Where can I get a 1/2'' spindle and router bit adapter for a Powermatic 23 shaper

So are you asking where to buy replacement parts, where to have it repaired, or how to repair it once you have the parts ... you will need to be a bit more specific. As it stands you have only made a statement.

A bit can wobble and cause vibrations is if it isn't in the router straight or something is out of balance, either motor or bit. A broken bit can cause this, try another bit to see if you have the same result. If the collet is broke or jambed in off center it can do the same. Make sure the collet is intact and in straight. Check the motor spindle for side to side movement which can be caused by a bad armature bearing.

Screw a starting pin ( see manual) into the base plate then cut a small block of wood that engages the face of the cutter and the starting pin. This locks the spindle and stops it moving. Use the supplied spanner and tap with a mallet. Tap the cutter to loosen it. Dave and Graham.

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Get a new collet and nut the 1/2" collet is crappy, it is too thin and pushes out of the nut easily.

You may also make sure that the collet did not seperate from the nut. remove the nut completely and if the collet is not attached, remove the collet from the spindle, insert inthe nut and then insert the bit through the collet while holding it and then put the hole thing back on the spindle (mtor shaft) and tighten it.

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Your router bits must have a 6mm shaft, whereas your router with the collet closes down on a 1/4" or 6.4mm shaft. You will need to get a metric collet for your router spindle, or get a new set of 1/4" bits

You didn't state the model number. The older Craftsmen routers had a red lever lock on the top of the router, one position allows the spindle to turn, the other position locks the spindle. Here's the instruction for the older style routers:

1. Unplug the tool.
2. To lock the spindle press the red button in and slide it to the locked position.
3. Unlock the height adjustment knob.
4. Raise the router motor using the height adjustment collar until you can get a wrench onto the collet nut.
5. Loosen the nut until it turns freely.
6. The bit may still be locked in the spindle, tap it gently (not on the blade!).
7. The bit will come loose in the spindle and can be removed.
8. Replace the bit, tighten the nut snug but don't use excessive force.
9. Unlock the spindle, returning the red lever/button to the free position.
10. Adjust the height of the bit as you wish, then lock down the motor using the locking knob.

If I understand this right you can't remove the bit from the collet. If this is true there might be dirt on the collet and you can try and blow it out with compressed air. What I would do if that doesn't help is support the collet nut allowing the bit to hang free and gently tap on the back of the bit and this will remove it. It is possible that you may have overtightened it or the bit has a burr on it. Good luck

im not familiar with that router but most have below the bit two nuts that you use wrenches to loosen. some have a pin to lock the spindle in place