Working with the large spar lathe

Dean is working on a new shaft for the Saugus Iron Work’s waterwheel.  Scott started with a large oak log and eight-sided it on the Lucas mill.


The log was brought into the main shop and set up on the spar lathe.  We’ve used this lathe in the past to make the spars for the Amistad, but for a number of years it’s been sitting under parts for the Charles W. Morgan.  It’s good to have it up and working again.


This spar lathe consists of a large motor on the left which connects to the log through the head stock.


The log is supported on the right side by the tailstock.


The tailstock is not powered, and only provides support and an axis of rotation.

The cutter head is mounted on the lathe track next to the log.


The cutterhead has a motor that drives a set of spinning cutters. These cutters are just like the kind that you would find in a table saw dado set.

The headstock motor spins the log slowly, and the cutter head moves along the length of the log cutting off the high points. After each pass, the cutter head is moved in towards the log slightly. With successive passes, the high points are cut off and the log gradually becomes a round cylinder.  Of course, it’s always easier to show these things than to describe them. Here is Dean working on the initial turning.

As the cuts progress, you can see that the log becomes more and more cylindrical.

The final shaft is not a single diameter. There are thicker and thinner sections along its length. Once Dean has rounded the entire log, he then marks the steps between the different diameters,


and cuts a groove into the log at the depth of that section.


The diameter of the log at each groove is measured using a pair of framing squares like giant calipers.


These diameters act as reference marks. Once they are established, he cuts away the remainder of the log down to those depths.


For more information on Saugus Iron Works, you can visit their page here.   There is also an interesting video on the restoration of the iron works here.