12ax7
Super Member
Got one of these?
A common result of trying to remove the lock nut or just aging and flexing is that the threads break off of the plastic armrest. There are options to replace these, such as a rest from a different table, but I wanted to retain an original appearance.
I got some 5/32"x.014" square brass tube from a hobby shop and some 4-40 thread brass screws, nuts and washers. I chose #4 thread because that is the original size and wouldn't require enlarging the hole in the steel deck although it does fit loosely in the tube (every mod I make to this table is reversible). Cut the tube to 1 5/16" in length. File, sand and polish the rough edges. File or grind the screw head evenly to a square shape to fit snugly in the tube and wrap single strand copper wire around about 1/8" of the thread below the screw head. This will center the threads inside the tube. Flux the screw head and wire, insert into tube and solder in place with a propane torch.
The bottom of the original armrest and the hole in the deck are diamond shaped to align the rest to the AR arm shape. If you've swapped arm wands, this alignment may no longer be correct. Also, the original armrest was quite flexible, which allowed it to move back and forth with the movement of the soft AR subchassis suspension. I made soft washers out of thin sheet neoprene by using a paper punch and a sharpened section of an old antenna as a smaller punch that allow the new armrest to also flex.
Cut the shaft of the old armrest to accomodate the shallower depth of the brass tube. The cross section of the shaft is slightly trapezoidal, so you may have to scrape the wide side slightly to fit. I found that no adhesive was needed to make a snug fit.
Some sort of threadlocker will be needed. Lock washers won't work if the rest is to remain flexible. That rubbery clear glue from junk mail seems to work well if stretched around the threads and then heated after the nut is in place.
These can also be used as a dress-up accessory by polishing to match a polished counterweight and logo badge. When painted satin black, you'd have to look twice to tell that they're not original.
A common result of trying to remove the lock nut or just aging and flexing is that the threads break off of the plastic armrest. There are options to replace these, such as a rest from a different table, but I wanted to retain an original appearance.
I got some 5/32"x.014" square brass tube from a hobby shop and some 4-40 thread brass screws, nuts and washers. I chose #4 thread because that is the original size and wouldn't require enlarging the hole in the steel deck although it does fit loosely in the tube (every mod I make to this table is reversible). Cut the tube to 1 5/16" in length. File, sand and polish the rough edges. File or grind the screw head evenly to a square shape to fit snugly in the tube and wrap single strand copper wire around about 1/8" of the thread below the screw head. This will center the threads inside the tube. Flux the screw head and wire, insert into tube and solder in place with a propane torch.
The bottom of the original armrest and the hole in the deck are diamond shaped to align the rest to the AR arm shape. If you've swapped arm wands, this alignment may no longer be correct. Also, the original armrest was quite flexible, which allowed it to move back and forth with the movement of the soft AR subchassis suspension. I made soft washers out of thin sheet neoprene by using a paper punch and a sharpened section of an old antenna as a smaller punch that allow the new armrest to also flex.
Cut the shaft of the old armrest to accomodate the shallower depth of the brass tube. The cross section of the shaft is slightly trapezoidal, so you may have to scrape the wide side slightly to fit. I found that no adhesive was needed to make a snug fit.
Some sort of threadlocker will be needed. Lock washers won't work if the rest is to remain flexible. That rubbery clear glue from junk mail seems to work well if stretched around the threads and then heated after the nut is in place.
These can also be used as a dress-up accessory by polishing to match a polished counterweight and logo badge. When painted satin black, you'd have to look twice to tell that they're not original.
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