So far having an accurate, soft and heavy_duty twin paddle key meant spending a lot of money .

My intention when designing this key was doing a paddle :

a)- Cheap --- It is made of plastic with a standard 3d printer

b)- Durable --- I have used ball bearing to make it precise and soft

c)- Accurate --- It is as accurate as the more expensives ones

d)- Nice to look --- Something to have in our desk might be nice.

I hope the result is to your liking .

I have printed with a chinese clone of the prusa i3 with 0,6mm nozzle and 0,3mm layer and the results are fine.

If you have a good printer and use 0,4mm nozzle and 0,15 mm layer or less the results will surprise you. Some people sent me some photos of their printings and I can say that their jobs are, by far , finer than mine.I have added a beautiful one made by Scotty GI0BEY. Thanks Scotty.

some people asked me about soften the paddles. I have added a new couple of them. They are the same than before , but I have softened the design. They are backwards-compatible with the base.

I have added a covered cap that looks more elaborate than the uncovered one. I personally love exposed ball bearings. For those who don't like to see ball bearings, here you are a second tap.

Enjoy..!

09/01/2021 I have added a weigthed base that increases the weigth of the key from 138grams to 565 grams. Look at the end of the article.

Step 1: Components.

This is the list of components: (click on the text for the Aliexpress link)

Four small magnets 5x2mm Pay attention to buy the 5mm diameter 2mm deep.

Four M3 Handle Locknuts

Four M3 x 20mm Knurled Thumb Screws

Four M3 nuts

Two stainless steel M4x30mm hex head and its nuts

Te nuts are the standard m4 nuts. I have chosen stainless steel ones but it is up to you.

Two M3x10mm and its nuts

3.5mm Female Audio Jack

Four ball bearing (MR117ZZ 7x11x3mm)

Four Neodymium Ring for magnetic feet 10x3 mm

four screws m3 x 8mm (flat countersunk head) for the magnet feet

Step 2: Start Printing

In the photos you can see the base of the key. The third photo is the cover .

My printer is a chinese mendel. It is a clone of the i3 with a Marlin firmware inside.

I have used PLA .A different material is up to you.

Layer height is enough with 0,3mm. Nozzle is 0,6mm.

Select generate support only on build plate. You would ruin the print if you selected support everywhere.

It is clear that 0,2mm layer heitgh and a nozzle of 0,4 or less would print with better resolution.

My slicer is Prusaslicer because it is free, easy to use and very efficient.

Step 3: Placement of the Parts on the Bed

I have placed all the parts this way in order to simplify the print. Other way would imply more support than necessary.

Step 4: The Paddles

The key have two symmetric paddles.

Left and right paddle are defined by the magnet. It is impossible to mistake.

There is an internal hole to introduce the electric wire.

I have used 1mm wire.

Biggers wires won't fit inside the paddle.

Step 5: Thread the Paddles

a)- Thread the wire in the paddle

b)- Peel 1cm at the end of the wire

c)- Introduce the wire until you can see the peeled wire through the lateral hole.

d)- With a screwdriver, pass the wire through the hole

e)- Introduce the M3x10mm screw through the paddle

f)- Screw the nut in the bolt trapping the wire.

Now you have the wire inside the plastic paddle and an electrical contact at the end.

Step 6: Neodymium Magnets for Strength Adjust

It's time to glue the magnets to the paddles and to the strength adjust.

Pay attention to the magnetic polarity.

At this point, you can install the ball bearings .

Step 7: Preparing and Soldering the Electric Terminals

I have used a common electric terminal that I have cut and soldered to the electric wires.

Step 8: Mount the Knurled Thumb Screws

Mount the nuts in its hole as you can see in fig 1.

Screw the Knurled Thumb Screws holding the electric terminals as you can see in fig 2.

At this point you can mount the neodymium magnet in its holder. fig 3.

Step 9: Mounting the Paddles

So far:

-You have installed the electrical wires inside the paddles.

-You have glued the neodymium magnets.

-You have mounted the bearing balls.

-You have Screwed the Knurled Thumb Screws .

It is time to introduce the electrical wires through the hole in the base (between the paddles) . Fig 2.

In figure 4 you can see the key almos finished.

Step 10: Mount the Cap

The key is almost finished.

Mount the cap and screw it with its nuts.

It is possible that the ball bearing would need some help in order to ensure them. I have done it with my soldering iron.

Some 3D printers have a calibration problem called elephant foot . It would difficult to introduce the bearing balls inside the holes. I have removed the problem with a plier.

Step 11: Wiring the 3.5mm Jack

The four wires must be soldered to the 3.5 mm audio socket.

Step 12: Magnetic Feet and Plastic Cover

To finish the key it is provided a plastic cover with magnetic feet.

Magnetic feet are necessary due to the lack of weight of the key (only 148 grams) . Professional keys are over 500 grams.

In order to provide stability I use a mouse pad with four magnet glued in it. The key is magnetically joined and very stable. You can also make a metallic foot . It is up to you.

Step 13: Downloadable Stuff

Step 14: Covered Cap

I have made a covered cap. It changes the look of the key but adds a problem. In this new design the printer tolerances play an important role.The uncovered cap doesn't need adjust because you can fix the ball-bearing manually.Is for this reason why I have made six differents caps. The one on the picture is a 2,9 one. It means that the distance between the external face of the cap and the ball bearing is 2,9mm.

In my case 2,7 is the ideal one. If you noticed that the paddles are loose you might increase the number of the cap. Every cap has its number carved in it.

Step 15: Printing the Covered Tap and the Paddles

No One of them need support. I have designed the parts to simplify the printing. In the photos you can see the way to put them in the bed for printing without support. I use prusaslicer as slicer. The nozzle is 0,4mm and the layer height is 0,125mm.