On Sat, 16 Dec 2017 18:12:57 +0700, John B.
wrote:

On Fri, 15 Dec 2017 18:38:09 -0800, Jeff Liebermann
wrote:

On Thu, 14 Dec 2017 19:23:37 +0100, Emanuel Berg
wrote:

Once there was a guy who had a bounce free
hammer and I asked how it worked. He explained
the little balls going up and down. I was
terribly impressed by this. But then one day
I used one myself and slammed it open and could
see it all first hand. It was still a good
answer but quite possibly that's the way he had
found out as well. Somehow took the magic out
of it.

Perhaps you are thinking of a "dead blow hammer"?
https://en.wikipedia.org/wiki/Dead_blow_hammer
https://www.google.com/search?q=dead+blow+hammer&tbm=isch
The good ones are full of tiny steel balls. The cheap junk uses sand.

"Learn by Destroying(tm)" also means that you really don't understand
how something works until you've broken it, taken it apart, and fixed
it. I've learned more from things I've broken than from playing with
the pretty knobs, reading the instructions, or using it for its
intended purpose.

Re "Dead Blow Hammers". For work in the shop we used to cast hammer
heads out of commercially pure lead. As we had the mold we used to
recast the hammers when the heads got badly banged up. Surprising how
little actual lead was lost in use.

Or, you can make your own:
https://i.pinimg.com/736x/ae/c4/b3/aec4b3b588620dcdf520590ffce00222--hammer-forging-war-hammer-weapons.jpg
When I was an impoverished student, I used one similar to this that
was lead fishing weights, larger size pipe, plastic caps, and a wood
handle. When it disappeared, I found a bronze hammer, which seemed to
work better than a lead hammer. I didn't have the facilities to
recast a lead hammer so brass worked well enough. Years later, the
plastic shot/sand filled hammers appeared, so I bought one of those
and retired the bronze hammer. When someone stole it, I replaced it
with a steel mallet with leather facing and a cheap soft face
(plastic) hammer with replaceable facing for the light pounding:
http://www.acehardware.com/product/index.jsp?productId=19377956&KPID=15216355

As for Learning by destroying". After a number of years of replacing
bent, busted and broke eventually the penny will drop.... Read the
F...ing Manual. First!

Never. I consider reading the manual a sign of weakness. If my
customers see me reading the manual, they would usually ask "do you
know what you're doing?" or "am I paying you to read this?" I reserve
reading the manual for after I'm finished, to see what I may have
missed, or when I get into trouble. Besides, if the product were any
good, it wouldn't need a manual.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558