My rack was built by my father in 1979. Due to the unavailability of equipment in New Zealand back then and in some cases to this day, Kiwi Kavers often manufactured their own kit. My rack was based on the 'Super Racks' made in the US in the 70s but with 3/4" square bars instead of 1" square. The frame is just a U-bend made from 1/4" 303 or 304 stainless with a pair of locked nuts on the top of each side of the frame.
This rack was tested to destruction in 1979 and I'm still using it!
??? you might say. It was assumed that the greatest force you could apply to a rack was plummeting down a rope till you hit a knot. The rack was therefore mounted in a rig that pulled on the frame and on a rope (12mm) with a knot jammed under the bottom bar and then an increasing force was applied until something broke. The rope broke and the frame bent a bit. After this test the frame was straitened and given to me. I still use it as my main abseil device.
As for the hardened bits... drill a hole in from one end a suitable depth. The first time I did this I hammered a 1"x 1/4" diameter piece of hardened silversteel into an interference size hole and then hammered a piece of Aluminium behind it. Later versions just used a hole the same size as the hard insert with the insert having a sharp point ground into the edge to be inserted first with an ally plug behind with just the hole peined over to stop it falling out. I have bars done this way that are now over 20 year old and have not worn since hitting the inserts.
If you want a quick and easy tip... The hole needs to be accurate to size, so if your crap at sharpening drill bits... Take a new 1/4" or 6mm bit, drill the hole with it then break or cut off the shank then grind a point on this and insert it. Dill bits are cheap.
