Robust Lathe Review - More Woodturning

CUTTING SCREWS IN WOOD BY THE HAND CHASERby James Lukin[Reprinted from Turning Lathes, Aguide to Turning, Screw-Cutting,Metal-Spinning, Ornamental Turning,Etc., Fourth Edition, 1894. Thisbook has been reprinted and is currentlyavailable from The AstragalPress, Mendham, New Jersey.]This somewhat difficult artis well worth all the trouble that itneeds to acquire it. As soon as it isgained, it renders the work moreindependent of all costly apparatusused to render the process easy tosuch as cannot succeed with handtools alone, and the screw can bemade in a shorter time than it takesto set up even the simplest of suchapparatus; but it would be a mistaketo suppose the art in question easy ofacquirement, and it needs constantpractice to keep up the knack of usingthe chaser.The directions given by mostof our leading authorities are asfollows: “Having turned smoothand true the cylinder upon whichthe screw is to be traced, round offthe edge or arris so that it shall notcatch into the teeth at starting, andcheck the traverse of the tool. Therest is placed very near the work,and must have its edge filed smoothand level if it is at all notched fromother work.The tool is to be held by itshandle in the right hand, and itsblade between the first finger andthumb, so as to cushion it somewhat,and allow it barely to lie on the rest.Then the Lathe is to be set in easymotion, and after a trial or two,without actually touching the work,just to get the swing of it, a steady,Figure 1. Shows the Methods of striking threads recommended byHoltzapffel in his book, Hand or Simple Turning. Holtzapffel directsthat the first stroke of the chaser be across the center of the curvewhere the sharp angle has been turned off. The arc a-b is the firststroke and arc c-d is the second.decisive cut is to be attempted, traversingthe tool without nervousnessor hesitation.”Exactly so; but, unless theworkman is already an adept, thechances are sadly against his hittingoff the thread; and, knowing this, hewill be as nervous as a skater makinghis first essay on the ice.Yet there is no royal road toscrew-cutting, and the above directionsare as good as any. The bestway is to cut threads outside chucks,and any odd bits of boxwood, on alloccasions: go at it and keep at it, andthe skill will not long be wanting.The inside thread has also tobe struck haphazard, only the movementof the tool is now straightforward into the hole. Many use forthis purpose an arm rest, which is along-handled, flat bar of iron, about1/2-inch. wide, tapering down toabout 1/4-inch. at the extremity. Theend is turned up 1/4-inch., and thechaser rests on the end just behindthis hook.The “T” of the rest is now retainedin its usual position parallelto the Lathe bed, and the arm restis held under the left armpit, withthe blade of it across the rest. Thisplaces the shank and hook at rightangles, or nearly so, across the faceof the hollowed work, and the toolis laid on it, instead of having toturn round the “T” of the rest itself.The hands grasp the end of the armrest as well as the tool, so that thetwo move as one. A great deal ofinside work, besides screw-cutting,is done with this contrivance, as itprevents having to shift round the“T” of the rest.Inside screws are easier to cutwith its aid, as it moves on the “T”Page 36 More Woodturning February 2010