Core77

How to Make Threads Without a Tapping Bit

Shop improvisation

By Rain Noe - January 27, 2022

in Tools & Craft

B-Star Crafts is the guy who demonstrated how magnets can be used in hidden cabinet and drawer locks. That post did pretty well, and maybe this will interest you too: He came up with this MacGyver-like method of creating threads without using a tap set.

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"The advantage is that you can create threads of any size and shape of bolt and in a variety of materials (wood, plastic, gypsum board, metal, etc.)," he writes. "The disadvantage is that [hot glue] is weak against heat, so you need to be careful about frictional heat when tightening bolts."

While the connection's probably not robust enough for furniture, I'd love to see Matthias Wandel do a scientifically-measured stress test to see how much force (or fastening/unfastening) it takes for the connection to fail.

I'm sure the more serious among you will pooh-pooh this method, but the more I live out here in the middle of nowhere, the more I'm coming to admire improvised solutions with whatever tools you have on hand.

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John Whitley

3 years ago

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Honestly, it’d be WAY better to go have a look at the Gougeon boat book (free PDF at: https://www.westsystem.com/the-gougeon-brothers-on-boat-construction/), which covers a ton of tecniques used in boat building and maintenance regarding epoxy to reinforce fasteners. This includes techniques for dropping threaded fasteners into holes where epoxy alone, without threads, secures the fastener. The book gets into discussions of pull-out force, etc. for anyone interested. I’ve occasionally reinforced threads in wood (made with a tap) via a technique inspired by this book: 1) drill and tap for your fastener as normal, 2) coat a sample fastener (which should be hex/Allen drive) well in mold release and let dry (hint: Aussie heavy hold hairspray is a great mold release for this. it’s just spray plastic), 3) put some epoxy in the threaded hole, 4) screw in the fastener and wipe up any squeeze out (have a little alcohol on hand) , 5) wait for the epoxy to set, 6) Use a tool with a bit of leverage and a hex driver bit to “pop” the fastener loose, then unscrew.

Extending that technique using what’s in the book to avoid tapping: with a sample fastener coated in mold release, “pot” that fastener in epoxy in a wide-clearance hole. Once cured, remove the fastener ala step 6 above. The fastener molds in the threads for the eventual final fastener.

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- Jason Blandford
  
  John Whitley
  
  3 years ago
  
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  Yes, I've seen where people use a variety of epoxy solutions very similar to what you're describing, though maybe not so well developed. My guess is that epoxy is about as easy to use as the hot glue and would hold better and stay stronger under heat.
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Billy Mack

3 years ago

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LOL. I like the MacGyver-ness, but this would strip out so fast. I can't imagine a suitable application. Just buy a set of taps...they can be affordable.

An ME could likely tell you the fail point with some hand calcs.

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- Jeffrey Warnock
  
  Billy Mack
  
  3 years ago
  
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  How do you know, Billy? Have you tried it?
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  - Billy Mack
    
    Jeffrey Warnock
    
    3 years ago
    
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    I'm speculating based on years of experience designing and building custom automation systems. Also, it's made of hot glue. Clearly I recommended some calculations because I don't know the pullout force of hot glue threads.
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  - Nathan D.
    
    Jeffrey Warnock
    
    3 years ago
    
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    You don't need a mechanical engineering degree to know that hot glue is not going to hold on to a metal fastener, just a little bit of common sense.
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  - Billy Mack
    
    Jeffrey Warnock
    
    3 years ago
    
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    Exactly, Nathan.
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