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Drawing Light Box

I’ve been running into a challenge with printing the over sized templates for guitar bodies and neck profiles. One can always ship drawings to a print shop and I have done this on a number of occasions with generally good success. The fee isn’t  bad at $3.00 a print and as long as you only need an occasional copy, the trip to store isn’t that much of a burden. In the old days we used to print things out and tape them together with aid from a light table which made it possible to see through several layers of paper and thus accurately line up the “cut marks”. I decided I wanted one but it needed to be a bit larger than the ones I found on Amazon. So….. I built my own.

As any sane person would do these days, I consulted the Internet for inspiration before drawing up my own design. Essential elements included an (inexpensive) glass top so that I could use a hobby knife to cut paper, LED ribbon lights for bright, compact, low power lighting and a wooden frame. For fun, I decided to add a light switch but it really isn’t necessary.

Parts List

SketchUp Model

DIY Drawing Light Box

DIY Drawing Light Box. (Cick on image to download the SketchUp drawing.)

I took much of this project from epicfantasy’s YouTube video How to make a light box including the exact parts for the LED lights and adapter, and a clever trick for diffusing light. I watched several other videos but the single-most inspiration came from Glass Impressions, How to build a light box.

Box Build

I decided to join my frame with dovetails so I cut the front and back pieces to 37″ and the side pieces to 25″. My glass top and bottom plywood pieces were both 24″ x 36″ so this would leave a 1/2″ of wood around the perimeter. A 1/4″ rebate was cut on both the top and bottom edges of all boards making sure to use a stopped cut on the tail board so I didn’t have any exposed hole. The ends of the rebates had to be finished by hand using chisel and mallet to make complete recesses for the top and bottom pieces. The base was easier as I could cut the plywood to size should my measurements be off  but the glass had to fit just right. Unfortunately I didn’t cut the rebates deep enough for the top and other than dry assembling the box and test fitting, there was no way to know this until after I glued up the box. To get the glass to fit, I marked and whittled until at last the glass would drop in. With all the tools I now have, I couldn’t think of an elegant way to widen the recess other than with marking knife, chisel and shoulder plane. Eventually I got a good fit but it would have been much easier to get it right at the router table.

Before gluing up the box however, I measured and cut a through mortise for the rocker switch on the right side. Rearward of the switch I drilled a 3/8″ hole and press fit the female 12 V jack (LED end) into it. Just to make sure it stayed I applied some hot glue with a glue gun. I was ready to glue-up the frame and attach the bottom.

Light Box Switch

I cut the plywood bottom to size and after a few passes with the block plane had a good fit. I attached the bottom using screws only (4×13 mm) making sure to pre-drill holes at a slight angle (towards the frame) so as to make sure I didn’t miss the rebate wall. I didn’t use glue just in case I have to remove the bottom for some future repair.

Box bottom.

Frame bottom panel.

Using 3M spray adhesive, I lined the box interior with heavy-duty aluminum foil to provide good light reflectance. I could have used aluminum tape but this was a cheaper option although more cumbersome to install.

Electrical

I unraveled the spool of LED lights to get an idea of how many strips and how close together I could make the rows. Epicfantasy didn’t cut his light strip opting to loop the ribbon back and forth along the bottom. I considered this but figured I would do it the harder but potentially “better” way by cutting the LED into individual strips and reconnecting them with hookup wire. This wasn’t difficult but I can give you a couple of tips that might help with your learning curve.

Tip #1 – The strip has marked cut lines with solder pads on either side. Cut the LEDs only in these areas and take your time as the solder pads are very close together. The pads are tiny to begin with and if you cut half of one away you are asking for trouble. Don’t ask me how I know this….

LED light strip

Safe to cut between the solder pads on the line indicated but cut accurately.

Tip #2 – Make sure you hook  + to + (Positive)  and – to  – (Negative) (see image above). I was using black and red hookup and for some odd reason kept trying to use the black wire for Positive connections. Not sure what that was about but of course, Positive is traditionally red and Negative is traditionally black. Using different colored wire isn’t necessary but it can help to prevent wiring mistakes and adds a bit of professionalism to your work. I used hot glue to tack the wires to the bottom.

Tip #3 – Leave very little of each end of the hookup wire exposed, about 1-2 mm. Tin the wire but more importantly, tin the solder pad before attempting the connection. Initially I tinned the wire but not the pad and this doesn’t work, flux goes everywhere. When done properly there will be a beautiful round dollop of solder mounded perfectly on the solder pad. Heating for connection is very fast but you must hold the wire in place for good while for the solder to harden (10-15 secs); otherwise the wire just springs back dragging solder with it and making a mess of it. Blow on it if you want, this helps cool the joint and blows the fumes out of your face so it can’t hurt.

Tip #4 – Test your connections as you go. I started my connections at the powered end and tested each strip as I went just to give me confidence as I progressed along the chain. If you don’t do this troubleshooting after will still be very straightforward with lights working up to the failure.

Tip #5 – Switches are installed in-line on the power side of a circuit. The light strip came with a DC jack and ready to go but there was no provision for a switch as such so I ended up peeling back insulation to expose wires which were stranded and very delicate. I didn’t have a lot of extra wire length to work with but I was able to get everything connected, soldered and covered with heat shrink tubing. If I were to do this over, I would come up with a cleaner approach to hooking in the switch or just left it out altogether.

The Top

Why Glass

I choose to use glass for the working surface of this light box for two reasons, cost ($13)  and resistance to scratches when cutting with a hobby knife. That said I can not emphasize enough the potential danger of working with a 2’x3′ pane of non-tempered glass. As a home-brewer, I myself have experienced a glass carboy explode when it fell off a stand on to the floor. My foot was cut in several places and I carried a large shard of glass in my toe for months before it was expelled. A co-worker of mine almost died carrying a glass vase and stepped in hole waking to her house. One of the pieces sliced her wrist area and had she and her husband not kept cool heads getting her to the hospital she would have been in real trouble. Glass is dangerous, and working with this piece concerned me. I reasoned the glass top would be “relatively protected” once I got it safely mounted into the frame. As luck would have it, I almost made it but on the second day, somehow the wrapped glass, standing against the wall shifted and a piece of it broke. Darn! I used super glue to reattach it and placed packing tape inside and out along the break to reinforce it. In hindsight, plastic is just an all around better choice for your top, even given the inevitable scratches that will come.

Frosting

I sprayed the underside of the glass top with spray paint, glass frosting. Can’t say it was a bad result, I just wanted something a bit more diffuse. I decided to attach a layer of that thin white foam they wrap electronics in to further soften the light. If you are using translucent plastic none of this is necessary of course. Glue Impressions sprayed a couple thin coats of white paint on his top. Epicfantasy used some white, plastic poster board as an inexpensive light diffuser. It’s your call but I probably wouldn’t spend the $5 on frosting paint if I was to do it again, I’d either use white or go with the attached plastic or foam.

Hot Glue Gun

I used a lot of hot melt glue on this project because I didn’t want anything coming loose on me. Hot glue was used to secure the press-fit DC jack into the wooden frame and also to secure wires, LED lights and wire hook-ups. Of course I tested and retested before entombing connections in glue.

Reluctantly I used hot glue to secure the glass top into the rebate making this a rather permanent mount. This means any repairs will need to made by removing the bottom which isn’t ideal but is feasible. I was terrified the glass top might fall out on accident. I considered using wooden strips to secure it but end the end opted to hot glue it in place.

Finished Light Box

Finished DIY Tracing Light Box

Closing Thoughts

I’m happy with the build although I hate that my glass pane has a break in it. If you are considering a similar build keep in mind that the frame could have been simply screwed or nailed together without need of dovetail or box joints. I gave serious consideration to simply using pocket screws but as a learning woodworker, I didn’t mind practicing the joinery. You might also give additional thought to the size of your light box. I looked over the available sizes of replacement glass panes and landed on 2’x3′ which would be long enough to join guitar neck templates and wide enough for body templates. But it’s big and I’m not sure where I’m going to store it/ protect it when not in use. I’m thinking about making a table out of it and possibly making a wooden top to cover it but time will tell if I get it done.

Thanks for hanging with the Turtlecovebrewer

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