Components required for the jackshaft assembly. Two skate bearings, shaft, spacer, key, timing belt, custom driven pulley (41 tooth), and new motor pulley. In addition to these parts, there are two bearing blocks, one back plate and two stiffener bars, all made of Aluminum, 6061-T6 alloy. The bearing blocks were sawn from a piece of 3/4" thick plate, then mounted on the lathe in the 4-jaw chuck to be squared to dimension. The center of the bearing bore was laid out and scribed on a coating of layout blue lacquer. The center point was dimpled with a prick punch (60 degree angle point). With the marked-out block remounted in the lathe chuck, the dimple was brought to center using a dial indicator in contact with a round bar that has a 60 degree point on one end and a center-drilled dimple in the opposite end. The bar is installed with the point in the marked-out dimple, and the other end is supported by the Tail Stock center. As the work is rotated slowly (and the bar prevented from rotating in case the outside surface is not concentric with the centers), The chuck jaws can be adjusted to bring the relative motion of the workpiece center mark to a perfect zero point. After the jaws are secured, machining of the through hole and the counterbore for the bearing may proceed. Be very sure that the face of the work is exactly perpendicular to the lathe axis. The bearing bore diameter must provide a light press fit for the outside diameter of the bearing. If the bore is too loose, consider using Loctite Bearing Locker solution at the time of assembly. After the machined components of the bearing housing are together, mount the assembly in the lathe with the shaft ends adjusted to center. Now, the contour on the backplate (which simulates the shape of the motor) can be machined to the specified radius. The distance from the middle of the shaft to the cutting point can be measured with a Dial Caliper (and add the shaft radius) to determine when the final radius of the contoru has been reached. In the photo, the left end of the assembly is held directly in the chuck. It can also be setup with no chuck mounted, and a 3MT center inserted in the Spindle bore to support the shaft by it's center dimples. A 1/4" diameter bolt about 3 inches long with two nuts can be mounted in a Spindle flange hole to provide a drive pin for the free-spinning Aluminum parts. Stop rattles with a strong rubber band to hold the part against the drive pin. Otherwise, it will surely bang hard every time the interrupted cut is entered by the lathe bit. If a dead TS center is used, be sure it is properly lubricated to prevent wear and (horrors) galling of the center-drilled dimple. Make sure that there is no interference anywhere of the rotating parts with any portion of the lathe. Note that the tool holder on the Compound of the lathe is mounted on a round post and is fitted with a brass height-adjusting screw. This arrangement allows the tool cutting point to be adjusted to the exact center-height of the spindle, and the holder can be rotated on the post to make the angle of attack of the cutting edge at the best possible position. plans can be found at http://www.savefile.com/projects/808585083 Machining of the contour on the backplate has begun. This is the second roughing pass at a depth of approximately .020" (did not keep exact notes, as usual) running from the middle of the backplate toward the left end of the assembly. When a nearly full radius had been achieved, a left-hand cutting tool was substituted in the holder to remove the material from the middle toward the right end of the assembly. The final clean-up cuts were made with a parting tool mounted at a right angle to the work, which left a nice finish from end-to-end and cleaned up the corners where the contour ended. The chuck jaws should have been padded with shims to avoid leaving tracks on the finished part. Tracks on a finished part are embarrassing! Keep a constant eye on the bearing point at the TS center, lube as needed. The interrupted cut makes lots of very small chips that fly about at high speed. Be sure to wear good eye protection to avoid an injury emergency! As the machining nears completion, do a trial fit of the motor-mount flag against the new cut to make sure that you have achieved a good fit. If the radius is too large, there will be a gap between the parts at the centerline, requiring the mounting bolts to spring the flag when fully tightened. This arrangement will be subject to loosening of the bolts because of vibration of the parts when in service on the lathe. Here is the 7x10 250 watt motor assembled with the motor mount weldment as furnished by Little Machine Shop in the 14 inch bed conversion kit. The two M6 flathead screws are really short, and engage the motor by only about 4 threads. Note that the shaft of the weldment has been modified to place the flag vertical behind the motor when installed, not horizontal under the motor as intended by the maker of the kit. This alteration was done by me in a fit of stupid, I did not study the instructions well enough to understand what was supposed to be done. This alteration did make the new jackshaft design easier to adjust the belt tension, I think, than it would have been if done as directed by the kit instructions. On the bottom of the bed casting you can see the lower belt adjusting screw and locknut, ready for insertion of the motor parts. I placed the hex key (Allan)under the motor to stop it from rolling to an angle not suited for the photograph, but, got in a hurry and did not position it out of sight for the actual snapshot. Grrr. Note that the lathe does not have the standard chip pan under it. What you see is a large baking pan from the restaurant supply isle of the local Smart and Final box store. The pan is round about 18 x 26 inches by 1 inch deep, made of Aluminum sheet with a steel reinforcing rod rolled into the edges. The first one we had was used as an oil catch pan for occasions when something containing fluids had to be disassembled for repair. Then, the wife wanted one for drying flower seeds and stuff. It is hard to keep one loose for shop needs. The assembled jackshaft and motor components are test-mounted in the lathe bed to check for the range of adjustments needed for final operation. The upper belt-tension adjusting screw and locknut are installed in the lathe bed, and the jackshaft is in the approximate working position. Since the threaded holes for the adjustment screws are included in the 14" bed kit, it was easiest to make the stop bars for the top and bottom of the jackshaft assembly rather than try to drill and tap new holes for the adjustment screws. The addition of the side bars also stiffen the assembly and reduce the possibility of racking if the belt tension in the various directions is too great for conditions. One less than perfect feature of this geometry is the fact that one of the motor brush ports ends up on the underside of the motor. Servicing the brush will require dismounting the motor, then having to re-do the belt tension. Not really a problem, though. Note that this lathe has had the Change-Gear arrangement modified according to the plan posted by Paul Hackathorn. The B/C idler gear shaft and bushing have been replaced with one that is 24mm long vs the 16mm standard shaft. The shaft is seen in the photo with two gears and a spacer installed to accommodate the speed reducing scheme designed by Paul. Also, note that there is no nut and washer on the Banjo standoff that mounts to the end of the lathe bed. Instead, there is a spacer that has an M6 hole drilled and tapped for a clamping screw. An extra thick washer with 82 degree countersink is used with an M6 flathead hex socket screw. Now, the banjo can be adjusted for mesh of the C/D gear pair using a 4mm ball end hex wrench with a T-handle. Much better than trying to tighten a nut with an open-end wrench. Another view of the Speed Reducer components installed. Note that there is a fair amount of adjustment available at the motor pivot point that threads through the side of the casting. Visible is the motor power cord that passes through the opening in the bed to reach the attachment points within the controller space. The jacketed cord is a little short of going all the way to the controller terminal strip. Male and female connectors similar to those in use were found to make extensions for the 3 conductors. Bad part - there should be some proctective jacketing around the loose wires, such as a piece of shrink tubing. The motor and jackshaft components are nice and rigid with this mounting system, and adjustments are quite easy to make. The motor is adjusted from side to side by loosening the two hex nuts under the mount with a 10mm open end wrench. In this view, the clumsy position of the underside motor brush holder can be seen. Also note that the long lathe bed provides a lot of extra length between the end of the 250w motor and the end of the motor cover that could be used to mount an auxiliary cooling fan. I have not checked, but there is probably an 120vac fan of about 3" diameter that would do a fine job of improving motor cooling when doing long turning sessions at less than optimum motor speed. If only computer fans of 5vdc or 12vdc were available, a "wall wart" power supply could be pressed into service to operate a fan at safe voltages. A short piece of extension cord with a female connector could be wired directly into the controller terminal strip, to accept the plug-in transformer. Here is a view of the jackshaft installation from behind the TS end of the lathe. The cover has been completed and has the AC power cord installed. The cable clamp was salvaged from the old motor cover by drilling out the two spot welds. The strain relief sleeve is included. Both the upper and lower (sort of) jackshaft belt adjusting screws can be seen supporting the jackshaft assembly in the desired location. Access is not too difficult, although the final adjustment is easiest done with the motor set aside. The motor and it's mount are secured to the foot-bar under the lathe by a single M6 button head cap screw. The hex in this size fastener is 4mm, as are most of the adjusting screws now used on this lathe. The issue rubber foot is installed on the underside of the foot (Unistrut rail), in accordance with the drawing details. Between the rubber foot and the open side of the rail is a large (1.5" OD) extra thick fender washer, happily available in onesies and twosies from the shelf of my local Industrial Hardware store. They stock every fastener I have ever wanted to use in the Minilathe shop, in every quantity from 1 to 1000 and up. Of course, small quantities of fastener are more expensive than buying by the box. Here, it is possible to see the bumper piece that was added to the bottom edge of the motor cover, needed so that the cover is supported by the bed casting, instead of hanging out in space to vibrate and rattle while the lathe is operated. I can see, as these words are written, that the left end of the cover should have been as long as the bumper extension, to more completely protect the moving parts from wayward chips that would get into the works. The motor cover is attached to the lathe bed, with all the moving parts well covered. You can see the gap left between the cover and the bed, which could invite the entry of chips. The clamp for the power cord is installed, but the cord is still missing. Final assembly is coming! The cover tends to vibrate and make noise in this condition because the metal stops clatter against the lathe bed. Another piece with a rubber nose has stopped all that. The cover was cut from a handy piece of Galvanized sheet metal that had a former life as an underpan for an electric cooktop. It is interesting what benefit you can realize by taking long walks around the neighborhook every morning. The bumps and holes in the shape were features of theoriginal part. Looks very nice in Minilathe Red. (Rust-Oleum American Accents Colonial Red #7925 Satin Aerosol Paint) Coupled with adjustments made to the three potientiometers on the controller board, this lathe modification (which requires no changes to the original hardware, save the clamp from the old motor cover) has greatly expanded the versatility of the machine, provides lots of torque at the slowest speeds and runs fast enough for all the jobs we have experiences. Marty, of the 7x12minilathe list, has expressed concerns about overloading the various gears between the spindle and the motor, but, no symptoms have appeared in several months of usage. Hopefully it will continue to perform for a long time, probably longer than the operator has before him. Look back to the photo on pages 19 and 23. Study the pulley arrangement. You may have noticed that the large pulley on the jackshaft is made of clear polycarbonate plastic sheet. The available sheet was .375, not the standard .394 inches thick. Works, too! downloaded from www.toolsandmods.com This document is issued for INFORMATION PURPOSES ONLY. The author and/or Manufacturers mentioned herein assume no liability for damages, injury and/or loss of life from performing the procedures mentioned herein.
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