Introduction: Pocket Grapple- a Toy Mechanical Claw Grappling Hook

About: Hi I'm Michael! I love all things Science, Engineering, & 3D Printing. If you've enjoyed my work then I've love to hear from you!

'Pocket Grapple' is a tiny grappling hook that grabs stuff! It's a key chain sized mechanical claw & retrieval hook that is both useful and fun! It has 3 configurations:

*Gravity- Suspend it from a cable and when it touches a surface gravity & leverage push the jaws open. Lifting the device then closes the jaws around your prize. The claw hooks are designed so that the weight of the object will not reopen the claw so it stays in!

*Triggered- Adding a rubber band and the triangular shaped trigger allows you to actively snap onto objects where the gravity-grip-leverage alone wouldn't be enough. See video where we were able to use it to grab the edge of a mason far!

*Grappling Hook- Grabbing onto the cross bar piece converts the claw into a magnetic 4 prong hook to give you even more retrieval options!

It is meant for retrieving hard to reach stuff like when you drop a tool behind the tool chest or sock behind the dryer! But even more so its a novel toy. 100% of kids I surveyed aged 9+/-3 yrs L.O.V.E. this thing! :)

*Yes my business card is plastered all over the pictures and that is because I created this device with the intent to profit, but I've finally decided that they are too painfully laborious to continue making peace meal with respect to their market value. So now im sharing the models for free so if you have access to a 3d printer you can easily build your own!

Step 1: Tools + Shopping List:

*Disclaimer: List includes affiliate links.
**Further disclaimer: I have yet to see anyone share a NON-affiliate amazon link in 2020. That's life folks.

Shopping list:

1X Badge Reel: Nice Steel one, or cheaper generic.

Key Ring + Key Chain (In the instructions I used fishing line but I recommend a chain)

Tiny Rubberbands- That brand specifically is excellent. The dollar tree ones work but they break in short order.

3X Short screws - (Or a 3mm screw 9.5mm long)

1x Long screw - (Or a 3mm screw 15mm long)

1x 8mm x 3mm Neodium Magnet

Alternately: Remaining inventory of Assembled Pocket Grapples on my store.


Just needle nose pliers and a Phillips screwdriver! I do recomend a dab of superglue for holding the magnet in place.

Step 2: ​3D Printing Notes:

STL Files attached to this step. >Please note the non-commercial-don't-share-modifications-license<

3D Print them solid, in any material, no supports necessary. Easy!

Having said that my material of choice is eSun PLA+.

Post process with a razor if necessary. The design intent is for the through-holes to be an unhindered clearance for the screws so the device can move freely.

-- One neat aspect of this design is just how little plastic it uses. Everybody with a printer has a ton of little leftover spools that are too small to use. Well that is all you need to make this!

--Another note: I know I use a lot of vitamins in this design. If I had tried to make the hinges printable then it would be substantially less strong, and have a greater susceptibility to locking up. You want the joints on this device to pivot like butter or it work work!

Step 3: Insert Magnet

The magnet press fits into the piece shown, however I like to add a dab of superglue to make sure it doesn't pop out. For that reason I list this step first so you can set it aside to let the glue dry.

Step 4: Screw Together Bottom Half

There are 3 hooks, note one of the hooks is different. It has smaller holes meant for the screws to bite into, and it goes on the bottom of the sandwich.

Stack the hooks as shown and attach with the short screws.

For now it can be useful to actually tighten the screws all the way temporarily to aid assembling. Later though we will loosen them so the device moves freely. The cool thing about the screws I specified is that they are made for plastic. They have a slightly triangular profile so it wont back out on its own. They are very useful for 3d printed projects!

Step 5: Screw Together Top Half.

Similar procedure with the links. There are 3 links and one is different, one of its two holes is tiny. This goes on the bottom of the sandwich and the tiny hole receives this screw. All other holes are large enough for screw clearance.

The 4th and final screw is the longest one that ties everything together. (You can see I used a bolt & nylock nut in the picture and that works just fine too.)

Step 6: Attach Key Ring & Trigger

In my photos I removed the chain in favor of fishing line. This works, but ive since learned that using two key chains linked together is nicer and doesnt get tangled up in stuff like the string does.

The chain is measured at ~2" so its long enough to reach the gripper without being annoyingly long.

Step 7: Enjoy!

Refer to the first step for the 3 different configurations & video for how to use. The mechanism is simple but it was fairly tediously designed to get the leverage working just right to open easily but not let go of things.

You could use this with any kind of string or even paracord, but I really enjoy the badge reel. The clip gave me a place to store the optional grapple-magnet part and its clean & compact. Plus the cable retraction makes me feel like mortal combat's scorpion when I play with this. :)

Rope & String Speed Challenge

Participated in the
Rope & String Speed Challenge