Desktop Tapping Jig

This tapping jig is perfect for making small threaded holes without fear of breaking taps. The jig ensures your taps are kept perfectly vertical for easy, repeatable operations. You can also use it for manually drilling small holes, driving small screws, or any other operation that requires maintaining a perpendicular orientation while rotating.

I have included a STEP file of the entire assembly; feel free to make modifications, etc. and if you do something cool with this design I'd love to see it!

Please read all instructions before starting!

Printed Parts

I highly recommend printing the arm and base parts out of something that can resist stress. I used PETG. PLA isn't ideal for those components as it's prone to distorting under continuous pressure, but it's fine for the rest of the parts. None of the parts require supports and should be in the proper orientation for printing already.

It is important that the arm and base pieces are completely flat. If you're having issues with warping or lifting during printing, a wide brim is recommended. You can also heat up the parts slightly with a hair dryer or heat gun and press them between two flat surfaces while they cool to ensure they are perfectly flat.

You will need one of each part. 

• tapping_jig_arm
• tapping_jig_base
• tapping_jig_bearing_retainer
• tapping_jig_knob - This part is designed for mid-print insertion of a hex nut. If you don't want to do that, try tapping_jig_knob-alt instead. There is no functional difference between the two, only aesthetic

Optional Accessories

These accessories are not required for the jig to function, but can improve the user experience. 0.2mm layer height is recommended for the chuck_key_holder and screw_holder accessories as they have built-in breakaway supports.

• tapping_jig_chuck_rest - This piece can be placed under the chuck when the jig is not in use in order to reduce strain on the frame and combat any deformation over time.
• tapping_jig_chuck_key_holder - A bracket for storing the chuck key when not in use.
• tapping_jig_screw_holder - A bracket for storing M5 screws (which fit into the holes in the base) as well as a 4mm hex wrench

Additional Hardware

The following hardware is required to assemble the jig. I've included links to each part from McMaster-Carr, but you can source them elsewhere.

Required Hardware

1x 3/8" threaded connecting rod - I trimmed down one end to match the thread depth of the drill chuck. This isn't required, but doing so adds a bit of extra clearance.

1x 3/8"-24 threaded drill chuck

1x 3/8" ID, 5/8" OD, 7/8" shoulder sleeve bearing

1x 40mm x 20mm T-slot rail, ~6" long - The length of this isn't crucial, but 6" is good for most applications.

4x 3/8"-24 hex nuts - You can get by with just two (for the knob) but two more can be used to provide a solid stop at the top of the shaft (see pictures).

7x M2 x 8mm flat-head screws - You only need 3 if you aren't printing any of the accessories. Each bracket requires 2 screws.

4x M5 x 20mm socket-head screws

1x M5 tap

1x M2 tap - This is only used for tapping plastic parts, and it is possible to do so by simply driving a screw in. That said, it's much easier and more reliable with a tap.

1x tap wrench

Optional Hardware

1x 3/8" shaft collar - Used as a depth stop. You can assemble the jig without this, but it makes inserting/removing bits much easier.

1x ¼"-20 thumb screw - To replace the set screw in the collar, allowing it to be adjusted without a tool

1x 3/8" ID, 3" compression spring - Used to protect the jig from any sudden drops of the shaft and provide the option to add a springback force to tapping operations.

8x M5 hex nuts - These are inserted into the bottom of the base and can be used in conjunction with M5 screws for workholding.

8x M5 x 10mm screws - Used in conjunction with the M5 hex nuts for workholding.

1x 4mm hex key - Used to drive the M5 screws. Any type of hex key will work for assembly, but there is a slot to store a 4mm L-key in the tapping_jig_screw_holder accessory if you want to make sure there is always one with the tool.

You will also need tools for tightening the screws and hex nuts.

Assembly Instructions

1. Print one of each part (see above for part descriptions and printing details).
   • If you are printing the standard tapping_jig_knob you need to pause the print at the top of the hexagonal pocket and insert one of the 3/8"-24 hex nuts.
2. Insert the sleeve bearing into the hole in the arm. It may require a bit of force to seat all the way down.
3. Tap the three holes around the shoulder bearing with the M2 tap.
4. Place the bearing retainer over the sleeve bearing and secure it with M2 screws. Be careful not to over-tighten these screws; it's easy to strip the small threads. The same applies for the accessories, which are also held in place with M2 screws.
5. Tap all four holes in the T-slot rail with the M5 tap.
6. (Optional) insert the M5 hex nuts into the holes in the underside of the base. They should press-fit into place and require no adhesives. I find it easier to insert a screw into the nut to act as a handle while pressing it in.
7. Attach the T-slot rail to the base with two of the M5 20mm socket-head screws. Make sure it is fully seated.
8. (Optional) Tap the screw holes on the accessories with the M2 tap. Also, make sure the outer hole is a slip-fit for an M2 screw. If not, you can drill it out with a 2mm or 5/64" drill bit. Make sure not to drill out the threads on the inner hole.
9. (Optional) Tap the holes in the screw_holder with the M5 tap - This may or may not be necessary, depending on how your machine prints. Try inserting a screw into one of the holes, and if it's too tight run a tap in to loosen it up.
10. (Optional) Insert the accessories into the T-slots on either side of the T-slot rail and tighten the M2 screws to lock them in position.
11. Attach the arm to the T-slot rail with the other two M5 20mm socket-head screws. Make sure it is fully seated.
12. (Optional) Screw two of the 3/8"-24 hex nuts onto the 3/8" connecting rod (the side you will attach the knob to). Screw the first one all the way down until it stops and then tighten the second one against it to lock it in position.
13. If using the alternate tapping_jig_knob-alt, insert one of the 3/8"-24 hex nuts into the hexagonal pocket.
14. Screw another 3/8"-24 hex nut onto the connecting rod and then screw on the knob. Once the knob is in place, tighten the other hex nut against it to lock it in position. Make sure this is really tight as you will be turning the knob during tapping operations.
15. Insert the connecting rod through the sleeve bearing.
16. Screw the drill chuck onto the end of the connecting rod.

And that's it! To use, simply insert your desired tap into the drill chuck and position it over a hole in your part. Then you can tap as you normally would, using the knob as your tap handle.

When the jig is not in use, I recommend storing it with the optional chuck rest accessory inserted into the center hole on the base to reduce strain on the frame. While in use, this accessory fits into the screw countersinks on the arm (or you can just set it aside).

If you want to make any jigs or fixtures for the bed of the machine, the holes are M5 (5mm diameter) and 40mm center-to-center.

Please don't hesitate to reach out with any questions or comments!