If you are an avid plastic modeler, sooner or later you will have to open a circular hole in your model. It may be something simply molded closed, or a hatch that you want to show open, a window, maybe, you name it. When the hole is small enough, we simply drill it using drill bits. If the hole is big, you may have to use compass cutters or do it manually using some sort of template. But there are those holes that are large enough to be difficult to oper accurately with drill bits, and small enough to forbid the use of templates or a compass. Other times the plastic is very thick, making impossible the use of a compass cutter.

That is when large reamers come to play.


Everybody probably knows reamers. The wood ship modeling folks use them almost as much as a hobby knife. However, when we talk about reamers we generally mean the fine ones, those used to bore small holes to the correct diameter. If you don't know reamers, please don't mistake them for drill bits. Reamers are tapered faceted rods with sharp cutting edges. You insert them in a pre-existing hole and turn/push until the desired diameter is achieved. By turning it you make the reamer scrape material, while by pushing it you increment the diameter progressively. Here are some common examples:
 

However, reamers are not always small tools. There are also heavy-duty models which are needed to bore larger holes. And from time to time they are exactly what I need to make my modeling life easier. Usually, you find large reamers in two basic types: the coarse and the finishing ones. The first is more suitable to remove larger amounts of material, while the finishing reamer can be used in the final steps when the final diameter is trued. Another thing to mention about these reamers is that they actually produce a conical hole because of the tapering. This may be an issue if you are reaming a hole through thick parts.


I will show you what is probably the simplest application of a heavy-duty reamer. I wanted to open the landing gear well of a D.H. Dove in 1/72 scale because the kit part was too shallow and not convincing. Since there was no pre-existing hole, I had to make one. I started making a center hole which I roughly enlarged using the hobby knife, just enough to make the coarse reamer start its job:


I then inserted the coarse reamer in the hole and started turning and pushing it, progressively enlarging the opening:


I stopped when the hole was close to the border of the well:


At this point, I switched to the finishing reamer. Because of the tapering, it is a good idea to alternate reaming from both sides of the wing.


The reamers worked so well that I barely needed to sand the wall of the wells. It was a job of a few minutes, literally:


You could argue that the same job can be made only with a hobby knife and sandpaper. It can. The thing about using the right tools is that you can do it very accurately, repeatedly if needed, and very fast. Note that with the reamer you obtain a perfectly circular hole. The wing in this example already had the hole partially done, which served as a reference. But if you are doing the same operation on a plain plastic card it may be more difficult.

Besides that, there are so many other applications where a good reamer can make your life easier. One that occurs to me as I write this text is the infamous engine nacelles whose opening is too small. If you have been there, you probably know that we have to find a suitable dowel, fix some sandpaper to it and remove the material very slowly. A reamer will do the job in seconds:


Ah, and don't forget to clean your tools after using them.

I hope you find this article useful for your next project. Let me know what you think.