I am new to this site and I posted a blog which now I am unable to find.
So I will do it here again.
I have a Lowden 035 which is about 10 years old.
I recently adjusted the relief in the neck and it the process I apparently came to the end of any further adjustment of the truss rod. It tightened up and allowed no further adjustment.
At the moment the neck is fine with a little relief and playability is good.
My problems is in the future. If I need to adjust the neck again I have no way of doing it.
Any ideas how I can fix this problem without major surgery? Any ideas are most welcome.
I have the Stewart MacDonald truss rod tool, I have it because it paid for it self the first time I used it. I made a deal with the customer saying that if it worked he would pay for the tool if it didn't I'd replace the truss rod minus the cost of the tool. It worked ten years ago and I've used it twice since then. I've replaced about 5 truss rods in that time.
I also have a neck heat press, a long metal box with a heating element in it and a small collection of U shaped clamps that have come in handy countless times over the years. The heat press, when it works, is great, there is a learning curve and a failure rate but that aside it's a really handy tool that has gone out of fashion in recent years. I mention the heat press because that's the approach Bobs talking about.
The best repair is one that leaves you with an adjustable truss rod. The idea of clamping the neck straight and shimming the truss rod nut aren't separate repairs, they are when combined your best bet next to a replacement truss rod. One other thing when you get the nut off put lithium grease or something like it in the nut, that will help too.
Here's a really good description of truss rods and how they work: