It is often desirable to achieve a very specific fit between a mortise and tenon (or similar situation). This instructable describes a set of gauges that make it easy to determine the dimensions needed to achieve the desired fit when using an Objet 3D printer at Pier 9. It also includes the AutoDesk Fusion 360 files and .stl files used to generate these gauges, so that those with access to other 3D printers can make their own gauges.

The gauges are stored in a drawer in the 3D Print Shop at Pier 9. If you can't find them, just ask Gabe.

Step 1: Description of the Gauges

There are three sets of gauges, one for each of the printing options: HS, HQ, and Auto. Each set of gauges consists of four pieces: three mortise pieces and one tenon bar. Each of the four pieces has either "HS", "HQ" or "Auto" debossed on the surface to indicate which print setting was used. Each of the four pieces also has an arrow "^" debossed on the surface indicating the positive Z-direction when printed.

Mortise Pieces: One of the mortise pieces has two mortises, the other two have one mortise each. All the mortises have nominally the same dimensions of .250" x .500". Together they represent mortises that were printed facing four different directions: +X, +Y, +Z, and -Z.

Tenon Bar: The tenon bar was printed with the inserts facing up (+Z-direction). It contains ten tenons dimensioned in graduated steps of .002" from .250" x .500" to .230" x .420". The dimensional information is debossed on the tenon bar.

Step 2: Using the Gauges

To determine the dimensions required for the desired fit, select the appropriate mortise-&-tenon pair and insert the mortise piece onto the various tenons until the desire fit is achieved. The difference in the dimensions between the mortise piece and the tenon piece is the difference you should apply to achieve the same fit for your mortise-&-tenon situation, regardless of scale.

Step 3: Notes:

If you use calipers to measure the actual dimensions of the mortises and tenons you will find that in some cases the dimensions vary considerably from the nominal dimensions, and the variances are different in different axes.

Step 4: Files

The image above shows what the fit test file models look like, and the orientation in which they were printed (+X axis direction is from bottom-left to upper-right, +Z is from bottom to top). Below are the fit test files. I have included both the original Autodesk Fusion 360 files (.f3d), and the .stl files. Fusion 360 is available as a free trial from AutoDesk.

Note that all of these files were printed with the tenons facing up (+Z). If you want to make fits test facing in a different direction, just rotate them before printing, but be sure to first change the location/orientation of the arrow "^" deboss to avoid confusion.