How to estimate BHN with sharpen pencil?

[tomo]

I am going to estimate hardness of lead alloy.
And I have found a measuring hardness method in Japan Industrial Standard (JIS) to check the strength of painted surface.
It uses a pencil. And this method was also used to estimate lead alloy hardness and discussed in past threads here.

According to JIS, pencil must have cylindrical lead. But if conical point lead can be used to do this, it is easier to maintain
shape of pencil lead because usual sharpener can be used.

The problem I guess is a pencil with conical lead can scratch harder lead alloy than it with cylindrical one at same pencil hardness.
Anyone have some conversion equation or chart between two? Or there are only a few difference between them?

[bangerjim]

There is a complete thread on here about using a set of artist pencils for hardness (guessing) testing.

There are 8 to 10 pencils of various hardnesses you need. And there is a chart in the thread that relates hardness of the pencil to Bhn.

Do a search.

bangerjim

[tomo]

Thanks for reply, bangerjim.
I have found a table. It can be applied with conical lead? not only cylindrical?

[DougGuy]

I use the Mars Staedtler pencils and they work pretty good. I sharpen mine to an angle similar to an engraver's gouge tool instead of square on the end. It still works the same way.

http://castboolits.gunloads.com/showthread.php?75455-Testing-hardness-with-pencils

[tomo]

Thanks, DougGuy
I am sorry that I don't know what is gouge tool.
Do you sharpen a point of lead flat like a slot driver?
OR sharpen normally, and after that, file tip to make a meplat?

[bangerjim]

When I tested the pencil method for a couple of buddies (comparing this SWAG technique to my Cabine tester) I just pointed them with a standard old crank-type school pencil sharpener. The method is really not that accurate and the shape of the end should just be a point of some kind.

[RogerDat]

I believe the instructions here call for a flat cylinder end rather than a point. Requires shaving back the wood to maintain the cylinder of graphite then running it across some fine sand paper to give it a flat end. The gouge is done with the edge of that cylinder formed by being sanded at 90* to the cylinder.

I'm guessing the idea is if you sharpen in a sharpener and then sand the point flat it will have a smaller diameter end which will gouge the lead just a bit easier.

I'm not sure it really matters, your only going to get approx. hardness with an art pencil. Which might allow you to adjust hardness for a specific purpose by adding other lead or lead alloys to the mix. Nice to know without any doubt that some unknown lead is either really hard and needs to be softened for pistol or too soft for rifle.

[tomo]

Thanks, bangerjim and RogerDat
I heard pencils from different makers act different. I guess it means calibrations with known hardness materials will be needed.
If it is right, I can test with pencils which sharpened normally after I obtained some conversion table of comparisons between
hardness testings with flat cylindrical leads and sharpened one.

[Teddy (punchie)]

Make sure you hold the pencils all the same way angle and have same tip. Works easy. Used it on soft (pure) lead, lino, ww and range lead and was easy to see a difference. Got a lee hardness tester and is allot slower and harder to pick hardness.

[bangerjim]

Thanks, bangerjim and RogerDat
I heard pencils from different makers act different. I guess it means calibrations with known hardness materials will be needed.
If it is right, I can test with pencils which sharpened normally after I obtained some conversion table of comparisons between
hardness testings with flat cylindrical leads and sharpened one.

Dougguy is correct in suggesting the Mars Staedtler brand. That brand is high quality and maintains the repeatability of the lead in those pencils better than other cheap brands I tested. And I believe the chart is based on that brand also! Spend a little more and get the brand that works.

banger

[tomo]

Teddy, OK. I will use pencil that way.


banger, Staedtler Japan located in my town. It is easy to buy Staedtler Mars Lumograph here.

According to Japanese Industrial Standard, Mitsubishi Pencil is referred.
They provide also very high grade pencil but its hardness might be slightly different from Staedtler's.
As a pencil to write, I'd rather choose Mitsubishi but I will get Staedtler for hardness testing.

[brassrat]

It took me a couple hours to get my M.S. pencils shaped

[tomo]

I bought Staedtler pencils, H, F, HB, B and 2B. They covers BHN 11 to 22.
It is difficult to get flat ends of cylindrical lead. So I use a sharpener with setting to NOT keenly.
It needs flat lead before sharpening and then makes a point of lead trapezoid. I think it works nice.

[RogerDat]

Those art pencil designations of H,F, HB, B and 2B are a standards based designation for art pencil hardness. Higher quality pencils will be more likely to be consistently matching the standard than cheap ones. And as noted be more consistent when purchasing another pencil of the same brand.

While they can be fairly accurate in terms of repeatability (if I do test the same then identical results means identical hardness) they are only approximate between different people doing it slightly differently. For industrial use one would use a guide to hold the pencil and included sharpener to make the test consistent when done by different people.

I have 4 of them in my car for use at the scrap yard. Approx. test for soft, little hard, WW, or printers lead hardness. Unlabeled ingots in the scrap bin are the main reason. Yeah that might be soft nearly pure plumbers lead or some alloy, pencils help narrow that down. Plus if it tests harder it may well be worth taking a piece up front to have it gunned if that service is available. If it pencil tests around 15 or 20 BHN I sure want to know what it is made of. Once or twice allowed me to gamble on a purchase based on having one more data point. While passing on some stuff that was too hard. Later testing showed hard stuff to be zinc.

Bottom line if MY pencil test shows same hardness that worked well for last batch of boolits then I'm probably going to like this batch too. If it measures too soft or hard the time to adjust is now as an ingot before I cast 500 boolits with it.

[Motard]

I have compared the stadler pencils wit the lee hardness tester and had same resoults.: 18 Bhn league un my cast boolits. Instead of sharpening you may peel off half an inch wood from the tip, expose the lead and flatten it on sandpaper. Or a simples whay is to buy just the core for replaceable pencils (caran d'ache, brooklins, sthadler etc). I feel that holding at the correct angle 45° while testing (eventually with aid of a hooden drilled block) is most important than the tip's shape.

[303Guy]

We don't have too many members located in Japan. Is shooting and boolit casting big in Japan? It's good to have you with us. :drinks:

[Patrick56]

$10 for a set of pencils seems fine but a mere of $200 for the stand and a sharpener is a lot of money.:?
http://www.elcometerusa.com/Elcometer-3080-6B-to-6H-Pencil-Hardness-Test-with-Stand.html