I’m always surprised by the number of people who are genuinely interested in my spring pole lathe. Many of them have asked me for more detailed information about its construction and use. So I thought that I’d take the opportunity to post some detail photographs of the lathe. Discussion about reciprocating lathe turning techniques will continue to be the subject of frequent posts for some time to come.
First, let me say that I learned of this design from Roy Underhill’s writing (human powered lathes play prominently in several of Roy’s books and I encourage anyone who may be reading this to become familiar with all of his books). I believe that he referred to it as being German in origin. It is quite sophisticated, as spring pole lathes go, as it uses two spring poles that are completely contained within the lathe’s framework. This makes the lathe both highly portable and amazingly stable. My lathe differs from Roy’s in several ways. First, it is larger; center height is 46″, swing – 20″ and capable of nearly 60″ between centers (tailstock removed and dead center positioned in the right side frame member). Second, the lathe is fitted with a fixed treadle that can be operated at any spot along the entire length of the lathe. Lastly, the ways are wider and deeper, and a set of lower “stretchers” were incorporated into my design. The stretchers may be overkill, but I wanted to insure the lathe’s rigidity and stability and that was accomplished.
The ability to adjust the amount of tension is very, very important. This design provides a number of ways to “tailor” spring tension and stroke length. The spring bridle, upper and lower connecting rod position, line position and treadle adjustment all come together to optimize the lathe’s performance.
Enough talking, let’s get to the pictures!
The "finished product"
Getting started
Tool rest - note steel wear bar
Tool rest slide
1/2" handle nut locks dead center into "weld nut" (available from McMaster.com)
Dead center (1/2" carriage bolt) held in place by "weld-nut"
Hickory wedges hold frame together - spring poles are "jam fitted" into "head post" (note grain orientation to avoid splitting)
"Main spring" with connecting rod (1/4" HR bar) and retainer
Crossarm rides on 1/4" carriage bolt in bronze bearing - notched keep connecting rod in position selected
Toolrest locking bolt - 1" wooden screw
Treadle - 3/8" rods ride on bronze bearings that drop into slots in the feet - allows for easy removal of treadle for transport
treadle detail - from rear
treadle detail - from rear
treadle detail - from rear
Spring bridle - note relief so spring is not damaged during movement
Tailstock or poppet, if you prefer
Just a couple of other points…
MATERIAL
Frame, toolrest and tailstock - Yellow pine dimensional lumber (2×12)
Treadle – Ash and yellow pine
Springs – laminated hickory
Threaded and tapped parts – cherry, maple, apple
FINISH – 50/50 Boiled linseed oil and Pure Gum Turpentine (elemental “long oil” spar varnish)
