Hello all,

I have two projects that are loosely related. One requires a tray that
is almost certainly a "build" and the other needs a box of specific
dimensions, and is a "build or buy" depending on what sizes are
available commercially.

Let's start with the tray. We have steel slotted angle on hand, and I
propose to use it to create an L-shaped structure that has some adapters
to support a printer, connecting to existing tapped holes to one side
and "reaching down" to another shelf on the other end. That shelf is
plastic-laminated particle board, so a couple of wood screws will make a
good connection.

Are there metal analogs to wood joinery techniques? I am learning how
to assemble pieces of wood with little more than clever cutting and glue
(see keywords such as mortise, tenon, rabbet, dado). Given the right
keywords, I am happy to read how do similar "correct" work with metal.

As an example, what would be the best way to joing the slotted angle
pieces at a corners of the tray? They can simply sit one on top of
other. I could miter them at 45 degrees and add something, or create
something like a wood lap joint (mill each to half thickness and then
bolt them in a couple of spots??). The simple overlap would work well
for the tray because the uneven surface that results will not be a
problem: the printer will be held by "feet" on rails or something.
Better ideas are most welcome.

Now for the box. If I can buy one of the correct size, then great.
Otherwise, I start thinking of aluminum, with mitered (at the corners)
extruded pieces along the edges and at strategic places along the length
of the edges (for holding the junk inside the box), with sheet metal
walls that carry the shear ("stiffen" the box).

Comments or better ideas? I want it simple, strong, easy to build,
cheap of courseg, and it potentially needs to be a certain size. The
size will hopefully be worked out shortly. I am starting to make full
scale models of the important pieces (single board computer, power
supply, safety equipment, etc.) and will look at various ways to package
them. The stuff needs to fit in the box, and the box needs to fit in a
space with fixed dimensions; hopefully it will end up being quite
forgiving. If all goes well, I will end up merely adding an externally
accessible bay to a commercially made box.

Bill

On Tue, 18 Oct 2005 13:54:15 -0500, Bill Schwab
wrote:

Hello all,

I have two projects that are loosely related. One requires a tray that
is almost certainly a "build" and the other needs a box of specific
dimensions, and is a "build or buy" depending on what sizes are
available commercially.

Let's start with the tray. We have steel slotted angle on hand, and I
propose to use it to create an L-shaped structure that has some adapters
to support a printer, connecting to existing tapped holes to one side
and "reaching down" to another shelf on the other end. That shelf is
plastic-laminated particle board, so a couple of wood screws will make a
good connection.

Are there metal analogs to wood joinery techniques? I am learning how
to assemble pieces of wood with little more than clever cutting and glue
(see keywords such as mortise, tenon, rabbet, dado). Given the right
keywords, I am happy to read how do similar "correct" work with metal.

As an example, what would be the best way to joing the slotted angle
pieces at a corners of the tray? They can simply sit one on top of
other. I could miter them at 45 degrees and add something, or create
something like a wood lap joint (mill each to half thickness and then
bolt them in a couple of spots??). The simple overlap would work well
for the tray because the uneven surface that results will not be a
problem: the printer will be held by "feet" on rails or something.
Better ideas are most welcome.

Now for the box. If I can buy one of the correct size, then great.
Otherwise, I start thinking of aluminum, with mitered (at the corners)
extruded pieces along the edges and at strategic places along the length
of the edges (for holding the junk inside the box), with sheet metal
walls that carry the shear ("stiffen" the box).

Comments or better ideas? I want it simple, strong, easy to build,
cheap of courseg, and it potentially needs to be a certain size. The
size will hopefully be worked out shortly. I am starting to make full
scale models of the important pieces (single board computer, power
supply, safety equipment, etc.) and will look at various ways to package
them. The stuff needs to fit in the box, and the box needs to fit in a
space with fixed dimensions; hopefully it will end up being quite
forgiving. If all goes well, I will end up merely adding an externally
accessible bay to a commercially made box.

Bill

New keyword: " weld". There is no analog in woodworking. "Glue"
works by adhesion, a weld works by fusing the metal into one piece in
the weld region.

Don

New keyword: " weld". There is no analog in woodworking. "Glue"
works by adhesion, a weld works by fusing the metal into one piece in
the weld region.

Fair enough, but welding metal seems analogous (in situations such as
mine) to using nails to join wood: it works, but there must be a better way.

I mention woodworking because there is a lot written on designing good
joints. In some sense, these books (whether the authors realize it or
not) show how to build joints that are balanced in the sense that they
have parts that fail at around the same load.

I am looking for insights into what makes a good metal joint. If by
some miracle I have an idea of the loads it will carry, then I will have
an excuse to go back to strength of materials and/or elasticity books.
For now, I am building things that are much stronger than they need to
be (put another way rigidity is more important than ultimate strength).

If there are books that will do as much for my metal designs as reading
about joinery has done for my wood construction, I stand ready for a
reading list. I prefer not to weld if I can avoid it.

For the project of immediate interest, there is a good chance that a
commercially made box will suffice for the tricky part. We are leaning
toward assembling it from two or three small boxes vs. trying to jam
everything into one box that would be a tight fit in the space allowed.
I am making models of the various components and will start trial
fittings as soon as they are ready. I just hope the final product looks
as good as the picture in my head

Thanks!

Bill

Bill Schwab wrote:
I have two projects that are loosely related. One requires a tray that
is almost certainly a "build"
....
Let's start with the tray. We have steel slotted angle on hand, and I
propose to use it to create an L-shaped structure that has some adapters
to support a printer, connecting to existing tapped holes to one side
and "reaching down" to another shelf on the other end. That shelf is
plastic-laminated particle board, so a couple of wood screws will make a
good connection.
....

Ordinary wood screws don't work well in particle board; instead
use "Euro screws" like at http://cabinetmart.com/69-63xxx.html
to spread out the holding force and to avoid the wedging action
of a wood screw.

I don't understand your description of the tray or its
environment. Also, roughly how many mm or yards long will the
tray be, and how many grams or tons does it need to support?

-jiw

James,

Ordinary wood screws don't work well in particle board; instead
use "Euro screws" like at http://cabinetmart.com/69-63xxx.html
to spread out the holding force and to avoid the wedging action
of a wood screw.

Thanks!


I don't understand your description of the tray or its
environment. Also, roughly how many mm or yards long will the
tray be, and how many grams or tons does it need to support?

I suppose if I could describe it well, I wouldn't need to ask the
question The tray is about 12x15 inches; the load is a small laser
printer. Steel slotted angle should do it. The question is how to join
it at the edges. Normally one simply overlaps and uses 5/16th (???)
bolts. I can do that because there will need to be some type of shaped
rails to "hook into" the printer, so I can hold the printer above the
bolt heads. I'm simply wondering if there is a better way.

Some time ago, I bought a copy of (don't laughg) The Robot Builder's
Bonanza, mostly for the electronics (originally for tilt sensors and the
parallel port interface was helpful too). I just hit me that it might
be of some value for metal construction, and sure enough the chapter on
a six legged walking robot includes a box frame: mitered extruded angle
with angle irons, overlapped (single shear), then bolted. He goes on to
square up with bolts and then one by one replace them with rivets
(probably overkill for me).

I guess I am looking for a survey of joint designs.

Bill