Laser knife goniometer (bevel angle finder)

This model is a Laser Knife Goniometer used to find the precise angle of knife bevels.

The knife is held by magnets below the edge and two additional magnets in the tilt mechanism.

Tilt mechanism with a knob on the side enables adjusting the knife tilt according to its thickness.

The laser module is fixed with oval holes under the screws, which allow for left/right adjustment of the laser.
(Up/down adjustment is not required - the only consequence of misalignment is that laser marks will be slightly higher or lower on the scale. Most lasers are shifted somewhat, but the beam is quite parallel to the body.)

PLEASE NOTE! Magnets DO NOT hold the knife very securely - HANDLE WITH CARE!

Laser modules:

This project is ready to use 3d printed modules for different kinds of lasers. 
Provided modules:
 

1. 13.9mm diameter pen laser with a momentary button
2. 3 in 1 cheap laser pointer with light and UV for LR44 batteries.
3. “Universal module” with selection of diameters.
4. Blank module for modification

3 in 1 laser pointer:

• Requires 2 pcs. M3 heat inserts and 2pcs. M3 set screws or M3x5 screws.

Universal Module:

• Select a hole size one step bigger than the diameter of your laser.
• Hot push two M3 threaded inserts into the holes.
• Use M3x10 bolts or M3 set screws to secure the laser inside the module.

Also, a blank module is provided that you can use to cut a place for your laser using 3D modeling software or a slicer.

Bil of materials:

• 2 pcs. 6x2mm cylindrical magnet
• 2 pcs. 8x4mm cylindrical magnet
• M3x25 screw
• 2 pcs. M3 nut
• M3 washer
• 3 pcs. M3 threaded insert
• 2 pcs. M3x10 screw (This is for the laser module, so check if it does not require a different hardware)
• Laser pointer appropriate for a module (or a custom one)

Body Printing instructions:

• I recommend printing in the orientation supplied in the files with a 0.2mm layer.
• “regulator.stl” will require brim - but supports are not necessary (bridge is easy to print here)
• “body.stl” has a sacrificial layer/bridge in the tilting mechanism pathway that must be cut after printing.
• “scaleA4.pdf” should be printed without scaling - verify that the testing line is 200mm after printing.

Assembly instructions: (PDF instructions contain photographs of the steps)

1. Body preparation:
   1. Cut the sacrificial layer/bridge inside the goniometer's body. It should be one layer thick and easy to remove.
   2. Check the regulator's fit in its canal - it should move freely.
   3. Insert/glue 8x4 magnets inside the holes under the V-cut (keeping the same polarity is recommended)
   4. Hot push two M3 threaded inserts on the lower part of the body.
2. Tilt mechanism:
   1. Hot push M3 threaded insert into regulator (Part is thin, so be careful.)
   2. Check the regulator's fit in its canal again - it should move freely.
   3. Glue the knob on the M3x25 screw
   4. Put on the washer on the M3x25 screw touching the knob.
   5. Put on two M3 nuts on the M3x25 screw and thread them to about 5mm from the washer.
   6. You must counterlock/jam the nuts in a position that allows the screw to be inserted from the top of the body into the adjustment canal and rotate freely, but does not allow the screw room to move forward and back. (alternatively, glue the nuts to the screw)
   7. Glue in two 6x2mm magnets in the regulator (keeping the same polarity is recommended)
   8. Insert the regulator into its canal until the insert touches the screw.
   9. Screw in the regulator a bit and verify that there is no play along the screw.
3. Scale:
   1. Print the scale without any scaling
   2. Verify that the test line has 200mm
   3. Cut out the scale. You may want to cut both sides a millimeter shorter to allow for some adjustment room.
4. Module for 13.9mm diameter laser pen:
   1. Sand a bit of the slight slope of the button/switch so it will glide smoothly on the laser pen button.
   2. Insert the button/switch into the module with a slight slope facing outwards.
   3. Insert the laser pen until its button is right beside the printed switch.
   4. If it is loose, use glue; if it is tight, sand the pen or module.
   5. Screw the module to the body lightly with M3x10 screws.
5. Calibration:
   1. If not cut too short, put the scale loosely into the body. (Please note that one end is „shorter”)
   2. Put a knife into the V-cut. (A utility blade is great for calibration)
   3. Align the tilt mechanism so the dots are roughly symmetrical on the scale.
   4. Shift the module sideways until the knife “cuts the red dot in half”.
   5. Tighten the module screws.
   6. Remove the knife
   7. Glue the scale in place so the “0” line is aligned with the dot.

Usage:

1. Put a knife in the V-cut, starting with the edge and touching the tilt mechanism later.
2. Adjust the tilt mechanism so the laser dots around the 3-10 degree marks are symmetrical (assuming your primary bevels are flat and symmetrical - different contours will have different laser shapes.).
3. Read the laser marks in the 8-35 degree range.
4. If the secondary bevel is flat, you will see laser dots on the scale (like factory grind or sharpened using some system).
5. If the knife was sharpened by hand (convex bevel), you will see a line spanning from the shallow to the steep part of the scale. The longer the line, the more convex the bevel is.