is rotated one turn AFTER it contacts the bullet's surface at which time the dial reading is taken.

The National Course (N.C.) thread pitch would establish the distance the point travels during that one turn rotation.

As said, on my bullets which test mostly in the 15 - 22 Brinell hardness range the "penetrating" point barely dents the alloy.

The dial indicator is a "mhc" Industrial Supply product.

Crusty Deary Ol'Coot

[fast ronnie]

Thanks. Got about 600 pounds of 1.8 pound ingots I need to check.

Ron

[popper]

Cabintree tester works by measuring the movement of the boolit when a force is applied to it. hooks law, x=F*K where K is spring constant. Angle of point is not that important but the area of it (PSI). K can be determined experimentally. Lee uses a ball as it measures the size of indention for a given force (spring applied). A more precise method uses a strain gauge, lever arm and indenter that allow a fixed displacement of the indenter. An oler type rig would work. Piezo pressure sensor would work but it doesn't have DC (static) capability so a strip chart has to be made and peak detected.