TexasMac's Web Site
1) HB is the same as a common #2 pencil
2) WW (wheel weights) – Depending on the manufacturer, wheel weights can
vary in hardness from 8 to 13 BHN.
3) An excellent high-quality set of drawing/drafting pencils is the Mars
Lumograph set made by Staedtler Mars GmbH & Co. ($10 to $15 at office
supply stores). Ranging in hardness from 6B to 4H, the set comes in a nice thin
aluminum box, which is easy to take along when searching for scrap lead. But
other brands of good quality pencils can be used including mechanical pencils
with replaceable cores of known hardness.
4) For lengthy discussion on the pencil test go to the following link: http:
Simple low-cost hardness tester
Finally, if price is the overriding factor, you can make a simple low-cost tester
with a single ball bearing and a vice, as long as you have access to a small
amount of lead or lead alloy of known hardness. Knowing the hardness of the
reference material is the key to this technique. The results will be at least as
accurate as using one of the commercially available testers noted above.
You’ll need two bottle caps, a vise, a ¼” to 3/8” diameter ball bearing and a
sample of lead or lead alloy of known hardness for the reference material. Pure
lead is an excellent reference material since it has a known hardness. You’ll
also need a caliper for measurements.
1. Start with two steel bottle caps. Set the caps on a brick and heat with a
propane torch to burn out the plastic inner seals. Let the caps cool and dump
out any burnt residue.
2. Melt enough lead to completely fill one bottle cap with the unknown
sample, and the other with the known hardness reference lead. The surfaces
should be as smooth and flat as possible when the lead hardens and cools. You
may have to skim off some crud or oxides and re-melt the samples a couple of
times to obtain good surfaces. Allow the samples to cool by themselves (do
not quench with water to speed the cooling).
3. When the samples are cold, put the ball bearing between the two lead
surfaces and squeeze the "sandwich" in the vise until the ball bearing is driven
partly into both surfaces (just enough to make fair size indentations, but
definitely not past the middle of the ball).
4. Remove the sandwich and, using the caliper, measure the indentation
diameters as accurately as possible. Using the following formula, calculate the
hardness of the unknown sample.
Hu = Hr(Dr)(Dr)/(Du)(Du)
...where Hu is the Brinell Hardness Number (BHN) of the unknown sample,
Dr is the diameter of the indentation formed in the reference sample, Du is
the diameter of the indentation in the unknown hardness sample and Hr is the
BHN of the reference sample
Assuming you know the hardness of the reference sample, this method is as
accurate as your ability to measure the indentation diameters. A relatively
smooth surface is necessary to provide a "clean" diameter to measure. A rough
surface will throw off the answer because you may not get a true diameter to
measure. As noted in the beginning of this article, the BHN value for “pure”
lead can vary. If you're using pure lead as the reference sample, you’ll have to
decide on the BHN value to use.
The measurements should be taken shortly after the samples have cooled as
lead/tin alloys will age soften and lead alloys such as wheel weights with
antimony will age harden.
Wishing you great shooting,
|EVALUATIONS & RECOMMENDATIONS FOR
LEAD-ALLOY HARDNESS TESTERS
By Wayne McLerran
Last update: 2/6/18
Having participated in online discussions concerning lead hardness testers some
time ago, I thought I’d post some of my comments and observations here. The
threads discussed the preferred tester for black powder cartridge rifle (BPCR)
shooters and the pros/cons of the four readily available units (SAECO, LBT,
Cabine Tree and Lee Precision). I’ve used all four. But before discussing the
individual testers, the subject of lead hardness and the Brinell Hardness Number
(BHN) should be touched on.
Until recently the BHN value of 5.0 has been assigned to what bullet casters
commonly refer to as “pure” lead. Therefore, three of the four testers to be
discussed are either calibrated to directly read “pure” lead as having a BHN of
5.0 or come with a BHN conversion chart based on the same value. More
recently, some well-controlled long-term testing has indicated that the correct
BHN of “pure” lead lies in the range of 4.0 to 4.5 depending on the true purity.
99% pure lead may measure 4.5 whereas 99.9999% pure lead may approach a
BHN or closer to 4.0, but would be unrealistically expensive for bullet casters
to purchase. I have very recently tested some “pure” lead and essentially
substantiated the above noted experiment. The lead measured a BHN of 4.2 to
4.3. But the penetration technique used by the following testers is not a highly
accurate method to measure and determine the true BHN value of a lead alloy.
Therefore, attempting to measure hardness to a decimal point is highly
questionable. Hence, assigning a BHN value of 5.0 may be as accurate as using
4.5. Fortunately the bullet caster does not benefit from knowing the hardness to
decimal point accuracy. With the above comments in mind, following are my
evaluations of the four commercially available testers plus a discussion on two
The SAECO tester has been around for many years. It certainly has a small and
handy form factor, but will not test ingots and is limited to shorter bullets unless
the bullet is cut shorter for testing. It’s the highest priced of all and requires
using a conversion chart to obtain the BHN. The chart is based on pure lead
having a BHN of 5.0. Although I have not owned a SAECO, I have tried one
and did not like it for soft alloy testing. It may work fine for the harder alloys
typically found in hard-cast bullets, but is inaccurate when measuring pure lead
or the softer alloys used by BPCR shooters.
The LBT tester has also been available for many years. It’s the only tester that
is directly calibrated in BHN (no conversion scale is required). It’s fast and
easy to use, but does not work well on ingots and is limited to shorter bullets
unless the bullet is cut shorter for testing. It seems to work fine for the harder
alloys typically found in hard-cast bullets, but is inaccurate when measuring
pure lead or the softer alloys used by BPCR shooters. I sold my LBT tester a
couple of years prior to authoring this article, so I’m unable to provide a decent
photo of the unit. You’ll have to go to the LBT web site listed above to see a
small image of the tester.
I own the Cabine Tree Dual Purpose Tester. Cabine Tree LLC offers two tester
models. The Standard Lead Tester is designed for only testing lead hardness.
The Dual Purpose Tester not only measures lead hardness, but also bullet
runout, case concentricity, case wall thickness and bullet roundness. The testers
are extremely sturdy, very well made and versatile. They will handle just about
any shape of lead, including standard bullets, thin sheets of lead and much
thicker ingots. Testing is fast and repeatable. Another big plus is the ability to
easily recalibrate the testers should something unforeseen happen such as
knocking the unit off the loading bench on to a concrete floor. Both testers do
require a cross-reference chart to obtain the BHN. The chart is based on a BHN
of 5.0 for pure lead. I really like the tester due to its flexibility and ease of use
and can vouch that Jim Cornaggia (owner of Cabine Tree LLC) is a great guy to
buy from. He continues to support his products after the sale. The Cabine Tree
tester is available through Buffalo Arms.
The Lee Precision tester is the latest lead-alloy hardness tester to be introduced
for bullet casters. I’m a sucker for new technology or new apparatuses,
especially when it comes to casting and reloading stuff. So when Lee Precision,
Inc. introduced their very reasonably priced tester (https://leeprecision.
com/bullet-casting/lead-hardness-tester/) had to get one to try it out and to
compare readings with the Cabine Tree unit. I highly recommend the Lee
Hardness Tester Kit. The three components (die, microscope & “V” block) are
very well made, relatively inexpensive and simple to use. It will work on any
bullet length and can be used on ingots with a simple modification to the setup.
By the way, having a background in optics, the one thing I always check for
when purchasing an optical device is what the lenses are made of. It's especially
important when cleaning the lenses as some cleaners can etch plastic. Even with
the appropriate lens cleaning solutions, plastic is softer than glass and therefore
more susceptible to scratching when cleaning. In the case of the Lee Precision
20X hand held microscope that comes with their hardness tester, the lenses
appeared to be glass, but many low-end optical devices have plastic lenses these
days. Since the instructions did not mention the lens material and did not
address cleaning the lenses, I checked with Lee. Lee confirmed the lenses are
made of glass. Still, as a precaution & to minimize contamination, it’s a good
idea to keep the microscope stored in a closed plastic bag when not in use.
The chart that accompanied the Lee tester starts at a BHN of 8.0, which is fine if
you’re a hard-cast bullet shooter. Since BPCR shooters tend to use softer alloys,
a chart extending the BHN value down to around 4.0 should be more applicable
and can be used to test for pure lead. An extended chart is available online and
has been passed around on some of the BPCR discussion forums, but it has
some errors. Using the original chart provided by Lee, I worked up an MS Excel
spread sheet, using it to check the accuracy of the original chart and also to
extend the indent diameters and subsequent BHN values. See the chart below.
Given a specific tester ball diameter and load, in this case a 5/32” ball and 60
pounds of load or force, the standard BHN formula was used. A couple of good
articles on the Lee tester can be found at the following links:
The Pencil Test
Using a set of drawing or drafting pencils of known hardness, for example, 6B,
HB, H, 4H, etc., the relative hardness of lead alloy can be determined by
attempting to scribe the surface using the flat tip edge of a pencil. Following is
a brief overview of the technique:
Start by selecting or flattening a small section of the lead alloy surface with a
file. The base of a large caliber bullet is sufficient. Prepare the pencils by
peeling or removing any wood for a short distance away from the tip, leaving a
short exposed section without any taper. Next, sand a flat surface on the tip
with a file or 500-600 grit sandpaper, being sure to completely remove any
taper. The exposed section should now be a short rod with straight sides, a flat
tip with sharp 90 degree edges.
From the chart below, select a pencil that you believe to be softer than the
alloy. Hold the pencil at 45 degrees to the lead alloy surface and press firmly
forward along the axis of the pencil with the sharp edge. If the pencil skids over
the alloy surface, even if it leaves a slight scratch, it’s softer than the lead
alloy. Work your way up to progressively harder pencils until you get to one
where the sharp edge digs into the surface, pushing up a curl or mound of alloy
in front of it. Using the largely subjective cross reference chart below, the
hardest pencil that will NOT dig into the alloy is used to determine of the
hardness of the alloy in question.
Following is a tabulation of subjective experimental data, some of which was
reported in a long thread on the Cast Boolits forum with the understanding that
it was accumulated by different untrained people, using different brands of
pencils and on alloys of unknown age-hardening/softening. At least it provides
a rough idea of lead hardness. As a “coarse” reference, I included lead alloy
Brinell Hardness Numbers (BHNs) from other sources based on the type of