Monday, June 6, 2016

My First [Simple] Lathe Project

Yesterday I finally found some space to setup the lathe.  Unfortunately I have no metal rounds to practice with, so I used a projection lens I bought from the camera show couple weeks ago as the practice piece and first project.  Yes, I know.  I am trying to walk before I learn how to crawl, but hey, I have many hours of YouTube experience under my belt.  That's got to be good enough to get started, right?

Immediately, I found many problems. The carriage had quite a bit of play.  A quick consultation with the Taig Micro Lathe guide fixed it by adjusting the gib screws. Then the 3-Jaw chuck is grossly out of true.  It's so bad you can see the wobble and it would be impossible to turn anything like this until I find a way to true it. The 3-Jaw chuck is supposed to be self centring, as all the jaws move at the same time when you tighten/loosen it, but it's not doing a good job at it. Luckily, there is the 4-Jaw chuck that was included with the lathe, but that brought up another problem.  The 4-Jaw chuck's jaws are independent.  You can tighten each of the 4 jaws individually.  But, in order to make the work piece perfectly centred, one needs a dial gauge, which I have, but I don't have the base to set it.  So in the end, I just did many trial and error tightening and retightening until it was visually running true. This is a laborious and imprecise process without the dial gauge.

Finished - I will not show you the 100% crop of the turned area.  It just looks disgusting.

I removed the lens elements from the lens; they came off easily by unscrewing the front and rear groups.  This is part of the reason I wanted to use this lens.  The lens barrel was then mounted on the 4-Jaw chuck with as true as I could visually tell, and started turning.  I just wanted to remove the grooves on the lens so that it would have a smooth surface, and it would also provide a stop for the step-up ring that I would use to mount it to the focus helicoid.  This turned out really bad ugly.  For one thing, the tool bits were all dull, and I think the speed I was using was a bit too slow.  I am not sure what kind of metal the lens barrel was made of, but it was not aluminium or brass. In the end, I removed the large, smooth grooves on the lens, but left behind tiny and sharp grooves.  It looks nothing like the smooth finish I see on YouTube!

Angenieux 70mm f1.5 Projection Lens on the helicoid

Next I wanted to bore the hole larger on the 30-52mm step-up ring, just large enough to slip on the lens barrel.  This part was done relatively painlessly.  The aluminium of the step-up ring was much easier to work with.

So, in a way, it was a success, only because I was able to use the lens and I didn't have to go nuts trying to find a ring that fits the lens barrel and trying to glue it so that it's parallel to the mount.

What did I learn from the first lesson in using a metal lathe?  It's kind of fun, but what overwhelmed me was the sheer amount of metal shavings from such a small and simple project.  A Shopvac is a must.  To make the lathe run smoothly and efficiently, it needs to be optimally conditioned: true chucks, sharp bits, right kind of bits, right accessories and most of all, the skills to make it sing.  I will keep doing simple projects until I am comfortable to convert a real lens.

Daisies - Angenieux 70mm f1.5 Projection Lens & Sony A7


  1. Keep up the good work and keep us informed. Practice makes perfect. Good luck.
    Gary B

    1. Thanks for the encouragement, Gary. Appreciated.

  2. to center my wood lathe brackets , i first clamped a metal sphere deep down in the drill chuck to get it tight . then i drilled the brackets up from the front to get a good center . after that i took the sphere out and used the not cutting shaft of a shortened drill to rest the brackets front on (semi-tight) and let the cutting part of the drill do clear out the deeper parts of the brackets centered . but the brackets metal wasnt very hard . it improved to my needs , but anyway , every change of mount of a workpiece will show other decentering . greets , gerhard