Selecting the Right Harvey Tool Miniature Drill

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Among Harvey Tool’s expansive holemaking solutions product offering are several different types of miniature drill options and their complements. Options range from Miniature Spotting Drills to Miniature High Performance Drills – Deep Hole – Coolant Through. But which tools are appropriate for the hole you aim to leave in your part? Which tool might your current carousel be missing, leaving efficiency and performance behind? Understanding how to properly fill your tool repertoire for your desired holemaking result is the first step toward achieving success.

Pre-Drilling Considerations

Miniature Spotting Drills

Depending on the depth of your desired machined hole and its tolerance mandates, as well as the surface of the machine you will be drilling, opting first for a Miniature Spotting Drill might be beneficial. This tool pinpoints the exact location of a hole to prevent common deep-hole drilling mishaps such as walking, or straying from a desired path. It can also help to promote accuracy in instances where there is an uneven part surface for first contact. Some machinists even use Spotting Drills to leave a chamfer on the top of a pre-drilled hole. For extremely irregular surfaces, however, such as the side of a cylinder or an inclined plane, a Flat Bottom Drill or Flat Bottom Counterbore may be needed to lessen these irregularities prior to the drilling process.

harvey tool miniature spotting drill with dimension callout marks

Tech Tip: When spotting a hole, the spot angle should be equal to or wider than the angle of your chosen miniature drill. Simply, the miniature drill tip should contact the part before its flute face does.

infographic showcasing proper spot angle for spot drilling in relation to drills included angle

Selecting the Right Miniature Drill

Harvey Tool stocks several different types of miniature drills, but which option is right for you, and how does each drill differ in geometry and overall tool coating?

Miniature Drills

Harvey Tool Miniature Drills are popular for machinists seeking flexibility and versatility with their holemaking operation. Because this line of tooling is offered uncoated in sizes as small as .002” in diameter, machinists no longer need to compromise on precision to reach very micro sizes. Also, this line of tooling is designed for use in several different materials where specificity is not required.

harvey tool extended depth miniature drill

Miniature High Performance Drills – Deep Hole – Coolant Through

For situations in which chip evacuation may be difficult due to the drill depth, Harvey Tool’s Deep Hole – Coolant Through Miniature Drills might be your best option. The coolant delivery from the drill tip will help to flush chips from within a hole, and prevent heeling on the hole’s sides, even at depths up to 20 multiples of the drill diameter.

harvey tool miniature deep hole coolant through gun drill

Miniature High Performance Drills – Flat Bottom

Choose Miniature High Performance Flat Bottom Drills when drilling on inclined and rounded surfaces, or when aiming to leave a flat bottom on your hole. Also, when drilling intersecting holes, half holes, shoulders, or thin plates, its flat bottom tool geometry helps to promote accuracy and a clean finish.

harvey tool miniature flat bottom drill with dimension callouts

Miniature High Performance Drills – Aluminum Alloys

The line of High Performance Drills for Aluminum Alloys feature TiB2 coating, which has an extremely low affinity to Aluminum and thus will fend off built-up edge. Its special 3 flute design allows for maximum chip flow, hole accuracy, finish, and elevated speeds and feeds parameters in this easy-to-machine material.

miniature drill for aluminum from harvey tool with dimension callouts

Miniature High Performance Drills – Hardened Steels

Miniature High Performance Drills – Hardened Steels features a specialized flute shape for improved chip evacuation and maximum rigidity. Additionally, each drill is coated in AlTiN Nano coating for hardness, and heat resistance in materials 48 Rc to 68 Rc.

miniature drill for hardened steel with dimension callouts

Miniature High Performance Drills – Prehardened Steels

As temperatures rise during machining, the AlTiN coating featured on Harvey Tool’s Miniature High Performance Drills – Prehardened Steels creates an aluminum oxide layer which helps to reduce thermal conductivity of the tool and helps to promote heat transfer to the chip, as well as improve lubricity and heat resistance in ferrous materials.

miniature drill for prehardened steel with dimension callouts

Post-Drilling Considerations

Miniature Reamers

For many operations, drilling the actual hole is only the beginning of the job. Some parts may require an ultra-tight tolerance, for which a Miniature Reamer (tolerances of +.0000″/-.0002″ for uncoated and +.0002″/-.0000″ for AlTiN Coated) can be used to bring a hole to size. harvey tool straight flute miniature reamer with dimension callouts

Tech Tip: In order to maintain appropriate stock removal amounts based on the reamer size, a hole should be pre-drilled at a diameter that is 90-94 percent of the finished reamed hole diameter.

Flat Bottom Counterbores

Other operations may require a hole with a flat bottom to allow for a superior connection with another part. Flat Bottom Counterbores leave a flat profile and straighten misaligned holes. For more information on why to use a Flat Bottom Counterbore, read 10 Reasons to Use Flat Bottom Tools.

harvey tool flat bottom counterbores with dimension callouts

Key Next Steps

Now that you’re familiar with miniature drills and complementary holemaking tooling, you must now learn key ways to go about the job. Understanding the importance of pecking cycles, and using the correct approach, is vital for both the life of your tool and the end result on your part. Read this post’s complement “Choosing the Right Pecking Cycle Approach,” for more information on the approach that’s best for your application.

Choosing the Right Pecking Cycle Approach

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Utilizing a proper pecking cycle strategy when drilling is important to both the life of your tool and its performance in your part. Recommended cycles vary depending on the drill being used, the material you’re machining, and your desired final product.

Start to Boost Your Accuracy with Harvey Tool’s Drilling Guidebook.

What are Pecking Cycles?

Rather than drill to full drill depth in one single plunge, pecking cycles involve several passes – a little at a time. Peck drilling aids the chip evacuation process, helps support tool accuracy while minimizing walking, prevents chip packing and breakage, and results in a better all around final part.

Miniature Drills

miniature drill pecking cycles

High Performance Drills – Flat Bottom

high performance drill pecking cycles

High Performance Drills – Aluminum & Aluminum Alloys

aluminum pecking cycles

Note: For hole depths 12x or greater, a pilot hole of up to 1.5X Diameter is recommended.

High Performance Drills – Hardened Steels

hardened steels chart
High Performance Drills – Prehardened Steels

prehardened steels chart

Key Pecking Cycle Takeaways

From the above tables, it’s easy to identify how recommended peck drilling cycles change based on the properties of the material being machined. Unsurprisingly, the harder the material is, the shorter the recommended pecking depths are. As always, miniature drills with a diameter of less than .010″ are extremely fragile and require special precautions to avoid immediate failure. For help with your specific job, contact the Harvey Tool Technical Team at 800-645-5609 or [email protected]

10 Reasons to Use Flat Bottom Tools

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Flat bottom tools, or tools with flat bottom geometry, are useful in a variety of situations and operations that tools with typical cutting geometry are not. The standard characteristics of drills or end mills are useful for their primary functions, but make them unsuitable for certain purposes. When used correctly, the following flat bottom tools can make the difference between botched jobs and perfect parts.

Flat Bottom Drills

Flat Bottom Drill

Flat bottom drills are perfect for tricky drilling situations or for creating flat bottom holes without secondary finishing passes. Consider using these specialized drills for the operations below.

infographic showing 5 different Flat Bottom Drill Operations

Thin Plate Drilling

When drilling through holes in thin plates, pointed drills are likely to push some material out the exit hole and create underside burrs. Flat bottom drills are significantly less likely to experience this problem, as their flat bottom geometry generates more even downward forces.

Crosshole Drilling

When drilling a hole that crosses the path of another hole, it is important to avoid creating burrs, since they can be extremely difficult to remove in this kind of cross section. Unlike drills with points, flat bottom drills are designed to not create burrs on the other side of through holes.

Irregular/Rounded Surface Drilling

Flat bottom drills initially engage irregular surfaces with their outer edge. Compared to making first contact with a standard drill point, this makes them less susceptible to deflection or “walking” on inclined surfaces, and more capable of drilling straighter holes.

Angled Drilling

Even if the surface of a part is flat or regular, a pointed drill is susceptible to walking if it engages the part at an angle, known as angled or tilted drilling. For the same reason flat bottom drills are ideal for drilling on irregular surfaces, they are perfect for angled drilling.

Half Hole Drilling

When drilling a half hole on the edge of a part, the lack of material on either side of the drill makes the operation unstable In this situation, a pointed drill is susceptible to walking. A flat bottom drill makes contact with its entire cutting geometry, allowing for more versatility and stability when drilling half holes.

Flat Bottom Counterbores

Flat Bottom Counterbore

Flat bottom counterbores are an excellent choice when a flat bottom hole is needed and a tool without flat bottom geometry was used to create it. Keep some of these tools on hand to be prepared for the operations below.

infographic showcasing 5 different uses of flat bottom counterbores

Bore & Finish Drilled Holes

Drill geometry is designed first and foremost for factors like stability, rigidity, and chip evacuation. Some holes will need secondary finishing operations. Flat bottom counterbores are often designed with a slow helix and low rake, which help them avoid part engagement and control finish.

Straighten Misaligned Holes

Even experienced machinists may drill a less-than-perfectly-straight hole or two in new and unfamiliar jobs. Fortunately, flat bottom counterbores are well-suited for straightening misaligned holes.

Spot Face & Counterbore on Irregular Surfaces

The unique geometry of flat bottom counterbores makes them  effective at spotting on irregular surfaces. Standard drills and spot drills are susceptible to walking on these kinds of surfaces, which can potentially ruin an operation.

Remove Drill Points

When a standard drill creates a hole (other than a through hole) it leaves a “drill point” at the bottom due to its pointed geometry. This is fine for some holes, but holes in need of a flat bottom will need a secondary operation from a flat bottom counterbore to remove the drill point.

Remove End Mill Dish

The dish angle present on most standard end mills allows proper end cutting characteristics and reduces full diameter contact. However, these end mills will naturally leave a small dish at the bottom of a hole created by a plunging operation. As with drill points, flat bottom counterbores are perfect to even out the bottom of a hole.

Most Common Methods of Tool Entry

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Tool entry is pivotal to machining success, as it’s one of the most punishing operations for a cutter. Entering a part in a way that’s not ideal for the tool or operation could lead to a damaged part or exhausted shop resources. Below, we’ll explore the most common part entry methods, as well as tips for how to perform them successfully.

Pre-Drilled Hole

Pre-drilling a hole to full pocket depth (and 5-10% larger than the end mill diameter) is the safest practice of dropping your end mill into a pocket. This method ensures the least amount of end work abuse and premature tool wear. It also facilitates smoother chip evacuation, reducing the risk of chip buildup and potential tool breakage. Machinists often use this technique when working with materials prone to chip welding or built-up edge formation, ensuring consistent machining performance.

tool entry predrill

Helical Interpolation

Helical Interpolation is a very common and safe practice of tool entry with ferrous materials. Employing corner radius end mills during this operation will decrease tool wear and lessen corner breakdown. With this method, use a programmed helix diameter of greater than 110-120% of the cutter diameter. Moreover, helical interpolation offers advantages in achieving precise surface finishes, making it a preferred choice for applications requiring high precision and surface quality, such as aerospace and medical device manufacturing.

helical interpolation

Ramping-In

This type of operation can be very successful, but institutes many different torsional forces the cutter must withstand. A strong core is key for this method, as is room for proper chip evacuation. Using tools with a corner radius, which strengthen its cutting portion, will help. Additionally, ramping-in allows for efficient material removal with reduced axial forces, minimizing workpiece distortion and enhancing dimensional accuracy. Machinists often employ this technique in contouring and pocketing operations, where maintaining part integrity is crucial.

ramping

Suggested Starting Ramp Angles:

Hard/Ferrous Materials: 1°-3°

Soft/Non-Ferrous Materials: 3°-10°

For more information on this popular tool entry method, see Ramping to Success.

Arcing

This method of tool entry is similar to ramping in both method and benefit. However, while ramping enters the part from the top, arcing does so from the side. The end mill follows a curved tool path, or arc, when milling, this gradually increasing the load on the tool as it enters the part. Additionally, the load put on the tool decreases as it exits the part, helping to avoid shock loading and tool breakage. Machinists often utilize this technique in mold making, die sinking, and 3D contouring operations, enhancing productivity and surface finish quality.

arching with end mill

Straight Plunge

This is a common, yet often problematic method of entering a part. A straight plunge into a part can easily lead to tool breakage. If opting for this machining method, however, certain criteria must be met for best chances of machining success. The tool must be center cutting, as end milling incorporates a flat entry point making chip evacuation extremely difficult. Drill bits are intended for straight plunging, however, and should be used for this type of operation.

tool entry

Straight Tool Entry

Straight entry into the part takes a toll on the cutter, as does a straight plunge. Until the cutter is fully engaged, the feed rate upon entry is recommended to be reduced by at least 50% during this operation. Machinists often resort to straight tool entry in simple machining operations with limited tool access or where other entry methods are impractical. However, it’s crucial to monitor tool wear and chip evacuation carefully to prevent chip buildup and potential tool breakage. Adjusting cutting parameters based on material properties and part geometry can further enhance machining efficiency and tool life.

tool entry

Roll-In Tool Entry

Rolling into the cut ensures a cutter to work its way to full engagement and naturally acquire proper chip thickness. The feed rate in this scenario should be reduced by 50%. Roll-in tool entry is particularly advantageous in slotting and profiling operations, where maintaining consistent chip thickness is critical for surface finish quality and dimensional accuracy. Machinists often utilize this technique in high-speed machining applications, maximizing material removal rates while minimizing tool wear and heat generation.

tool entry

Mastering various tool entry techniques is essential for machining success. By understanding and implementing these methods effectively, machinists can optimize performance while prolonging the lifespan of their tools. Continual evaluation of cutting conditions and adaptation of entry strategies based on material properties and part geometry are key to achieving superior machining results.

Overcoming Composite Holemaking Challenges

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Harvey Tool’s Miniature High Performance Composite Drills are specifically designed with point geometry optimized for the unique properties of composite materials. Our Double Angle style is engineered to overcome common problems in layered composites and our Brad Point style is built to avoid the issues frequently experienced in fibrous composites.

Common Composite Problems

Drilling in composite materials is a unique challenge. There are a wide variety of regularly machined composites, each requiring different considerations and approaches. Overcome common composite holemaking problems by identifying and selecting the right tool for your job.

Delamination

Defining Delamination

Delamination occurs when high drilling forces cause laminated layers to separate, yielding less structurally-sound parts. The more blunt a drill point is, the more force it will take to move through a part, increasing the chance of delamination.

Delamination and Push-Out

Identifying Delamination

The separation of layers may be difficult to identify through visible scrutiny. Closely inspecting and testing the hole quality is ideal when looking for delamination.

Ideal Drill Choice

Double Angle Composite Drills

Uncut Fibers

Defining Uncut Fibers

Uncut fibers are largely caused by dull tooling. If a drill’s cutting edge is not sharp enough, fibers will remain uncut, frayed, or splintered, potentially ruining the part.

Identifying Uncut Fibers

Uncut fibers should be easily noticed: look for splintered or frayed fibers around the edges of your hole.

Ideal Drill Choice

Brad Point Composite Drills

Tear-Out

Defining Tear-Out

Rather than leaving uncut fibers hanging on to a workpiece, dull tools can also grab fibers and tear them out of the material altogether. This can leave voids in your material and cause damage to even greater areas of the workpiece.

Tear Out

Identifying Tear-Out

Tear-out can be more difficult to spot than uncut fibers. However, it is often seen as an area of material completely removed around the edge of a hole.

Ideal Drill Choice

Brad Point Composite Drills

Choose Your Tool

Harvey Tool’s new Composite Drills are engineered with point geometry optimized for fibrous and layered composite materials. Each design is specifically built to overcome common composite drilling challenges and achieve excellent results.

Double Angle Composite Drills

Avoid Delamination and Push-Out

composite drills Harvey

v

Harvey Tool’s Double Angle Composite Drills help combat delamination and push-out in layered composite materials with specialized point geometry. The primary 130° point angle allows the drill to efficiently engage laminated composites without lifting the top layer of material. The shallower secondary 60° point angle reduces the amount of force required to move the drill through the material, further reducing the probability of delamination. The higher shear angle also aids in reducing push-out at the back of the workpiece by more gradually breaking through the part.

Brad Point Composite Drills

Avoid Uncut Fibers and Tear Out

composite drills

Harvey Tool’s Brad Point Composite Drills are designed specifically for superior performance in fibrous materials. The trident-like brad point ensures that holes in fiber filled and reinforced materials come out clear and free of fraying. The outer points accurately score the outer diameter of drilled holes, eliminating uncut fibers, tear-out, and splintering.

For more information on Composite Drills and all of Harvey Tool’s new products, visit the Harvey Tool website.