Me personally? I qualify hoppers as machines. Simple machines, mind you, but machines nevertheless. Plus a hopper is working a large amount of iron into shape. Something like the Bibliocraft tool rack, or the Book Binder has iron as mainly a structural element. You could have replaced the iron with wood or stone and probably worked out just fine, except for limitations with the crafting grid.
The detail I plan to base my judgements off of is small amounts of iron that don't need to be particularly strong or complex. If I could shape the metal part(s) with a hammer, a charcoal forge, and an anvil; it doesn't use more than 3 iron ingots; I could accomplish the metalwork in under a day (I'm part of a medieval reenactment group, so I have a bit of basic blacksmithing training); and the metal isn't a working part more complicated than one of the Simple Machines (lever, inclined plane, etc.); then it is good to go for me. The Chisel is a great example. That's a wedge, that you could work-harden and even cold-forge (tempering is a higher-tech operation). The tool rack uses it for the clip/rack things. The book binder is a heavy metal plate (mostly used for weight/pressure).
Probably the only "tools" I would allow myself in stone, and maybe wood would be the saw from Forge Multiparts, and the pots/pans/whatever from Pam's Harvestcraft.
The detail I plan to base my judgements off of is small amounts of iron that don't need to be particularly strong or complex. If I could shape the metal part(s) with a hammer, a charcoal forge, and an anvil; it doesn't use more than 3 iron ingots; I could accomplish the metalwork in under a day (I'm part of a medieval reenactment group, so I have a bit of basic blacksmithing training); and the metal isn't a working part more complicated than one of the Simple Machines (lever, inclined plane, etc.); then it is good to go for me. The Chisel is a great example. That's a wedge, that you could work-harden and even cold-forge (tempering is a higher-tech operation). The tool rack uses it for the clip/rack things. The book binder is a heavy metal plate (mostly used for weight/pressure).
Probably the only "tools" I would allow myself in stone, and maybe wood would be the saw from Forge Multiparts, and the pots/pans/whatever from Pam's Harvestcraft.