Materials for Mods

The usual route is to get a 1/8" (3.5mm) jack and same sized plug for the cord.  If you're going to completely fabricate your own main wire, you'll need two 1/8" (3.5mm) plugs (unless you specifically want your cable to terminate in a 1/4" jack or something else, but the 1/8" is the stock size).

Here is the 1/8" jack panel mount I used, which I installed in the right cup using the same openings that the stock wire comes through (widening them a bit, of course):

http://www.radioshack.com/product/index.jsp?productId=2103451

Then you'll need a plug like this:

http://www.radioshack.com/product/index.jsp?productId=2103990

Again, there are a lot of other options for manufacturers out there.  Here's some suggested to me.

http://www.head-fi.org/t/560806/sr60-mod-part-ii/2805#post_7958873

You'll also need to acquire speaker wire or some other type of wire to run sound from right to left.  The stock wires from Grados that go from the Y to the individual drivers are too short for this task, so I used 24 AWG copper speaker wire, which was $6 for a spool at Radio Shack.

http://www.radioshack.com/product/index.jsp?productId=2102499

Again, lots of different options for wire.  Using 99.99+% pure silver wire for all wiring is a popular solution since it has 7% more conductivity than copper, but is costlier -- a three or four conductor braided wire in sizes useful for headphones (24-26 AWG) can go for $12-20 per foot.  I just used the stock main wire from my Grados, cutting them off just below the Y joint.

Here's a link if you're interested in going with silver wire.

www.homegrownaudio.com

As far as tools, I used a multimeter, box cutter, wire cutters, 30 watt soldering iron, and power drill with an assortment of bits.

Does it matter what kind of silver wire I should use for these mods? I'm kind of confused by the myriad of wires on this website :P
http://www.homegrownaudio.com/categories/Solid-Core-Wire/Bulk-Silver-Wire/?sort=pricedesc

Well, for your main wire, you want either three or four conductor.  The ones you're looking at are single strand wires.  You're better off getting something like what's on this page:

http://www.homegrownaudio.com/categories/Braided-Wire/?sort=pricedesc

For maximum conductivity, you want one where each conductor is 99.99% silver -- some of the braids are combinations of silver and copper.  Homegrown Audio differentiates between the two by using an S (silver) or H (hybrid) after the model number for a particular braid. You also want enough thickness to carry the signal.  You should be able to get away with 26 AWG, although 24 AWG is preferred.  This is especially true if you want a longer cable.  The IC-3.24S or IC-3.26S are good choices for a main cable, as you would have one conductor for ground and one for right and left channels, respectively.

You'll also need a few feet of either a braided wire or the teflon coated single strand wires for hooking up the drivers (unless you can find pure silver speaker wire, which is infinitely more convenient).

I think this applies: http://www.instructables.com/id/Make-Your-Headphone-Cable-Removable/

There are some kits out there that people sell. Also get in touch with cable companies as they'd be happy to give you the materials necessary for your modification.