This is a hacksaw grip that accepts a standard 12mm / 1/2 inch wide metal hacksaw blade. It's very useful to get into small spaces and for flush cutoffs.
Last but not least it allows to recycle broken or partially worn blades.
Mount the blade to cut in pull direction like a Japanese wood saw, this helps to straighten the blade while cutting.
26/07/2018 uploaded v2
In addition to the printed piece you will need a ca. 3x18mm dowel pin or cut off bolt to secure the blade in the grip.
The piece is printed best standing on the back as positioned in the STL. In general support is not needed, only the hole at the back could use some support if you want it to look pretty.
I printed with a 0.4mm nozzle, 4 walls, 7mm cubic infill distance. I highly recommend 3D infills like Curas or Slic3rs "cubic" when you need maximum strength.
You really don't need more infill, the layer adhesion of the average PLA at the right temperature is much better than you might think. And as the layers run at an angle to the centerline the effective surface area for layer adhesion is increased.
You will need at least 150mm print height.
Depending on the thickness of the blade and the dimensional accuracy of you printer you can choose from two files with different slot widths.
I put the Fusion360 file on github.