Joshua PollackNorth Korean Flow-Forming Lathes

Update | A video of the panel is now online.

Further update | February 13, 2014 | It’s yet another flow-forming machine inside North Korea.

Greetings from Seoul, where I’ll soon be speaking at the Asan Institute’s conference on North Korea. I’m joining a panel on North Korea’s nuclear capabilities. (Surprised?)

By now, readers of this blog probably have an idea of the role of flow-forming lathes in the making of maraging-steel rotors for gas centrifuges, and are aware of their presence inside North Korea. MIT’s R. Scott Kemp, followed closely by Jeffrey Lewis and Amber Lee of CNS, has blazed a trail on this subject. The short version is, these specialized machine tools are needed to make rotors for P-2 gas centrifuges. That’s the technology for uranium enrichment that North Korea reportedly received from A.Q. Khan of Pakistan in the late 1990s.

It’s the judgment of the Asan Institute that visual aids hurt more than help in a conference setting. Fair enough: PowerPoint often detracts from the quality of presentations. But sometimes, too, a few pictures are just what’s needed.

This Calls for a Blog Post

My presentation will describe evidence, based on research conducted with MIT’s Kemp, that North Korea has set about establishing domestic production for crucial components and technologies for gas centrifuges. The story involves much more than flow-forming machines; if you happen to be in Seoul, come to the conference on Wednesday morning to hear all about it. But the evidence for flow-forming machines is especially striking precisely because it’s visual. Words don’t quite say it. Thus this post.

After the jump: Photographs of not one, not two, but at least three generations of flow-forming machines inside North Korea.

But First, A Short Primer

Before getting into those details, you’ll want to know how to recognize a flow-forming machine. So here’s an arbitrarily selected picture from the WWW. (Not from North Korea in this case.) It happens to be from China, but that’s not important.

On the left, partly obscured by a CNC control panel, is the headstock. You can’t see much of it in this picture, but that’s where a series of spinning parts is located: a drive ring, spindle, and mandrel. The mandrel is a specially shaped component where the metal workpiece — the object being worked — mounts onto the machine. (Those appear to be “before” and “after” workpieces lined up on the right side of the photo above.) On the far end of the whole setup is the tailstock, which keeps the workpiece in place during operation.

In the center of the machine is where the magic happens. It’s a carriage equipped with rollers that passes over the rapidly spinning workpiece, working it into a thin-walled, elongated form. A typical flow-forming carriage has three rollers, resulting in the distinctive triangular form you see above. Notice, too, the hydraulics projecting from each roller, 120 degrees apart from each other. More than anything else, this carriage is the visual signature of a flow-forming machine.

Got it? Good. Now, let’s move on to the flow-forming machines that keep appearing on North Korean television broadcasts.

Kusong Machine Tool Plant, Sept. 2006

This machine, displayed during a Kim Jong Il guidance tour to the Kusong Machine Tool Plant, and first shown in these pages by Scott Kemp in June, appears to be a prototype. There’s no CNC panel. Dark-toned cables run on the exterior, connecting to an exposed hydraulic element. It might be North Korea’s first indigenously produced flow-forming lathe.

Here’s the non-computerized control panel:

In the background of the shot below appears the carriage, with exposed hydraulics and dark-toned cables at the top:

And now for something new.

Kanggye General Tractor Plant (Dec. 2009)

The “tractor plant,” which Lewis and Lee describe as a munitions factory (see more details about it here) received a Kim Jong Il guidance tour in late 2009. Not only can we see a flow-forming machine, but we can see the cylindrical shape of its mandrel, shown projecting through the carriage:

This machine appears to be more advanced than one seen at Kusong. It has a free-standing CNC panel, typical of up-to-date flow-forming lathes. The opening in the carriage is squared-off, not round. The one visible hydraulic element is of a different design. External cables are white and placed differently.

Note, too, that what appears to be a finished workpiece stands upright upon the machine in the background, next to the headstock.


Kanggye General Tractor Plant (June 2013)

It was Kim Jong Un’s own televised guidance tour to the “tractor plant” that occasioned the Kemp post. Here again is what we can tentatively call the third generation of North Korean flow-forming technology, as it appeared at the Rodong Sinmun website (via North Korea Leadership Watch):

Notice the enclosed hydraulics, cabling, and other details that distinguish the machine from the one displayed in Dec. 2009.

Not only was this still picture of the “3rd-gen.” machine shown in the newspaper, but it appeared on television, too. And in the television broadcast, the very next image was this other flow-forming machine:

It could be the same machine as the one photographed at Kanggye in Dec. 2009. Notice what appear to be a pair of historical markers on the headstock.

The Bigger Picture

Like Kemp or Lewis and Lee, I cannot confidently assert that some or all of these specific machines have been producing centrifuge rotors. The metal cylinder shown standing on the flow-forming machine at the “tractor factory” in Dec. 2009 might be something else, perhaps part of a weapons system. It remains to be seen.

Clearly, though, North Korea has these kinds of machines, which are important for making maraging-steel rotors for gas centrifuges. These photographs represent just one (visually striking!) part of a larger body of evidence indicating that the North Koreans have set out to master, and perhaps have mastered, domestic production of crucial centrifuge-related components and technologies.

This bigger picture may help us to understand the surprising appearance of the Yongbyon centrifuge enrichment plant in late 2010. It also may help to explain how it is that North Korea lately appears to have doubled the floor space there.

Interested in the rest of the story, beyond just flow-forming machines? See you this Wednesday morning at Asan.


  1. Allen Thomson (History)
  2. krepon (History)
    • Anon2 (History)

      Guardian picked up Joshua as well.

  3. Nick (History)

    Do we know if they have sold the latest flow forming machine to others?

  4. jeannick (History)

    I don’t see the electric cable on the first picture ,
    it looks like hydraulic tubing

  5. Gregory Matteson (History)

    Been pondering this for a while. I realise that machine-tool technology is highly amenable to bootstrapping by competent, motivated people. But I don’t have a good feel for how big a leap roll-your-own CNC Flow Forming is. I expect you could send your guys to learn at a Chinese factory, but would that be necessary? Could someone already versed in CNC machining reasonably work it out from blue Prints and/or a sample machine?

    • jeannick (History)

      The tech is nothing really out of this world
      but the machining of the component has to be really good
      the first was 1960 electro-tech generation
      the second and the third looks like digital command
      that’s for the control part ,
      the operator pulpit has a family look on the second and forth pictures , not indigenous that’s for sure
      the mechanics are high rectification finish for the machining part certainly
      having the full blueprint is only telling you the full extend of the difficulties.
      those lathes are also used for machining metal bellows
      in one piece without weld
      since there probably is only a very few machines the logical conclusions is that they were purchased
      maybe from China , possibly a re-export from Japan or Europe

    • Gregory Matteson (History)

      Found this interesting You-Tube video from an Indian manufacturer: which shows their flow-forming machines in use. Wide variety of configurations are seen on You-Tube, vertical, horizontal, 3 tools, 2 tools. The very first image in the video, that flashes by and is gone, is a very similar to the last machine pictured in this post.

      After watching how these things work (yeah, flow forming is a fancy version of spinning) the bed and frame of these descendants of a lathe are massive and high precision. You’d not want to one-off one, and it wouldn’t look so much like a finished commercial product. So it would seem likely someone sold NK one or two.

  6. Rebecca G (History)

    Nice interview on NPR Josh!

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