Thursday, March 24, 2016

What is Tribology and Why Should You Care?

By Patrick de Vos, Corporate Technical Education Manager, Seco Tools AB

Tribology is a relatively new area of metalcutting load analysis. It studies how surfaces in contact with each other, such as the cut chip and tool, interact at certain temperatures and pressures. Its main focus is e.g. learning what causes the negative phenomenon of built-up edge and what can be done to minimize the problem.

Tribological research has determined that the cutting process does not simply involve a single shearing event and subsequent disconnection of chip and tool. In fact, secondary and tertiary connections and disconnections also occur. The chip shears away, adheres to the rake face and then shears away again before finally sliding off the tool. The main wear mechanism is repeated shearing, not friction.

Built-up edge occurs when thin layers of the workpiece material adhere to and build-up on the tool rake face. If a significant amount of material accumulates on the tool, it can change the profile of the cutting edge. The built-up material can also break off and damage the edge or be deposited on to the workpiece. Regardless, edge buildup makes the cutting process unpredictable and results in poor surface finishes and a need to change tools frequently.

We know that the prime factors that promote edge buildup are high ductility, high adhesion tendencies, abrasiveness and the high pressure and temperatures that are generated when machining tough alloys that have poor thermal conductivity. The possibility of built-up edge formation is much greater in newer workpiece materials such as low carbon steels, aluminum, and the family of aerospace and energy industry materials encompassing titaniums, nickel-based alloys and heat-resistant metals.

Tooling engineers are applying the findings of tribological research in the development of machining processes and tools that will meet the higher demands from these new materials. On the process side, we know that minimizing adherence and the chances for forming built-up edge involves reducing the contact time between the chip and the rake face.

The most straightforward solution is to increase the cutting speed and apply a sharper tool. Faster cutting speeds reduce the time the tool and workpiece material are in contact with each other. The resulting higher process temperatures can also reduce the strength of any edge buildup or eliminate it entirely. The sharper tool has a higher primary rake angle that forces the chip to move more quickly. Other tool geometry choices, such as use of positive rake tools, can help direct cut material away from the workpiece.

We have also used tribology research findings to understand the role tool coatings play in minimizing edge buildup. For example, the newest generation of Seco’s CVD aluminium-oxide Duratomic® coating is based on tribological principles. Development engineers manipulated coating components in response to expanded knowledge of the interactions between the chips and the cutting tool.

Another example of Seco coatings aimed at controlling built-up edge is the new silver PVD uni-coating developed for MS2050 milling inserts. The coating has high heat resistance capabilities and also practically eliminates the occurrence of built-up edge when cutting sticky materials such as titanium. With the absence of built-up edge, the inserts last about 50 percent longer and run at much higher cutting parameters as compared with existing tools.

Tool engineers are also using tribology to research ways to turn edge buildup from a liability into a positive contributor to machining productivity. For example, in some cases, a thin layer of workpiece material on the surface of the cutting tool actually slows the progress of wear. The key is to find a perfect thickness of this tool protection layer that does not affect tool geometry and also does not separate from the tool surface.

While tribology may not be a topic you think about everyday, it is offering an important new perspective for developers of cutting tools and machining processes. It’s giving us another tool to use as we respond to and solve increasingly tougher machining challenges in innovative ways.

If you have questions about tribology, please contact me.

About the Author
Based in The Netherlands, Patrick is the corporate technical education manager for Seco Tools AB with global responsibilities for the technical education activities that help train Seco employees and customers worldwide. He led the creation of the Seco Technical Education Program (STEP) and since its launch more than 200,000 people  worldwide have participated in the program. He has been with the Seco organization for more than 30 years, and during that time he has trained more than 70,000 people in   over 57 countries. He is also the author of the books “Metal Cutting, theories in practice”, “Tool Deterioration, Best Practices” and “Applied Metal Cutting Physics, Best Practices”.

Monday, February 8, 2016

Don’t Let Mechanical Loads Weigh Down Your Milling Process

By Patrick de Vos, Corporate Technical Education Manager, Seco Tools AB

When planning a milling application, there are several factors you must consider for optimum results. First and foremost, you want to have the right cutting tool for the job. But before diving too deep into a tooling supplier catalog, it’s important to understand the variables that impact cutting tool performance, with mechanical loads being one of them.

A mechanical load, not to be confused with cutting force, can be thought of in terms of pressure (force per unit of surface area). This pressure has significant influence on tool life and failure. Consider this: a high cutting force spread over a large tool area produces a relatively insignificant load, while a low cutting force concentrated in a small section of the tool can create a problematic load.

Milling exposes multiple cutting edges to continuously changing loads that go from small to large and back again. And, no matter what milling cutter type you use, its cutting edges will repeatedly enter and exit the workpiece material. Loads on the milling teeth will go from zero before entry to peak values in the cut and back to zero at exit.

Therefore, you want to moderate these intermittent loads so you can achieve the best possible tool life, reliability and productivity in your application. Elements such as cutter positioning, entry and exit strategies and chip thickness are key to controlling mechanical loads and ensuring your success.

Cutter Positioning
When approaching a workpiece, you must consider what milling direction will best meet your goals. In conventional “up” milling, the cutter rotates against the direction of the workpiece feed, while climb “down” milling moves in the same direction as the feed.

Whether you go “up” or “down,” you’ll want to position the cutter to one side or the other of the workpiece centerline. Central positioning mixes the forces of conventional and climb milling, which can result in unstable machining and vibration.

Entry and Exit Strategies
The way the cutter and its cutting edges enter the workpiece largely determine mechanical loads in milling. More times than not climb milling will offer the best point of entry over conventional milling, but there are pros and cons to both.
  • Climb milling pros: Full-thickness entry into the workpiece allows for proper heat transfer into the chips, protecting both the part and the tool. Chips flow behind the cutter, minimizing recuts and yielding better part surface finishes.
  • Climb milling cons: Full-thickness entry into the workpiece can subject the tool to heavy mechanical loads (which is not a problem for most cutting tool materials). Face milling via the climb method creates a downward force that can cause backlash on older manual machines.
  • Conventional milling pros: Gradual entry into the workpiece protects brittle, super hard cutting tools from damage when machining rough-surfaced or thin-walled materials. It also handles heavy cuts on less stable machines.
  • Conventional milling cons: Shallow-thickness entry into the workpiece creates excessive friction and heat that can have detrimental effects on a tool. Chips drop in front of the cutter, increasing recuts and lowering part surface finish quality.
Furthermore, how your cutter exits the workpiece is just as important as how it enters. If your cutter’s exit is too sudden or uneven, the cutting edges will chip or break. When handled properly, however, you stand to benefit from up to 10 times more tool life. The exit angle, defined as the angle between the milling cutter radius line and the exit point of the cutting edge, should be the primary focus of your exit strategy. Keep in mind your exit angle can be negative (above the cutter radius line) or positive (below the radius line).

Chip Thickness
Chip thickness is the thickness of the non-deformed chip at the right angles of the cutting edge, and it’s influenced by the radial engagement, edge preparation of the insert and feed per tooth.

When chips are too thick, they tend to generate heavy loads that can chip or break a tool’s cutting edges. When chips are too thin, cutting takes place on a smaller portion of the cutting edge, creating friction and increased heat that results in rapid tool wear.

Cutting tool manufacturers typically have the average chip thickness data for their milling products, so be sure to ask your supplier for this important information. When the average chip thickness data for your cutting tool is applied and maintained, you benefit from maximum tool life and productivity.

Milling cutters have significantly evolved over the years, allowing us to achieve levels of productivity and profitability never before possible. However, many fail to take full advantage of this technical progress. Don’t be one of them. By taking the time to understand the variables that influence cutting tool performance and planning out a proper milling strategy, you’ll have it made.

Metal cutting is definitely a complex process, so any time you have questions or require applications advice, please don’t hesitate to contact our technical support team. Also, be on the lookout for future posts on thermal and tribological loads in milling.

Read the published Seco technical article “Controlling Mechanical Loads In Milling.”

About the Author
Based in The Netherlands, Patrick is the corporate technical education manager for Seco Tools AB with global responsibilities for the technical education activities that help train Seco employees and customers worldwide. He led the creation of the Seco Technical Education Program (STEP) and since its launch more than 200,000 people  worldwide have participated in the program. He has been with the Seco organization for more than 30 years, and during that time he has trained more than 70,000 people in   over 57 countries. He is also the author of the books “Metal Cutting, theories in practice”, “Tool Deterioration, Best Practices” and “Applied Metal Cutting Physics, Best Practices”.

Thursday, January 28, 2016

How to Best Deal With (Part) Rejection

By Todd Miller, Manager of Product Marketing

No one likes rejection, especially in the world of parts production. Manufacturers running critical applications know there’s nothing worse than having to scrap expensive, time-consuming components because of burrs or unacceptable edge conditions. Sound familiar? Then it might be time for you to tackle these unsightly manufacturing blemishes differently.

Mechanized Edge Profiling, or MEP, could be your answer, especially if you’re deburring components using hand grinders or other manual processes. Because, even when performed by skilled craftsmen, manual techniques are slow and lack the required process consistency from part to part.

MEP, however, is a controlled strategy involving precision engineered tools, guided by a machine tool’s CAM program, to remove burrs and sharp edges quickly and consistently. It’s also a documentable method that can increase your repeatability and reduce your setup and part handling expenses.

Before implementing MEP, it’s important to make sure you have the right tools for the job. When machining non-rotating components, such as aircraft engine casings, it’s best to use solid-carbide chamfering end mills and edge-break tooling. However, when profiling edges on contouring components, ball nose and lollipop-style tools are your best bet.

Custom MEP tooling is necessary when cutting critical rotating parts that require perfect surfaces, such as aircraft engine fans. These special tools have specific radii, chamfers and angles that are essential to machining flawless, lab-certified edge profiles. The most sophisticated deburring tools have edge designs that produce a chamfer with a radiused edge preceded by lead-in and lead-out angles to prevent formation of secondary burrs.

When putting MEP into action, you should use it as a portion of the actual part feature machining operation for maximum accuracy, consistency and productivity. Deburring should occur after all machining operations are completed. The CAM program directs the MEP tools to deburr all the holes and break sharp edges in sequence. Some MEP tools can be used to deburr a variety of holes, and some profiling tools can be applied on three or four different locations or features, such as the bottom of a hole as well as the bottom of a scallop contour.

To ensure that the edge profiling takes place in the correct location and with the proper amount, your part’s hole or feature must be defined or measured before the MEP operation begins. When part tolerances are very tight, the location of the part surface should be well defined and in-process measurement may be unnecessary. However, if the location is in question, measurement will be necessary after initial machining to determine the location of the edge or feature to be profiled.

In addition, the tool itself must be measured and located to ensure that it will profile the part correctly. Because the tool radii are so small — and for practical purposes, unmeasurable — the tool length is specified in the CAM program. You can confirm the tool length away from the machine with a presetter or on the machine via a laser or touch probe. Feed rates are calculated relative to the measured dimensions of the part features and the tool.

Overall, you should consider the deburring or chamfering process as a finishing pass, with your primary focus on quality. Productivity is always important, but especially in the case of expensive components, pushing the tool to maximize output can have negative, and costly, repercussions. Consistency, reliability and elimination of scrap parts are paramount because no one likes the feeling of rejection.

If you have questions about MEP, please don’t hesitate to contact me or our technical support team. You might also want to check out the published Seco technical article “How MEP Takes the Edge Off Parts Manufacturing.”

About the Author
Todd oversees the product marketing team at Seco Tools LLC. and works with the company’s sales department to further enhance the customer experience. He and his team also support product introductions while working globally on new product testing to ensure customers gain access to the industry’s most advanced tooling as quickly as possible. In his spare time, Todd likes to go bowling as well as cheer on the University of Michigan football team.

Thursday, January 14, 2016

Take the Load Off Your Turning Tools

By Chad Miller, Product Manager – Turning and Advanced Materials

Do you find yourself frequently frustrated by premature tool deterioration or failure during turning operations? Understanding the four basic types of machining loads and how each affects your cutting tools can help you achieve slow, predictable tool deterioration as well as increase productivity and profitability.

The four load types are: mechanical, thermal, chemical, and tribological, and each one contributes to the wear and failure of your cutting tool. You’ll find these loads do not act independently, but rather interact and influence the sum of their effects on tool deterioration.
  • Mechanical loads in turning are steady; however, any interrupted cuts during the process produces impact loads that can chip or break the tool. 
  • Thermal loads occur when workpiece deformation generates heat up to 1,650 degrees Fahrenheit, causing tool deformation and blunting. 
  • Chemical loads occur when heat and pressure combine between the cutting and workpiece materials, producing tool wear in the form of diffusion or cratering.
  • Tribological loads happen when there is friction between the tool and chip, creating abrasion and erosion-type wear.
You can, however, mitigate the negative impact these loads have on your tools using two strategies.

Strategy 1:

Manipulating your cutting parameters can influence the level of load impact on your tool. Keep in mind, however, depth of cut, feed and speed all have differing effects on machining loads, so you should consider the following:
  • Doubling the depth of cut doubles the cutting force but also doubles the length of the cutting edge in cut. This results in the load remaining the same per unit of cutting edge length.
  • Increasing feed rate increases cutting forces, but to a lesser, non-linear degree. Because the greater feed increases chip thickness, not the length of the tool in the cut, loads are seriously increased on the cutting edge.
  • When increasing cutting speed, forces generally remain the same, but power requirements rise.
  • Cutting forces rise at lower cutting speeds and decrease at higher cutting speeds. Watch closely for a built-up edge, which may indicate inappropriate cutting speed.
  • Too high of cutting speeds can reduce the reliability of a process through uncontrolled chip formation, extreme tool wear and vibration that can make a tool chip or fracture.
  • Higher feeds and depths of cut combined with low or moderate cutting speeds offer the best potential for operational security and reliability. Higher cutting speeds, if depth of cut and feed are sufficiently low to limit cutting forces, can provide greater productivity.

Strategy 2:

The basic size and shape of a tool determines its strength and capabilities. Often times, tool geometries are engineered with a specific application or workpiece material in mind. So, it's critical to have the best tool for the job right from the start. Here are a few things to keep in mind when selecting tools:
  • A large, strong insert enables use of highly productive feeds and depths of cut because cutting forces acting on a large insert will result in lighter loads than the same forces would create on a smaller insert.
  • A round insert shape is the strongest, and a 90-degree corner of a square insert is stronger than a 35-degree corner of a diamond insert. However, a round insert cannot cut the same variety of part profiles as a 35-degree tool. There is a tradeoff of strength for flexibility of application.
  • Generally, the best tool for cutting steel, where toughness is required, has a honed edge. The best tool for cutting stainless steel, which tends to be gummy, has a sharp edge.
  • Very sharp cutting edges may not necessarily provide the best surface finish. The best results often are obtained after an edge has run for a period of time.
Tool deterioration during machining is inevitable, but as you can see there are ways to slow the process and better predict when a tool will fail. Metal cutting is definitely a complex process, so any time you have questions or require applications advice, please don’t hesitate to contact me or our technical support team.

Read the published Seco technical article “Mechanical Loads and Cutting Geometries in Turning Operations.”

About the Author
Chad manages Seco's turning and advanced materials product lines, including all CBN and PCD products. When he's not helping customers implement advanced metal cutting solutions, you can find him training for and running 5K, 10K and 1/2 marathon races and triathlons.

Tuesday, December 15, 2015

High-Speed Hard Milling Tips for Successful Mold Production

By Jay Ball, Product Manager – Solid Carbide Endmills, Seco Tools LLC

If your mold shop would like to reduce or eliminate roughing of mold cavities pre-heat-treat and go straight to post-heat-treat roughing and finishing, you might want to consider high-speed hard milling. Why? Because, when applied correctly, the process, which involves light depths of cut and accelerated feed rates, can boost your productivity and reduce your setup costs.

With hard milling, depending on your application, you could drill holes and water lines in a block, perform heat treatment and then apply high-speed strategies to rough and finish in one setup. But, to be successful, there are several factors to consider, including the 6 mentioned below.

1. Think in Terms of Machinability

Typical hardened mold steels fall into the 48-65 HRC hardness range, but Rockwell numbers are only half of the equation in terms of real-world machinability. D2 tool steel, for example, hardens to about 60-62 HRC, but machines more like 62-65 HRC material due to its 11-13% chromium content. So, when machining multi-constituent alloys, it’s best to apply the recommended machining parameters for hard materials set forth by your cutting tool supplier.  

2. Maintain Constant Chip Load

Maintaining a constant chip load on a tool’s cutting edge is important, otherwise it will wear out prematurely, chip or break. Certain situations, such as machining 3D contours into a mold, make chip load management especially challenging. There are, however, steps you can take to simplify the process, including manually reducing your rpm/feed rate via override controls, or backing the rpm and feed rate down using the combined efforts of your machine’s CAM program and CNC.

3. Minimize Tool Run Out

On average, tool run-out greater than 0.0004" can cut your tool life in half. Therefore, it’s important to do everything you can to minimize it, especially when working with smaller tools. One way to reduce runout is by using high-precision holders such as shrink-fit, hydraulic, and milling chucks in your operations.

4. Reduce Finishing Stock

Be sure to remove as much part stock as you can during the roughing process. If you’re working with cutters that are larger than 1/8" in diameter, it’s best to leave about 1 percent of the cutter diameter for finishing. Smaller tools, however, determining a sufficient amount of stock for finishing may be a case of “feel,” or trial and error. 

5. Beat the Heat
Extreme heat has a significant impact on tool life, especially when processing materials harder than 48 HRC. When working with these materials, it’s better to use an air blast or oil/air mist instead of coolant to avoid thermal shock.

6. Apply the Right Tool

When processing molds with tight tolerances, you want to make sure you have the right cutting tool for the job. Because milling hard materials generates a significant amount of heat, it’s best to use tools with a high thermal-barrier and abrasive resistant coatings such as AlTiN. CBN tools are great for premier finishing applications, while inserted end mills prove highly effective in roughing and some finishing operations.  

While high-speed hard milling is a great alternative to lengthy rough milling processes, careful consideration of your entire machining system is critical to successful application. Understanding these 6 factors is a good place to start, but you should also consult with your cutting tool supplier to gain the best possible results.

About the Author
Jay has been with Seco for more than 10 years. As a key member of the product management team, he is responsible for Seco’s solid carbide end mill products in North America. He works closely with global R&D on new innovations to ensure they meet the necessary market requirements. He also provides technical support for high-speed hard milling and micro milling operations, including CAD file review, tooling selections and programming recommendations.

Friday, July 31, 2015

Passive-Aggressive Tooling Approach to Vibration Damping

By Mike Smith, Product Manager – Reaming, Boring and EPB

Steadyline Turning Bars
Long tooling overhangs while machining difficult-to-access part features, such as deep cavities, create perfect conditions for high levels of vibration that are extremely detrimental to cutting operations. Fortunately, vibration-damping milling holders and turning bars for long-reach applications negate the effects of vibration and allow for higher metal-removal rates, increased productivity, improved surface finishes and longer tool and spindle lives. 

Today’s tooling systems can be passive, aggressive or a combination of both when it comes to dealing with vibration. Passive tooling controls vibration via their material make up, while active ones use some type of moving mechanism typically housed in internal cavities.

Tooling that combines the two methods – “passive-dynamic” – uses, for instance, systems that are passive until a first hint of vibration activates them. At that moment, a damper mechanism counter-vibrates against the vibration. The damper is at the same frequency as the holder itself and that kills the vibrations entering it.

The key to passive-dynamic tooling is to actually put enough load on the toolholder to trigger the damper into action. Typically in long-reach operations, machinists tend to run slow to limit vibration, but doing so may fail to activate the damper.

Vibration-damping tooling, such as Seco’s Steadyline, actually needs to run hard. Substantial feeds and depths of cut will ensure optimum tool performance and the best possible workpiece surface finishes, along with increased productivity. 

One of the greatest advantages of the Steadyline milling and turning systems is the flexibility they offer. Steadyline Combimaster, for instance, is a two-piece milling system with a wide range of shank types, lengths and interchangeable cutter heads. This makes for a wide range of applications such as square shoulder milling, end milling, copy milling, face milling, plunge milling and disc milling.

For turning, Steadyline turning bars feature Seco’s GL turning heads that make it possible to perform rotating and static operations with the same bar. Once the bar is set, a shop can mount heads without having to reset the system, requiring only the use of a spanner wrench to loosen and tighten the heads. Available in 6xD, 8xD and 10xD lengths and with a broad selection of turning heads, these turning bars handle a variety of operations, including roughing, finishing, boring, threading and grooving.

Because of the rigidity and anti-vibration properties of the Steadyline turning bars, they handle very high machining parameters. This makes it possible to leave them in the turning machine’s turret and use the tools for short work as well to eliminate the need for multiple tools. 

For large holes, shops can circular interpolate at high feedrates to rough machine with the Steadyline, then finish cut with a finish boring head or reamer. The Steadyline bar also accommodates twin boring heads for staggered boring. This provides a much more stable setup as compared with a modular system constructed of separate pieces.

Seco offers several tips to get the most benefits from its Steadyline tooling. One recommendation is to cut off portions at the end of a toolbar for an optimized fit into a turning machine’s turret block. In fact, Seco puts lines on the Steadyline turning bar to indicate where it can be cut.

However, care should be taken when clamping the bar in a vise for cutting. The damper is in the front of the hollow tube, and the vise pressure could crush it internally if the bar is clamped on the wrong portion. Also, soft jaws should be used for best results. 

Another tip is to pay attention to temperature fluctuations. Rubber O-rings surround the damper, so excessive heat or cold could cause the rings to become too soft or hard. This doesn’t permanently change how the damper operates, but the rings need to get back to the right consistency prior to tool use.

While some milling operations run dry, too much heat affects how the Steadyline milling holder operates, so coolant should be applied. And if the holder has been sitting in cold conditions for several days or weeks, there should be a warm up period prior to using it to allow the damper to “unfreeze.”

Another tip is to store the holder in a vertical position, as opposed to on its side. When stored lying down, the damper might get stuck and require some effort to free it.

Steadyline tooling benefits aerospace, heavy equipment, moldmaking and automotive applications, along with many others, where long-reach operations are needed. In addition, Steadyline tooling is well suited for where there are issues with fixturing being in the way or when machining tough materials prone to extensive vibration, even without a long-reach situation.

Download the Steadyline turning and milling brochure. 

About the Author
Mike is Seco's product manager for reaming and EPB tool holders, which includes EPB’s line of rough and finishing boring heads. In his spare time, Mike enjoys spending time with his wife and two daughters as well as running when he gets a chance. 

Wednesday, June 24, 2015

Are You In Over Your Head With Deep Hole Drilling?

By Manfred Lenz, Product Manager – Drilling

Seco Feedmax SD230A deep hole drills
Machinists often find deep hole drilling – at depths from 12 to 30 times drill diameter – daunting. Many are unsure about the process along with all that is required to maintain good hole straightness, tolerance/size and surface finish. Fortunately, there are some simple tips that will allow machinists to achieve near-perfect deep drilled holes while also increasing productivity as well as tool life.

1. Match pilot drill diameter.
When deep hole drilling, a machinist must first produce a pilot hole, typically at a depth of 2 to 3 times the pilot drill diameter. Pilot holes should be the same size diameter as the deep hole drill to be used. This matching hole size creates a starting point and helps guide – almost like a bushing – the long drill, keeping it straight and preventing it from walking. Without a pilot hole at all, the long drill would vibrate back and forth at the start of the hole and eventually break.

2. Switch off the spindle when entering the hole.
A very common mistake machinists make is to feed an already rotating deep hole drill into a pilot hole. This causes the long drill to slap the sides of the hole, decreasing the tool’s life. Instead, leave the spindle off, fast feed the drill into the hole, then turn on the spindle when the drill tip is about 0.020" (0.5 mm) above where the pilot hole ends and begin to drill without pecking

Rapid feeding drills out of deep holes is a mistake as well. At the end of the drilling depth, the machinist should reduce the spindle speed to a few hundred rpms and retract the deep hole drill at a slow rapid to where drilling started. At that point, the machine spindle is switched off, and the drill exits the remainder of the hole.

Stopping a drill’s rotation before it enters a hole, retracting it slowly and at reduced rpms can increase drilling cycle times, but by barely a fraction of a second. The resulting gains in tool life far outweigh that little amount of added time.

3. Pay attention to drill geometry.
Drill geometry is a key factor in successful deep hole drilling. Pilot drills, for instance, can have 140-degree point angles, while long drills may have 136-degree point angles. This ensures that the center of the long drill will contact the material first while in the pilot hole and seat itself. Then, the corners make contact.

Some deep hole drills also have two land margins per flute. The drill tip does the cutting, while the land margins at the sides help hold the drill in place during operation. On long drills, land margins are located only at the very ends of the flutes for clearance that prevents drag. The more flute drag, the more heat generated and the higher the risk of drill breakage.

Solid-carbide drills are a must for producing hole depths greater than 12 times the drill diameter. Carbide tools are stiffer and less likely to wander as compared with HSS and cobalt tools in deep hole drilling. However, deep holes with large diameters – 3” or more –, will require the use of insertable deep hole drills.

4. Ensure proper chip evacuation.
The number one reason drills fail is due to inadequate chip evacuation. While most long drill geometries provide affective chip breaking, they must then efficiently evacuate the chips out of the hole. Those drills with both polished flutes and back tapers will work best.

Coatings minimize frictional heating and thus contribute to increased tool life. Coolant, however, is the most important factor for chip evacuation. Even one chip left in the hole can break the drill, so high-pressure through-tool coolant is the only option. High-pressure coolant forces them up the drill flutes and out of the hole. Through-coolant drills also eliminate the need for pecking cycles.

5. Use the right toolholder.
Hydraulic and shrink-fit toolholder systems generate the least amount of runout, making them ideal for deep hole drilling applications. Both systems can cost a bit more, and precision collet chucks are one alternative. But they must be high quality and provide very low runout.

A final and very important tip is to consult a tooling expert. A partnership between a shop and its tool supplier makes all the difference in choosing the right drill for deep holes, or any holes for that matter.

About the Author
Manfred has been with Seco for more than 16 years. In his current role as drilling product manager, he is responsible for every aspect of the company’s drilling products in North America. He works closely with global R&D on new innovations to ensure they meet the market’s tough manufacturing demands. Manfred also supports the Seco sales force by providing them with technical information and cost saving solutions that bring value to customers. In his spare time, he enjoys boating, bowling and golfing.