source for steel bar stock?

[Bob Blarney]

If the parts fit together well, then I'd guess that little clamping pressure is needed - maybe not much more than clothespins.

 

I'd go with the K&S brass (easy to find too) - homecenter aluminum is too soft, and while steel is more than plenty strong it is more difficult to work.  A lubricant such as Tap Magic will make drilling and tapping of metal significantly easier, or 3in1 or other light oil will help too. Also, hardwood such as maple can be drilled and tapped too, and the threads can be strengthened with CA glue.

 

Guitarbuilders also make spring "C" clamps with PVC pipe of different diameters - just cut off a width and saw a slot to make it.

 

Here's a clever idea:  https://sharing-know-how.blogspot.com/2015/04/clothes-pins-into-modelers-clamps.html

[Griphos]

I had totally forgotten about the PVC "spring" clamp idea.  I used to work as a finish carpenter with a guy who made guitars.  He had lots of cool clamps, but he also had a few PVC "clamps" as well.  

 

I've got lots of reversed clothes pins of several sizes.  Those do work well when there's room for them.  

[Griphos]

I thought I should post the results of everyone's assistance.  I decided to make some C-clamps from brass and screws.  And some miniature wooden screw clamps from, well, wood and screws.  🙂

 

I couldn't find the screws I wanted for the wood clamps from the local hardware store, so had to order them.  Those clamps are pending. 

 

Here are the C-clamps and the materials I used.  I made some that are 1" on each side, and some that are a little deeper throated (1 1/2").  Thanks to everyone again for the help.