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Taps and dies are the two tools you use for cutting threads into material around a hole (tap) and for cutting threads into a rod (die) for mating with that hole. The basics of how to do it are quite simple. All you need to know are a few steps and you need a tap and die set. The above video gives you the most rudimentary rundown. Although the tap and die set linked here is from a 2007 Toolmonger review (that we included in one of our old This Week in Tools roundups), it at least gives you a good idea of what to expect in a decent Tap and Die Set.

Oh, and you also need to know what tap and/or die sizes you need for your specific fastening job. You can find tap and die calculators online. Here’s one.

Tip: As one of the commenters on YouTube reminds us, it’s a good practice to “clean the threads” as you tap (or die) by backing out three turns for every three turns you cut forward. This helps insure that you get a good clean cut.

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Gareth Branwyn

Gareth Branwyn is a freelancer writer and the former Editorial Director of Maker Media. He is the author or editor of a dozen books on technology, DIY, and geek culture, including the first book about the web (Mosaic Quick Tour) and the Absolute Beginner’s Guide to Building Robots. He is currently working on a best-of collection of his writing, called Borg Like Me.


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Comments

  1. It’s possible to make a tap guide to keep your taps perpendicular with the material you are tapping. It’s also well worth getting the right drill for the job so your tap is not cutting more metal than you need. More on tapping

  2. Making threads is a very useful skill. being able to fasten parts with their own threads can reduce the total parts count and complexity of a project.
    When I worked in a tooling shop I tapped hundreds of holes. Here are some tips:
    1) for thick material where ultimate hold is not necessary you can use the next size larger drill. This will result in less thread depth but the tap will cut easier. The standard for 1/4″ – 20 is a #7 drill (0.201″). A larger #6 hole (0.204″) or 13/64″ will tap easier because the tap is taking off less material.
    2) Definitely back off the tap 1/2 turn for every turn forward in thick material. The swarf must be broken loose or it will jam the tap in the hole. Everyone makes that mistake once and then never forgets the hassle of making the repair.
    3) When tapping deep holes periodically run the tap out, blow it off and blow the swarf out of the hole to prevent jamming.
    4) There are different types of taps. The tap shown in the video is for through holes. Taps for blind holes have a squared off rather than tapered end.
    5) if you have to tap a bunch of holes in thin material you can use the tap in a cordless drill on low speed. This is quick, but be careful because removing a broken tap from a hole is very slow.
    6) tap oil is essential to lubricate the working surfaces. Tap-eze is a good one. ATF will work in a pinch.

  3. johngineer says:

    A few more tips I’d like to add, in addition to Ross’ excellent suggestions:

    7) Know your material — aluminum, brass, and steel all behave differently when cut, and each requires it’s own approach. Steel and brass tend to make chips better, which means a cleaner cut but also that you need to clean out chips early and often. Aluminum, on the other hand, can be more “gummy”, and requires that you break chips yourself. (do this by backing out slightly every 1/4 turn, in addition to the backing out you’re already doing to clear chips). Further, some brasses contain lead, which can “bind up” a tap. If you feel any sudden change in resistance, back it out 1/4 turn (or more).

    8) A small tap means a small force — the amount of force you should exert on a tap varies in proportion to the size of the tap. This means that the force applied to tap a 1/4″ thread is at least half that required to tap a 1/2″ thread. Smaller taps break much more easily. For holes smaller than about 3/16″, you really need the kid gloves.

    9) Know if your material can “hold” the threads. Plastics and soft metals like Aluminum don’t hold fine (UNF) threads very well. Stick to coarse threads (UNC) If you’re going to be using them with steel or brass screws, which can easily strip fine threads in soft material.

    10) A vertical hand tapping machine can be a godsend. Every metal shop I’ve ever been in has had at least one of these around. Grizzly sells one for about $80. I’ve also heard them referred to as “Lassy Tappers”.

    11) (just to repeat what Ross said) USE TAPPING FLUID. If you don’t have proper tapping fluid, you can get away with WD-40 or even mineral oil in a pinch. I use RapidTap myself.

  4. Karl says:

    I’m not a tradesman and I just made a mistake using a tap and die set and was wondering if anyone can help me rectify the situation. In a nutshell, I’ve taken too much off the male and female parts and now the nut pulls off. Rookie mistake, I know. But is there any sensible way of repairing this? The background is this – I’m re-doing the rear leaf springs for a 1949 ford car and the shackles at the back are what I’ve done this to. I even went and bought lock nuts but same thing happens. The nut size is 7/26″ with a 20 thread which I believe is fine not coarse.