CNC Toe Clamps - Workholding

These are some toe clamps inspired by the Mitee-Bite clamps. They are low profile and hold very strong and fast to the work peice without covering any part of the work area. The specialty part for this Instructable is the eccentric nut from Inventables. This combined with the threaded inserts on your waste board provide a sturdy and reliable workholding for hours of milling fun.

I made two designs for this project, but have only completed one. One is a simpler clamp with a bit based on the golden ratio, and the second is a angled clamp which provide both normal force along with horizontal to prevent the workpeice from lifting. Hobby CNC machines do not create the forces that would been seen on a commercial CNC machine, so the aluminum and brass threaded inserts are plenty strong to hold our projects.

I choose to make 8 of these little guys, but one or two of these items may be enough for all your needs. The materials to be make ONE of these is below ( link the Inventables materials:

For the simpler clamps

• 1 - 5mm eccentric nut (https://www.inventables.com/technologies/eccentric-nut#30158-01)
• 1 - 25mm 5mm Button head cap screw ( https://www.inventables.com/technologies/button-head-cap-screw#25286-04)
• 1 - length of 1" x .125" aluminum stock (I bought 4 foot length at hardware store)

For the angled clamp:

• 1 - 5mm eccentric nut ( https://www.inventables.com/technologies/eccentric-nut#30158-01 )
• 1 - 25mm 5mm Button head cap screw ( https://www.inventables.com/technologies/button-h...
• 1 - 8mm 5mm Button head cap screw (https://www.inventables.com/technologies/button-head-cap-screw )
• 1" x 1/2" peice of aluminum bar stock

Tools:

• A 9/32" drill bit (be sure it can handle metal)
• A hand drill or drill press
• A hack saw or sawzall, (or other cutting method)
• A scale (I use a machinists scale with 10th's and 100th's graduations)
• A scribe
• A metal file

1. measure and etch a line at 1.60 inches (I use a machinists scale with 10th’s graduations)
2. Cut the bar stock and clean up as necessary (I used a file to clean up the edge since I used a sawzall to cut) -Alternatively you can use the X-carve to cut a 1.60″ × 1.00″ rectangle out of 0.125 aluminum plate.

1. Measure 1" down the long side of the rectangle and etch a line across
2. Etch a diagonal line corner to corner on the aluminum rectangle
3. Etch a diagonal line corner to corner across the 1.00″ × 0.60″ square created in step 1 above
4. Drill a 9/32" hole at the point the two diagonal lines cross, this is the center of the golden ratio
5. This will be your clamping bit – for lack of a better term.

1. screw the eccentric nut all the way down to the root of the 5mm screw
2. arrange the bit in a way so that it is barely or nearly making contact with your workpiece and lined up with the wasteboard threaded inserts, feel free to use the corners as well as the flat edges of the bit.
3. hand screw the eccentric nut into the wasteboard through the bit until the eccentric fully inserts into the bit,
4. tighten the screw, it should clamp your work piece.