Category Archives: Tooling

Basic Machining Tools – Terminology

There are a lot of tools used in machining today, so it’s often hard to keep up with the names of all of them, especially if you’re new to this career. Every tool has a specific job, and while a variety of tools may be able to get the job done, some are better than others.

Just so I don’t overload you, I’ll go through a list of the most common tools used in Machine shops, as well as Machine Tech schools. Each tool has a specific purpose, and there are many different kinds of the same tool. The more tools you use, the more knowledge you will get and know what works better for a certain material or operation. However, you must get an understanding of the of machining tools before just using any specific one without knowing what it’s meant to do.

End Mill

The almighty ‘End Mill’ is one tool that you will use almost every day if you run milling machines. If you need to cut both ends of a part to get it to a certain length, and end mill will side-mill the ends to make a clean and parallel surface. It can cut out pockets, and make square or round features in a part. There is so much that you can do with an end mill on a CNC milling center.

3-Flute End Mill
3-Flute End Mill

Whether you need to rough out a large solid piece of steel, or you’re just making some finish passes on aluminum, there’s an end mill for each job and every one in between. There are many different kinds of end mills. Here are the main variables you will have to decide when ordering tools: size (diamter), length (flute length), material/coating, roughing/finishing, number of flutes, and more.


Need to drill a hole? How about a few hundred holes? While there may not be quite the selection for drills as end mills due to the fact that you can only do so much with them, there are definitely right and wrong drills for any given job. 118 degree HSS or coated drills are the most common since they work well with most basic materials. However, you may need a drill for a hard stainless job, or perhaps a copper part that requires a deep hole with a close tolerance.



There’s not much else you can do with a tap other than tapping holes. Are you doing a blind or a thru-hole? Is it a metric or a U.S. standard thread? If you’re on a mill, the most popular taps are: cut tap, roll form, spiral point/flute, as well as a thread mill.

Cut taps produce chips because they literally cut a thread into the existing hole. You must use a drill that meets the minimum diameter tolerance for the specific thread you want. They are used on thru-holes because the chips won’t get in the way of the tap.

A roll form tap does not make chips because it forms and pushes the threads into place. It’s great for blind holes because the tap won’t break from chips collecting at the bottom.


A ream is used after a drill or a bore to meet a close tolerance call-out on the blueprint. Cheap drills are far from perfect and can easily make a hole over-sized, which will be rejected if it’s not within print. However, if you drill the hole .010″-.015″ under-size, you can then use the correct size ream to get a much more accurate and consider hole.


However, you should know that a ream will not ‘fix’ a hole. A ream just follows a hole, so if it’s crooked or out of round, the tool will follow that path. This is one reason why you may need to drill the hole then use a boring bar to make it perfectly round and straight before you ream it to size.

That’s it for the basic tools on this article from CNC Machinist Training. Stay tuned for another article that explains more advanced tooling that makes it much easier to do a job…

Roll Forming Taps Vs. Cutting Thread Taps On A CNC Mill

This is a question that comes up quite often for machinists new to the industry, and even experienced machinists that don’t know a lot about tapping. While form taps and cut taps can both do the same job, which is making a threaded internal hole in a part, they are quite a bit different in how they work.

After using both kind of taps for a while, you’ll see the difference in looks right away. A cut tap doesn’t have a full thread until about the third time around, while a form tap looks the same from bottom to top. A cut tap also has clearance cut around the tool so that chips will move out of the way and not break it.

Cut Tap

Tapping with cut taps has been the most popular for decades because that’s what there was available. They are easy to use; just drill the hole with the correct tap drill size, making sure you go deep enough so that the tap will get enough threads, then run the tap into the hole. Depending on your machine’s capabilities and what material you’re running, you may only be able to run it at 200-300 RPM.

Rigid tapping is a very useful option on newer CNC Mills such as a Haas. It allows you to tap at higher RPM without putting so much load on your spindle. This equates to much faster tapping cycle times.

A cutting tap is great for thru-holes, as you won’t have to dig into the hole to pull out the chips. You also won’t have to worry about running into anything unless your table or fixture is under the hole.

Since this type of tap “cuts” threads into the hole, you can get away with using various coolants and mixtures without breaking tools, especially on soft materials like aluminum.

Form Tap

Form Tap vs. Cut Tap
Form Tap vs. Cut Tap

What’s better about form taps? Well, they have several advantages over cut taps that will make you want to use them more often. For one, they don’t make any chips. A form tap does just that, it “forms” the threads in the hole with pressure, as opposed to “cutting” threads.

That brings us to the next advantage; the threads are much stronger because they are “formed” into place. If you need strong threads in your parts, form taps are the way to go.

Form taps are stronger and will last longer than cut taps. This will save you time and money in the long run, as you won’t have as many taps breaking in your parts.

Not only will everything be stronger, but you can run at faster speeds, greatly reducing cycle times.

With all of these advantages, there’s gotta be some downfall, right?! Well, due to the higher pressure on the tool and part hole, it will require some better coolant or oil with high lubricity. If your coolant isn’t good enough, the tap will be have to work harder to form the threaded hole and eventually will break.

This is especially true on small form taps such as an M3 (Metric), as there just isn’t enough space for the average coolant to lube the tap. You need something with better lubricity that will reduce the load on the tool. Also, if your countersink isn’t big enough, the first thread will be pushed up above the material’s surface and will cause interference if it’s a mating part.

Other than that, there really isn’t much else to say about form taps. Sometimes you just have to experiment until you find out what works the best. If your tap keeps breaking, change it up with different speeds, coolant, or a different tap.