Reamer for 3d prints. Parametric

Turn your flat wood drills in to reamers for 3d printed holes and get perfectly round holes with tight tolerance. Parametric Fusion360 file.

3d printed vertical holes are usually ok without any post processing, but horizontal or sloped holes will not have perfect roundness and will usually not have the exact diameter. This can be fixed by printing slightly smaller diameter holes than intended and then drill out the right diameter. Most drill bits however are not ideal for this job. Spiral drills for example, will tend to screw in to the hole if you try to enlarge an existing hole. A reamer is the best tool for the job. For smaller sizes (1-12 mm) i recommend buying a cheep set, but as the diameter gets larger reamers get expensive and bulky. They will also not fit in a common drill chuck. They are also more accurate then needed when working in plastic, as they are intended for mechanical metal work. I therefor made a plastic holder to make a common flat wood drill work as a reamer. I included a parametric Fusion 360 file so you can print reamers that fit your flat drill bits.

You can also wrap sand paper around the end of the reamer if you need to get the hole slightly bigger still to fit your parts. Just lock it in place by folding it in between the two tip parts and make sure you wrap it in the same direction as you spin it.

Plastics, especially PLA, will quickly get warm and melt due to friction. I recommend using hand power or slow speed with a drill and pause for cooling. You can also cool with water.

For more support when starting the reaming you can make the end bit longer. For reaming closed-end holes you can make it just as long as the flat cutter. To get all the way in a closed-end hole you might need to cut of the pointy end of the drill bit.