The milling cutter is perfectly clamped – and yet sudden tool life problems occur during milling. How is this possible? One reason that is often overlooked is the compatibility of the clamping surface and the tool holder. There are three types of clamping surfaces on the tool shank: HA, HB and HE. In this article, we take a closer look at the three clamping surfaces.

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Stevie (Jennifer Jason Leigh) is a consolation. They have sex, yes, but that's the least of it. She sees his need. Trevor is reading Dostoyevsky's The Idiot and perhaps there is a parallel between Stevie and Nastassia, Dostoyevsky's heroine, who is drawn to a self-destructive and dangerous man. Leigh has played a lot of prostitutes in her career, but each one is different because she defines them by how they are needed as well as by what they need.

We get up in the morning in possession of certain assumptions through which all of our experiences must filter. We cannot be rid of those assumptions, although an evolved person can at least try to take them into account. Most people never question their assumptions, and so reality exists for them as they think it does, whether it does or not. Some assumptions are necessary to make life bearable, such as the assumption that we will not die in the next 10 minutes. Others may lead us, as they lead Trevor, into a bleak solitude. Near the end of the movie, we understand him when he simply says, "I just want to sleep."

Therefore, it is important to always remember: HB shank to Weldon tool holder and HE shank to whistle notch holder – for optimum concentricity.

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The HB clamping surface is characterised by a small flat surface which is ground parallel to the axis. However, the small flat surface is more intended for milling cutters. The clamping chuck is also referred to as the Weldon holder, one of the most common forms of clamping chuck. The clamping screw of the holder is specially adapted to the HB surface of the tool – it ensures a form-fitting connection. However, you should make sure that you only use genuine Weldon clamping screws. If these are replaced by a standard screw, the form-fitting connection is lost. For shank diameters between 25 and 32mm, there are two flats on the shank and the holder is clamped by two clamping screws.

Tool shankmeaning

Marie (Aitana Sanchez-Gijon) is the other side of the coin, a cheerful presence in the middle of the night. "You're lonely," she tells Trevor. "When you work graveyard shift as long as I have, you get to know the type." She wonders why he comes all the way out to the airport just for a cup of coffee and a slice of pie. She wouldn't mind dating him.

Shank toolholder

For drilling, a HE clamping surface is the better choice. It is slightly inclined – as is the screw with which the tool is clamped in the so-called whistle notch holder. This will push the drill into the chuck and prevent it from pulling out of the chuck. The 2° angle acts like a wedge placed under a car tyre to prevent the vehicle from rolling away. As an additional feature, this system offers length adjustment from the drilling tool to the length of the clamping surface.

And by the way – Whether Weldon or whistle notch – you always have some play when drilling, as the tool must be minimally smaller than the holder. As a result, the tool is pushed slightly “off centre” during clamping with the lateral clamping screw. The result? A concentricity error of up to 10 µm.

The whistle notch holder is a clamping fixture primarily used for drilling. Here, the HE clamping surface of the tool is held by a slightly inclined surface.

The interaction between the tool shank and clamping chuck is crucial for perfect concentricity when machining workpieces. An optimum result can only be achieved if the tool shank and clamping chuck are perfectly matched to each other according to the rule of thumb: “Same to same”. In this article, we present the various clamping surfaces HA, HB and HE and explain how the selection of the wrong clamping surface can have an impact on the tool life of drills and milling cutters as well as on component quality.

The Weldon holder is a common clamping chuck used primarily for milling cutters. Here, the HB clamping surface of the tool is held by a small flat surface.

Then there is the matter of Ivan (John Sharian), the distracting and disturbing co-worker who perhaps contributed to the accident. He lost some fingers in a drill press once, and the docs replaced them with his toes. "I can't shuffle cards like I used to," he says. Nor, apparently, can he punch in on the time clock: The guys at the shop claim he doesn't exist. Is Trevor imagining him? And what is the meaning of the Post-It notes that look like an incomplete version of a Hangman puzzle?

"The Machinist" has an ending that provides a satisfactory, or at least a believable, explanation for its mysteries and contradictions. But the movie is not about the plot, and while the conclusion explains Trevor's anguish, it doesn't account for it. The director Brad Anderson, working from a screenplay by Scott Kosar, wants to convey a state of mind, and he and Bale do that with disturbing effectiveness. The photography by Xavi Gimenez and Charlie Jiminez is cold slates, blues and grays, the palate of despair. We see Trevor's world so clearly through his eyes that only gradually does it occur to us that every life is seen through a filter.

The same applies in reverse: If you clamp a milling cutter with a HB clamping surface in a whistle notch holder, the angled clamping screw presses on a straight surface. There is no frictional connection and you run the risk of the milling cutter being pulled out of the chuck. Similarly, the milling cutter’s shank can also break due to the point-like pressure.

If you clamp an inclined surface with a straight screw, the tool is only clamped with one corner. The pressure that presses the tool towards the machine spindle is too low. This can cause the tool to move axially  or even break.

If concentricity problems arise when using the appropriate clamping surfaces, other factors such as the machine spindle or workpieces may be important. We recommend checking these factors as well.

Roger Ebert was the film critic of the Chicago Sun-Times from 1967 until his death in 2013. In 1975, he won the Pulitzer Prize for distinguished criticism.

If the tool needs to have very good concentricity for machining, a tool shank with a HA clamping surface is recommended. Gühring therefore, offers only this smooth surface on the shank for all drills with a diameter-length ratio from 7xD.

Tool shanktypes

"If you were any thinner," Stevie tells him, "you wouldn't exist." Trevor Reznik weighs 121 pounds and you wince when you look at him. He is a lonely man, disliked at work, up all night, returning needfully to two women who are kind to him: Stevie, a hooker, and Marie, the waitress at the all-night diner out at the airport. "I haven't slept in a year," he tells Marie.

In addition to the different suitability of the shank shapes for the respective machining task, one thing above all must be taken into account: The tool and the holder must always match up – otherwise you run the risk that the machining will not run smoothly in the truest sense of the word. For example, if you combine a drill with a HE shank with a Weldon holder, you are clamping an inclined tool clamping surface with a straight screw – the drill is only clamped with one corner. As a result, the drill may move axially. In the worst case, the drill can break due to the wedge effect when clamping in the holder.

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Christian Bale lost more than 60 pounds in preparation for his performance as the gaunt, troubled Trevor Reznik in "The Machinist."

The HB clamping surface is a small flat surface that is ground parallel to the axis and is primarily intended for milling cutters.

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Trevor works as a machinist. There's a guy like him in every union shop, a guy who knows all the rules and works according to them and is a pain in the ass about them. His co-workers think he is strange; maybe he frightens them a little. His boss asks for a urine sample. One day he gets distracted and as a result one of his co-workers loses a hand. The victim, Miller (Michael Ironside) almost seems less upset about the accident than Trevor is. But then Trevor has no reserve, no padding; his nerve endings seem exposed to pain and disappointment.

When machining workpieces, choosing the correct clamping surface on the tool shank is critical to achieving perfect concentricity. If the clamping surfaces of the tool do not match the clamping chuck, this can lead to problems with the tool life of drills and milling cutters.

Christian Bale lost more than 60 pounds to play this role, a fact I share not because you need to know how much weight he lost, but because you need to know that it is indeed Christian Bale. He is so gaunt, his face so hollow, he looks nothing like the actor we're familiar with. There are moments when his appearance even distracts from his performance, because we worry about him. Certainly we believe that the character, Trevor, is at the end of his rope, and I was reminded of Anthony Perkins' work in Orson Welles' "The Trial," another film about a man who finds himself trapped in the vise of the world's madness.