I have read a lot of solutions on this forum relating to worn Norton lower legs/sliders.The people involved whilst they must be very good engineers seem to have got in a mindset about the best way to solve this problem.The solutions I have seen have a bit of sending a rocket to the moon.They also weaken the original legs.I had this problem over 50 years ago when I was using a pair of long roadholder fork legs on an Ariel special I was building.Money was tight but the solution is far better than any I have seen on forum.You simply bore out the legs/sliders until they are round.You then make or have made bottom mild steel bottom bushes to suit and purchase suitable shim material to fit OD of top bush to suit ID of legs/slider.I did this 50 years ago and still have same forks. Simples as the ad goes. Jim
About 30 years ago the AMC spares crowd started to offer replacement sliders for their big twin forks. These have a profile and innards that are similar to Norton forks. Almost immediately reports came in of exploding sliders caused by hydraulic shock in the damping area. An investigation seemed to indicate that the thickness of the walls and choice of alloy made these replacement sliders inherently weak in some areas. My guess is that boring out a Norton slider might thin the metal to the point where it too would struggle to cope with the damping forces imposed on it. Which is possibly why this good suggestion (& sleeving) have not been widely advertised as a fix for worn Roadholder sliders..
A few years ago i had an email conversation with the late John Robert Bould concerning the 'snaking of front fork springs. In the chat we talked about the Jig he used in his lathe to bore out worn fork sliders and what and what not to do to avoid 'reamer wander' and the requirement to remove as little as possible to achieve a true bore.
I think this repair for worn sliders isn't popular because brand new replacements are available at a price that makes repair uncompetitive