Turning Tapers

A couple weeks ago I started using a metal lathe again, working on what could generously be dubbed a "pen." I was back at it again this weekend, trying to finish the pen. Here's a couple of things I learned:

• Cutting a Taper: I have never cut an intentional taper before (although I usually come out with parts that are accidentally tapered through poor machining skills) so I looked up some YouTube videos and figured out how to do it. The key is to ONLY use the cross slide to feed the tool into the part at the desired taper angle. The other key is to keep the tool mounted perpendicular to the z-axis of the part. I did my first pass with the tool parallel to the direction of feed of the cross slide and only got away with it because my part was a small aluminium rod.

• Cutting External Threads: Turns out that you need to start with a blank that is the major diameter of the threads you want to cut. For 3/8"-24, that's 0.375". This confused me last week!

• Seamlessly Screwing Parts Together (Harder Than You Think!): I want the front and back halves of my pen to screw together leaving barely any visible seam. However, I consistently had a gap between the two halves. I'm not sure why this is happening. Either I have too long a threaded end on the inner piece (preventing the outer piece from screwing all the way on) or there is interference caused by the lack of cylindricity between the two halves. For now I am putting a metal sleeve over the join to conceal it. I need to figure out the correct way to machine this, though, for next time.

• Sandpaper is Your Friend: My pen may not have the best concentricity ever, but at least it's shiny! I held a little sandpaper to the parts while turning them and it made them much smoother than I could achieve with the lowest feed settings.

In other news, I wanted to share this series on how to make a clock in the home machine shop - it is a beautiful piece of craftsmanship and there are 23 videos that are full of cool machining techniques.