Can you just rout off a single outside layer of rotted binding if that is the only plastic that's rotting?

[Joseph Capra]

Its a Gretsch Van Eps model, and the outer later of body binding is the only plastic that's rotting. 

The purfling and neck binding seems to be made from materials which are immune from this affliction.

I've seen people chisel the binding out of the slot inch-by-inch to remove binding and purfling, but couldnt that be routed away with a laminate trimmer and bearing guides, gradually, in shallow depth cuts?

Ever tried this?

[Frank Ford]

Potentially, yes, but the binding may not be exactly uniform in dimension due to sanding after original installation, so you'd want to take it easy.  Me, I'd chip it off bit by bit. . .

[Hesh Breakstone]

I'd chip it off too.  

Lots of folks have paid dearly for specialized binding router jigs or built their own because the job is getting a uniform result on irregular surfaces is nearly impossible if your tolerances are down to a couple thou.  The guitar dome will vary, side thickness, the neck is in the way potentially and there are climb cuts to consider and understand unless you want a large, chipped out hole in the your Gretsch.

Stuff happens, router bits come loose, the depth of the original bindings vary because of the same issues above during manufacture and as such you may have and have project scope creep....  Routing off all of the binding and purfling is easier than attempting to literally split compositions layups.....

The guitar is now finished as well and one slip on your part and you may be learning a lot more about guitar finishing than you ever wanted to learn.

Sometimes there is just not a safe, reasonable substitute for endlessly toiling with sharp chisel in hand by candle light as some think that we do.... and are not always incorrect...

Or, in other words, what Frank said. ;)

PS:  If you want to google binding router jigs you will see what I mean.  It's a real trick to keep a spinning bit precise on an irregular surface.  Did I mention that Lam trimmers have runout and that ..005 to .007" that some lam trimmer collets produce may just eat up that next level of purling or layered binding that you are attempting to save.

[Joseph Capra]

A chisel seems kind of large and unwieldy for this job. Any tips on a good tool for chipping this binding out?

[Hesh Breakstone]

Chisels come in many sizes and shapes.  There is also a tool call a gramil often use for binding work that could be helpful.