A Simple Machine to make large diameter wooden screws – cont’d

So here’s a pic of the lunettes in place:

The “lead” (or master screw) and the workpiece are connected with a socket and stub joint that is locked with a  screw.  The stub should be the same diameter as the socket, close to the shoulder, but should be a little tapered away from the shoulder.  This will allow for some very probable misalignment.  Remember, we’re dealing with wood here and my shop is 90 degrees with a fair amount of humidity.

Set the router to depth (several passes are probably, but experiment), turn ‘er on and start twisting the lead screw.

Forty odd hours later, $50 lighter in your wallet, here’s what you end up with:

Wooden screws, these will be seated into hubs - but blanks with integrated hubs will work just the same

Have fun.  You’ll need to experiment a little.  But I think you’ll find that it’s very worthwhile.

Explore posts in the same categories: Roubo workbench, wooden screws

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12 Comments on “A Simple Machine to make large diameter wooden screws – cont’d”

  1. curt carter Says:

    Thank you very much for posting this.

  2. Blair Says:

    Any chance I could purchase one of these wood screws from you? I’m working on a project and can’t find one anywhere and we don’t have the tools in our shop to make one. Let me know!

  3. Jerome Hanby Says:

    Great project. I’ve been following you over on Lumber Jocks. Question. Can this machine be used to turn any diameter screw that is at least thick enough to handle the tenon on the end just by using properly placed ‘Stantions” with the correct diameter hole? Sure would be nice to build this beasty one time and use it for multiple diameter screws!

    • D.B. Laney Says:

      Yes, you could use different diameter “stantions” with the existing lead screw. However, the screw pitch (threads per inch) would remain the same. What this would mean is that as the diameter would increase, the “relative” pitch would become finer. You would get to a point of diminishing return in short order, with the thread being so fine that the pitch angle would become, effectively, a “locking taper”. The main reason large diameters are desirable is that they move the “object” (in this case vise chops) a greater distance per revolution. The basic rule is to determine the “pitch distance” (from point to point) by dividing the screw circumference by twelve. For example, the circumference of a 2 1/2 diameter is a little more than 7.5. If you divide that by 12 you come up with approximately 0.6. So the distance between threads is 6/10ths, or about 2 1/2 threads per inch. So, in order to move the object 1″, you’ve got to turn the screw about 2 1/2 revolutions. So a bigger diameter gets you, mostly, more closing speed. (It’ll get you some other benefits like thread strength, etc.) The long and short of it is that “screwmaking” could become a lifetime obsession, if you let it.

  4. cmdevans Says:

    Nicely done! And your comment about screw making becoming a lifelong obsession is quite accurate! I got into it after my first experience with a wooden screw, and have been making ’em ever since!

  5. Stan Thompson Says:

    Quite true but success is satisfying and I’m keen to try when time is
    on my side. Stan.

  6. Daniel Says:

    Any suggestion for how one could make the corresponding “nut” for a screw like this?

    • D.B. Laney Says:

      If you do a little more searching on my blog you’ll find a number of posts about making nuts. Also, if you consult Roy Underhill’s books, you’ll find out how to manufacture both a standard tap and a tapping machine. Mike Darlow, has a considerable amount of information about making nuts for large and “one off” nuts in his book “Woodturning Techniques”. Of course, Holzapfel’s classic work, “Hand and Simple Turning” is full of information. But if you’re only making one or two screws, save yourself a lot of headaches and buy a nut from Lake Erie Toolworks. Their standard is 2 1/2″ dia x 2 pitch. But double check it, just to be sure.

  7. ceratocone Says:

    Asking questions are really pleasant thing if you
    are not understanding anything fully, but this post provides
    nice understanding yet.

  8. nelson1890 Says:

    A two start thread would make the screw advance twice as fast per turn. Can your design be modified to make double treads?

    • D.B. Laney Says:

      I see no reason why it wouldn’t. If I remember my “screw theory” correctly, a multi start would not, necessarily, require a change in pitch. The screw is the easy part. Making the nuts is always the problem. They of course would need to be cut with the corresponding number of “starts”. If you decide to give it a go, I’d be very interested in hearing about your result. I’m not sure if the guys at Lake Erie Toolworks have played around with multi starts, but it might be worth a call. They’re really good guys to work with. The one thing that I would change about my screws would be the thread angle. I used 60° as I had that bit on hand. I’d go a 90°, as that would make for a stouter thread. That said, I have not experienced any thread breakage with the 60°.

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