Drill Speeds and Feeds Calculator [RPM, Chart, Formulas] - hss drill feeds and speeds

Whisker-reinforced ceramics have sufficient hardness (and more than sufficient toughness) to machine most of the materials where carbide tools lack hardness and CBN lacks toughness. In addition, the tooling costs associated with indexable ceramics are significantly lower per cutting edge than they are for CBN.

Just as the name implies, these long, skinny “bell hanger” wood drilling bits are used for electricians pulling wires or performing similar installation work. In addition to their long length, installer bits often feature a hole near the front of the bit for use with pulling wire.

As we mentioned above, twist drill bits (or “twist bits”) can range in price from affordable black oxide coated bits to expensive carbide bits used in milling. When it comes to choosing a drill bit for your wood project, a nice set of high-speed steel (HSS) bits should do just fine.

These bits perform double duty as they drill a pilot hole and countersink the hole at the same time. This ensures that the fastener head sits just below the surface of the wood.

“Current insert substrates and pressing technology allow for free-cutting positive geometry that doesn’t easily chip,” he said. “Positive geometry can even be added to inserts with negative basic shape or even tangentially mounted inserts.”

These odd-looking bits bore through wood or create flat-bottomed holes if the hole doesn’t go all the way through the piece. Use them when setting up cabinet hinges or similar applications.

Greenleaf Corp., Saegertown, Pa., is continually working to develop improvements in geometries to match the capabilities of its ceramic and carbide grades. The following is based on a written assessment of product and technology advances provided by the Greenleaf Applications Engineering Team.

“In turning, everybody has the same ISO standard toolholders so it’s technology like our Steadyline anti-vibration holders, Jet Stream tooling holders and second generation Duratomic coating that makes a big difference,” said Miller. “In milling, there have been many technological advancements as well as process improvements. Today, processes like dynamic milling require high-tech tools that take a full axial DOC and a light radial DOC at an extremely high feed rate.”

There is still room to maximize ceramic indexable tooling. “Unless we are running on state-of-the-art, purpose-built, latest generation machines, we are limited by the rigidity, dynamics or power when applying ceramic indexable tools. In an ideal environment we are able to turn Inconel 718 at 1,476 sfm (450 m/min) with WG-300, or at 820 sfm (250 m/min) with XSYTIN-1, but with a very heavy chip,” according to the team.

Spade bits have a broad, flat area for boring larger diameter holes in wood. The spade bit has no flutes so you may have to back off the bit as you go when drilling deeper holes. While a traditional spade bit has a perfectly flat face, products like the Bosch Daredevil spade bit feature a self-feed tip and a slightly curved face.

For deep-hole applications, Iscar offers a line of BTA drills in single-tube and double-tube variations; indexable gun-drills including the Sumo-Gun and Tri-Deep; and standard gundrills. Indexable reaming tools include the Bayo-T-Ream, Index-H-Ream, and Solid-H-Ream.

A hole saw uses a pilot twist bit to guide a large diameter rotary saw that removes a plug from the wood. This allows conduit or wires to pass through. You also use these bits when drilling out locksets for doors. You can find hole saws for both wood and metal.

Cutting tool improvements range from some actual grades that are being refined with additives in the substrate for better wet or dry machining to product upgrades. Improvements to Seco’s Perfomax indexable insert drill, for example, include an improved, highly polished body with wave pattern technology for chip evacuation, increased hardness for wear resistance and elimination of coating altogether.

According to Ewing, Iscar now offers indexable head drills from 0.157 -1.575″ (4.0-40.0 mm) dia. Most of that range is offered in 0.004″ (0.10 mm) increments. Drill bodies are offered in 1.5xD, 3xD, 5xD, 8xD and 12xD drilling depths with some bodies offering chamfer collars for combined operations. In addition, standard tooling designs are also being incorporated into special tool applications to increase productivity in medium to large quantity part runs. The special tool is often more expensive than a standard tool, but because it utilizes standard indexable carbide inserts the consumable costs can be greatly reduced.

Most of us are guilty of using the wrong tool for the job—either out of necessity or laziness. Still, there’s something satisfying about using the right tool for the job. Often, using the right tool helps bring about the best possible result. When drilling, accessories matter—possibly even more than the tool you choose. Knowing the various types of wood drilling bits and how to use the right one can really increase both speed and quality.

High speeds or high cutting forces amplify even the smallest instabilities in a machine, leading to deflection and, since the process is inherently cyclic, vibration. No matter how tough a ceramic is, vibration leads to irregular mechanical loads that bring about irregular wear that then translates into poor tool life.

Improvements in indexable cutting tools extend to virtually every cutting process. Until the day when it will be sufficient to establish a baseline for comparative and competitive tooling performance through data analytics (a distinct future possibility of digitization and the IIoT), cutting tool manufacturers will rely on tried-and-true processes.

“We are integrating the same positive cutting action and effective cutting rake angles of our single-sided insert cutters into our double-sided insert cutters. Incorporating the geometry of the single-side, four-edge square type insert into double-sided inserts allows you to get free cutting action and economy,” he said.

“These features have contributed to increases in operating parameters and tool life and resulted in innovations in indexable tools for holemaking,” said Craig Ewing, national product specialist-drilling for Iscar.

The purpose of the hole affects bit choice. Will the hole accommodate an anchor to hold a picture, will it be used for wire or conduit, does the fastener that goes in it need to be countersunk?

By now we think it’s clear when and how to use the right wood drilling bit.  Have anything to add from your experience? Sound off on Facebook, Twitter, and Instagram to let us know what you think!

Positive cutting geometry can maintain acceptable, if not increased, tool life and allows for lower horsepower cuts and less torque on the machines, according to Pollock. However, this can create a weak cutting edge.

Wood species are divided into the two general categories of softwoods and hardwoods, but there is also much hardness variation within those categories. The wood type makes a significant difference in bit choice. Drilling a soft pine will be much easier on a drill bit than drilling a hard hickory. You can drill softer wood with steel (although we’d recommend HSS for any job) but as the hardness increases, it must be matched by bit hardness. This means a titanium or black oxide coating is appropriate for hardwood.

Improvement in indexable tooling requires a holistic approach, according to John Winter, product management-East U.S. for toolmaker Sandvik Coromant, Fair Lawn, N.J. “We are pushing every aspect of the process to produce the best cutting tool solution possible, from coating technology to the macro and micro geometries that produce a stronger edge line to the post-treatment processes that give the coatings a harder, smoother surface.”

Self-feed bits can be a tad more aggressive than other large-diameter wood bits. They can also use either one or two cutting heads in addition to the perimeter cutting teeth. Check out our review of the Milwaukee self-feed bits and the Diablo SPEEDemon self-feed bits.

Within its milling family of products, Seco Tools is launching a double-sided face mill called the Double Quattromill 14, building on the success of its Double Quattromill 22 face mill for roughing and semi-finishing introduced at IMTS 2018 for heavy DOC machining.

“New indexable cutting tools often require faster spindle speeds, increased feed rates and multi-axis capabilities that today’s modern CNC machines are capable of to maximize their performance,” said Ewing. “For example, a 0.157″ [4[4-mm]umoCham drill can run above 11,000 rpm and up to 40 ipm [1[1 m/min]n mild steel. Even at the low end, you need more than 6,000 rpm for this tool. Some machines from 10-15 years ago would not be able to properly run this tool.

Iscar continues to expand the line of drilling tools with new cutting geometries. In the Sumo-Cham line there are different edge preps for steel (P), stainless steel (M), cast iron (K) and non-ferrous (N) materials.

They will mix and match data about chemical makeup, substrates, geometry and machine capability to advance technology the old-fashioned way—by R&D expertise, trial and error, internal testing and validation of new concepts in the field. Here’s how major cutting tool manufacturers are advancing the technology of indexable cutting tools.

In recent years, Iscar Metals Inc., Arlington, Texas, has made performance improvements by adjusting the alloying elements in tungsten carbide substrates, using new combinations of various coating layers and applying post-coating treatments. Iscar has also developed different edge prep geometries for a variety of material group applications.

WG-600, a coated whisker-reinforced ceramic, in particular is showing “outstanding performance in turning. Finally, applications where even large-grain carbide lacks toughness (heavy interruption, impurities, forging scale) can now be addressed with XSYTIN-1 where other ceramic and carbide tools break.”

Winter pointed to Sandvik Coromant’s CoroPlus digital machining system as an example. “With the use of CoroPlus, you can use machine analytics to see exactly where you can make improvements to maximize your production. CoroPlus is data-driven process control that will push the tools and machines to the highest level of productivity possible with modern tooling,” he said.

When it comes to performance of indexable cutting tools compared with brazed PCD, CBN and carbide tip tooling, “it’s a question of cost and application,” Winter said. “Anytime you can use an indexable tool, the cost will be lower. The performance is in the cutting material (PCD, CBN, or carbide) and it’s a matter of if the tool can fit into the application.”

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For drilling, along with the SumoCham and DR-Twist lines, Iscar offers the LogIQ-3-Cham, Cham-IQ Drill, Combi-Cham and Modu-Drill, as well as solid-carbide drills. The LogIQ-3-Cham three-flute drill offers higher feed rates due to the extra flute and creates more accurate holes in terms of diameter tolerance and roundness. The Modu-Drill series [1.299-1.575" (33-40 mm)] has interchangeable heads for different sizes and styles (Cham-IQ Drill, Combi-Cham and DR-DH).

Pollock said that there are some machines and applica-tions where the machines can push the capability of the tools in aluminum machining. “But I think the more common point is that modern cutting tools allow machines to do more. Carbide substrates and free-cutting geometry increase the capability of smaller machines to process a wider variety of materials and large parts,” he said.

Winter said that the latest developments for indexable milling, turning and drilling tools are more application-specific tools designed to perform a set operation at the highest level of performance. The processes will be optimized to maximize the machine tool, workholding and the tooling for a set application or component.

Another material that has not been an application area for ceramic indexable tooling is stainless steel. Duplex, 300 series and precipitation hardening steels are now being machined effectively with Greenleaf’s whisker-reinforced ceramics, according to the company.

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Before we get to drill bit types, you should be familiar with the various treatments drill bit manufacturers use to increase bit life and reduce friction. Drill bits are made from steel, high-speed steel (HSS)—which is steel alloyed with tungsten and/or molybdenum, HSS with a cobalt alloy, HSS with titanium coating, HSS with black oxide coating, or carbide tipped.

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This wood drilling bit’s distinguishing feature is in the name. The sharp point on a brad point bit helps position the bit for a precise hole. These bits don’t walk on you when you start a hole. This makes this the right wood drilling bit for when you need a truly accurate start.

No one can accuse cutting tool manufacturers of not trying every possible combination of coating, substrate, material and geometry in their quest to gain a competitive edge for their customers.

One example is boring a large bore where an indexable boring bar will fit vs. using a small bore where only a brazed tipped bar can fit. The same is true of milling and drilling. “Here you can find advancements with PCD-veined tools versus brazed tools where the PCD is pressed into the tool not brazed,” he said. “This allows us to shape the PCD to the mill or drill tip, giving these tools better performance.”

You’ll immediately notice a threaded tip on auger bits. This type of wood drilling bit uses the tip to quickly pull the bit through the wood. Auger bits maintain a constant flute throughout the length of the bit. These bits challenge cordless drills because they “force” the drill to maintain speed throughout the hole due to the self-feed tip.

Indexable cutting tools are being used for innovative applications. “The biggest advancement for indexable tooling is in the application of those tools,” said Winter. “We are getting away from the ISO standard and pushing the limits of both tools and machines with creative designs. PrimeTurning is a perfect example of this. Using multi-directional turning, we see big gains in productivity and tool life. It used to be that ISO milling was the popular choice but now you would be hard pressed to find ISO milling in shops. By looking outside of ISO turning, we can push the tools, machines and the limits of the carbide inserts.”

Brazed tooling is generally considered to have tighter tolerances since the assembled tool can be finished (ground and polished). These harder materials in brazed form are usually limited in the cutting geometry that can be used in the tool design. Indexable inserts have the opportunity of geometry pressed into the insert so that different machining applications can be handled simply by using a different insert with different geometry or grade.

“Today’s mill-turn machine offerings make it easy to combine many operations into one setup that often had to be done in multiple setups in the past. Iscar offers indexable tooling solutions that take advantage of these machine capabilities, such as multi-function tools for turning, facing and threading operations.”

Maximizing indexable cutting tool performance depends on whether or not operators are pushing their machines to their fullest potential for both tooling and process. “We need to educate our customers on best practices to be more aware of their machine utilization,” he said. “Many shop owners or plant managers can only give you an educated guess of their actual machine utilization and that utilization is sometimes much lower than they think. And on-lights, stopwatches and clipboards are being replaced by machines and tooling with sensors that can give thousands of data points.”

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“Indexable tooling exists for almost every type of application: milling, turning and grooving, drilling, slotting, boring, and reaming,” explained Luke Pollock, product manager, Walter USA LLC, Waukesha, Wis. “They all use different styles of inserts designed for the needs of the applications. Typically, indexable tooling is considered larger and therefore stronger, capable of taking higher horsepower cuts and higher material removal rates compared to solid tooling. As a result, indexable tools have become more competitive in applications traditionally dominated by round tools.”

Indexable tools can be used in almost every application. “We are seeing more use in high-speed aluminum machining,” he said. “Advances in insert geometry and grades, as well as balanced tools and rigid holding of the insert, allow indexable tools to be used at higher rpm and sfm. Aluminum machining can take advantage of high rpm and machine tool builders have been developing spindles to run at these speeds. Traditionally, solid tools would have to be used in these applications due to balance and rigidity.”

“We’re seeing a split in the market, a split where the indexables are being used for roughing and solid-carbide end mills do the finishing, especially as production components are becoming more near-net shape,” said Todd Miller, product marketing manager. “There is an equal need for indexables today as there is for solid tools.”

A related bit to the installer bit is the flex bit which just uses a flexible shaft to let you get into tight spaces as needed. These can exist in lengths up to 72-inches.

For deep-hole applications (>8xD), Iscar has also added double-margin drilling heads as well as inserts designed with self-centering, chip-splitting and flat-bottom geometries. In the DR-Twist line (four cutting edge inserts), there are geometries for general applications (medium to high feeds), soft materials (low to medium feeds) long-chipping materials (added chipbreakers) and aluminum (ground sharp edge, polished face).

Greenleaf’s latest advance and newest offering is the phase-toughened XSYTIN-1 ceramic which has “unprecedented edge strength, transverse rupture strength (the ability to support large forces, i.e. heavy chip flow), thermal shock resistance and toughness. XSYTIN-1 is also the most versatile ceramic in Greenleaf’s portfolio, successfully machining soft mild steel, weld-overlaid cobalt-based alloys and anything in between,” according to the Greenleaf team.

“Time is money. By pushing the machines and the machines pushing the tooling, we can meet the needs of our customers and help save time and be more profitable,” Winter explained.

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Often confused with a Forstner bit, self-feeding bits include a threaded tip like the auger bit. This pulls the bit through the wood. These bits are meant for holes that go all the way through the wood. This is exactly the right type of wood drilling bit when you want to make a lot of larger holes for rough-in. Typically, self-feed bits are used for boring larger holes.

“By pairing our patented Excelerator ball nose insert geometry with our WG-600 and XSYTIN-1 grades, we provide customers with the ability to mill hardened and difficult-to-machine materials with a full-radius ceramic indexable tool. Our Excelerator ball nose inserts with patented geometry offer better performance, longer tool life and superior cutting action across a wide variety of materials.”

“To be fair, there are other uncertainties that could be contributing to instability—lack of rigidity and vibration dampening in the fixture, for example,” according to the team. “Comparatively few machines are also equipped with high-pressure coolant, which is extremely beneficial in the rough- and medium-turning of heat-resistant superalloys in that it greatly improves chip management (and to some extent also improves the dissipation of heat from the tool).”

This is the type of bit that probably comes to mind first when you hear “drill bit.” It’s the most common type of bit and used for general purposes around the jobsite and home. Softwood can get stuck in the flutes, so gently remove it with a brush or by blowing it off.

Seco Tools LLC, Troy, Mich., has developed advanced coatings such as a Niobium PVD thin coating for machining titanium and plans further advances in its Duratomic aluminum oxide-based CVD coating for general types of steel and cast-iron machining.

Drill bits appropriate for wood drilling are steel, HSS, titanium coated, and black oxide coated. Those other bits work best for metals. We’ve written about black oxide coating and have reviewed the best drill bits as well as the best drill bits for metal.