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Thread: 1/2 x 13 tap for wood

  1. #16
    Thanks to all of you. Mr Buxton I should have realized that and didn't. Some of my blanks are end grain and I will mark those for another use.

  2. #17
    Join Date
    Feb 2008
    Location
    E TN, near Knoxville
    Posts
    12,298
    Quote Originally Posted by Jamie Buxton View Post
    Tapped holes in wood are much stronger, and much easier to make, if the hole runs across the grain direction. Tapping into end grain creates threads which are little short-grain parts which are easily ripped away from the body of the wood.
    I agree in principle. But I think the type of wood makes a huge difference.

    I like to use dogwood for threading since it is quite hard, very tough, and fine grained. I almost always drill and tap into the end grain.

    I've made lots of things that screw onto the Oneway live center (3/4x10) and the headstock spindle of my lathe (1-1//4x8). The threads cut cleanly with a tap made for metals for the live center and one made by Beall for the headstock spindle. There is typically no tearout. I do treat inside of the hole with CA glue after drilling and lubricate the tap with beeswax. I think lubrication is important as well as is tapping very slowly. Something else that is important is keeping the tap perfectly aligned with the hole. I use a spring-loaded guide held in a Jacobs chuck in the tailstock, hold the tap with a wrench to keep it from turning, and tap by turning the wood held in a scroll chuck on the lathe. Taps are typically made with either a center depression or a center cone to allow such alignment. A tap guide is not expensive: https://www.amazon.com/gp/product/B005317ZMC

    This is a spring compression chuck I made to hold wooden eggs for finishing the round end. I made the chuck from eastern red cedar since it is soft and glued in a cylindrical dogwood end-grain plug to drill and tap. The threads remain clean and unbroken after many uses. I think the combo of the dogwood and the coarse thread helps. (I do lubricate the wooden threads with wax occasionally for use.)

    eggs_com_A.jpg

    Things tapped with the finer thread do have more tearout in end grain in some woods. The two wooden adapters for the live center in this picture are made from maple and lignum vitae (which is pretty tough.) Although there are more torn threads in the maple piece enough remain to hold it nicely.

    live_center_threaded_IMG_7917.jpg

    However, there is not much force on these things, just compression from the tailstock. Something made for a fine-threaded lathe spindle to make jam chucks or faceplates might experience a lot more force.

    JKJ

  3. #18
    Would t-nuts perhaps work for this application?

    Cpb

  4. #19
    Interesting question. The ultimate purpose of the threads is too hold the wooden chucks for metal spinning. The force is applied to the metal to cause it to form to the shape of the chuck and the stock and chuck dpin. So if there is a shape out 5 inches from center, the chuck must be solid enough to hold fast despite the pressure pushing against the wooden chuck. That would be quite a bit of leverage against the chuck out from the center, Trying to get the metal pressed into that final outer shape would create a great deal of stress on the threads holding the chuck. I suspect a "T" nut might just be a weak link. I'll have to think about it a bit more.

  5. #20
    My guess is t-nuts would be many times stronger than wood threads. If installed properly they clamp the wood between the t-nuts and the spindle. That's a very firm connection.

    Spindle, face plate, t-nuts installed from the face of the faceplate, then a wood plug to make the faceplate surface all wood.

    To fail the t-nuts would have to be ripped through the wooden faceplate. Much stronger than wood threads in my opinion.

    If installed improperly from the spindle side of the faceplate yes they probably fail spectacularly.

    Cpb

  6. #21
    I worked with cable on large wood spools. Three feet in diameter or so loaded with several hundred pounds of cable. The spool ends were held together with long bolts and t-nuts. Occasionally the spools would fall off the truck and break the spool. The t-nuts never failed. Ever... They earned my respect.

    Cpb

  7. #22
    Join Date
    Apr 2018
    Location
    Cambridge Vermont
    Posts
    2,282
    Would it be possible to use a bushing? Say aluminum, since it's easy to work with that had an inner hole that was 1/2-13 and the outside could be threaded in a different pitch that works better with wood? I'm not sure how much you want to invest in this project but depending on the outside diameter of the bushing you would get quite a bit of strength. If the wood shapes are going to be reused you could even glue the bushing into the wood.

  8. #23
    I rely on the tap I got from Beale for my Oneway headstock, It is similar but not quite the same as a metal tap. Still makes a huge difference depending on the wood I tap I always drill coat with CA tap then redcoat then run the tap again. Air tight as well.
    Pete


    * It's better to be a lion for a day than a sheep for life - Sister Elizabeth Kenny *
    I think this equates nicely to wood turning as well . . . . .

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