Wednesday, January 24, 2024

Fiber Fun

I have been trying to make an extended counterweight shaft for a small equatorial mount.  This is not the carbon fiber project, more a short-term fix for the current mount.  The standard counterweight shaft is 12mm diameter with an M12x1.75 male thread and an M6x1.0 female end for a bolt to prevent runaway counterweights from ending up on your toe.

My attempts to turn a .5" carbon steel shaft to the 12mm diameter before using a die to thread it have been for naught.  I cannot reduce the diameter enough to successfully use the die in the tailstock.

Then I thought, "Do not make an entire shaft.  Turn something to 12mm diameter, thread the end to M6x1.0 so it screws into the hole at the end of the current shaft and tap the far end to M6x1.0.  I had some 12mm carbon fiber composite rod but the die did not cut threads.  It produced a fiber disaster that reminded me to wear rubber gloves when working with stuff.  It is almost as ugly as fiberglass in the poke your skin area.

Curiously, there are YouTube videos showing successful tapping.  This 12mm carbon fiber is Chinese and for all I know they build fighter planes from it.

I am not sure why cutting steel and aluminum is so hard.  Perhaps some 12mm acetal?  More flexible than steel but easier to turn to size and cutting threads in a known process.

I see encouragement on YouTube to use a reamer to get a very exact size and concentricity before tapping. Of course, this also means carbide. Carbon fiber is apparently very hard on high-speed steel.  I can see how reaming would be less stressful if you already have the through hole largely complete.  Drill a 6-32 pilot hole then use a 13/64 reamer to get to size for a 1/4"-20 tap.  I already have one made of solid carbide.  As nervous as I am about it's brittleness, it is amazingly fast on steel.

1 comment:

  1. Would 12mm threaded rod bypass part of the problem? or is that too expensive?