Non marring clamp screw

[Don42]

The roll of paper towel in my lab keeps rolling off out of reach. It’s annoying! I decided to make a paper towel holder.
There’s a painted sheet metal lip on the back of my MIG welder where the gas bottle goes. I thought I might clamp a vertical post to that lip to hold the paper towels.

The clamp was just a bit of ¾” wide x 1/8” thick steel bent in half with a nut welded on one side. I then brazed a bit of tubing to that to be the towel roll holder. I didn’t want to mar the paint on the lip of the welder. Solution: a nylon clamp screw – but I wanted a knurled knob I could get hold of.

I found a ¼-20 nylon screw in my goodie box. The head of the screw is .505 dia. I made an aluminum knurled knob, bored out a cavity to .502 dia the depth of the screw head which was about 0.150". The knob is 0.300” thick. I drilled and tapped it ¼-20. I lightly chamfered the entrance to the larger hole and filed a slight chamfer on the head of the nylon screw, then screwed the screw into the knob with a wide blade screwdriver. There was some resistance when the screw head met the metal because it was an interference fit, but it went in OK and it can now withstand more than enough torque to achieve clamping with no risk of marring the paint on the welder lip. Apologies for the fuzzy focus on the nylon screw but I think the photo illustrates the idea.

[Scotsman Hosie]

Nice work!