Replacing knurled thumb screws


[Pete] bought himself an old South Bend lathe, but unfortunately some of the thumb screws were missing from this fine old machine. Originally, the lathe had knurled thumbscrews, and with a thumbscrew from Ace hardware the lathe itself was functional, but by no means looking its best. With a lathe you can make just about anything, so [Pete] decided he would make his own knurled thumbscrews and bring this lathe back to life.

Knurling is a diamond or linear pattern of indentations usually found on fancy metal knobs, flashlights, and other equipment that needs a good grip. While there are knurling tools for lathes, [Pete] decided to use his knurlmaster – a handheld device that looks like a pipe cutter – to cut a few knurls into a steel bar.

As for making this knurled bar into a proper thumbscrew, [Pete] shows us two methods: the first is tapping the knurled steel, putting in the right screw for the job, and securing the parts with Loctite. The second method involves cutting the threads on the lathe, an excellent example of how a lathe can make just about anything, even parts for itself.


  1. Adam Munich says:

    Correction: A milling lathe can make just about everything.

  2. Ren says:

    It reminded me of Richard Feyman’s talk about miniaturization, a lathe making a smaller duplicate of itself, and that lathe making a smaller duplicate of itself, and so on…

  3. Brando says:

    A lathe is probably one of the only tools that can make all of it’s own parts. A must have even if it’s just a benchtop.

  4. wretch says:

    I so want a lathe now. (c:

  5. spyoxide says:

    could a similar effect be made by threading the surface in both directions? it seems like a pretty easy method of making a grip texture, as long as the second threading doesnt wipe out the first.

    • bluewraith says:

      You’ll get a texture, but it won’t look very good. When you knurl material, you’re not removing much material at all, but rather mushing it around to raise the diamonds.

      Also, bearings don’t have to be the round balls you’re used to. Bearing bronze makes a great bearing, hence the name.

    • macona says:

      Not really, the knurling is multi start so you would have to do a massive amount of work to get it.

  6. macona says:

    When knurling you need the OD of the material you are knurling to be a multiple of the pitch of the knurl to get a nice knurl without the double lines you see in the photo above. He is very close to the right diameter, shaving a few thou off will make it look better. Also use fluid for knurling, cutting oil for cut knurls, lubricant for forming knurls.

  7. Joejoedancer says:

    So he’s using a lathe to make a screw that he already bought at ace?

    • ChalkBored says:

      And he bought the screw at Ace to replace a screw that already replaced the original one.

      He must not have anything better to do than to make his tools not look like they’ve been cobbled together.

  8. mike says:

    I actually highly suggest watching ALL of mrpete222’s videos… he’s a (retired?) high school shop teacher and has a clear and practical-minded instruction style that I find very easy to understand.

    Makes me wish I took metalworking when I was in high school… a sadly lost program of study at most schools.

  9. static says:

    I wouldn’t have known there where brass inserts under the set screws. The only knurling hand tool I ever used is dirty repair of engine valve guides. Now that I have a bench machine to insert new valve guides I don’t use the knurl type of rep repair. I suppose push comes to shove a sharp cold chisel or a center punch could be use to create knurl on an exterior surface Now I have another YouTube channel to check out further. Curses ;)

  10. C.Ham says:

    Tubalcain, or Mr. Pete222 has plenty of videos on his youtube channel. It’s really a good resource when it comes to machining.

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