Checking Lead Hardness With Drawing Pencils

  • 11K Views
  • Last Post 12 August 2020
mashburn posted this 27 June 2019

I thought that this information would be interesting to a lot of you readers. A month or so ago I saw a video on u-tube where a guy was checking lead hardness with a set of drawing pencils. He had checked alloys of a known BHN and by trial and error he came up with a chart that you could use to check the BHN of a unknown alloy. How it works is, take a piece of alloy of unknown BHN and start seeing if the pencil would write on the alloy but not scratch it.When you finally fnd a pencil that will scratch the alloy and you know the hardness of the alloy you have found a pencil hardness that is a little harder than the alloy. I copied his chart down and ordered a full set of drawing pencils. Believe it or not I could not find a full set of drawing pencils from an American manufacturer or distributor on ebay or amazon. I ordered mine from Mylasia and finally got them today. I couldn't get them opened fast enough so that I could try them. I had some alloys of known BHN and a few of unknown BHN. Yes,  it did work fine. My known BHN alloys checked exactly to his chart. So I am sure that the unknown alloys checked right. Instead of me posting his chart here, you can pull his video up on u-tube and watch him do his thing and copy down his chart. Much cheaper that a lead hardness tester and very quick.

Pencil Hardness    BHN

6B                           4-5

5B                           7-8

 

4B                            9

3B                            10

2B                            11-12

B                               13

 

HB                             14-15                        

F                                16-18

H                                20-22

2H                              26-28

 There is a lot of supposedly lead hardness testing means on u-tube, however this one is cheap, inexpensive, quick and I guarantee you it WORKS. Please excuse my messy columns in the above info.

Mashburn                               

 

 

 

 

 

 

 

 

David a. Cogburn

Attached Files

  • Liked by
  • M3 Mitch
Order By: Standard | Newest | Votes
max503 posted this 28 June 2019

Is this the video you're talking about?

Attached Files

  • Liked by
  • shootzem6.5
joeb33050 posted this 28 June 2019

 

THE PENCIL TEST FOR LEAD ALLOY HARDNESS

 

Ken Mollohan

 

 

 

The pencil industry manufactures what are called 'art pencils' for draftsmen, artists, etc. They are available as either conventional wood sheathed graphitic cores, or as a mechanical pencil for which you only buy the graphitic cores and insert them as desired.

 

The hardness of art pencils is controlled very strictly, and they are designated by a letter-number combination.  The scale runs from at less than 6B (VERY soft) and gets slightly harder with each step up, going to 5B, 4B, 3B, 2B, B, HB, H, 2H, 3H, 4H, 5H, 6H, 7H, 9H, 10H, 11H and 12H that I know of.  6B is softer that most scrap lead, while 12H will cut into some grades of aluminum and copper, which are far harder than most lead alloys.

 

This provides 18 steps in hardness, but you won't need much more than about the range of 6B to about 2H.  Oh yes, there ARE even softer and harder art pencils, but they're not often used, and can be pretty hard to find.

 

They are used industrially to measure the hardness of paints, among other things.  I have a background in the paint industry, and have used the technique for my alloys for decades.  It's really quick, simple, easy, and reproducible from one time to the next, and from one person to

 

the next.

 

To use them to measure hardness properly does take a certain technique, but it's easy to learn:

 

You prepare the pencil by peeling away the wood sheath (or simply advancing the replaceable core in the mechanical version) to leave a cylindrical graphitic core.  It's best to do this with your fingernails to avoid scraping the core if you want to get the best (most consistent) results.

 

Now hold the pencil straight up and down as you smooth the tip on a bit of fine sandpaper.  I usually use something like 360 to 400 grit.  The objective is to form a perfectly square sharp wadcutter configuration on the end of the pencil core, so that you can reproduce the exact same cutting edge every time.  Blow a puff of air on the tip or wipe it very gently with a bit of cotton to remove any loose graphite.

 

Now hold the pencil at a 45-degree angle to the surface of the lead, and push along the

 

length (the long axis) of the pencil.  If the sharp edge of the core is harder than the lead, it will

 

dig in and scratch the surface.  If the core is NOT harder than the lead, the sharp edge will crumble, and it will skid across the surface of the lead.

 

You should be aware of a couple of easily avoided problems that can mess up your results:

 

1.  You need to move to a new spot on the lead for each test.  Otherwise, the next pencil core could skid more easily on the surface, which is now lubricated with graphite from the previous test.

 

2.  Likewise, the pencil should be rotated slightly for each test:  Skidding across the

 

lead surface will blunt the sharp edge, and unless you rotate the pencil in your fingers to present a fresh cutting edge, the blunted edge will not cut in as well.

 

3.  These graphite cores were not originally designed for this test, as I mentioned above. Mixing of the clays, graphite, etc. is not always perfect, and you may occasionally (!!) encounter a tiny pinpoint of grit that will give you a false indication.  For this reason, you need to make several tests with the same pencil, rotating it for a fresh edge each time.  You can easily get three or four tests from the same tip before it needs to be resharpened.  If it gouges on one test, but slips on the others, assume the one gouge was due to a pinpoint hard speck, and rate it as equal to the majority results.  It's not a real problem, just something to be aware of.

 

Hardness is rated as being equal to the hardest pencil that will NOT cut into the surface. For example, if a 'HB' pencil skids across the surface, but an 'H' pencil makes gouges, your alloy is 'HB' in hardness.

 

One of the nice things about this technique is the very small area needed to test.  Once you have the knack, you can easily get meaningful results on loaded ammo, sprues, or most any surface that gives you a uniform surface about an eighth of an inch long for each pencil.

 

Hope you find this interesting and useful.  Feel free to ask any questions that may occur

 

to you.

 

 

 

Attached Files

  • Liked by
  • M3 Mitch
joeb33050 posted this 28 June 2019

 

 A Simple Method oF MEASURING Alloy Hardness

 

David Berry

 

 

 

This describes a method for the determination of lead alloy hardness. It is a simple, quick, and economical means to test hardness of unknown alloys, and I have found it to be reliable and accurate.

 

Using a common staple gun, I have found that measuring the penetration of the staple into the alloy can be used to determine relative hardness when compared to a series of "standard" known lead alloys. I simply inject a staple into the sample and measure the post of the staple that protrudes. I obtain 5 readings on each known standard, average them and prepare a calibration chart versus known BHN values. A sample chart is shown below. Unknowns are then subjected to the same procedure and the resulting measurements are compared on the chart to determine relative hardness.

 

Alloy

1

2

3

4

5

Avg.

BHN

Lead

0.102

0.107

0.115

0.109

0.120

0.111

5

WW

0.209

0.180

0.186

0.177

0.186

0.188

9

2-6 Alloy

0.223

0.216

0.217

0.190

0.214

0.212

15

Linotype

0.255

0.240

0.238

0.258

0.234

0.245

22

 


5 readings for each alloy in inches

 

Arrow T-50 stapler

 

3/8" staples

 

I first started working on 1-pound ingots of the same size, but found that size or shape is not all that important, the sample just needs to be large enough to hold the staple gun onto it. I apply about 20 pounds of pressure on each sample (determined with a bathroom scale) while I inject the staple. I have used a Bostich electric staple gun and this works well also. A 3/8-inch staple is about the largest that can be used as longer staples deform. This can be overcome by measuring the actual penetration by subtracting the protrusion as measured above, from the total length of the staple post.

 

Each staple gun must of course be calibrated as will the batch of staples being used.

 

I find this to be an extremely easy method to determine alloy hardness, and by measuring several samples have determined it to be very reliable and fairly accurate. It works very well on odd sample shapes and sizes.

 

 

 

 

 

Attached Files

  • Liked by
  • M3 Mitch
joeb33050 posted this 28 June 2019

 

A Cheap way to test lead alloy hardness

 

James Carter

 

 

 

I was reading a book from the late 50's at a friend's home that was put out by the NRA on how to test lead hardness on the cheap. I gave it a whirl and it works great so I thought I would share for those of you who are cheap like I am.

 

You need about 2 pounds or so of pure lead, your test lead and a steel ball bearing and a vise and a set of calipers/micrometer and that is it.

 

To get the pure lead you can find it in a metal supply shop but it runs about 3-4 bucks a pound or you can save the stick-on weights when you find them in your bucket of wheel weights. I bought a couple of pounds to see what the difference was between it and the stick-on version and the BHN number is about 5.2 or 5.3 instead of the 5 for pure lead, so close enough.

 

Drop by a bearing shop and pick up a 1" steel ball bearing and that costs about 2 bucks or so.

 

Melt the pure lead (stick on weights) in a muffin tin and your test lead in the one muffin slot next to it. I waited a day to test because I am anal that way.

 

Pad the vise with aluminum or steel on the jaws so that the lead doesn't dig into the teeth of the jaws. Hold up the lead in one jaw and the test lead on the other jaw and slowly squeeze the two together with the ball bearing in the middle. Just squeeze till there is a good dent on both surfaces of the lead or about 1/5 or the way in on both sides of the ball bearing.

 

Here is the formula BHN= 5 X (lead dia./test dia.) ^2

 

With the calipers measure the diameter of the indent in each of the leads and plug in the values.

 

I had some WW and an unknown lead from a Radiator shop that I wanted to test and here are the results.

 

Diameter in Lead=0.479

 

Diameter in WW=0.325

 

So, 5 x (0.479/0.325) ^2 and that gives 10.8 BHN where it should be for air-cooled Wheel Weights.

 

I had my friend test the WW on his Lee Hardness tester and he came up with 11, so close enough.

 

Unknown lead from radiator shop

 

Dia. in Lead=0.520

 

Dia. in Unknown=0.279

 

So, 5 x (0.520/0.279) ^2 which gives us 17.4 BHN

 

I knew it was harder just with the old thumbnail test but I had no idea it was that hard.

 

Again, on the Lee it came back as 17 BHN

 

So, this is a great cheap way to test lots of lead, it won't work so good on single bullets like the expensive models but at least you know what the raw materials BHN number is approximately.

 

Attached Files

  • Liked by
  • M3 Mitch
blackout52 posted this 12 August 2020

I found a 14 piece pencil set at Amazon , it's a Markart  14 piece set for $ 6.99 and it all of the pencils listed and a few more.

Attached Files

  • Liked by
  • Bud Hyett
mashburn posted this 28 June 2019

Hello max503

That is the correct video. It works good and is fast and cheap.

Mashburn

David a. Cogburn

Attached Files

mashburn posted this 02 July 2019

Hello pondercat,

I don't see an H pencil in the set. H grade pencils will test close to Linotype and 2H is as hard as you need that I have found.

Mashburn

David a. Cogburn

Attached Files

BigMan54 posted this 11 August 2020

I remember My Dad doing this 60yrs ago. 

Long time Caster/Reloader, Getting back into it after almost 10yrs. Life Member NRA 40+yrs, Life S.A.S.S. #375. Does this mean a description of me as a fumble-fingered knuckle-draggin' baboon. I also drool in my sleep. I firmly believe that true happiness is a warm gun. Did I mention how much I HATE auto-correct on this blasted tablet.

Attached Files

mashburn posted this 12 August 2020

Hello Big Man,

If your dad was doing this, 60 years ago you must be getting on up there yourself. At least 35 or so. Ha.

Mashburn

David a. Cogburn

Attached Files

sluggo posted this 12 August 2020

Back in the dark ages before C.A.D. systems I sat behind a drafting table for a couple years. It wasn't for me but I kept my equipment. Thanks to this post I have a new use for it. Sometimes it pays to be a pack rat. Thanks, and stay safe

Attached Files

Close