When my AP-900 clutch (nylon) plugs “MUSHROOMED” out into the channel space between the axle and the head/knobs – because I didn’t fully appreciate the warning in the manual, about the harm of tightening the clutch plugs down hard, (even once), with a hex wrench would cause. I bought the AP special plug extraction tool to extract the flattened plugs. The AP screwdriver tool was a total waste of money, time and effort – as even AP warned me about. Perhaps it might work for those you NEVER used the hex wrench on the plugs, and were oiled regularly, rather than locked in permanently.
But I thought it was worth a shot. The AP tool - or your own “ground off and file shaped” screwdriver blade tip, just “bites” into the plastic, chipping it into grain-like particles, and never gets a foothold into the plug. Even if it would, it would require super human strength to unscrew, since the inside portion is now much fatter than the part still in the plug hole – so will never squeeze back to its original diameter to come back out. Like child birth – one way out only :-)
The only option is sending the mount in, for AP to work on it - or much quicker – dismantle the axis “head cap” by trying to crank it off and free from the 4 plugs death grip. I tried to do that manually after removing the 5 or 6 head screws from the axle top, then planting my feet on the mount and risking back pain while pulling upward - it didn’t budge. I even attached a long D-Plate to the head, “for leverage”, and tried to gradually twist off the axle head cap with all my arm strength. It turned a bit, but just would not twist up and off, but maybe you will be lucky, if your swollen plugs are still gripping the shaft center more lightly than mine did.
Hopefully, the following procedure won’t be required.
If they are really stuck - the far easier way, expecting to spend a couple or a few hours for this job - is to use the two totally “UNDOCUMENTED PURPOSE”, 1/4-20 tapped open holes, in the end of the head cap. These are tapped holes for two “PUSH SCREWS”.
I had to insert a “bottoming tap” since AP failed to tap the holes all the way through, so the screws would be blocked near the end anyway.
Place the “separated” DEC or RA mount base section in a “large but shallow cardboard box” – I used the lid from a XEROX PC Paper carton, since the cardboard won’t let any fallen out bearing race plugs bounce out onto the floor, and be lost. You will need to buy a KIT package, of at least a dozen plugs, to replace the 8 clutches on both axes, and the spares to replace any lost ones from the bearing race. More plugs might be better, in case even the new plug diameters differ, depending which manufacturing batch they came from, and still won’t slide in easily into the clutch knob channel. So, test each one in the kit in each clutch hole, to find the ones which are slim and thus loosest, so they won’t swell out in later years. Do this BEFORE you re-assemble and bolt the axle top cap back on, later.
Here’s AP-900/1200 mount axle disassembly, clutch plug replacement job ...
Insert a couple of very long (3”-4”) hex head machine screws, and torque each one “alternately” a few degrees at a time, with a socket wrench. These screw tips push with tremendous force against the axle surface, just under the cap. I would suggest filing these screw tips “round”, so their tip slips as it pushes down, or scratches against the inside mating axle top (invisibly, doesn’t affect anything). Eventually, the head will “walk itself up” and away from the axle top, exposing a couple of dozen “identical” nylon plugs, used as RA or DEC “roller bearings” around the axle. Note, there will be ONE LESS plug cylinder in the track, so don’t think it was lost on the floor – the obvious gap provides space between the race train plug/bearing rollers, so they don’t rub against each other.
Final step is to force each clutch plug through the hole, out into the now “empty center” with that head cap removed. You can try to “screw-in” the old plug using that AP screwdriver tool, since the old originally smooth surface plugs have now gotten the channel threads pressed permanently into them. Mine still refused to screw in, so had to be drilled in with a slightly smaller diameter drill bit – which grabbed into the nylon, and easily “spun it” inward, quite quickly – as the drill bit into the plastic and grabbed it tightly. If you must, do so with a VERY slow drill speed,. making sure to keep it perpendicular to the surface, drilling straight into the old plug. If it still doesn’t budge by spinning, you will end up drilling a hole through, into the nylon, which you can then carefully chip its wall out, at one point, and the rest will loosen enough to be pushed or screwed through to the empty center.
Just be very careful not to gouge the clutch knob channel threaded through hole, or you may need to repair it using a threading tap to “rework” it.
Finally – BEFORE replacing the axle head cap - test fit each new nylon clutch plug to select the best, 4 or 8 loosest ones. Otherwise, you may have to push/hammer through, even these new ones, if they bind and also won’t slide smoothly into the threaded hole.
It still requires a “FAIR amount” of work, hope to never do this again – Lesson learned about not using hex wrench for plugs, finger tight only - but eventually the task was not that difficult with this method. Your other choice is to send your mount in to AP, lose the use of your mount for perhaps months, and the hassle and costs of shipping. After having done the job myself, I can really appreciate the hard work and time, someone at AP tech support would have to put in, to do this repair. Not easy, but doable.
Makes upgrading to a modern AP-1100/1600, with no clutches to eventually jamb, such an appealing idea,
Hope this outline helps.