Another spin on PCB clamps

Description

Way back when, I saw the PCBite spring-loaded magnetic PCB workholding devices and decided I Must Have Some. Then I saw the price. So I designed and 3D printed a set. They've worked great for years, and I want more, but am really demotivated to make them because, frankly, they are too hard to build.

Then I saw https://hackaday.io/project/202189-stupid-simple-hardware-store-magnetic-pcb-clamp featured yesterday in the post https://hackaday.com/2025/01/16/simple-hardware-store-hack-keeps-your-pcbs-right-where-you-want-them/ which inspired me to respin the project.

Here's the result.

Details

Following Dylan's lead, here's the recipe:

Preparation time: 5 minutes, plus printer time (an hour each in my case)

Ingredients:
1x Threaded rod: Material, size, pitch and length to taste.
1x Nut for threaded rod
1x Cup magnet with mounting hole, size to taste
1x 3D printed base
1x 3D printed nut holder

Step 1: Print the base part

Step 2: Print the nut holder part

Step 3: Insert the threaded rod into the base

Step 4: Screw the magnet onto the base

Step 5: Insert the nut into the nut holder

Step 6: Spin the nut+holder onto the threaded rod

Done!

I got the cup magnets off Amazon (arrived in 12 hours): cat number B09ZX7SXMF "MAGXCENE Strong Magnets with Holes" in 16 mm size.

The printed parts are modeled in Fusion 360, and printed in PLA. I used a 0.3 mm nozzle and 0.1 mm layers. It's helpful to chase the threads with a tap (1/4-20 in my case), and ream the hole for the magnet screw to size with a twist drill (2mm or 3/32 work for the mystery screws I got with the magnets).

They work splendidly, though they do grab the plate a lot more aggressively than the ceramic magnets I used in the previous iteration, and I'll have to get used to that.

Files

With-EPDM-ring.jpg

Added a bit of EPDM rubber (left over pond liner, aka roofing rubber) to grip the bottom side of the PCB

JPEG Image - 173.13 kB - 01/29/2025 at 01:15

Preview

PCBholder2-F360.jpg

Fusion 360 screen shot of the two printed parts

JPEG Image - 124.42 kB - 01/18/2025 at 03:49

Preview

PCBholder2-2parts.jpg

Two PCB holders, one with the top not yet screwed on

JPEG Image - 68.30 kB - 01/18/2025 at 03:49

Preview

PCBholder2-6parts.jpg

6 parts of the PCB holder screw together. One prior to assembly (foreground), one open, laying down, and one holding a Pi Pico. In the background are the Dalek-like previous spring-loaded version.

JPEG Image - 259.18 kB - 01/18/2025 at 03:46

Preview

PCBtop.stl

STL file for PCB holder top, aka nut holder or knurled knob. To fit 1/4-20.

Standard Tesselated Geometry - 8.39 MB - 01/18/2025 at 03:43

Download

Components

1 × Threaded rod 1/4-20 nylon because I had it on hand, about 30 mm long. Plain steel would work fine, or even a carriage bolt.

1 × Nut To fit the threaded rod. !/4-20 here, and nylon again because I had it on hand, but steel will be fine

1 × Cup magnet with mounting hole See the photo: A standard magnet type, it's a rare-earth magnet in a steel cup with a countersunk mounting hole through it, typically supplied with a mounting screw. I used Amazon part B09ZX7SXMF. MAGXCENE brand "Neodymium Disc Magnets with Holes in The Center and Magnets with Stainless Screws". I used 16 mm size, which are plenty strong for this application.

1 × Printed base STL file for 16 mm magnet, 1/4-20 threaded rod

1 × Printed nut holder top STL file for 1/4-20 nut

Project Logs

Collapse

Get a grip.

Paul • 01/29/2025 at 01:23 • 0 comments

So, in actual use, when you tighten down on the knob, it tends to grip the PCB and pull it along a bit, sliding it along the bottom surface of the PCB.

So I added a component: a washer made from EPDM rubber, cut from a bit of leftover garden pond liner (aka, roofing rubber).

I added a picture to the gallery to show it.

I cut about a 2cm square of rubber, drilled a 6 mm hole in it, put a bit of all-purpose cement on the bottom "jaw", put the rubber on, and tightened the top nut. After a few hours to let the cement dry I trimmed it to the circle with a craft ("Exacto") knife.

Much nicer now: the board doesn't walk around when you clamp down on it.

Discussions

Antonio wrote 01/30/2025 at 18:00

Your suggestions are all great but I didn't read your reply in time, so I went the most convoluted way of designing a M6 nut with a larger hex head and printing that instead... yes, I can be that dumb! :)

Anyway, I think it turned out great!

Here's a picture of the clamp holding a 5x7 stripboard: https://i.imgur.com/GsMY5dS.jpeg

It should work ok with bigger boards too, now I just need some magnets.

Thanks for posting the project!

Are you sure? yes | no

Paul wrote 01/30/2025 at 16:34

Ironically, the part is designed in metric. The distance between flats is 11.0 mm. After printing it's a tight fit for a 1/4-20 nut (which is 10.9 mm wide) and requires no further securing.

A M6 nut is 10.0 mm wide and should fit easily (or even loosely), but might require a bit of glue to secure it. Or you could resize the part a few percent, or design your own.

The threads on the bottom part definitely won't fit a M6 though. You'll need to rescale appropriately (78% in Z), or redesign with your intended thread, or print a clear hole and tap it. If you're printing 0.2 mm layers, you're best to just go clear and tap.

Are you sure? yes | no

Antonio wrote 01/30/2025 at 16:09

It looks great, too bad it's not metric. I think M6 is the closest to imperial 1/4, but an M6 nut does not sit in the holder.

Are you sure? yes | no

Another spin on PCB clamps

Description

Details