You can stick a tombstone arrangement on a vertical mill too, there’s just less clearance available so you’ll want relatively “flat” parts to use one: This is a powerful technique for improving shop productivity, but it’s not strictly limited to Horizontal Mills. As you can see, they have things set up so they can even do more than one kind of part on a tombstone. They load and unload the tombstone (which is the big upright chunk of cast iron the parts are held to while machining) while the machine is busy cutting new parts on a tombstone in the machine.

Pictured is a great example from our article on a successful manufacturer that is so productive with their Horizontal Mills they only need 2 1/2 machinists–it’s a family business. But another reason is that almost any Horizontal Mill has a 4th Axis Tombstone arrangement:Ī 4th Axis Tombstone on a Horizontal Mill… One reason is that the chips are easier to keep clear on a Horizontal since gravity is helping rather than forcing them further down into the hole where they’re harder to get at. They say that Horizontal Machining Centers can be tremendously more productive than Vertical Machining Centers. In a future article, we’ll get into programming 4th axis indexing. Or, you could also use a 4th axis to index the sides so more than one can be machined with a single setup. You could build fixtures and do a bunch of setups, one for each side. Suppose you have a part like a throttle body that has holes on all sides. But, there are much simpler cases where indexing is also extremely helpful.

Gears are kind of an extreme case because it would be hard to imagine how to make one if we couldn’t index the teeth. They the next tooth is indexed into position. The 4th Axis indexes each tooth into position, stops, and then the cutter makes a pass back and forth until the tooth is done. Suppose you’re making something complex, like a gear: The most obvious case for indexing is to gain better access to the part. It’s very powerful, but plenty of work (perhaps even the majority of 4th axis work) is done simply with indexing. Also, you’ll need much fancier CAM software to program continous machining. You may wonder why you’d ever want anything but continuous machining, but bear with me–there are lots of useful ways to take advantage of indexing. By contrast, “continuous” means that machining happens as the part is being rotated. In fact, there are some types which are called “indexers” that can only be used to index in fixed degree increments rather than continuously rotating to any desired position. When indexing, no cutting happens until the 4th axis is stopped (and often locked with a brake of some kind). A 4th axis is typically either used in an “indexing” mode or a “continuous” mode. But there are also many other applications.įirst thing to talk about is this term “indexing”. There are cases where we do continuous machining with a 4th axis–in other words, we want the cutter to be machining as the 4th axis turns. With CNC, cutting along an arc is easy–that’s what the G02 and G03 g-codes are for. Most manual machining 4th axis work is about cutting features along an arc, something that’s hard to do with a manual machine. While there is a grain of truth to this idea, largely it’s incorrect. Indeed, there are many projects out there where someone converted a manual rotab to become a 4th axis. If you’re new to CNC, your first impression may be that the 4th axis is used in the same way a rotary table is used for manual machining. In the second, we’ll look at how they work. In the first installment, we’ll look at what a 4th axis is used for.

This is an article series to help beginners understand how and why a 4th Axis is used on CNC Mills. Haas actually got it’s start building a 4th axisbefore it ever built entire CNC machines (pictured on the right). 4th Axis machining is an interesting and important sub-part of the CNC milling world.

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