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I'm fortunate to have a blue ribbon trout fishery and testing ground a stone's throw from my shop. I headed out on May 21st and the conditions, while beautiful, were less than desirable - bright sun. Despite this, the epeorus vitreus, a/k/a pink ladies, hatch was on and adults were in the air. These sizable mayflies are found in the eastern United States and have a pink/orange hue. With the bright sun, there was no sign of rise patterns on the river's surface. So, I fished below the hatch, targeting feeding lies in pocket water and tailouts. Aided by my 100% shop made 8' 5wt. bamboo fly rod and early 1900's vintage Hardy Perfect reel, I was rewarded...  Lathe tailstocks suffer from backlash, as do family members after political discussions on Thanksgiving. In the machining context, this occurs when engaging the tailstock hand wheel in one direction, stopping, and reengaging the hand wheel in the opposite direction. This results in a lack of accuracy when reading the total net measurement from the analog numbers affixed to the tailstock spindle. Essentially, there is a void in the tailstock mechanisms that is not reflected when reading the measurement. "Play" prevents accurate measurement. This is a very common problem in many areas of machining. This problem can be minimized by making manual adjustments, but it cannot be fully eliminated through these adjustments. One solution is to install a digital readout (DRO) to track the net travel in both directions. Another solution is to machine a tailstock travel accuracy jig, to be used in conjunction with a dial indicator. Below is the way I made such a jig. Lathe tailstock accuracy is critical for many bamboo rod making tasks, especially when machining metal ferrules from raw bar stock. The use of such jigs, while drilling and reaming, will allow accurate repeatability and save time. Here is my process: (1) I measured the diameter of the tailstock spindle. (2) After securing a scrap piece of aluminum, I milled it flat on all sides. The aluminum was supported with machining parallels. Then, I chamfered all edges and made a consistent finish with 80 and 500 grit sandpapers. (3) The next step involved preparing the stock and measuring for the tailstock spindle hole. I planned to have the tailstock spindle hole on one side of the jig but centered. Further, I made sure to leave about 0.5" of solid stock from the end of the hole to the end of the jig. My goal was to eventually drill and tap through this 0.5" section of stock so that it would accept a hex cap screw. This will be discussed in more detail below. The photo on the left represents the starting point and the photo on the right represents the finished product in this next step. (4) I supported the jig with machining parallels and made sure that the jig had unobstructed clearance (top, bottom, sides) to cut the entire 1.25"-ish hole. With plenty of lubricant (AlumTap or oil for cutting), I used a center to make the preliminary shallow hole to accept the first drill bit. Then, starting with a small drill bit, I made a hole through the jig. Thereafter, I used progressively larger drill bits, and eventually larger end mills. (5) Without an end mill measuring 1.25", I moved to a boring bar and a manual offset boring head. I incrementally and slowly adjusted the offset boring head outward to make a progressively larger hole. Measuring often, I stopped cutting when my hole reached 1.25"-ish. (6) I tested the fit on the tailstock and achieve my goal of a snug fit. (7) Back at the mill, I secure the jig sideways in the milling vise. On the side of the jig with the hole, I left about 0.5" of solid stock from the end of the hole to the end of the jig. Making sure I had drilling clearance below the jig, I used a center to make a shallow centered hole. Using progressively larger drill bits, and ending with a #7, I drilled through the jig. (8) I tapped through this #7 hole using a 1/4-20 tap. (The picture on the right is the direction I tapped. The picture on the left is just to illustrate the process.) I tapped about 75% through the hole. The tapping process was started on the mill for proper support, rotating the head by hand. Thereafter, I finished tapping by hand. (9) On the side where the tap commenced, I used a 1/4" drill bit to drill just over 50% through the hole. My goal was to remove the tapped thread through the first half of the jig, just over the midway point. A simple piece of painter's tape can be used as a depth guide. (10) With a metal bandsaw, I cut through the midpoint at the bottom of the jig into the tailstock hole. I placed a hex screw with a 1/4-20 thread into the side of the hole where the thread was removed. The screw freely slid into the hole, stopping around the mid-point. Thereafter, I was able to tighten the screw, allowing it to catch the remaining thread after the mid-point. (11) It fit snugly and securely. Any slack was taken up by tightening the hex screw. (12) I attached a dial indicator with a 2" travel to a Mighty Mag Magnetic Base. I then attached the base to the top of my tailstock, retracting the dial indicator and making contact with the jig. Now, I can accurately track the net travel of my tailstock. |
