CNC Progress Report

This week many of the parts to the table were made. The legs were made by a Computer Numeric Control (CNC), the table boards were glued together, and the crossbar was made as well.

A significant problem with routing white oak is the risk of tear out. Tear out is when the rotation of the router pulls out the grain of the wood and damages the surface particularly edges as seen in the image below. The approach path of the router has a large impact. A path called a climb cut helps to minimize this by pushing the grain into the piece as opposed to pulling it up. A larger router bit diameter also helps by providing a more ideal cutting angle that cuts parallel to the path.

Here one can see the tear out on the corner. Again we tried to minimize it but sometimes it’s unavoidable. However we thought this would happen and planned to remove that material in the next cut completely getting rid of the tear out.

Above, pockets are being routed for the tenon joints. Normally an upturning bit is used to route the wood to pull away the waste from the stock. However here that would cause tear out on the top surface by again pulling up the grain. Thus a down turning bit was used to push the grain into the stock.

The picture above is the bottom of the table top. It has to be connected to the cross bars via a mortis and tenon joint. The bottom of the table wasn’t planed to preserve the thickness, but the joinery needed to fit flush. Thus there needed to be a flat surface on the bottom at least the size of the joint. The green rectangles are where the table will be worked on. The large green one is where a flat surface will be created and the smaller one is where the mortis joint will be made. Below is a 3 dimensional rendering of the cuts made in the table top.