In the course of working on my Shadow motor I have come across several large nuts that have been punch locked, including PD7 and G23. I hope that in this day and age of "lock tite" and equivalent threadlockers that indiscriminant practice of this dark art has fallen by the wayside, but here is a little tip to correct damage of the nuts. Old hands may have been using this, but I haven't seen it in writing. Obviously the best method of reclaiming the damaged nuts is cleaning the threads with the proper tap, but the big taps are expensive and seldom used, so it is hard to justify the expense. Purchasing anything new when the old can be reclaimed goes against my frugal grain, so here goes the fix-- first clamp the inner third of the large nut using the lateral face of your vise, long axis of the nut perpendicular to the vise, with the damaged area of the nut at the bottom. Next take a triangular needle file, corner downward, and stroke back and forth briskly. Remove file periodically to inspect. When the offending defect is removed, you will have a clean, sharp "V" in the threads. A 90 degree bend dental pick can be used to clean the threads further. If additional punch damaged areas exist, rotate nut and repeat above. Since only a small amount of material is removed, the nut is still structurally sound. An alternative method is to use the file to cut a "V" on the shaft the nut threads on, then run the nut down on the shaft. Both methods create crude "taps" and "dies" thereby allowing one to clean and salvage shafts and nuts that in some projects (non Vincent) might be well nigh impossible to replace.