Can Interconnects be converted to speaker cables

Yes it can be done, but is will sound terrible. Each strand or wire should match and that is not the way IC's are made.
But in honesty the signal can be sent across most conductive material. You have only to lose and nothing to gain.

Many speaker cable users employ quite thin wires very successfully.

Yes that is true but usually many wires. My Nordost frey speaker cables use 28 24 gauge wires where the ics use 6 26 gauge wires. Capacitance and inductance is quite different too.

The 47 Labs OTA cable kit uses 26 gauge solid core copper wire, one for the positive and one for the negative. I never encountered a problem with these cables.

I think it just may come down to the IC you want to convert. However, it can be done and successfully.

I've been on both sides of this one. As to the thin wires I can assure you it does not sound terrible. Far from it. Back when Listener magazine was alive I read the late Harvey Rosenberg's treatise on thin solid core cables, using Radio Shack magnet wire, and gave it a try between speakers and amps at a time when I was using biwired Kimber 8TC between my SET amps and ProAc Response 3 speakers. Two single strands of 28 gauge magnet wire sounded a hell of a lot better as speaker cables than the Kimber, at that time, in my system, to my ears, though I was not alone.

Since then I've tried thin ribbon cable (Omega Mikro) and everything up to 14 gauge stranded. As noted, I'm back to the thin solid core Morrow Audio IC/speaker wires.

As Clio notes, it can be done and successfully. Try it and see.

If you are adapting to binding posts or banana jacks that have standard 3/4 inch spacing, you can use these adapters, costing $16.60 each:

http://parts.digikey.ca/1/1/435200-adapt-phono-jack-dbl-banana-plug-1442.html

The manufacturer's data sheet can be found here:

http://www.pomonaelectronics.com/pdf/d1442_1_01.pdf

As several people have stated, though, gauge is a major concern. If the center conductor of your interconnect is in the area of 26 or 28 gauge, which is the case for many interconnects, a 10 foot run will have a resistance in the vicinity of 0.5 ohms. That will reduce whatever your amplifier's damping factor is to something less than 16.

If your speakers do not have low impedance at any frequencies, especially in the bass region, and if they do not require a lot of power, and if their woofers do not require tight control by the amplifier, and if the run length is not long, you MIGHT get reasonable results with that kind of gauge.

Regards,
-- Al