I've shifted from game development models to engineering (mostly quality control and reverse-engineering). I have such types of tasks:
-To compare real machine part to it's CAD model (to find out if our old models are accurate enough, or to make sure the detail has proper characteristics as it is showed in it's cad file)
-To make 3d drawings (cad) of old machines. Some has proper "old-fashioned" drawings, some not.

What me colleagues did before and what we do now is we measure object we work with and than compare this numbers with numbers in cad file. Or model according the measurements.
It's not the fastest and accurate process.
On my previous job I used 3d scanner to scan people for character creation. I think, that same technique can help at my new job, but i know that engineering needs more accuracy than game-development.

Speaking shortly. I was offered Space Spider scanner (I left the link to be clear), and i'm not sure if it will be suitable for me. Manufacturer says "yes", but i used their other product "Eva" and I saw, that equability was not enough. As this guys costs huge amount of money i need to be sure if i have to buy Spider, or people who have huge experience in CADs can suggest me a better option.

I guess it really depends on what kind of parts you have to remodel. If your parts have complex surfaces, you probably need some kind of 3d scanner (like the one you mentioned). For simple mechanical parts, you're better off with stuff like calliper, height gauge and micrometer.

I think photogrammetry would be suitable, because you know the "design intent" (as SW fanciers are fond of pontificating) of a machine, you know what it's intended to do. Fasteners and stock part sizes will often give you dimensions (how many pitches along a lead screw, how many teeth in a gear when you can find its diametral pitch, gear-train axle centres from the same detail), manufacturers specifications for centre height and distance-between-centres for lathes, etc. As well as that, "aesthetic" features like ball handles or fillets are more "add-on" on older machines, which give strong dimensional clues. You can take some manual measurements to give driving dimensions, and use photogrammetry to give you proportional relationships of the features for the machine overall. In older machines that I've seen, even when they're complex, their parts have been developed and added in fairly obviously linear sequence, and they have almost no freeform aesthetic adornment, everything is functional, or composed of analytical shapes, like a real-world implementation of constructional solid geometry, because that made things easier to produce.

What arm is it? Could you pm me details?

Cheers