I had a customer bring me his to retip for him. I kept looking at the shaft, and thinking something just did'nt look right. Finally figured out that facing had broken off, and part of the threads with It. I told the owner It was missing, and only part of the threads still remained. He was bewildered looking, and wondered where It was. May have thought I broke It somehow, who knows, but I only had the shaft in My possesion, and told him It may have fell off while breaking the cue down, but to look on his handle for It just in case, because He had been playing with It like this, and did'nt even notice It before, so I was thinking It was possible It was still on the butt section If It was'nt clicking or making It obvious that something just was'nt right. Sure enough It was on the joint pin, and I believe what threads were left were holding It on there. It was'nt one of the fancier models they make, and the shaft still screwed on, so he did'nt bother to ask me to fix It thankfully. It looked to me that the facing & inside threads were one piece, and on this one the threaded part broke clean in two, leaving part of the threads on the facing (which came loose), and part of them remained inside the shaft, so It does'nt seem like delrin the way It broke like that, altough It does look like It. I have fixed inserts in some production cues that did have 3/8 delrin inserts, the glue broke down, and they backed out. I roughed up the od, used a poly glue, and they held up fine. I tried a delrin insert on a extra shaft I made for one of My production cues one time, same thing happened with epoxy, It backed out. I switched to the poly glue, and It held up. Too bad the feel of the delrin insert is so mushy though, because they make nice snug threads, but I don't like the feel of them at all.
I have'nt done inserts on these cues yet, but have made inserts for other cues, and had luck Keeping everything faced to the cue. I have done coring, then tapping but what I like better, and have also tried, is I drill,champer the centers, bore, and tap the core, then true It up between centers before installing into the shaft. I finish up the shaft bore with a small boring bar, and that seems to keep everything running true. I also work off of the steady rest when possible instead of out of the headstock, because It seems to center easier for me most of the time, and helps with runout It seems like. I am relying on the glue and not a mechanical bond though, but with the right glue, those things don't move at all. Epoxy may not be good enough though depending on the joint type or epoxy type. I fixed one that the pilot was shallower then the hole was on a cue joint, and so the insert backed out alittle. Tried epoxy & same thing, finally tried a different type glue, and It never happened again. I have never had one back out since either. Sizing the tenon/core to the bore is always easier, but in this case I am sizing the bore to the tenon, and have to be carefull because I want a snug fit, and don't want to overshoot My bore/inside diameter. I'm going to see If I can set My mini up to grind outside threads on inserts, but so far I have been able to get by without them when doing a custom insert. I like the standard self centering inserts, they go in easily, and center out well, but the little bit of fine threads on the bottom, does'nt seem like alot of extra protection anyhow. The full threaded inserts never seem to be true enough for me though, and I end up having to screw around with them to get them aligned properly. When I make My own inserts, or use the self centering I do not have those type problems, but at the same time I hate the thought of relying that much on any glue, even if It does work & hold well.
Greg