Spot Drilling: The First Step to Precision Drilling

Drilling an ultra-precise hole can be tough. Material behavior, surface irregularities, and drill point geometry can all be factors leading to inaccurate holes. A Spot Drill, if used properly, will eliminate the chance of drill walking and will help to ensure a more accurate final product.

Valor Holemaking’s High Performance Spotting Drills Are Fully Stocked & Ship The Day of Your Purchase

Choosing a Spot Drill

Ideally, the center of a carbide drill should always be the first point to contact your part. Therefore, a spotting drill should have a slightly larger point angle than that of your drill. Common drill point angles range from 118° to 140° and larger. Shallower drill angles are better suited to harder materials like steels due to increased engagement on the cutting edges. Aluminums can also benefit from these shallower angles through increased drill life. While these drills wear less and more evenly, they are more prone to walking, therefore creating a need for a proper high performance spot drill in a shallow angle to best match the chosen drill.

Five Valor holemaking high performance spot drills displayed on top of a workpiece with a purple product packaging container in front

If a spotting drill with a smaller point angle than your drill is used, your drill may be damaged due to shock loading when the outer portion of its cutting surface contacts the workpiece before the center. Using a drill angle equal to the drill angle is also an acceptable situation. Figure 1 illustrates the desired effect. On the left, a drill is entering a previously drilled spot with a slightly larger angle than its point. On the right, a drill is approaching an area with an angle that is far too small for its point.

Proper Spot Angle Diagram

Marking Your Spot

A Spotting Drill’s purpose is to create a small divot to correctly locate the center of a drill when initiating a plunge. However, some machinists choose to use these tools for a different reason – using it to chamfer the top of drilled holes. By leaving a chamfer, screw heads sit flush with the part once inserted.

Spot Drill

What Happens if I Use a Spot Drill with an Improper Angle?

Using a larger angle drill will allow the drill to find the correct location by guiding the tip of the drill to the center. If the outer diameter of a carbide drill were to contact the workpiece first, the tool could chip. This would damage the workpiece and result in a defective tool. If the two flutes of the drill were slightly different from one another, one could come into contact before the other. This could lead to an inaccurate hole, and even counteract the purpose of spot drilling in the first place.

spotting drill ad

Avoiding CNC Drill Walking With a Spotting Drill

Few CNC machining applications demand precision like drilling. The diameter hole size, hole depth, part location, and finish are all important and provide little recourse if not up to specifications. That said, accuracy is paramount – and nothing leads to inaccurate final parts faster than drill walking, or the inadvertent straying from a drill’s intended location during the machining process. So how does drill walking occur, and how can one prevent it?

To understand drill walking, think about the act of striking a nail with a hammer, into a piece of wood. Firm contact to a sharp nail into an appropriate wood surface can result in an accurate, straight impact. But if other variables come into play – an uneven surface, a dull nail, an improper impact – that nail could enter a material at an angle, at an inaccurate location, or not at all. With CNC Drilling, the drill is obviously a critical element to a successful operation – a sharp, unworn cutting tool – when used properly, will go a long way toward an efficient and accurate final part.

To mitigate any variables working against you, such as an uneven part surface or a slightly used drill, a simple way to avoid “walking” is to utilize a Spotting Drill. This tool is engineered to leave a divot on the face of the part for a drill to engage during the holemaking process, keeping it properly aligned to avoid a drill from slipping off course.

When Won’t a Spot Drill Work for My Application?

When drilling into an extremely irregular surface, such as the side of a cylinder or an inclined plane, this tool may not be sufficient to keep holes in the correct position. For these applications, flat bottom versions or Flat Bottom Counterbores may be needed to creating accurate features.

Harvey tool spot drill zoomed in on the tip of the drill
Harvey Tool Spot Drill

Titan USA Carbide Drills: Jobber, Stub, & Straight Flutes

When navigating Titan USA’s offering of carbide drills, it is imperative to understand the key differences among the three carbide drill styles: Jobber Length, Stub Length, and Straight Flute Drills. The right drill for your application depends on, among other factors, the material you are working in, the job requirements, and the required accuracy.

PRO TIP:

Chip evacuation can be an obstacle for hole making. Pecking cycles can be used to aid in chip removal. Peck cycles are when the drill is brought in and out of the hole location, increasing depth each time until the desired depth is reached. However, pecking cycles should only be used when necessary; this process increases cycle time and subjects the tool to added wear from the repeated engaging and disengaging.

Jobber Length Drills

Titan USA jobber length drill

A carbide Jobber Length Drill is the standard general-purpose drill within Titan USA’s offering. It has a long flute length and an included angle of 118o. These drills are great for general purpose drilling where the tolerances are not as tight as the Stub Drill or Straight Flute Drill. Due to the length of these drills, however, they will be more affected by any lack of rigidity in the set up and can have higher runout, or straying from a desired location, during the drilling operation.

PRO TIP:

To achieve high accuracy and great finish, consider utilizing a Reamer. Reamers are designed to remove a finite amount of material but bring a hole to a very specific size. To do this, first drill 90% – 94% of the desired hole diameter with a Jobber Drill. After 90% – 94% of the material is removed, go in for a finishing pass with a Reamer. Reaming tools are highly accurate and leave a beautiful finish.

Stub Length Drills

Titan USA stub length drill

Titan USA carbide Stub Length Drills have a shorter flute length, wider included point angle, and a significant drop in helix angle, when compared to Jobber Length Drills. The shorter length and wider tip create for a more rigid tool and, in turn, more accurate holes. The stub drill is the best option when drilling with tight tolerances on shallower holes.

Straight Flute Drills

Titan USA straight flute drill

Carbide Straight Flute Drills have the smallest core of the three drill types mentioned within this post. Titan USA offers Straight Flute Drills with 2 flutes and a 140o included angle. These drills are designed for hole making in materials that create short chips. Materials in which the Straight Flute Drill typically performs best include cast aluminums and cast irons, as well as copper. In addition, this type of drill can work very well in high hardness materials, but the core diameter should first be adjusted to accommodate the increased hardness. For these difficult to machine materials, casting the part with a core hole and then opening it up with the Straight Flute is a great option. This removes some of the stress caused by chip removal and allows for the drill to do what it does best.

Chip removal can be more difficult in this style of carbide drill because the chips are not guided along a helix. With helix flutes, the motion of chip removal is mostly continuous from their initiation point, through the flute valleys, and finally out of the flute valleys. The helix creates a wedge which helps push the chips along, but the straight flute does not have that. It interrupts that natural turning motion created by the drill face which can affect chip evacuation. Due to the interruption in motion this type of drill is better suited for applications involving chips of smaller size.

PRO TIP:

Helix drills create multiple different forces on the part, which can create micro imperfections. The Straight Flute Drills do not create those forces, so the finish is much more consistent down to the micro level. The margins of the Straight Flute Drill also burnish the inside of the hole as they spin, which improves the finish as well. When comparing the Straight Flute Drill to a helix drill, the length of the overall contact point is much shorter in the Straight Flute Drill, and has less heat generation. The decreased heat will also reduce the probability of work hardening.

Selecting Your Perfect Titan USA Carbide Drill

Selecting the correct carbide drill for your application is a crucial step in hole making. The Jobber Drill is a great general-purpose drill and should be utilized in applications requiring long reach. The Stub Drill increases the rigidity with its shorter length of flute, allowing it to drill with higher accuracy. Applications which involve tight tolerances and more shallow holes can be done with the Stub Drill for high-quality results. Lastly, for difficult to machine and hard materials, the Straight Flute Drill is the perfect solution. When the core diameter and chip evacuation is properly addressed, the Straight Flute Drill produces beautifully consistent surface finish and extremely tight tolerances. Similarly, Titan USA offers its carbide drills in both an uncoated option, and AlTiN coating. Traditionally, uncoated tools are general purpose workhorses in a wide variety of materials both ferrous and non-ferrous. AlTiN or Aluminum Titanium Nitride is an enhanced coating specifically made for ferrous materials that extends tool life and performance across a wide range of steels and their alloys.

For more information on Titan USA Drills, and to view its full selection, click here.

Drill / End Mills: Drill Style vs. Mill Style

Drill / End Mills are one of the most versatile tools in a machinist’s arsenal. These tools can perform a number of different operations, freeing space on your carousel and improving cycle times by limiting the need for tool changes. These operations include:

  1. Drilling
  2. V-Grooving
  3. Milling
  4. Spot Drilling
  5. Chamfering

Shop Harvey Tool Dill/End Mills Today – Fully Stocked in Multiple Styles

The ability of the Drill / End Mill to cut along the angled tip as well as the outer diameter gives it the range of operations seen above and makes it an excellent multi-functional tool.

drill mill operations

Drill Style vs. Mill Style

The main difference between Drill / End Mill styles is the point geometry.  They are defined by how the flutes are designed on the end of the tool, using geometry typically seen on either an end mill or a drill.  While mill style tools follow the features of an end mill or chamfer mill, the drill style geometry uses an S-gash at the tip.  This lends strength to the tip of the tool, while giving it the ability to efficiently and accurately penetrate material axially.  While both styles are capable of OD milling, mill style tools will be better for chamfering operations, while drill style will excel in drilling.  The additional option of the Harvey Tool spiral tipped Drill / End Mill is an unprecedented design in the industry.  This tool combines end geometry taken from our helical flute chamfer cutters with a variable helix on the OD for enhanced performance. Versatility without sacrificing finish and optimal performance is the result.

drill mills
Left to Right: 2 Flute Drill Style End, 2 Flute Mill Style End, 4 Flute Mill Style End

Drill Mills: Tool Offering

Harvey Tool currently offers Drill / End Mills in a variety of styles that can perform in different combinations of machining applications:

Mill Style – 2 Flute

This tool is designed for chamfering, milling, drilling non-ferrous materials, and light duty spotting. Drilling and spotting operations are recommended only for tools with an included angle greater than 60°. This is a general rule for all drill mills with a 60° point. Harvey Tool stocks five different angles of 2 flute mill-style Drill / End Mills, which include 60°, 82°, 90°, 100° and 120°. They are offered with an AlTiN coating on all sizes as well as a TiB2 coating for cutting aluminum with a 60° and 90° angle.

drill mill

Mill Style – 4 Flute

4 flute mill-style Drill / End Mills have two flutes that come to center and two flutes that are cut back. This Drill / End Mill is designed for the same operations as the 2 flute style, but has a larger core in addition the higher flute count. The larger core gives the tool more strength and allows it to machine a harder range of materials. The additional flutes create more points of contact when machining, leading to better surface finish. AlTiN coating is offered on all 5 available angles (60°, 82°, 90°, 100°, and 120°) of this tool for great performance in a wide array of ferrous materials.

drill mill

Drill Style – 2 Flute

This tool is specifically designed for the combination of milling, drilling, spotting and light duty chamfering applications in ferrous and non-ferrous materials. This line is offered with a 90°, 120°, and 140° included angle as well as AlTiN coating.

drill mills drill style

Helical Tip – 4 Flute

The Helically Tipped Drill / End Mill offers superior performance in chamfering, milling and light duty spotting operations. The spiral tip design allows for exceptional chip evacuation and surface finish. This combined with an OD variable helix design to reduce chatter and harmonics makes this a valuable tool in any machine shop. It is offered in 60°, 90°, and 120° included angles and comes standard with the latest generation AlTiN Nano coating that offers superior hardness and heat resistance.

Selecting the Right Harvey Tool Miniature Drill

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.

spotting drill

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.

spotting drill correct 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?

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.

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.

miniature drill coolant through

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.

flat bottom drill

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.

drill for aluminum

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.

drill for hardened steel

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.

drill for prehardened steel

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. miniature reamer

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.

flat bottom counterbores

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.

10 Reasons to Use Flat Bottom Tools

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.

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.

Flat Bottom Counterbore Operations

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.