A FLEXIBLE SHAFT TOOL HOLDER
This is a very neat and useful device for those of you who own either a Dremel type high speed moto tool with a flexible shaft attachment. Why bother, you ask? Imagine being able to drill the tiniest #80 and up to 1/8" diameter holes not only centered on the workpiece as with the previous attachment ( drill-1 ), but because the drill itself is powered, you will be able to drill any number of holes, with the work piece stationary, at any radial location from the center of the workpiece as well as to exact depths. By combining this device with an index plate on the spindle to index the workpiece's position, you will be able to even make if you felt like it, a solid brass clock face with perfectly spaced second, minute and hour holes. To extract the full versatility of this concept you will need a moto tool with variable speed provision or if money is no object, you may consider one of 1/4 horse power self contained variable speed units such as the Foredom or Dremel equivalent. There are many versions of this tool by several manufacturers, including of course, several imported Asian examples. The hand pieces come in different diameters and chuck arrangements. The most accurate chucks will use collets but will only accept one size shank tool per collet size. If you intend to drill most of your drilling with numbered drill series bits, you should consider the 1/4" jacobs type chuck version. No matter which tool use, it will have to be hung above the tail stock and the flexible shaft with its handpiece held in the special tool holder we will now build. The main point to remember about flexible shafts is that they must not be allowed to bend beyond a 6" to 8" radius and any kinking of the shaft will greatly reduce its life span.
The handpiece holder is extremely simple to build and is no more difficult than the boring bar holder described earlier. For the TAIG or SHERLINE lathes that have double slotted cross slides, you will be able to build the holder out of a 2" cube of aluminum cut from 2' square bar. The rough cut cube can be milled on the lathe very easily with the use of a four jaw scroll chuck. It will grip it centered every time. Grip the rough block so one of sawn faces is facing out toward the tail stock. Check that the block is square to the chuck face with a small machinist's square and lightly tap with a small hammer to adjust if needed. Once you are satisfied that it is indeed square, tighten the jaws and proceed by taking a facing cut across the rough end of the cube. With one face now machined clean and square, flip the work end for end and machine the opposite face. Flip the work sideways, machine the remaining four faces in order and check the finished block for squareness. File all twelve. now very sharp edges, to slightly chamfer them. Decide which face will become the top and which face will face the spindle and draw a T for top and an S for spindle with a magic marker. Take the block and lay it on top of the cross slide in the final orientation with the S face toward the spindle and the T face on top. Measure 1/2" from the side edge away from you and scribe a line from the S face to the tail face. Set your calipers for exactly one inch and center the two points by eye along the line you just scribed and make two cross marks to lay out two hole positions one inch apart along that line. Drill these holes with a #11 drill bit and counter sink them with a 1/4" bit to a 1/4" depth to allow the cap screw head to clear the top. Now that the hold down cap screw holes are drilled, you can install the block on the cross slide with a pair of 2" long 10-32 cap screws and " T " nuts. Square the block so the "S " face is perpendicular to the long axis of the lathe. All you need to do is to install a faceplate on the spindle, run the cross slide to the head and square up the front face of the block against the faceplate while you tighten the cap screws. The block now has its S face squared to the spindle axis. Install a drill chuck on the head spindle with a #1 or 2 center drill and locate the drill point 1/2" in from the side edge facing you. The height position for the hole will off course be automatically set since the spindle itself is drilling it. Begin to drill the hole for the hand piece with gradually larger bits until you reach the proper size hole to accept the body of the handpiece in a snug but not tight sliding fit. As with the boring bar holder, you will need two vertical set screw holes, centered and in line with the hole to secure the handpiece in place during use.
To use your drilling tool post, you just dial in the radial position with the cross slide. If you set a pot magnet and dial indicator so it bears along the rear face of the tool holder, you can bring the drill point so it just touches the work while you zero the indicator dial. As you advance the drill into the work, you will be able to directly read the depth of the hole to the nearest thousands of an inch. After the first hole has been drilled to the exact required depth, you can set the depth stop on the TAIG head stock to limit the travel of the drilling tool post to that same depth for any other holes you may have to drill to that depth. Other lathes may not provide a depth stop like the TAIG so the dial indicator will have to used as long as the bed is made of steel. Equally spaced radial holes can easily be made as I mentioned earlier, with an indexing plate on the spindle.