I've been getting my TIG welding of stainless up to snuff recently and I considering building a machine. If you could build a machine around any grouphead that can be bought whole or in parts, what would your custom dream machine have? I think a saturated design might be best and a paddle seems very cool. So what would your machine have?

You should contact Lino Verna, he has some experience with "out of the box" thinking about group design. See this post for a photo of his 2006 prototype.

Conti levergroup directly from their website. Glorious linkage system.

Groups sold as a whole tend to be expensive, for instance, the E61 is around $600, as much as some machines with E61 groups! Many groups are available in their entirety as multiple parts, and when added up, they are just as expensive. In this respect, espresso parts are like the car parts, the whole is massively less than the sum of its parts.

Because of this, roasters who place a lot of espresso machines with their client cafes have a graveyard of dead machines that they cannibalize for parts. I'm guessing Ebay and Craig's List could work as well as a graveyard; and that you might get a non-functional machine with several good groups for less than you could get a single group at a parts house. Since groups tend to be robust, this may be the way to go.

another_jim wrote:Groups sold as a whole tend to be expensive, for instance, the E61 is around $600, as much as some machines with E61 groups!

You should search around a bit.
I can get a MCaL head for ~€230, complete E61 levetta for ~€180 and the mentioned complete Conti levergroup runs ~€300 directly from Conti.

I have noticed the disheartening trend that groups are exorbitant. I guess what I'm trying to do is avoid reinventing the wheel (i.e excess use of milling machine or learning how to investment cast). Broken machines for scrap is a great idea. To build a group, the only part I stumble over in the mental assembly is the bayonet and dispersion block and gasket, because of the tolerances required and the desire to use non custom baskets and PF. As an aside for group discussion, if cost were not a consideration, what group would your dream machine have and why? Maybe I can incorporate some design features. Some notable groups (non-lever for now) include La Marzocco, NS Aurelia, Elektra, E61, Slayer, Synesso.

I like the over-engineered dispersion block and group bell used on Elektra/Bezzera/Brasila machines (they are not interchangeable, just the same design). A nice laminar flow through the puck is, as far as I'm concerned, contributory to a good shot. All three companies mate this section to a number of back sections (the section containing the three way valve, gicleurs, and attachment to the rest of the machine) that either bolt directly to the boilers or have thermosyphons for heat. If you are using a steam boiler, I'd go with one of these, and use a needle valve on the thermosyphon like Faema or NS, so you can dial in the head temperature to whatever you like.

If you are going with a double boiler, one of the flooded groups, like LM or Synesso, would be best. However, scrap machines from them cost more than the more common scrap machines from one of the above.