Quite a specific tool here. It lifts a Raspberry Pi HAT board from its connection to the 40-pin connector on the lower board. That's it!

I was a little surprised not to find something like this already, but supposedly most people just wiggle and tug the boards apart and hope they don't have a mishap. Realistically, it's not super useful for occasional users, but if you do this a lot and/or dislike the slightly dicey experience of separating the boards, then this is the tool for you.

In terms of effort vs. practical reward, it wouldn't have normally been worth it, but it was a set of tempting design challenges and I'm happy with the result. Thanks go to the various makers whose models of parallel pliers gave me some inspiration for the mechanism.

Height of the regular jaw spreaders is 9.6mm when closed and about 18.8mm when fully open. This should work fine with most normal height HATs, but maybe not so well for those with an greater or lesser height between boards. There is also a slightly shorter version with 8mm spreaders for shorter offset boards such as the PoE+ HAT.

During use, it helps to keep both boards held reasonably parallel to each other to ensure a smooth and fully straight separation.

This is, of course, a light duty tool and may break if used for the wrong purpose or put under excessive load. Used normally, it provides enough force to do what it is designed for.

It could have wider use for different inter-board connectors or similar, so please let me know of any examples, or remix it (full FreeCAD project is included.)

Hardware required:

• (4) M3x10 countersunk screws
• (4) M3 hex nyloc nuts, or ordinary M3 hex nuts with thread locker or glue
• Optional but highly recommended: M3x12 countersunk screw and another M3 nyloc nut, to hold the centre pivot together.

Printing

• Print both levers and both of either 9.6mm or 8mm jaws.
• Designed to print best with 0.4mm nozzle, 0.25mm (all) layers.
• PLA works very well as the parts benefit from being quite stiff. The spring holds up fine.  I've not tried other materials yet, but I'm sure they will do the job if printed solidly enough.
• Three or more perimeters and plenty of infill are worth it for extra strength. The handle ‘paddle’ regions are best modified to be 100% solid, as they need to resist flex caused by the off-centre load from the spreaders pushing the boards apart.

Assembly Notes

• The part “Lever_2” should be fitted on the side of the jaws which the spreaders protrude from. (The ‘paddle’ on this lever is thinner and gives 1mm more effective spreader length when facing the Pi/HAT.)
• It doesn't matter much which jaw part is top or bottom, but it does determine which direction the pair will drift slightly, relative to the levers when they're squeezed.

1. Place the lower jaw on one lever ‘paddle’ and place the other lever over it.
2. Partially fit screws and nuts into the jaw and centre pivot of lever.
3. Slot the other jaw into place and drive all screws in fully (but not too tight.)
4. Back off about a quarter turn on each screw so that the linkages are very close but loose enough for free movement. Adjust finely as needed.