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Archive for March 25th, 2015

Build Platform Chisel Handle

My father used a little chisel for some unknown purpose while he was an instrument repair tech at Olmstead AFB during the mid-60s. Its homebrew wood handle eventually disintegrated and I made a quick-and-truly-dirty replacement from epoxy putty and heatshrink tubing, promising that I’d eventually do better.

Seeing as how I use it to pop objects off the M2’s build platform and being in need of a tall, skinny object to see how PETG works with towers, that chisel now has a nice magenta handle:

Platform Chisel - PETG handle

Platform Chisel – PETG handle

Well, OK, it may not be the prettiest handle you’ve ever seen, but it’s much better than an epoxy turd, as measured along several axes.

Incidentally, epoxy putty bonds to clean steel like there’s no tomorrow. I had to file the last remaining chunks off and sandpaper the residue down to clean steel again.

The solid model shows it in build-a-tower mode:

Chisel Handle - solid model

Chisel Handle – solid model

I think at least one rounded end would improve its appearance. Two rounded ends would make it un-printable in that orientation, although a low-vertex polygonal approximation might have enough of a flat bottom to suffice. Given how long it took me to replace the epoxy, that could take a while.

The central slot fits snugly around the handle, requiring persuasion from a plastic mallet to set in in position.

Once again, the nozzle shed a small brown PETG booger after the first few layers:

PETG Chisel Handle - oxidized plastic

PETG Chisel Handle – oxidized plastic

I’m beginning to think PETG infill needs more attention than I’ve been giving it: that’s 15% 3D Honeycomb combined over three layers.

The OpenSCAD source code:

// Chisel Handle
// Ed Nisley KE4ZNU - March 2015

Layout = "Show";			// Show Build

//-------
//- Extrusion parameters must match reality!

ThreadThick = 0.25;
ThreadWidth = 0.40;

HoleWindage = 0.2;

Protrusion = 0.1; 				// make holes end cleanly

function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit);

//-------
// Dimensions

Shank = [16.0,2.4,59];			// width, thickness, length to arched end

BladeWidth = 27.0;

HandleSides = 8;

//-------

module ShowPegGrid(Space = 10.0,Size = 1.0) {

  RangeX = floor(95 / Space);
  RangeY = floor(125 / Space);

	for (x=[-RangeX:RangeX])
	  for (y=[-RangeY:RangeY])
		translate([x*Space,y*Space,Size/2])
		  %cube(Size,center=true);

}

module PolyCyl(Dia,Height,ForceSides=0) {			// based on nophead's polyholes
  Sides = (ForceSides != 0) ? ForceSides : (ceil(Dia) + 2);
  FixDia = Dia / cos(180/Sides);
  cylinder(r=(FixDia + HoleWindage)/2,h=Height,$fn=Sides);
}



module Handle() {
	difference() {
		scale([1.0,0.5,1.0])
			rotate(180/HandleSides)
				cylinder(d=BladeWidth/cos(180/HandleSides),h=Shank[2],$fn=HandleSides);
		translate([0,0,Shank[2]/2])
			cube(Shank + [0,0,2*Protrusion],center=true);
	}
}

//-------
// Build it!

//ShowPegGrid();

if (Layout == "Show") {
	Handle();
}

if (Layout == "Build") {
	translate([0,0,0])
		rotate([0,0,0])
			Handle();
}
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