Steel/Jig Strength

[Dave Davis]

Terry,
  There is a place in Seattle called "Metal Shorts"
that carries remnants, etc.  (The name always makes me
think that metal shorts would be a little
uncomfortable and chilly in the winter.)
  But to the point, Glen is right in that lighter
pieces with angular supports can be stronger.  The
trusses in the roof structures of newer warehouse type
buildings are often designed this way.
  Also, if a small I-beam isn't available, you can use
two light channels welded or bolted back to back for
more vertical support.
  Not an engineer, but I've been around steel, etc.
quite a bit.

Dave Davis
Renton, WA

--- Farrell <mfarrel2@tampabay.rr.com> wrote:
> Thanks for the input. What other specifics might you
> have in mind?
> 
> I think recycling metal is an excellent ideal to
> pursue. But sometimes you just need what you need. I
> usually go to  http://www.metalsupermarkets.com/ . 
> Great place. They have anything you might want and
> will cut to your specs. Just order, load up your
> trunk, and assemble your jig (well, almost that
> easy).
> 
> Terry Farrell
>   ----- Original Message ----- 
>   From: Crashvalve@aol.com 
>   To: pianotech@ptg.org 
>   Sent: Monday, November 10, 2003 7:54 AM
>   Subject: Re: Steel/Jig Strength
> 
> 
> 
>   In a message dated 11/10/03 7:17:11 AM,
> mfarrel2@tampabay.rr.com writes:
> 
> 
> 
> 
> 
> 
>     I've made myself a little pneumatic contraption
> for laminating ribs. I seem to have just about
> everything worked out for proper function (actually,
> works quite a bit better than I had hoped!) except
> for some excessive jig flex. I have a 1.5-inch-thick
> Delignit pinblock incorporated into the jig for
> stiffness, but I still seem to be getting several
> millimeters of flex in the middle of the 5-foot long
> jig when I pressure up. So I think the solution is
> to put a couple of angle irons, or steel channels
> along the length of the jig. This thing is getting
> VERY heavy, so I prefer to not use any more steel
> than needed.
> 
> 
> 
> 
>   I've no science background, but i've made numerous
> structural steel jigs.
>   My first jigs used steel as a monoblock material,
> a "one piece big enough to resist" approach.
>   That is off target. What you want is a little
> teeny bridge structure. In other words, multiple
> pieces of steel with lots of triangle shapes for
> rigidity. This way there is not too much mass, but
> great rigidity. If you don't want this large "fab"
> job, use a steel channel or even an "I" beam, but
> then it will be heavy; I store my big jigs outside
> and paint them. A necessity after my first 14 foot
> long soundboard jig. BTW don't order steel from your
> friendly supplier, check the scrapyards for
> material. You can't pick and choose as much, but
> it's way cheaper. You may consider this close to
> dumpster diving, but It is invaluable to the machine
> builder. At the scrapyard you don't worry so much
> about the calculations, just buy way over what you
> need, and start an outside storage rack area. If you
> start fab work like this, access a sawzall for cuts,
> or a torch. A resinod cutting disc in a tablesaw is
> a BAD idea. If you have specifics shoot them back,
> happy to answer from no-training and 12 yrs. of
> practical experience.
>   Glenn C. 


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