Every metal cutting operation requires selection of proper cutting parameters for success.  As a DML TA, you need to understand basic calculations that will allow the tools you use to work as intended.

Note that these speed and feed values are guidelines assuming adequate (flooded) lubrication, workpiece stiffness and drill depth less than 3 drill diameters (0.75″).  When applying oil manually (as in the lab), scale the feed and speed back to 60%, so N = 900 rpm and f = 3.6 in/min (final answer).

HSS bits can drill through hardwood and softwood. A titanium-coated HSS bit will perform better than a standard HSS when drilling hardwood.

Example 3: Calculate the speed and feed for a HSS countersink used to countersink a #10 clearance hole in aluminum using a manual milling machine.

First, lookup the recommended surface speed in Table 1 (V ≈ 625 ft/min) and calculate the spindle speed from Equation 2:

Next, lookup the recommended feed per tooth (chipload) in Table 3 (ft ≈ 0.008 in/tooth) and calculate the feed rate using Equation 3:

However, you can drill composite materials with a black oxide HSS drill bit. Manufacturers create the black oxide coating by heating the HSS to 950 degrees Fahrenheit. The black oxide reduces friction and makes the bit more corrosion- and wear-resistant.

TIP1: Recommended peck depth when drilling less than 3xD (e.g. 3 drill diameters) with flooded coolant is one drill diameter, or when applying oil manually, or under low pressure, is 50% of drill diameter.

First, lookup the recommended surface speed in Table 1 (V ≈ 250 ft/min) and calculate the spindle speed from Equation 2:

TIP: When working with plastics with good machinability, use the cutting parameters for aluminum up until the point that the plastic melts.

Standard HSS twist drill bits are unsuitable for composite, which contains a combination of two or more materials with different chemical and physical properties. A standard HSS bit will dull too quickly and generate excessive heat that damages the composite.

Example 2A: Calculate the speed and feed for a 1″ diameter, 4 flute HSS endmill in aluminum using a manual milling machine in lab.

Please begin by reviewing the comprehensive course document on this topic, as it clearly explains the process of calculating these parameters for drilling and milling operations.  The governing equations are summarized below.

* multiply feed values in table by 0.5 for difficult to machine materials, flexible toolholding or workpieces, or lighter-duty machines*

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Note that these speed and feed values are guidelines assuming adequate (flooded) lubrication and workpiece stiffness.  When applying oil manually (as in the lab), scale the feed and speed back to 60%, so N = 330 rpm and f = 2.0 in/min (final answer).

The table below contains a recommended surface speeds for common materials when using DML equipment.  These values are conservative because our primary goal is fostering a safe learning environment (for our users and our tools!), not trying to squeeze every second out of each operation.

First, lookup the recommended surface speed in Table 1 for a 1” HSS endmill cutting aluminum (V ≈ 250 ft/min) and calculate the spindle speed from Equation 2 using the aforementioned 75% speed reduction:

Next, calculate the feed rate used for plunging.  Remember annular cutters should be fed at approximately 25% of the feedrate for an equivalent sized endmill.  From Table 3, lookup the recommended feed per tooth for a 1″ HSS endmill (ft ≈ 0.008 in/tooth) and calculate the plunge feed rate using Equation 3:

We carry the best quality drill bits for metal work. Shop our selection of HSS drill bit sets today to ensure you have proper cutting tools in various sizes for all your projects.

High-speed steel (HSS) drill bits are a popular, versatile cutting tool that can help you cut precisely and efficiently. Coatings such as titanium and black oxide can make HSS suitable for drilling a wider range of materials. To work safely and get the most out of your tools, learn what an HSS drill bit is and when you would use it.

TIP: Countersinking should generally be performed at 25% of the speed and the same feed per revolution as the equivalent sized drill.

TIP: IF this was being performed on a CNC lathe, typical parting feed rates vary between 0.001 in/rev (for steels) and 0.005 in/rev (for plastics).  But remember, do NOT use the power feed when parting on a manual lathe unless you own the machine!

Note that these speed and feed values are guidelines assuming proper (flooded) lubrication, workpiece stiffness and depth of cut.  When applying oil manually (as in the lab), scale the feed and speed back to 60%, so N = 570 rpm and f ≈ 18 in/min (final answer).  Note also this problem assumes we peripheral milling versus plunge milling (since we never teach the students the latter in lab).

Next, lookup the recommended feed per tooth (chipload) in Table 3 (ft ≈ 0.004 in/tooth) and calculate the feed rate using Equation 3:

Note that these speed and feed values are guidelines assuming adequate (flooded) lubrication, workpiece stiffness and drill depth less than 3 drill diameters (0.75″).  When applying oil manually (as in the lab), scale the feed and speed back to 60%, so N = 450 rpm and f = 3.6 in/min (final answer).

HSS can drill into softer steels, iron, brass, copper, and aluminum alloy. Do not use standard HSS drill bits for harder metals or stainless steel. Instead, use a harder drill bit, such as cobalt, carbide, or a titanium-coated HSS.

Example 2B: Calculate the speed and feed for a 1/2″ diameter, 3 flute carbide endmill if peripheral and plunge cutting in aluminum using a CNC milling machine in lab.

TIP2: When drilling deeper holes (> 3xD) without high pressure TSC (thru spindle coolant), reduce spindle speed an additional 50%.

As you can see Acetal (Delrin) is one of the most machinable plastics and nylon is four times less machinable (which is why it should usually be avoided!).

Next lookup the recommended feed per revolution for the equivalent size drill bit in Table 2 (fr ≈ 0.006 in/rev) and calculate the feed rate using Equation 3:

An HSS drill bit is made of high-speed steel, and you can use it to drill wood, plastic, and softer metals. If you need a tougher bit, such as for hard metals or hardwood, you can successfully use a titanium-coated HSS drill bit. Also, you can cut composite materials using a black oxide HSS drill bit.

Note: since applying oil manually, scale the speeds back to 60%, so NALUM ≈ 1425 rpm and NSTEEL ≈ 570 rpm (final answer).  Note these are MAXIMUM values and lathe chuck safety must take precedence; spinning the lathe chuck at 570 rpm is about the upper limit of what we safely do in the lab, so for smaller or easier to machine workpieces, DO NOT EXCEED 600 RPM regardless of the calculation results, unless you are running a collet chuck.

A general rule of thumb for materials which are strong enough to support the drilling process is that fr is between 1 - 3% of the drill diameter, depending on the material strength.

Next lookup the recommended feed per revolution for the drill bit in Table 2 (fr ≈ 0.004 in/rev) and calculate the feed rate using Equation 3:

No drill bit will stay sharp forever, and resharpening your HSS drill bit is an essential maintenance requirement. Sharpen your drill bit to prevent damage to the tool and workpiece, optimize cutting efficiency, and ensure your safety. Use a specialized bit sharpener tool or sharpen the bit by hand with a belt sander or bench grinder.

TIP: Plunging should generally be performed at 75% of the speed and 25% of the feedrate of the calculated peripheral cutting parameters.

TIP2: Do not plunge an annular cutter at a feedrate less than 0.001 ipt (inch per tooth) in strain hardening materials like 304 stainless or titanium.

As this information shows, HSS bits are highly versatile, and you should equip your workshop with a high-speed steel drill bit set from Drill Bit Warehouse.

First, lookup the recommended surface speed in Table 1 (V ≈ 250 ft/min) and calculate the spindle speed from Equation 2:

First, lookup the recommended surface speeds in Table 1 (VALUM ≈ 625 ft/min, VSTEEL ≈ 250 ft/min (notice the 2.5 multiplier))

HSS can also drill plastic. Spur-point drill bits, called dowel bits, are best for drilling into plastic because twist drills are more likely to cause the plastic to break.

Note: when applying oil manually, scale the feed and speed back to 60%, so N ≈ 420 rpm and f ≈ 4.8 in/min (final answer).  This is close enough to 500 rpm that I would first try this tool at the low end of high range with good oil application and see how it goes.

TIP1: Since annular cutting is a plunging operation, it should generally be performed at 75% of the speed and 25% of the feedrate of the calculated peripheral cutting parameters (as with endmill plunging).

Note that these speed and feed values are guidelines assuming proper (flooded) lubrication, workpiece stiffness and depth of cut.  When learning how to use the CNC, always start lower (around 60% on the spindle speed and feedrate override buttons) and work your way up as you gain confidence or purchase your own tools (lol).

High-speed steel is carbon steel alloyed with more than seven percent tungsten or molybdenum, and it contains chromium, vanadium, and cobalt. This steel is called high-speed because it cuts faster than older high-carbon steel tools, such as those used in the 1940s.

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Example 4: Calculate the speed and feed for a 1″ diameter, 6 flute HSS annular cutter in ¼” thick aluminum on a manual milling machine in the lab.

HSS can withstand high temperatures, and the reliability of HSS makes it the most common drill bit material. HSS drill bits can cut various metals, wood, and plastic.

Example 5: Calculate the speeds for parting off 1” diameter aluminum and 1” diameter mild steel workpieces on the lathe using the standard carbide part-off inserts.

First, lookup the recommended surface speed in Table 1 (V ≈ 100 ft/min) and calculate the spindle speed from Equation 2:

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TIP: Reamers should generally be run at half the spindle speed and twice the feed per revolution of the equivalent sized drill bit.