homemade gravity hardness tester

[corey012778]

been doing some experiments with an gravity style hardness tester. using an 16oz hammer and an screwdriver. just hold the hammer about 6in above the screwdriver and letting it fall under its on weight. problem is I keep wanting to swing the hammer which is giving me inaccurate data. I still need to really figure out the force with an more predictable set up.
from the figures I got, some lead I melted down from fishing sinks I found came out to 6 to 7 bhn and ww lead came out to 8 or 9 bhn. the numbers seemed way off for from everything I have read.

so this is my idea.

some type of weight around 1 to 2 lbs. (melt some zinc ww's or harden sand mix molded in an can)

an wood or metal stand (wood would be easier for me to work with)

something to help glide the cylinder. (pvc pipe cut in half with an pull rope system or just the bottom 2 to 3" half moon cut out, with notches cut every 1/2" to 1" to see the where the cylinder is.)

8mm punch pin for the impression

something to hold the punch pin and allow it to free float.

base to hold the ingot or boolit.


basically, an gelatin type set up.

any ideas or thoughts?

[Matt3357]

sounds like a solid repeatable set up, but it could really only be used for your own comparison. I am not sure how it would translate into BHN. The only way you could do that is to test some known BHN lead on your setup and see what it does.

Matt

[zomby woof]

I use an arbor press, 22lb weight and a .312" ball for 30 seconds, very repeatable.



http://www.hunt101.com/data/500/medium/100_2996.JPG
http://www.hunt101.com/data/500/medium/100_29981.JPG

[Pepe Ray]

Great stuff!!
Looks like a Potter Engineering Hardness Tester on LSD
Gravity is much more reliable than springs, but not quite as convenient.
Pepe Ray

[lwknight]

The gravity hammer fall is still an impact measure.
All pressures should be held for constant several seconds to get reliable measurements.

[Pepe Ray]

Your correct in that the time element must be consistant, however there need not be an impact as such. The weigt x time is sufficient.
Pepe Ray

[corey012778]

still just in the early concept and testing.

I don't own an arbor press nor able to get one. using what I have on hand. with that said, I was doing a little searching on this site. I found where someone used and vise (which I do have on hand) ball bearings, problems, I really have not been able to find the ball bearings. figuring the steel shot for sling shots should work. can't find any right now. hope here in an few weeks I can get to a few places that has some.

but will not give up on this.
few changes to my first plain
since I have an vice. and attach an piece of pvc.
piece of 2 to 3in steel or iron pipe, about an 3/8's to 1/2in, filled with sand. hoping to hit the 1lbs mark.

[calaloo]

If you have an Ace Hardware store near you they have bearing balls of various sizes.

[Pavogrande]

I was thinking about using an old valve spring tester and torque wrench with suitable ball bearing and anvil. I haven't used the tester in thirty years so might be a good use.

[mold maker]

The screw that works a vice jaw, wont provide consistent pressure due to friction. Even a small piece of dust/dirt in the threads wont allow repeated torque transfer to the jaw. You can however use a vice to determine harder and softer than a known piece.
Just close (lightly) the vice with a ball between the known and the questioned piece. Harder piece will dent the least.

[corey012778]

started gathering parts for my project. tried to use the seam where the cap was casted. it is so back to plan B, drilling an hole to and setting an 8mm pin punch in the hole.

plan D, giving up an buying an lee tester lol

http://i225.photobucket.com/albums/dd231/corey012778/003-4.jpg

http://i225.photobucket.com/albums/dd231/corey012778/002-12.jpg

[corey012778]

this is scrapped,

could not get the time x weight to work out to get the data I needed. gone to another plan that is already giving me what I am looking for with out the full data (just guess on on the pressure)

[usmcscout]

I use an arbor press, 22lb weight and a .312" ball for 30 seconds, very repeatable.



http://www.hunt101.com/data/500/medium/100_2996.JPG
http://www.hunt101.com/data/500/medium/100_29981.JPG

I know this is old thread but I am attempting to copy your method just picked up arbor press the 1 ton which are u using 1/2 or 1 ton or did ya give up

[usmcscout]

arbor press 29.99 harbor freight
ball bearing 0.17
empty paint can free
21.25 pds soft lead the dif between the weight of paint

total cost 30$ cheapest hardness tester around

[zomby woof]

the press has no markings on it. It only stands 10 inches high.