Fracturing Aluminum

We're making propellers over on the Chugger's Group. Right now guys
are mostly gluing-up the blanks that will become propellers. One of
the things that needs doing is creating the TEMPLATES that will be
needed in the final stages.

The templates are in the Files archive, full scale, so all we need to
print-out the templates then GLUE them to whatever we're using to make
our templates from.

Beer can stock will work. Ditto for shim brass, card stock and so
forth. Glue the pattern to the paper, cut it out with a scalpel. Or
glue it to the metal, SCORE the metal and flex the metal back & forth
until it breaks along the line of the score mark.

"Doesn't work," sez the Big Fella on the phone. He's been flexing his
templates for TWO DAYS and hasn't had one break yet. In doing so he's
convinced himself that the PROCESS is in error; that it's impossible
to cause beer-can stock to break along the score mark. And along
about there he pops the top on a cool one... which of course proves
he's wrong.

Soup cans. Sardines Bully beef... are all examples of having metal
FRACTURE along a SCORE MARK. Clearly then, the process DOES work.
Which means, when it DOESN'T the fault must lay somewhere OTHER THAN
in the basic principle.

(So... where? Probably in the flexing. I recall having some
problems with it when I first did it (using shim brass... beer came in
STEEL cans back then). The alloy used for shim stock is fairly soft
and takes longer to fatigue..)

-R.S.Hoover

wrote in message
...
We're making propellers over on the Chugger's Group. Right now guys
are mostly gluing-up the blanks that will become propellers. One of
the things that needs doing is creating the TEMPLATES that will be
needed in the final stages.

The templates are in the Files archive, full scale, so all we need to
print-out the templates then GLUE them to whatever we're using to make
our templates from.

Beer can stock will work. Ditto for shim brass, card stock and so
forth. Glue the pattern to the paper, cut it out with a scalpel. Or
glue it to the metal, SCORE the metal and flex the metal back & forth
until it breaks along the line of the score mark.

"Doesn't work," sez the Big Fella on the phone. He's been flexing his
templates for TWO DAYS and hasn't had one break yet. In doing so he's
convinced himself that the PROCESS is in error; that it's impossible
to cause beer-can stock to break along the score mark. And along
about there he pops the top on a cool one... which of course proves
he's wrong.

Soup cans. Sardines Bully beef... are all examples of having metal
FRACTURE along a SCORE MARK. Clearly then, the process DOES work.
Which means, when it DOESN'T the fault must lay somewhere OTHER THAN
in the basic principle.

(So... where? Probably in the flexing. I recall having some
problems with it when I first did it (using shim brass... beer came in
STEEL cans back then). The alloy used for shim stock is fairly soft
and takes longer to fatigue..)

-R.S.Hoover


RS, drawn aluminum has a type of grain pattern, like wood. Mebbee you're
plastering the cans down in the wrong orientation? Try cutting 90-degrees
different?

Flash

Flash wrote:
wrote in message
...
We're making propellers over on the Chugger's Group. Right now guys
are mostly gluing-up the blanks that will become propellers. One of
the things that needs doing is creating the TEMPLATES that will be
needed in the final stages.
... Glue the pattern to the paper, cut it out with a scalpel. Or
glue it to the metal, SCORE the metal and flex the metal back & forth
until it breaks along the line of the score mark.

"Doesn't work," sez the Big Fella on the phone. ...
-R.S.Hoover


RS, drawn aluminum has a type of grain pattern, like wood. Mebbee you're
plastering the cans down in the wrong orientation? Try cutting 90-degrees
different?

Flash


If you don't want to use scissors on thin aluminum shimstock, perhaps a
hardboard, oil-tempered even, would do the trick. That needs a
jigsaw, no doubt.

Brian W

On Mar 14, 8:01*pm, Brian Whatcott wrote:
Flash wrote:
wrote in message
....
We're making propellers over on the Chugger's Group. *Right now guys
are mostly gluing-up the blanks that will become propellers. *One of
the things that needs doing is creating the TEMPLATES that will be
needed in the final stages.

*... Glue the pattern to the paper, cut it out with a scalpel. *Or glue it to the metal, SCORE the metal and flex the metal back & forth
until it breaks along the line of the score mark.

"Doesn't work," sez the Big Fella on the phone. ...
-R.S.Hoover

RS, * drawn aluminum has a type of grain pattern, like wood. *Mebbee you're
plastering the cans down in the wrong orientation? *Try cutting 90-degrees
different?

Flash

If you don't want to use scissors on thin aluminum shimstock, perhaps a
hardboard, oil-tempered even, would do the trick. * *That needs a
jigsaw, no doubt.

Brian W

The thinner, the better, for this purpose. I made my templates way
too thick. They worked, but I'd never do it that way again.

http://users.lmi.net/~ryoung/Sonerai/Carve_Prop.html

And scissors on Coors brand shim stock is fine for straight lines, but
it's not accurate enough on curves, IMHO, for this sort of work, plus
it tends to crimp the edge.

If you can't manage this on aluminum can, try it on card stock with a
brand new X-Acto, then varnish the results.

Anymore, I scribe and snap ALL my aluminum cuts. The knives used to
scribe plexiglass are handy for this, and the ELFA brand truly is
superior to any other I've found. But again, as Veeduber pointed out,
on beer can stock, a sharp machinist's scribe is all you need.

" wrote:
We're making propellers over on the Chugger's Group.

I've been meaning to ask - what's a chugger (online urban dictionary gives
a meaning I'm not sure is the one perhaps intended,) and out of curiosity
where is this group?

Beer can stock will work. Ditto for shim brass, card stock and so
forth. Glue the pattern to the paper, cut it out with a scalpel. Or
glue it to the metal, SCORE the metal and flex the metal back & forth
until it breaks along the line of the score mark.

"Doesn't work," sez the Big Fella on the phone. He's been flexing his
templates for TWO DAYS and hasn't had one break yet.

Perhaps it's the scoring knife he's using? You probably already know about
this, so forgive me if this is redundant, but I've read good things about
the Olfa P-800 scoring knife ("Plastic/Laminate Heavy-Duty Ratchet-Lock
Cutter (P-800)"):

http://www.ch601.org/tools/olfa.htm
http://mthobby.pcperfect.com/ch601/chtools.htm

This is the online product page:

http://www.olfa.com/UtilityKnivesDetail.aspx?C=8&Id=58

flybynightkarmarepair wrote:
The knives used to
scribe plexiglass are handy for this, and the ELFA brand truly is
superior to any other I've found.

Spelling of the brand name is Olfa. Their P-800 is specifically designed
for scoring. About US$12.

Dear Flash & Brian,

Scribing & flexing works perfectly well on any thin metal. The harder
the alloy, the better.

Orientation is of little importance. On thick airfoils such as NACA
0024 ( used for struts, etc ), the curvature exceeds 90 degrees,
making the matter of grain moot.

The scriber appears to make more difference than the grain in that a
#11 scalpel works better than a machinist's scriber. Or perhaps it is
the surface on which you lay the metal for scribing. While it works
okay using a book or piece of wood, as a general rulle, it works best
if the scribing is done atop a metal surface.

-R.S.Hoover

And scissors on Coors brand shim stock is fine for straight lines, but
it's not accurate enough on curves, IMHO, for this sort of work, plus
it tends to crimp the edge.

If you can't manage this on aluminum can, try it on card stock with a
brand new X-Acto, then varnish the results.
-------------------------------------------------------------------------------------------------

A big Roger on this. Even when using tiny scissors such as for
cuticle or those nifty scissors on a Swiss Army knife, it is simply
impossible to make a cut having as small a radius as you can get when
using a scalpel or X-acto knife. But don''t take our word for this
(or anything else :-) Go ahead and try it WHILE WE'RE STILL HERE
(ie following the thread). Perhaps we can offer advice you can use.
In fact, I'll go ahead and make a separate post covering how to make
precision KNIVES suitable for this kind of work.

-R.S.Hoover