Is the swing arm drillable?

I have an extra and beat up cradle/swing arm I will practice on before attempting the real thing.

If you’ve got a beat up cradle, you could grind off the existing thin tube and have a very thick wall tube machined up and weld that in place. No nuts needed, just tap the wall of the tube. Now if I could work out how to post photos I’d show you.

You can as I did purchase a new tube section from AN. a local engineering company removed the old unit and welded in the new one
It needed no reaming just the protruding ends of the tube through the side plates filing down

While it's out just convert it to MK3! Do people not do this anymore?

The tube I will be working on, the spindle has a slight movement, no awful clunking but noticeable. The two 1/4-28 bolts placed as far apart as possible will be pulling the spindle to the rear when tightened up. That should be sufficient for everyday riding. my biggest concern is making a drill guide so I don't wallow out the hole trying to drill. The bike will be up on a stand, wheel and fender removed, and an awkward position for drilling.

Drilling and tapping hardened steel requires good drill bits turning at low speed to keep heat down. Most drill presses do not have a really low gear, but vertical mills usually do. I've actually had my best experience using an autofeed so that pressure on the drill bit is constant. Feeding by hand it is easy to apply too much force on a small bit and overheat the tip or break it. Or so is my limited experience.

Russ

Ludwig's modification is more than just 2 bolts parallel to each other. He uses the 3rd bolt to lock the spindle in a perpendicular direction to the other two..