Advice on tapping fork caps

[Morse]

98 STD

Finally got around to replacing my leaking fork seals, worn bushings, etc...

The left side went smoothly but when I took the right fork cap off i found the hole in the underside was all buggered up.  The damper rod that generally screws in underneath wasn't put into the cap right or possibly at all by the PO. The threads on both the rod and the cap are too bad to put back together right now.

 I think I'll be okay using a triangle file and a die on the damper rod (but if anyone knows the bolt and thread size you could save me a trip to the hardware store  ).  I'm not sure exactly what the best course of action would be for the cap though.  I've had some poor experiences in tapping stripped aluminum in the past.  Has anyone done this before or have a good method for tapping aluminum? 

Right now I'm between trying to tap it or drilling a bigger hole in it until I pass the first few threads that are bad and just screwing in to the remaining good threads.

[Chrisj CMA]

Drilling it out like you said doesn’t sound too horrible but I’d make that plan B. I think you should run the tap first and see what happens unless you feel it’s so bad you might screw up all the threads

[Large]

Helicoil maybe  I have had good
luck with them

[MarkT]

Besides the above advice you can likely just replace the cap from the breakers.  Not to mention a new part.

[Factor]

If you have a drill press, put the tap into the chuck and hand spin it with the cap secured to the deck. That will at least hold the tap along the axis steady. If you have exposed belts on your drill press (like mine), you can just pull on those with one hand while applying pressure to get smooth up/down with the other.

After proof reading that, it occurs to me that this thread may need censoring.

[98valk]

use a thread chaser first before using a tap.  might be all u need to use and that way zero material will be removed.

https://www.matcotools.com/catalog/product/TDK15/15-PIECE-METRIC-THREAD-RESTORING-SET/#to-details

[h13man]

I'd use "bottom taps" for thread chasers if you can pick up the beginning threads. Be sure to use a lubricant of some sort once you get a good start to avoid further galling. Go easy. Can't tell you what size for sure as I've only been in the forks once changing springs and oil 30,000 mi. ago.