The traditional method for a Nut & Bolt fixing, is a Nut & Bolt. However I am going to test a different method; Insert & Bolt.



Threaded Brass Inserts as they are known to those in the know, provide fixing points inside all manner of products. You're most likely to find them in plastics, in Laptops for example, which is where I know them from as I spent six years working as a Laptop engineer.



Tappex are a UK company which manufactures Threaded Brass Inserts. I will be using their line of Microbarb inserts as anchor points for the screws and bolts holding the LittleBox together. The Inserts are captive so if for any reason I need to take apart the LittleBox I shouldn't lose any fixings, which is what might have happened had I decided on using nuts.



Layer Four of the LittleBox will not have the centre cut out like all the other layers. I will cut holes to take a selection of inserts which will act as anchors for screws holding the electronics in the LittleBox. The Tappex website provides specifications for the diameter of the holes needed for each insert size. For example an M3 Microbarb brass insert requires a hole of 4.66mm. Having previously checked the cutting specifications (Kerf) with CLC I know to expect a loss of material of approximately 0.1mm. Taking those specifications for an M3 insert hole I drew a hole diameter of 4.6mm (whether this is too large a hole I will see when the relevant parts arrive).



1 | Create layer Four. Make sure to remove the cutting lines for the viewable area of the LCD and the LCD's outer dimensions. You should have a solid layer where we can mark cut-holes for the inserts. Leave the touch cable cut-out and of course the speaker cut-outs.



When marking cut-holes for mounting the PCBs remember that you are looking at the layer from the front and that the PCBs will be mounted from the back. Any cut-holes are mirrored looking at them from the front.



2 | Turn the LCD face down. Position the PCBs on the back of the LCD where you want them to go. I placed the Raspberry Pi so that the SD Card sticks out the middle of the LittleBox at the top.



3 | Mark cut-holes for each of the PCBs that are going into the LittleBox (remember to mirror the holes). Don't forget a cut-out for the LCD harness to pass through. Each hole has text next to it saying which Microbarb insert should be fitted.



I took measurements for the Raspberry Pi from a template, measurements for the Logic Board are included in the datasheet, and the rest I had to measure by hand. Remember when placing the PCBs that you'll need to leave at least a 10mm gap around the outer edges. Consider to, the connections to the PCBs like headphone jacks, power inputs, and USB plugs, they all need clearance from not only the sides but each other.



All the PCBs sit on 3mm spacers, with the exception of the M4 mounted PCB (RKAmp2) which rests on 4mm spacers.



4 | Copy & Paste the Fascia into layer Five.



5 | Create cut-lines at the top for the SD Card to go into the Raspberry Pi.



6 | Draw two cut-lines 5mm apart on the centre of the upper boarder for the two speakers. The speaker wires will pass through these holes.



The USB Hub has no mounting holes so we have to get creative. I'm going to alter the border so it can be used to hold the hub in place. I'll have to take into account the M3 screw which will have to be routed between the lower two USB sockets. I'll be using an 18mm M3 spacer so the plywood isn't bent when the screw is tightened.



On the base of the USB Hub's PCB I plan to stick some strips of 3mm foam. This wil help to hold the hub but also keep any through-hole wires off of layer Four.



7 | Measure the Hub.



8 | Draw two cut-lines making space for the hub.



9 | Copy & Paste the Fascia into layer Six.



10 | Duplicate the cut-lines for the Hub. Centre of the 10mm border around the base of the speakers draw two cut-lines 10mm apart. This will create a hole to help improve the speakers bass performance.



11 | Copy & Paste the Fascia into layer Seven, and duplicate the cut-lines for the USB hub.



12 | Copy & Paste the Fascia into layer Eight.



13 | Alter the border so that the plywood slots between the USB sockets.



14 | Create two cut-outs for M2 Microbarbs, to help strengthen the assembly.



The LittleBox has a stand, and the stand will enclose the DC DC Converter and the Power PCB designed in Step 3. The stand has to attach to the screen pack so we must add brackets to do so. We'll be using M6 Microbarbs as part of the brackets.



I put the brackets for the stand near where the M3 screws are to go. Doing so should help combat any stresses in the wood and increase the strength around the bracket area.



15 | Modify the cut-lines around the two top and bottom centre M3 holes so that you can fit in brackets to hold four M6 Microbarbs.



16 | Copy & Paste the Fascia into layer Nine.



17 | Duplicate the alterations for the USB Hub remembering to reduce the M2 hole sizes, but do not copy the brackets.



18 | Copy & Paste the Fascia into layer Ten.



19 | Duplicate the alterations for the USB Hub, and the brackets remembering to reduce the size of the M6 holes.



20 | Copy & Paste the Fascia into layer Eleven.



21 | This is the final layer so we wont need to make any alterations but you will need to remove the cut-lines for the speakers, and increase the size of the M3 holes to take Microbarbs. I also put in a note to say the brass inserts should be inserted from the other side.