Choosing Speeds, Using the Drill Bit Speed Chart

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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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.