Choosing Speeds

Using the Drill Bit Speed Chart

The chart shown in Figure 25 is intended as a guide only. Always follow the manufacturer's speed recommendations if provided with your drill bits, cutters, or hole saws. Exceeding the recommended speeds may be dangerous to the operator.

The speeds shown here are intended to get you started. The optimum speed will always depend on various factors, including tool diameter, drilling pressure, material hardness, material quality, and desired finish.

Often, when drilling materials other than wood, some type of lubrication is necessary.

Lubrication Suggestions

Wood

None

Plastics

Soapy Water

Brass

Water-Based Lubricant

Aluminum

Paraffin-Based Lubricant

Mild Steel

Oil-Based Lubricant

Larger bits turning at slower speeds tend to grab the workpiece aggressively. This can result in the operator's hand being pulled into the bit or the workpiece being thrown with great force. Always clamp the workpiece to the table to prevent injuries.

Twist/Brad Point Drill Bits

Soft Wood Hard Wood Plastic Brass Aluminum Mild Steel

1/16" – 3/16"

3000

2500

2500

2500

3000

2500

13/64" – 3/8"

2000

1500

2000

1250

2500

1250

25/64" – 5/8"

1500

750

1500

750

1500

600

11/16" – 1"

750

500

1000

400

1000

350

Spade/Forstner Bits

Soft Wood Hard Wood Plastic Brass Aluminum Mild Steel

1/4" – 1/2"

2000

1500

 

 

 

 

9/16" – 1"

1500

1250

 

 

 

 

1-1/8"1-7/8"

1000

750

 

 

 

 

2–3"

500

350

 

 

 

 

Hole Saws

Soft Wood Hard Wood Plastic Brass Aluminum Mild Steel

1/2" – 7/8"

500

500

600

600

600

500

1" – 1-7/8"

400

400

500

500

500

400

2" – 2-7/8"

300

300

400

400

400

300

3" – 3-7/8"

200

200

300

300

300

200

4" – 5"

100

100

200

200

200

100

Rosette Cutters

Soft Wood Hard Wood Plastic Brass Aluminum Mild Steel

Carbide Insert Type

350

250

 

 

 

 

One-Piece Type

1800

500

 

 

 

 

Tenon/Plug Cutters

Soft Wood Hard Wood Plastic Brass Aluminum Mild Steel

3/8" – 1/2"

1200

1000

 

 

 

 

5/8" – 1"

800

600

 

 

 

 

Figure 25. Drill bit speed chart.

G7947/G7948 12 Speed Floor Drill Press

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Grizzly G7947, G7948 instruction manual Choosing Speeds, Using the Drill Bit Speed Chart, Lubrication Suggestions

G7947, G7948 specifications

The Grizzly G7948 and G7947 are powerful, professional-grade milling machines designed for precision metalworking. These models cater to the needs of machinists and hobbyists alike, combining innovation with robust features ideal for various milling tasks.

The Grizzly G7948 is a vertical mill with a large working table, allowing users to handle bigger workpieces efficiently. It features a 2 HP motor, providing a spindle speed range from 50 to 3,000 RPM, enabling operators to tackle a wide range of materials and applications. The G7948’s dovetail column ensures stability and rigidity, minimizing vibrations during operation, which is crucial for achieving precision in milling tasks.

On the other hand, the Grizzly G7947 is a versatile combination of a lathe and a mill, perfect for those looking to maximize functionality in a smaller workspace. It also boasts a robust 1 HP motor, allowing for smooth operation with adjustable spindle speeds, enhancing its versatility. The G7947 is particularly user-friendly, featuring a quick-change tool post that facilitates faster tool swapping and changeovers, which is a significant advantage when working on multiple projects.

Both models come equipped with advanced features such as a digital readout (DRO) system that aids in precision measurements. The DRO provides real-time feedback on the machine's positioning, helping eliminate guesswork and ensuring accuracy. Additionally, the machines' power feed for the table enhances efficiency, making it easier for users to execute repetitive tasks without the strain of manual cranking.

Another notable characteristic of the Grizzly G7948 and G7947 is their user-friendly controls, designed with ergonomics in mind. The intuitive layout ensures that operators can easily navigate through the machine’s settings, allowing for quicker setup times and smoother workflow.

Lastly, the sturdy construction of both milling machines means they are built to withstand rigorous use, making them reliable choices for both industrial applications and serious hobbyists. These models exemplify Grizzly's commitment to quality and performance, making them exceptional additions to any workshop.