Precision Wrench Rebuild

Decades ago, one jaw on my little 1/4 inch wrench that fits 4-40 nuts broke off. I brazed it back on, fully aware that one day it would break off again, because brazing isn’t really a suitable repair technique for a wrench, even one labeled as “Precision” in that time-honored manner of all low-cost tools.

Time passes, I’m tightening screws against 4-40 nuts, and the jaw gives way:

Precision wrench - broken jaw
Precision wrench – broken jaw

So I sawed off a strip of bedframe steel that fit the nuts better than the original stamped steel, did a bit of hand filing, and came up with a reasonable replacement:

Precision wrench - detail
Precision wrench – detail

I rammed it into the handle, just as they’d done with the original stamped steel shape:

Precision wrench - rebuilt
Precision wrench – rebuilt

That should last approximately forever…

Quilting Circle Template: Why I Loves Me My 3D Printer(s)

Mary just started an ambitious pieced quilt that requires 50-some-odd precisely sized 1-1/2 inch circles, with marks to locate a 1 inch circle in the middle. She started using a drafting template to mark the smaller circle on freezer paper (don’t ask, it’s complicated), but we couldn’t find the template I know I have with the larger circles.

[Update: It’s a Bittersweet Briar traditional quilt. See all those little dots-for-berries?]

So I says to my wife, I sez, “Hey, we have the technology. What would really simplify what you’re doing?” After a bit of doodling, we came up with a ring having the proper ID and OD, plus a flat handle of some sort.

Half an hour later, I had a solid model:

Quilting circle template - solid model
Quilting circle template – solid model

An hour after that I handed her a warm piece of plastic:

Quilting circle template
Quilting circle template

The bottom ring is exactly 1-1/2 inch OD, 1 inch ID, and thin enough to draw around. The handle keeps her fingers out of the way and even has grips and a hole for a string.

The print quality near the hole isn’t as good as I’d like, because the slicer turned that entire volume into a solid slab of plastic. I can fix that in the second version, but right now she has something to work with, evaluate, and figure out what would improve it.

3D printing isn’t for everybody, but it’s a vital part of my shop!

The OpenSCAD source code has parameters for everything, so we can crank out more templates without fuss:

// Quilting - Circle Template
// Ed Nisley KE4ZNU - July 2013

Layout = "Show";                    // Show Build Circle Handle

//- Extrusion parameters must match reality!
//  Print with 2 shells

ThreadThick = 0.25;
ThreadWidth = 0.40;

HoleFinagle = 0.2;
HoleFudge = 1.00;

function HoleAdjust(Diameter) = HoleFudge*Diameter + HoleFinagle;

Protrusion = 0.1;           // make holes end cleanly

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

inch = 25.4;

// Dimensions

CircleID = (1) * inch;

SeamAllowance = (1/4) * inch;

CircleOD = CircleID + 2*SeamAllowance;

CircleThick = 6*ThreadThick;

CircleSides = 12*4;

HandleHeight = (2) * inch;
HandleThick = IntegerMultiple(5.0,ThreadWidth);
HandleSides = 12*4;

StringDia = 4.0;
StringSides = 8;
StringHeight = 0.75*HandleHeight;

DentDepth = HandleThick/4;
DentDia = 15.0;
DentSphereRadius = (pow(DentDepth,2) + pow(DentDia,2)/4)/(2*DentDepth);


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

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

  RangeX = floor(100 / Space);
  RangeY = floor(125 / Space);

	for (x=[-RangeX:RangeX])
	  for (y=[-RangeY:RangeY])


// Circle ring plate

module CircleRing() {

		difference() {
				cylinder(r=CircleID/2,h=(CircleThick + 2*Protrusion),$fn=CircleSides);

// Handle

module Handle() {

	difference() {
#		for (i=[-1,1]) {
			translate([i*(DentSphereRadius + HandleThick/2 - DentDepth),0,StringHeight])


module Template() {

// Build it!


if (Layout == "Circle")

if (Layout == "Handle")

if (Layout == "Show")

MFJ-260B HF Dummy Load – Impedance Nudging

If you happen to own an MFJ-260B dummy load and it’s giving you weird SWR values, take the cover off and roll the power resistor in its mounting clips:

MFJ-260B HF Dummy Load - power resistor
MFJ-260B HF Dummy Load – power resistor

My buddy Aitch discovered that oxide / corrosion / dirt buildup between the resistor and the clips can produce absolutely baffling results, even while passing enough current to warm up the element, far more power than you’d think would burn away any crud.

Checkout Code 111

The Stop & Shop we normally use outsources their cash register function to us; we carry a scanner around, plink each item on its way into the basket, then do a credit-card swipe on the way out. On the last trip, this popped up after I scanned the “We’re done!” barcode at the Scan It! kiosk:

Stop-and-Shop - scanner code 111
Stop-and-Shop – scanner code 111

That means we were selected for a “random” audit, apparently triggered by the fact that we bought some non-typical items: ice cream! We proceeded to a nearby register, waited in line, I re-re-scanned my card, and … the whole fifteen minute process would have been a lot more amusing if said frozen items hadn’t been warming up while the harried clerk performed numerous ritual acts on the contents of our cart.

The main reason I use the scanner: there’s no other way to determine the price of any given item, what with all the unit pricing nonsense, mis-marked labels, pop-up sales, must-buy-N bundling, and so forth and so on. Secondarily, during a normal trip there’s no waiting in a lengthy queue (“Price check on Register 12!”) on the way out.

Mary hates the scanners, for well and good reason.

Turkey vs. Hawk: Aftermath

Based on this evidence, the hawks seem to be tackling larger prey:

Turkey feathers in the garden
Turkey feathers in the garden

Mary found turkey feathers drifting across the garden, with the largest concentration near this assortment, much along the lines of the pile left at our back door. Given the 6 ft deer fence surrounding the garden and the complete absence of yummy debris, we think this wasn’t the work of a land-based predator.

Parents, guard your children…

Along those lines, once upon a time, long ago and far away, we attended a show-n-tell featuring a (rescued) California Condor. The exhibitors ushered us into a tight group and told parents to keep their small children close beside them, because condors attack stray animals and pay particular attention to infants of herd animals. Of course, one couple didn’t get the word (or didn’t think it applied to them) and let their toddler wander off. As soon as the kid got a few feet away from the pack of people, the inert condor abruptly powered up and got weapons lock on the kid; a warning from the exhibitor sent the parents scurrying to correct collect their blunder.

Raptors are not friendly birds.

Makergear M2: Mechanical Setup

That Slic3r configuration presumes a somewhat nonstandard mechanical setup for my M2…

I put the XY coordinate origin in the middle of the platform, so that laying objects out for printing doesn’t require knowing how large the platform will be: as long as the printer is Big Enough, you (well, I) can print without further attention.

The RepRap world puts the XY coordinate origin in the front left corner of the platform, so that the platform size sets the maximum printable coordinates and all printing happens in Quadrant I.  This has the (major, to some folks) advantage of using only positive coordinates, while requiring an offset for each different platform.

Yes, depending on which printer software you use, you can (automagically) center objects on your platform; this is often the only way to find objects created with Trimble (formerly Google) Sketchup. I am a huge fan of knowing exactly what’s going to happen before the printing starts, so I position my solid models exactly where I want them, right from the start. For example, this OpenSCAD model of the bike helmet mirror parts laid out for printing:

Helmet mirror mount - 3D model - Show layout
Helmet mirror mount – 3D model – Show layout

… exactly matches the plastic on the Thing-O-Matic’s platform, with the XY origin right down the middle of the platform:

Helmet mirror mount on build platform - smaller mirror shaft
Helmet mirror mount on build platform – smaller mirror shaft

It’d print exactly the same, albeit with more space around the edges, on the M2’s platform.

Similarly, the Z axis origin sits exactly on the surface of the platform. That way, the Z axis coordinate equals the actual height of the current thread extrusion in a measurable way: when you set the Z axis to, say, 2.0 mm, you can measure that exact distance between the extruder nozzle and the platform:

Taper gauge below nozzle
Taper gauge below nozzle

Now, admittedly, I fine-tune that distance by measuring the height of the skirt thread around the printed object, but the principle remains: a thread printed  on the platform with Z=0.25 should be exactly 0.25 mm thick.

The start.gcode file handles all that:

;-- Slic3r Start G-Code for M2 starts --
;  Ed Nisley KE4NZU - 15 April 2013
M140 S[first_layer_bed_temperature]	; start bed heating
G90				; absolute coordinates
G21				; millimeters
M83				; relative extrusion distance
M84				; disable stepper current
G4 S3			; allow Z stage to freefall to the floor
G28 X0			; home X
G92 X-95			; set origin to 0 = center of plate
G1 X0 F30000		; origin = clear clamps on Y
G28 Y0			; home Y
G92 Y-127 		; set origin to 0 = center of plate
G1 Y-125 F30000	; set up for prime at front edge
G28 Z0			; home Z
G92 Z1.0			; set origin to measured z offset
M190 S[first_layer_bed_temperature]	; wait for bed to finish heating
M109 S[first_layer_temperature]	; set extruder temperature and wait
G1 Z0.0 F2000		; plug extruder on plate
G1 E10 F300		; prime to get pressure
G1 Z5 F2000		; rise above blob
G1 X5 Y-122 F30000	; move away from blob
G1 Z0.0 F2000		; dab nozzle to remove outer snot
G4 P1			; pause to clear
G1 Z0.5 F2000		; clear bed for travel
;-- Slic3r Start G-Code ends --

The wipe sequence, down near the bottom, positions the extruder at the front center edge of the glass plate, waits for it to reach the extrusion temperature, then extrudes 10 mm of filament to build up pressure behind the nozzle. The blob generally hangs over the edge of the platform and usually doesn’t follow the nozzle during the next short move and dab to clear the mess:

M2 - Wipe blobs on glass platform
M2 – Wipe blobs on glass platform

I’ve also configured Slic3r to extrude at least 25 mm of filament in at least three passes around the object. After that, the extruder pressure has stabilized and the first layer of the object begins properly.

Which brings up another difference: the first layer printed on the platform is exactly like all the others. It’s not smooshed to get better adhesion or overfilled to make the threads stick together:

Robot cookie cutter - printing first layer
Robot cookie cutter – printing first layer

I print the first layer at 25 mm/s to give the plastic time to bond to the platform and use hairspray to make PLA stick to glass like it’s glued down.

After that, it’s just ordinary 3D printing…

Makergear M2: Slic3r config.ini

A stick in the ground…

I think the exported config.ini file corresponds to the currently selected set of sub-configurations; I find it difficult to keep a myriad of selections up-to-date while tweaking things, so mostly I don’t bother with named configurations.

The start.gcode and end.gcode lines go on forever, with embedded newlines.

# generated by Slic3r 0.9.11-dev on Mon Jul 22 09:28:22 2013
avoid_crossing_perimeters = 
bed_size = 190,250
bed_temperature = 70
bottom_solid_layers = 3
bridge_acceleration = 0
bridge_fan_speed = 100
bridge_flow_ratio = 1
bridge_speed = 150
brim_width = 0
complete_objects = 0
cooling = 1
default_acceleration = 0
disable_fan_first_layers = 0
duplicate = 1
duplicate_distance = 6
duplicate_grid = 1,1
end_gcode = ;-- Slic3r End G-Code for M2 starts --\n;  Ed Nisley KE4NZU - March 2013\nM104 S0		; drop extruder temperature\nM140 S0		; drop bed temperature\nM106 S0		; bed fan off\nG1 Z180 F2000	; lower bed\nG1 X0 Y0 F30000	; center nozzle\nM84     	; disable motors\n;-- Slic3r End G-Code ends --
external_perimeter_speed = 50
external_perimeters_first = 0
extra_perimeters = 1
extruder_clearance_height = 20
extruder_clearance_radius = 20
extruder_offset = 0x0
extrusion_axis = E
extrusion_multiplier = .99
extrusion_width = 0.40
fan_always_on = 0
fan_below_layer_time = 45
filament_diameter = 1.72
fill_angle = 45
fill_density = 0.15
fill_pattern = honeycomb
first_layer_bed_temperature = 70
first_layer_extrusion_width = 0
first_layer_height = 100%
first_layer_speed = 25
first_layer_temperature = 175
g0 = 0
gap_fill_speed = 50
gcode_arcs = 0
gcode_comments = 0
gcode_flavor = reprap
infill_acceleration = 0
infill_every_layers = 1
infill_extruder = 1
infill_extrusion_width = 0
infill_first = 1
infill_only_where_needed = 1
infill_speed = 125
layer_gcode = 
layer_height = 0.25
max_fan_speed = 100
min_fan_speed = 45
min_print_speed = 15
min_skirt_length = 25
notes = 
nozzle_diameter = 0.35
only_retract_when_crossing_perimeters = 1
output_filename_format = [input_filename_base].gcode
overhangs = 1
perimeter_acceleration = 0
perimeter_extruder = 1
perimeter_extrusion_width = 0
perimeter_speed = 100
perimeters = 1
post_process = 
print_center = 0,0
raft_layers = 0
randomize_start = 1
resolution = 0
retract_before_travel = 0.5
retract_layer_change = 0
retract_length = 1
retract_length_toolchange = 5
retract_lift = 0
retract_restart_extra = 0
retract_restart_extra_toolchange = 0
retract_speed = 80
rotate = 0
scale = 1
skirt_distance = 5
skirt_height = 1
skirts = 3
slowdown_below_layer_time = 20
small_perimeter_speed = 25
solid_fill_pattern = rectilinear
solid_infill_below_area = 15
solid_infill_every_layers = 0
solid_infill_extrusion_width = 0
solid_infill_speed = 100
spiral_vase = 0
start_gcode = ;-- Slic3r Start G-Code for M2 starts --\n;  Ed Nisley KE4NZU - 15 April 2013\nM140 S[first_layer_bed_temperature]	; start bed heating\nG90				; absolute coordinates\nG21				; millimeters\nM83				; relative extrusion distance\nM84				; disable stepper current\nG4 S3			; allow Z stage to freefall to the floor\nG28 X0			; home X\nG92 X-95			; set origin to 0 = center of plate\nG1 X0 F30000		; origin = clear clamps on Y\nG28 Y0			; home Y\nG92 Y-127 		; set origin to 0 = center of plate\nG1 Y-125 F30000	; set up for prime at front edge\nG28 Z0			; home Z\nG92 Z1.0			; set origin to measured z offset\nM190 S[first_layer_bed_temperature]	; wait for bed to finish heating\nM109 S[first_layer_temperature]	; set extruder temperature and wait\nG1 Z0.0 F2000		; plug extruder on plate\nG1 E10 F300		; prime to get pressure\nG1 Z5 F2000		; rise above blob\nG1 X5 Y-122 F30000	; move away from blob\nG1 Z0.0 F2000		; dab nozzle to remove outer snot\nG4 P1			; pause to clear\nG1 Z0.5 F2000		; clear bed for travel\n;-- Slic3r Start G-Code ends --
start_perimeters_at_concave_points = 1
start_perimeters_at_non_overhang = 1
support_material = 0
support_material_angle = 0
support_material_enforce_layers = 0
support_material_extruder = 1
support_material_extrusion_width = 0
support_material_interface_layers = 0
support_material_interface_spacing = 0
support_material_pattern = rectilinear
support_material_spacing = 2.5
support_material_speed = 125
support_material_threshold = 0
temperature = 175
thin_walls = 1
threads = 2
toolchange_gcode = 
top_infill_extrusion_width = 0
top_solid_infill_speed = 50
top_solid_layers = 3
travel_speed = 250
use_relative_e_distances = 0
vibration_limit = 0
wipe = 0
z_offset = 0