FILENAMES: pwrfeed1.gif pwrfeed2.gif pwrfeed3.gif pwrfeed4.gif pwrfeed5.gif pwrfeed6.gif DESCRIPTION: These are drawings for a power feed addition to a Smithy 3-in-1 machine as built by Ted Edwards . Ted provided the following description: ======================================================================== Power Feed for Smithy Long Axis by Ted Edwards Ted_E@bc.sympatico.ca files: pwrfeed.txt this file pwrfeed.dxf a .DXF for those with a CADD program pwrfeed1.gif ... pwrfeed6.gif parts of the drawing as .GIFs for those who don't have a CADD program. The motor I used a 120 volt permanent magnet DC gearhead motor rated at 230 rpm and 14 in. lbs. torque. This would be about a 1/10 hp motor. I got mine from Princess Auto in Canada but Surplus Center has similar ones. Any permanent magnet gear head motor in this general range should do fine. My Smithy does not have half nuts on lead screw (the newer ones do). The only way to move the carriage is to crank on the lead screw so I had to compromise on the reduction ratio from motor to lead screw. A larger drive sprocket would give more speed for slewing but poorer control at the low end and vice-versa. This setup is a pretty good compromise for my machine. YMMV. The drive The motor is mounted under the lathe bench on an adjustable bracket. The 1/4" bolt can be loosened slightly and the motor mount part slid up or down to adjust the chain/belt tension. A 12 tooth sprocket on the motor shaft drives a 38 tooth sprocket on the lead screw with miniature roller chain running through a slot in the bench top. I used roller chain and sprockets for the simple reason that my wife and a friend brought home a scrapped photo copier from the dump which was just full of such useful things. Timing belts and pulleys would presumably work just as well. Here's how I made the drive hub to fit on the Smithy lead screw and mate nicely with the 38 tooth sprocket. Since your parts will almost certainly be at least somewhat different, you'll have to make appropriate changes. See drawings. The pin to lock the hub to the sprocket is a piece of 1/8" drill rod with a groove for a tiny o-ring near one end. The other end is pressed into a little knurled knob I made from a bit of 1/4" rod. The o-ring keeps the pin from working its way out. Pull the pin to return to normal manual operation. Mark ctr. pt. on a piece of 1/4" plate Scribe 63mm diam. circle and cut out disk oversize Lay out and prick punch for pin & keyway on surface d Drill 1/4" hole at center and mount on face plate w. standoffs & clamps Center using a tailstock center in hole, clamp w. ready rod thru center hole and remove clamps Machine surfaces a & b. Replace ready rod w. clamps. Machine surface c and drill and bore center hole to 12mm Remove, turn over & remount centered Machine surfaces d & e Cut keyway Remove from lathe Clamp sprocket and hub together Drill and ream pin hole 0.126" and lightly counersink The speed control and reversing switch For speed control, I used a small vaiac from Boeing Surplus. The reversing switch and bridge rectifier came from Radio Shack. Surplus center also has suitable ones. For safety, a three prong plug and three wire cord should be used for the line with the neutral line connected to the common between in and out. In addition both the box for the speed control and the motor body should be connected to the ground. The box for the speed control is shown in the drawings. The holes marked punch, I punched with a Roper Whitney hand held punch as this is much quicker than drilling. Drill 'em if you don't have a punch. Another trick: I printed out the box layouts from my CADD program at 1:1 and stuck them to the aluminum with a light coat of 3M spray adhesive. This saves a *lot* of layout work. I found this unit made working with the machine *much* more pleasant. In addition, the smooth constant motion of the carriage gave a big improvement in the finish I was getting.