Tap Straight Holes in Aluminum Extrusion With a 3D Printed Tap Jig (20mm / Openbuilds V-slot, Misumi, Makerslide / Universal)

If you're building a 3D printer or project that uses Aluminum Extrusion, chances are it will require tapping holes in the ends. The right tools and steady confidence can make the difference between a secure thread or a ruined hole. This Instructable shows you how to do this easily with some shared experience and a 3D printed Tap Jig you can download here.

I designed this to fit several types of 20mm aluminum extrusion including: Openbuilds V-slot, Makerslide and Misumi 20x20. Other 3D printed jigs at the time were not universal or included secure mountings. After using it for a project, I found it to be a easy and reliable for threading.

There are 2 Jig versions made for (2) or (4) screws and t-nuts for secure mounting.

In addition, you will need:

• Access to a 3D printer (if not, visit your local hackerspace, or try 3Dhubs.com for local providers)
• (2) or (4) 7mm M5 screws and t-nuts
• An M5 Tap for tapping and treading holes
• A Tap handle
• Machine oil, 3-in-one, WD40 or lubricant of almost any kind (water or oil based are fine for aluminum). Tapping holes without oil can lead to binding and stripping.

Procedure for tapping
If you have a standard tap handle, you will need to be very careful. My favorite is a ratchet tap. Either way, the method is the same.


Setup
1) Clamp the piece of extrusion to a vice or sturdy table. A lot of force will be needed to start the hole, so make sure any sudden jolts aren't likely to occur.

2) Attach the screw and nut hardware to the printed part. The model should be printed with at least 80% fill.

3) Assemble the Tap & Handle tightly and line up through the guide. The tap should be able to stay free standing.
Apply 1-2 drops of lubricant to the end of the tap.


Tapping
1) Lineup the tap end to the hole and apply several pounds of force evenly while turning 1/2 turn at a time. Release, re-position and repeat until the end of the tap has begun to tread it'self. The tap should begin to thread after 3-4 turns. As long as your tap is lined up straight, the initial hole start at about 2-3mm deep should be a fairly risk-free proposition.

2) Turn the tap slowly, 1 full turn at a time. Continue until only the taper of the tap is fully sunk into the hole or until the tap is too difficult to turn or if binding and popping occurs. If binding occurs, reverse and restart.

3) Reverse the tap and remove it to clear the chips. Reversing may require gentile forward and reversing to pass over chips. Some binding on these chips normal.

4) With less pressure, screw the tap back into the hole to and check that the tread being cut will hold the tap on it's own.

5) Continue to tread another 1cm depth then reverse and repeat. See step 2 for notes.

*Tapping requires quite a bit of force. I have found that erring on the side of more force inward is less likely to result in stripped threads.*

Hope you found this helpful. Comments and feedback are always appreciated.

Thanks,
Marshall P.
protobuilds.com