Re: Making lots of square holes

Two questions did not resolve exactly to my mind:

Question #1:
Resolution, (exactness).
MUST this be a thoroughly *EXACT* item, following all the mathematical
hole-structure throughout??

- - - - - - - - OR - - - - - - - -

Could there be some part of it that is "hidden", therefore, not viewable,
and by reasonable extension of that thought, "not necessarily exactly per
mathematical description?

By that I mean, could there be some sort of surface-layer that could be
"correct", while internally, the invisible parts could be non-existent? In
other words, is "appearance" more important or is it paramount to adhere
exactly to formula?

If you could do with appearance, it might be possible to make the outside
layer of brass (of a thickness to equal the smallest hole diameter), cut the
holes properly in the outer layer, assemble the cube by brazing, and polish
accordingly. You might have to make surfaces inside the big holes through
the middle, if visibility were deemed an issue. But at a 4" cube, I think
you might be able to do the outside with a degree of precision, and as for
the inside, it would be much easier to create the "appearance"" without
having the exact substance.

Question #2: SIZE.

You did say a 4" cube, but you seem to suggest that you might perhaps want
bigger. In that case, you would have to take much more pains with the
interior structure.

Flash




"Thomas Womack" <twomack@xxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:UHF*dn7fs@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
I'd like to make a Menger sponge
(http://en.wikipedia.org/wiki/Menger_sponge) in metal; that is, I want
to make a number of intersecting through holes of square cross-section
through a cube of metal.

I don't know what the relevant metal would be; it's a decorative item
with a lot of operations done on it, so ease of machining is the major
requirement and attractiveness a secondary one. Free-machining brass
looks good.

Even the base cube of metal seems quite hard to find; I can find
various suppliers for two-inch square aluminium bar stock, and one
ebay auction for an offcut of four-inch square aluminium bar stock,
but I can't find brass square bar stock of more than one inch, which
would be too small.

With four-inch square stock I could presumably produce a cube with
97.2mm sides by face-milling, and it looks as if the big square holes
would not be too hard to mill - what sort of radius is it reasonable
to get on the corners of a 32.4mm x 32.4mm hole?

But I don't have a good idea how to make the third-level holes - 3.6mm
square holes, 97.2mm deep. It seems both a bit small and a bit deep
to mill, and I've no idea how happy milling machines would be with a
hole that repeatedly broke into air - I presume the edges around the
break-throughs would be horribly burry. And I'd need 216 holes to
that spec.

[for second-level holes I could fill the first-level holes with
square-section dowels, mill, then remove the dowels; would it make the
third-level milling easier to fill the first- and second-level holes
with some kind of low-melting alloy that could be melted out
afterwards?]

Could I drill them and then make them square with a broach of some
sort? Custom broaches sound likely to be crazy expensive, so I
presume I'd have to size the project for the size of the nearest
round-to-square broach, and I'm not sure where to look for a
round-to-square broach.

I presume the fourth-level holes, 1.2mm x 1.2mm x 97.2mm, would be
completely impractical by any affordable means - it's 80 times
diameter, which looks barely possible in a good EDM shop, but 648
holes at a good EDM shop would leave me vastly out of pocket.


Plan B is to glue together eight thousand 1cm^3 plastic cubes, which
would involve some trivial jig-making and a lot of very tedious
assembly, and lose a lot of the gee-whizz of fractal geometry machined
in metal, though would make a nice big block in the end. It looks as
if eight thousand little cubes would cost a few hundred dollars; I'm
getting a feeling that small deep holes with reasonably sharp corners
are not to be had for a dollar.

Tom


.

Relevant Pages

  • Re: OT TigerSHARC to PC Interface
    ... Jerry Avins wrote: ... I asked our machinist to mill a *PERFECTLY SQUARE* hole in a block of aluminum;] He gave me a "reality" check and asked what I was trying to accomplish. ... Many aluminum alloys are fairly easy to broach, so square holes are not beyond reasonable machine-shop practice. ... My solution required removing a *PERFECT* cube from a piece of material. ...
    (comp.dsp)
  • Re: Making lots of square holes
    ... to make a number of intersecting through holes of square cross-section ... through a cube of metal. ...
    (rec.crafts.metalworking)
  • Re: Making lots of square holes
    ... to make a number of intersecting through holes of square cross-section ... Even the base cube of metal seems quite hard to find; ... round-to-square broach. ...
    (rec.crafts.metalworking)
  • Making lots of square holes
    ... to make a number of intersecting through holes of square cross-section ... Even the base cube of metal seems quite hard to find; ... round-to-square broach. ...
    (rec.crafts.metalworking)
  • Re: OT TigerSHARC to PC Interface
    ... I asked our machinist to mill a *PERFECTLY SQUARE* hole in a block of aluminum;] He gave me a "reality" check and asked what I was trying to accomplish. ... Many aluminum alloys are fairly easy to broach, so square holes are not beyond reasonable machine-shop practice. ... I make square-hole drills out of old untapered three-square files. ... My solution required removing a *PERFECT* cube from a piece of material. ...
    (comp.dsp)
Loading