This job used to be so hard that guitar necks got thrown away as “unfixable.” Dan Erlewine shows that it’s now pretty simple with StewMac Truss Rod Rescue Tools:

Choose the Rescue Tool Set for your specific truss rod, or equip your shop with the Master Set for a wide range of truss rod repairs:
http://www.stewmac.com/item/6203

Individual components are also available separately:
http://www.stewmac.com/item/6190

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