Home brewed hardness testing

[Drew P]

So, I alloyed some tin and antimony into my unknown (but probably pure) lead stash recently and I did some experimenting on hardness testing and want your opinion on the results.

Okay so so I cast slugs in pure, and then tried some 45cal 200 gr flat points that I both air dropped and water dropped out of the new alloy I created with hunk of antimony and a pewter cup. So, these are the three test subjects I wanted to measure.

The tools I found in the shop for testing were:

1. an arbor press (geared lever type, olde schoole)
2. a bath scale
3. a ball bearing that fell out of a swivel caster
4. dial calipers

So, I put the bath scale on the arbor press, a block of wood on that for spacer, and the boolit on that. The ball bearing was then placed on the boolit and pressure added with the arbor press until the bath scale said 100lbs. This left a good sized dent under the ball bearing. I measured the impression width and entered the data on a webpage that accepts the poundal force(100), ball diameter(.219") and impression width and it spit out these numbers:

pure lead 12ga slug - 5.7bhn
Alloyed air dropped 45 cal - 10.7bhn
alloyed water dropped 45cal- 15bhn

do these results seem consistent with typical practice between air and water dropping? I know that my data isn't complete without actual percentages on the alloy, but I don't have that.

The calculator was obtained here.
http://www.ajdesigner.com/phphardnes...ess_number.php

[tigweldit]

Looks about right to me.

[bangerjim]

A poor man's Rube Goldberg setup, but if it gives what you want, go for it.

A Cabine tester is faster, more accurate, more compact for my hardness testing needs.

[Yodogsandman]

It shows that your unknown lead stash alloy is close to COWW's.

Your hardness test method is sound and considered more accurate than the faster testers available to hobbyists.

[Drew P]

Interesting thanks. Yeah, if nothing else it at least gives me relative hardness results, which after shooting ultimately might be of equal value.

Curious however, why do you think my stash is similar to COWW? I thought pure lead was around 6 hardness and the COWW was typically closer to 10-12?

[Yodogsandman]

Hugh, That's because I get between 10 and 11 BHN with COWW's with tin added, air cooled using basically the same test method you used. I use a 7/16" ball bearing and a 200 pound force, figuring it using the same calculator. I make 3 indents and average the indent sizes for calculations.

[Drew P]

Ah okay but my stash when cast pure was reading 5.7bhn before I tossed a pewter mug and a hunk of antimony into it. Then it was up to the 10's air cooled and not aged. Also, my powder coating temps are around 400° and I'm wondering if that process is affecting the hardness on the final boolits. I'll find out in a week I suppose!

[Yodogsandman]

I wait 3 weeks for air cooled and 5 days for heat treated boolits to age harden to where they're fairly stabilized.

[P Flados]

Your method is actually consistent with the "official" standard for BHN hardness testing. The standard is it to push a sphere into the surface and measure the dent diameter.

When I PC, the oven temp is only over 320 °F (they are all shiny by this point) for around 15 minutes and with a big batch it never gets to 400 °F. I can pass the smash test with only 10 minutes above 320 °F, so I have good margins to assure adherence. This is air temperature. The lead temperature will lag behind the air temperature. This temperature profile is not enough to have much if any affect. Using the drafting pencil method, I found harness of PC boolits with the coating scraped off to be the same (as close as i could tell) when compared to uncoated from the same batch of water dropped COWW boolits.

I am another DIY tester. I first looked at a number of internet postings showing DIY versions. I cobbled together a tester. I have updated it several times and it is now working pretty good.

It uses a lever to give me an applied force that is 4x my test weight, and it uses a pulley so that the lever can be vertical so that the lever weight does not affect results. I drilled in the end of a good sized Phillips head wood screw and pressed my ball bearing into it. My test weight is a bucket. The current contents are 61.6 lbs (zinc wheel weights + one gallon of lead alloy). I place the sample up against the ball, lift the entire assembly, lower it and measure the dent.

I initially used it for ingot testing.

I have found that I can slice a boolit in half (anvil type pruning shear) file it flat & get good results. The "test surface" hardness was confirmed to be consistent with the boolit OD surface using the drafting pencil method.

I use a spreadsheet to get results.

	B	C	D	E	F	G	H	I
	Lead	Date	Dent (in)	Force (lb)	Multiplier	Ball (in)	Ball (mm)	BHN
3	Roof Vents	10/09/15	0.200	72.4	4	0.2189	5.560	4.6
4	Roof Vents	11/14/15	0.197	66	4	0.2189	5.560	4.4
5	SOWW	10/09/15	0.171	72.4	4	0.2189	5.560	7.2
6	3xPb, 1xCOWW	10/17/15	0.170	59.6	4	0.2189	5.560	6.0
7	3xPb, 1xCOWW	11/13/15	0.150	61.6	4	0.2189	5.560	8.5
8	3xPb, 1xCOWW	11/13/15	0.154	66	4	0.2189	5.560	8.5
9	WD COWW	10/09/15	0.122	85.6	4	0.2189	5.560	18.8
10	WD COWW	10/17/15	0.100	59.6	4	0.2189	5.560	20.2
11	WD COWW	10/17/15	0.110	66	4	0.2189	5.560	18.2
12	3-1-2.5 Boolits	11/28/15	0.153	61.6	4	0.2189	5.560	8.1
13	11/28 Boolits 1-3-2.5	11/28/15	0.135	61.6	4	0.2189	5.560	10.8
14	11/28 Boolits 1-3-2.5	11/29/15	0.127	61.6	4	0.2189	5.560	12.4

Equation for I14: =2*(0.453592*4*E14)/(PI()*H14*(H14-(H14^2-(D14*25.4)^2)^0.5))

[Silverboolit]

I like your method for measuring and sure it works well. However, have you tried it with a steel/iron spacer instead of wood? Wood may 'give' a little and your measurements may be off. Just a thought on a good idea.

[Drew P]

Very nice test rig! I love this kind of stuff!
I Pondered the flex issue with my setup too, although I don't think it matters because force is force and even if it flexes a lot it will receive the same weight applied ultimately. In fact, some "give" in the system may increase precision because it would buffer any shock loads a little. In my case, using the bath scale I was essentially inducing a lot of flex in the system by way of the spring in the scale.

Question: you're using a lot more force than i did, do you feel that is a good amount of applied force? I chose 100 lbs because it seemed to make a reasonable dent, and it was a round number. Maybe more accuracy could be had by using variable force to create an approximately similar dent, since the calculator allows for any input of data?
Now you've inspired me to make a permanent testing setup for this purpose! Thanks!

[popper]

I've started using a lever torque wrench fastened to a vice. Clamped a modified scribe (JB weld stopper on the scribe point for 0.010" penetration) to it and press directly on the boolit. Watch the needle, note the reading just before the stop hits. Not absolute accuracy but gives me a relative number. I should be able to calculate real psi for deformation. Cheap as I already have all the parts and it should be accurate for ingots also.

I found harness of PC boolits with the coating scraped off to be the same (as close as i could tell) when compared to uncoated from the same batch of water dropped COWW boolits.

I need to try this, it may help with the HiTek coating.

[P Flados]

For my setup, I have attached a small piece of aluminum (1.25" wide x 0.25" thick strap material) onto the wood where the sample rests.

I was pushing boolits into the wood before I did this.

The way I am set up now, I have eliminated all of the flex problems I had with earlier versions.`

I use different amounts of weight as needed. I think it is most accurate when I get the biggest possible dent without "bottoming out" the sample up against the ball holder. A bigger dent means that my measurement inaccuracy is a smaller fraction of the total. This is also why I went from a BB to a 0.2189" steel ball.

[Retumbo]

Only problem I see is that bathroom scales, unless electronic, are inherently inaccurate.

Every time my wife gets on the scale I hear,"this can't be right, stupid scale".


(But seriously, they are)

[P Flados]

Decent bathroom scales are likely to be a couple of pounds off, but not 10 pounds off. Other items probably result in more error.

I am using a cheap digital "luggage scale" to weight my bucket. It reads in 0.1 lb increments, but the accuracy is probably closer to ± 0.8 lbs if I am lucky. Again a 2% error in weight is not a big deal.

[Retumbo]

No, I've seen cheap scales off by 10 pounds....

[Drew P]

My scale is cheap, but I'm not trying to "force it" to read a particular value like my girl might, which I believe decreases it's perceived accuracy

[RogerDat]

These are some neat ideas. Have seen a weight hung on the arbor press handle to provide consistent weight/pressure Think hanging "T" with weight on it. I guess you could determine the amount of weight required on the handle end to give you the desired pressure on the scale.

Art pencils get one close enough for target practice or plinking. They provide a relative point of measure that is fairly consistent and repeatable.