These plastic cases are readily available at garage sales and swap meets. This one contained a cordless drill kit when new. They usually sell for about $1 or $2 each. I have about 10 of them. I keep different tools and supplies in each. That way, when I need to add freon to my car's A/C, I just grab the one labeled "CAR A/C, and it has everything inside it that I need. Another has air staplers and staples, and so forth.
The only problem is that they usually have an inter liner molded to fit a specific tool. This must be cut out & discarded to meet your needs.
Step 1: TOOLS NEEDED
You will need something to cut out the plastic inner liner.
I use an air saw and a "Oscillating Multi-Tool" from Harbor Freight. It's an excellent tool & is the one I use.
It can be found here: http://www.harborfreight.com/variable-speed-multif...
They also have in in the electric powered model here: http://www.harborfreight.com/Variable-Speed-Oscill..
The air or the electric do the same jobs. They oscillate side to side, cutting, sanding, or scraping with different blades to cut light weight steel, wood, plastic. With a different attached blade, they can sand or scrape up something like like floor tile. HF's air model sell for about $17.00 . It's one of the best tools appearing in recent years.
HF's air saw # P-36843 is made in Taiwan & is an excellent saw. The # 91753 is made in China & is not good.
The last photo is another brand showing some of the different blades available.
Step 2: CUTTING OUT INNER LINER
The outside of the case and the inner liner are molded as one piece with a hollow area between them. By using an air saw or electric saw, it only takes about 15 minutes to carve out the inner liner and remove it.
On most of it, you can just cut straight down where the outer case meets the inner liner.with the cutting tool You could use a high speed cut off tool or even a Dremel tool & disc.There are usually spots in the bottom of the case where the outer & inner parts are heat welded together. By cutting the inner liner into small pieces, you can get your tool down to cut this part out without damaging the outer case.
Step 3: THE FINISHED PRODUCT
This case is 8.5" deep x 16" x 20". According to my calculator, that's 2720 square inches inside of it. A comparable new case would cost about $30.00. I finished this one to store a variety of tools in my grandson's car trunk.. Portable tool boxes made of steel are obsolete and expensive.