A die is used much the same way as a tap as far as how to cut the threads. You'll want to make sure the stock you are using is small enough for the die to be able to make the initial cuts. You'll also want to hold the stock in a bench vise so it will stay still while cutting the threads. Sometimes it makes it easier to start the cut if you bevel the leading edge using a bench grinder. To start the cut, keep the die perpendicular to your stock. While starting to turn, press down on the die until you start to feel the teeth bite into the stock. Again, use some type of cutting oil to keep things lubricated. Run the die down some, then back it off to clear the cutting teeth. Continue cutting down the stock for the length of threads needed.

A die stock is used in conjunction with a die to create external (male) threads, usually on plain rods, for nuts to fasten onto.

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Make sure you keep the tap straight as you start the cut. Tap wrenches are symmetrical to help you avoid applying sideways force on the tap. When using a small tap, try to obtain and use a correspondingly small wrench (a 3mm tap with a wrench designed for 12mm is a pretty clumsy combination.)

Drill a straight hole in the correct diameter (It's easy to google tables for the correct drill size, and some of them are slightly unusual.) Depending on your application, you may be able to get away with a slightly larger hole diameter. Going even 0.1mm smaller because you don't have the right drill is asking for a broken tap, unless you are using aluminium.

The fly mill is just one example of a milling cutter. As with drill bits, these are rotary tools used on CNC machining centers, live-tool lathes, and yes, manual milling machines. But where a drill bit's cutting edges are positioned at the very end of the tool, limiting it to axial material removal (i.e., holemaking), a milling tool also boasts cutting edges along its periphery, allowing it to remove material radially, from side to side. A huge variety of such tools exists:

A tap wrench is used in conjunction with a tap (that looks like a drillto create internal (female) threads in metal sheets or blocks, for screws and bolts to fasten onto.

Dies are generally no problem, provided you start with a rod of the correct diameter. A high quality die will be split on one side. With the correct die stock, that enables you to spread the die open for an initial cut (hold it using the centre screw in Zaid's image), then start again but close it more for a final cut (hold it using the other two screws in Zaid's image.)

There's some overlap between all of these. For example, it's no problem using an end mill to machine the top surface of a small metal workpiece, but the wider and longer that surface becomes, the more reason there is to use a face mill. And some face mills can be used to cut square shoulders like a shoulder mill would, provided that shoulder is fairly shallow in depth. As stated previously, there’s a huge variety of milling cutters out there. The trick is knowing which one to use and how to apply it.

The set will come in SAE or Metric, covering both fine and coarse thread pitches. There are three basic items to be found in the set. The tap (long straight pieces) which are used to cut threads on the inside of metal, like in making a bolt hole. The die (round pieces) are used to cut threads on the outside of metal, like for creating threads on bar stock. The two two long pieces at the top of the set are the handles which allows you to use the tap (top) and die (bottom).

Each of these is an application-specific cutter, limited to relatively small amounts of material removal and the creation of distinct part features. In a moment, we'll talk about the more general-purpose tools—the end mills, shell mills, and other workhorses of the machining industry. For now, though, it’s important to recognize that all milling tools (with one or two exceptions) are just as described previously—multi-toothed rotary cutters that utilize a shearing action to remove material along the periphery of the tool and, in some instances, can act like a drill as well.

In the world of industrial milling, two broad classes of cutting tools exist. These are solid milling cutters and indexable milling cutters. As the name implies, the first of these is made from a solid piece of cutting tool material—usually tungsten carbide, although high-speed steel (HSS) and cobalt milling cutters are also available for hobbyists and low-volume or light-duty machining operations.

Taps are hard and therefore brittle. Small taps break very easily. Larger taps don't break so easily (though I have managed to break an M12 tap on stainless after it got stuck and refused to move forwards or backwards.) Any decent tap is too hard to drill out, so proceed with caution, as a broken tap can be a real problem. Do all of the following.

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That's where Kennametal comes in. Granted, they're not the only cutting tool supplier out there, but they are one of the oldest, filled with experienced applications and support people. The tooling manufacturer also carries an extensive lineup of most every cutting tool mentioned here (sorry, no fly mills).

Straddling the fence between these two are so-called modular end mills, which employ a solid carbide head that threads onto a steel body. As with modular carbide drills, these cutting tools provide the performance and accuracy of solid carbide but at a far lower cost. And because a worn head can be swapped out in a few seconds, modular tooling also increases productivity.

A good set of taps will contain three taps of the same thread diameter/pitch. The first will be strongly tapered, enabling an easy first cut. The last will have a square end for bottoming out blind holes. The second will be intermediate between these two in form. If you only intend to make through holes, you can get away with the first one. On the other hand, trying to start a thread with the last one is impossible.

One of the first lessons in many machine shop programs is learning how to set up a fly mill or fly cutter. Used primarily on manual knee mills, this most basic of cutting tools is equipped with a hand-sharpened bit that's secured to the tool body with a series of set-screws. As the tool rotates, the machine operator engages a mechanism that moves the workpiece beneath it, removing a small amount of material from its top surface with each pass.

One of the most commonly used of all milling cutters is the end mill. Solid carbide, indexable, and modular versions are available, as are ones with square, ball, and radiused cutting ends. They are used to machine slots and shoulders, mill pockets, and cut the inner and outer perimeters of various part features. As suggested earlier, some end mills have center-cutting capabilities, allowing them to plunge like a drill or ramp into a workpiece surface.

Shell mills or shoulder mills can be thought of as an end mill's larger, heftier cousin. They cannot plunge or ramp, but they can remove large amounts of material quickly. Due to their large size, most are indexable, often filled with dozens of carbide inserts. So are face mills, modern, multi-fluted versions of the venerable fly mill that opened this article, used to true up horizontal surfaces and make them both smooth and flat. And copy mills are similar in shape and function to ball-nosed end mills. These are a favorite of moldmaking shops, which use them to rough out large cavities before finishing with a solid carbide or modular end mill.

To use a tap, you need to have a starter hole of the appropriate size. This is going to be just a bit smaller than final size of the threaded area you are trying to create. Take the tap out of the case and insert the square end into the tap handle. Place the tap square to the drilled area and carefully begin turning the handle. You'll want to use copious amounts of cutting fluid (WD-40 works well for this). You start to feel the teeth on the tap bite into the metal. As soon as you feel an appreciable amount of resistance, you'll want to back the tap off of it some to allow the cutting teeth to clear the debris, then turn the tap back into the cut. Run the tap down the distance needed for threads.

Make sure the tool you are using is hard enough for the metal you are trying to work. There are cheap sets out there that will only work on nonferrous metal and will be instantly ruined even by use on mild steel. Don't waste money on such a set. Decide if the hardest material you will cut will be mild steel or stainless steel and buy a decent set accordingly. The dies should last a lifetime. The taps less so (see below) so you should expect to buy individual taps periodically.

Mount your work firmly. If you are tapping a blind hole, you should also make sure you can invert your work easily to remove chips. (Yes this may be a major issue with something like an engine block, but tackling anything more than chasing out existing threads without proper access is unwise.)

You'll also hear the term "chase the threads" or just "chase threads" used in conjunction with taps/dies. This is the process of cleaning up threads which may have been damaged during whatever work may have been going on. It is the same basic process as creating new threads, but you are only trying to get the old threads back to a usable state.

It is of note that cut threads on stock using a die will not create the same strength as rolled threads you'll get from a normal bolt you pick up that the hardware store.

Its Duo-Lock series of modular end mills, for example, provides a best of both worlds solution to anyone needing solid carbide performance at an indexable price range. There are also high-feed “Beyond” style milling tools, the Mill 4 and KSSM series of shoulder mills, Fix-Perfect face mills, and much more. Most are available in material-specific or general-purpose carbide grades, and all are available either online or in-person through an authorized distributor. Long story short, Kennametal has milling cutters covered.

Due to its material cost, solid carbide tools are generally smaller than an inch or so in diameter. Above this size, almost all milling cutters use indexable carbide inserts attached to a steel cutter body via small screws or clamps. They provide an effective yet affordable solution for the vast majority of all machining operations, although solid carbide tools are still used for small part features and for finishing work.

A tap and die set are tools used to cut (ie: create) threads in metal as well as cleaning up already exiting threads. A typical tap and die set will look something like this: