5 1/4 Floppy Disk Notcher
Introduction: 5 1/4 Floppy Disk Notcher
With the current pricing of vintage floppy notchers on eBay these days, I decided to reverse engineer mine and build a 3D printed modern equivalent. I've tried to stick with inexpensive parts available at the hardware store.
Examining the vintage notcher, we see only a handful of parts:
Top and Bottom halves of case
Cutter with attached knob.
Spring
Cotter pin
Screws
The cutter is ground across the diagonal of the face creating a V shape. This creates 4 cutting edges to punch out the notch.
Supplies
3D Printer and Filament of choice
1/4 x 1/4 inch Steel Keystock (such as SteelWorks 0.25 in. W X 12 in. L Steel Keystock - Ace Hardware)
#4 x 1/2 Sheet Metal Screws or similar size self taping screws (Qty 2)
13/32 x 11/16 OD x 1 inch Compression Spring or Similar (I found one in the spring drawers at the local Ace, similar to Cox Hardware and Lumber - Compression Spring, 13/32 In x 11/16 In x 1 In)
3/32 x 1 inch Cotter Pin
5 Minute Epoxy
Disk Sander
Bench Grinder
Vise
Hacksaw with metal cutting blade.
Drill Press or Hand Drill
3/32 Drill Bit
Step 1: Print 3d Parts
Print the knob, top, and bottom from filament of your choice. The top is printed fastest when the top surface is oriented to the build plate as that will minimize supports. If you want a cleaner top, print with the bottom to the build plate but the necessary supports will increase the print time. Print the bottom and the knob with their bottom surface to the build plate.
Step 2: Grind the Cutting Surface on the Cutter
First, the end of the keystock needs to be ground to 15 degrees along the diagonal of the face. I used a disk sander with a miter gauge set to 75 degrees to give the 15 degree face. Since we are grinding along the diagonal, place a corner of the stock on the sander table, not a face. Gently grind the desired angle by sliding the bar against the disk while applying steady gentle pressure. Repeated passes are required to fully grind the face. Don't jab the bar into the disk and don't hold it in one place.
Second, a shallow curve is ground into the face to create the cutting edges. While the vintage cutter has a v shaped grid, the shallow curve from a bench grinder will be easier to create. I used a slow speed bench grinder with a white wheel. 807
To help maintain the necessary angle, I placed masking tape on the tool rest and marked a line at 15 degrees to help visualize the proper angle. As before, the keystock will be held with the corner on the tool rest, not a face. Adjust the tool rest so that the cutting end is perpendicular to the wheel and meets in the middle of the face. Grind using the same approach as with the disk sander. Gently press the bar end into the wheel and slide against the wheel, using multiple passes. Be careful to maintain the marked angle and the bar upright on the edge. Holding in one place can grind a groove into the wheel.
If the resulting face is not even or otherwise flawed, just go back to the disk sander to restore the flat face and regrind.
Step 3: What About Heat Treatment?
I used the keystock as it is inexpensive, readily available at the local hardware store, and the proper 1/4 x 1/4 dimension for the cutter. However, it is low carbon steel and zinc plated. Heating zinc plated steel to the necessary high temperatures will release dangerous fumes. Additionally, low carbon steel is not suitable for heat treatment. If you can get a high carbon tool steel bar suitable for heat treatment in the necessary 1/4 x 1/4 dimension for your cutter, then heat treatment is an option to increase the lifetime of the cutting edge.
Step 4: Drill the Cotter Pin Hole and Cut the Cutter to Length
Place the cutter so that the highest point of the face is on the left. Measure 18 mm (a bit less than 23/32 inches) from the highest point of the cutter face and mark the center of the 3/32 hole. Its best to punch the location to drill so the bit doesn't wander. Drill the 3/32 hole through the keystock.
Cut the cutter from the keystock 42mm (1 5/8 inches) from the highest point of the cutter face. I clamped the keystock in a vice and cut it off with a hacksaw. 56