I made these board holders after working for a company that used Martin brand rework equipment. Martin makes high quality and expensive equipment that is out of reach for most amateur electronics enthusiasts. The original Martin brand board holders have a magnetic base and a single spring loaded shaft that clips to the edge of a pcb. The magnetic base allows the board holders to be moved to any position based on the board shape. It's a very simple and elegant design. Unfortunately, the original board holders are $64usd each. This Instructable is my DIY version of those board holders using off the shelf parts.
Step 1: Required Tools & Parts
- Drill Press or Mill (hand drill possible, but less accurate)
- Dremel or Hacksaw
- Tap & Die set
- Threadlock (optional)
- Glue/Epoxy (optional)
Step 2: Drill the Aluminum Base
Drill the magnet hole 1/2" from the edge. The hole for the magnet only needs to be 1/8" deep using a 1/2" drill bit. Test fit the magnet. If the hole is loose, you can use glue/epoxy to secure the magnet in place. If the hole is too small, drill/dremel/hand file it until the magnet fits securely.
The hole for the post was drilled 1/4" from the edge directly opposite of the magnet hole. It should be drilled to match the threading on the bolt used. The bolts I linked in the parts list are 6mm 1.0 pitch. I drilled the hole using a 7/32 bit which is slightly larger than the recommended hole of 5.2mm for the tap. Tap the hole and test fit your bolt.
Step 3: Cut Bolt to Length
Hand tighten the bolt into the threaded hole on the aluminum plate. Using a marker, mark the bolt where it exits the bottom of the aluminum plate. Remove the bolt from the aluminum plate and using a hacksaw or Dremel tool, cut off the excess threading.
Step 4: Assemble the Parts
With the holes drilled, you can now assemble the board holder. Slide the parts onto the bolt in this order:
- Bronze flange bearing (flange first, facing the head of the bolt)
- Compression spring
I used the 3/8" x 3/4" compression spring from the Harbor Freight spring assortment and had to extend/stretch/pull the spring to get the tension/pressure I wanted.
Add the optional threadlock liquid to the bolt threads and screw it into the aluminum base. Securely tighten the bolt.
Step 5: Final Thoughts
The parts used can be substituted based on local availablility. The bolt length can be as short or long as needed. I chose the 55mm length because it had a good distance for my board preheater. My first attempts used a standard hex bolt without the flange but I found that without the flange, boards would slip out of the holder. The flange is the key element to keeping the board clipped securely.
The washers are not necessarily required, but they help keep the spring aligned on the flange bearing.
The aluminum discs I used were cut locally from a 2" diameter rod. You could use smaller or larger diameter disc based on your needs. I would prefer a smaller base, but the 2" diameter aluminum was free from a family member.
Hole placement on the aluminum base can be adjusted. I like having the magnet off center for adjusting/rotating the holder. You could center either the magnet or bolt if your aluminum base is big enough.