This is intended as a guide and an explanation of an exploit; where such goes, I am not sure. I will be showing how to replicate the steps in this exploit, and later explaining why this process works.
How to craft arms with 2 sockets:
To start with, make sure you are a Droid Engineer. Being level 90 is a plus, although a lower level DE should be able to acheive similar results at the cost of more material.
Firstly, it should be noted what is needed for each arm. At it's simplest, you will need copper, steel, inert gas, polymer, lubricating oil, and steel, in the form of Control Units, Micro Sensor Suites, and Electronic GP Modules. Note that the quality of these materials are of no importance, as I'll discuss later- indeed, I used smelted steel, copper, etc. whenever possible, and had no issues getting sockets on my cybernetic arms. The process of making an arm can be made time efficient by utilizing equipment factories; note that utilizing a factory is not neccesary, and every cybernetic arm must be crafted by hand anyhow.
Okay, so to make an arm, you need 6 Electronic GP modules and 2 Micro Sensor Suites; to make the Micro Sensor Suites, you need 1 Control Unit and 1 Electronics GP module per sensor suite (this is why I recommend to make factory runs; large runs will save huge amounts of time). Once you have all the electronic components for the arm, go ahead and make a test one- this is to see if you *can* craft one with 2 sockets. A single PUP and a knife with assembly attached are all I have- just like crafting armor, shoot for 160 assembly, and you'll get a socket 99.99% of the time.
The RE Process (and where you probably went first)
Okay, so you've made a cybernetic arm, and it has two sockets. What now? Now it's time for an armorsmith to make two attachments for that arm. Make sure that the attachments equal a power of 35 or greater, and are of the same attribute; i.e., 25 constitution and 17 constitution = 42 constitution. Attach them to the arm, RE the arm, and viola- +35 bit! Adding a 3-4 stat loot when RE'ing makes a +35 3rd order bit in one step as well.
Why does this work? Quite simply, when you have 17 Constitution in one socket, and 25 Constitution in another on the same piece, it gets "merged" into a single stat- so we see two single separate stats instead of one- in this case, 42 Constitution. We've seen before that certain items over 35 on a stat get RE'd to a +35 bit, and the same is happening here.
Good luck folks, and get to RE'ing before this (likely) gets nerfed!