Introduction: DIY Electro-mechanical Prototyping Board
When physicists do experiments they often fasten parts down to an 'optical table' which is often a massive, vibration isolated, solid chunk of metal or granite with an extremely accurate grid of tapped holes for attaching pieces of equipment. They look very useful (and pretty) but they cost thousands of dollars.
At the other end of the spectrum, some of us just want something to let us connect up a motor without it rolling away on us. This is just a board with holes in it - but with a few enhancements.
(1) This seems like a good idea to me but I haven't used it as much as I'd hoped.
(2) This is my first instructable.
[Note for American viewers. Substitute 1/4-20 for M6, 3/8 for M10, 1 inch for 25mm, 2 inches for 50mm]
Step 1: Materials Required
The main bits needed:
1 x sheet of MDF, mine is 500 by 300 and 18mm thick.
Some M6 T-nuts (threaded cylinder with a flat plate and spikes to dig into wood).
Some M6 barrel-nuts (10mm diameter cylinder with a threaded M6 hole through the middle, perpendicular to the axis, not along it).
Ruler, pencil, and two colours of marker pen.
The barrel nuts aren't required but I found them handy for fastening things down firmly.
The t-nuts aren't required. If you wanted to swap time for money you could tap the M6 holes directly into the MDF. But steel t-nuts aren't expensive and they are *much* stronger.
Step 2: Draw First Grid
Draw a grid for one set of holes, with spacing of 50mm, starting 25mm from each edge.
Step 3: Draw the Second Grid
Draw another grid, again spaced 50mm apart, but offset by 25mm so each point falls in the centre of the squares from the previous step. Draw this grid in a different colour to make it easier when lining things up.
Step 4: Drill the First Set of Holes
These are 7mm diameter to take the t-nuts. Check the size of the nuts you have in case they're different.
If you decided to tap the MDF instead of using the t-nuts, then 5mm should work as a tapping drill.
Either way, you need to try and make these holes nice and vertical. A drill press helps.
The inner, smaller, set of holes (45 holes) gets the t-nuts (which cost money) while the outer, larger, set (60 holes) will be plain holes.
Step 5: Drill the Second Set of Holes
The 60 alternate holes are drilled 10mm. No nuts fit into these holes. In use they can either take a M10 bolt *or* they can take an M6 bolt with several millimeters of adjustment. Sometimes you want one, sometimes the other.
Step 6: Install the T-nuts
The t-nuts go into the underside of the board. This way, when you tighten a bolt into them, they are pulled into the board rather than popped out.
I've seen instructions saying to just hammer them in but I've found they don't tend to be very straight if you do that. I pressed some of these in with a vice which worked well. Where I couldn't do that (which was most of the ones in the middle of the board) I used my standard technique of a large 'fender' washer and a bolt. Tighten the bolt and it draws the t-nut into the hole. If the holes are tight then it takes a *lot* of force to pull them in. They don't come out under any sensible treatment.
Since I wasn't certain that the whole prototype board was worthwhile, I only fitted a small number (9) of t-nuts to start with. I've slowly added more as I needed. If I'd had a note of how much they cost I suspect I'd have just installed the lot since they're probably quite cheap.
Step 7: Glue Spacers / Supports Under the Board
Spacers go under the board to lift it off the surface. The spacer needs to be deeper than an M10 bolt-head + M10 washer. In my case I just used more of the 18mm MDF. I tried to be tricky and get a decent area while leaving clear space around the bolt holes. I wasn't particularly successful and trying to use a wide washer in the corner holes is not very easy. Trying to get a spanner in to tighten a bolt is also not easy.
The photo shows the 4 corner spacers and two side spacers being glued down with ordinary PVA (white) glue. You can also see the underside of the 9 t-nuts I put in.
Step 8: The Completed Board
This photo shows the completed prototyping board.
However, there's a bunch more parts you can make which make it easier to use and more flexible.
Step 9: Cordless Drill Motor
The sequence for mounting it was:
- Cut a piece of MDF.
- Drill a hole in the face large enough for the body with a holesaw.
- Drill a 10mm hole in the face, near the bottom. This will take a barrel nut.
- Drill a 6mm hole from the bottom edge, so that it intersects the 10mm hole. This will take a bolt from underneath the board, screwing into the barrel nut and pulling the MDF down hard against the board.
- Drill two 5mm holes down from the top edge, about half way into the board.
- Saw a horizontal cut across the MDF, in the centre of the large hole for the motor.
- Drill out the two 5mm holes in the top to 6mm (clearance for an M6 bolt).
- Tap the two 5mm holes in the bottom part to M6.
- Insert the drill motor into the hole (with a bit of rubber to get a good fit) and bolt down from the top.
Step 10: M6 Studs
I made up some studs to screw into the board. These are just a length of M6 threaded rod (about 150mm), with a t-nut and a large washer soldered on near the bottom. The section of threaded rod beyond the washer is long enough to go through the prototyping board but not too far. Screw it in and you have a vertical length of threaded rod to attach other things to.
Step 11: Using the Prototyping Board
[Soldering a ball]
A typical use for the board. I needed to solder some threaded rod into a hole I'd drilled in a ball bearing. The various bits I'm using here allowed me to hold the threaded rod vertical and in position.
I wanted to hold a funnel (containing coffee filter paper) in mid air above a container so I could filter some crud out of some used copper sulphate solution. In a chemistry lab one would just grab a retort holder but this lash-up worked fine.
[clamping some parts]
I needed to clamp some bits of wood at exactly 90� while I glued it. The board made it easier to hold down the ball-bearing race I was using as a precise reference.
I salvaged a tri-filar winding (3 wires) from the yoke coils of an old monitor. My setup here is to wind the wires off onto three separate spools. (I'd already used the setup to wind the wires off my crude hand-wound tangle and onto a spool).
On the left is a small forward/reverse switch fastened down to the board and a peg for keeping tension on the wires when I paused.
The spools may look rather odd but they were free. Our local council thrift store was giving away dubbed video-cassettes for free. I just had to unspool huge amounts of tape and drill a hole in the centre.
[tumbler cleaning brass]
I found some old brass screws and nuts which were black with dirt and tarnish. This is my trusty drill motor spinning a rubber coated shaft (from the paper feed of a printer) while another shaft rotates freely.
A plastic jar (with some high friction rubber mat around it) sits on the two shafts and turns over. The brass tumbles inside with a mixture of dry rice and a bit of sand. I splodged some hot-melt glue on the inside of the jar to help the tumbling action.
Step 12: Conclusion
Is it useful?
Yes. I built a smaller board initially and found myself wanting a bigger one which must indicate something. I've probably made up about 15 different configurations since I made it though some
of those were very simple.
Another really handy advantage is space. I can assemble a setup, use it for a day or two, then tear it down and just have to store the board and some bits and pieces (ok, lots of bits and pieces now). It still takes up far less space than a bunch of different gadgets.
What would I change?
A suggestion I saw on a website (now misplaced) was for a fixture like this but sealed so it could be used for gluing. I didn't apply any varnish or paint because (a) I'm lazy, and (b) I often heat things on the MDF and it copes with it much better than paint. If I was doing it again, I think I might glue down a piece of steel (cut from a pc case with nice non-stick enameled surface) so I could fasten things down with some of my many hard-disk magnets.
The other thing I'd change is to make many more of my attachements with slots rather than bolt holes. The lack of flexibility has proven annoying on more than one occasion.
Any comments, good or bad, welcome.