How to set drilling speed on a vertical drilling machine
Set the spindle speed on a Vertical Drilling Machine by selecting a cutting speed for the workpiece material and drill, calculating the corresponding revolutions per minute (rpm), and choosing an available machine setting close to that value. For a first trial, use the lower setting when the calculated speed falls between two fixed speeds. Secure the workpiece, drill a test hole, and adjust according to the tool and cutting conditions.
Calculate the spindle speed
Cutting speed describes how fast the cutting edge travels across the material; spindle speed describes how many times the drill rotates per minute. The drill diameter connects the two. Obtain a starting cutting speed from the drill manufacturer’s data for the specific material, tool material, coating, and cutting conditions. Then use:
Spindle speed (rpm) = (cutting speed in metres per minute × 1,000) ÷ (π × drill diameter in millimetres)
For example, if the selected cutting speed is 25 m/min and the drill diameter is 10 mm, the calculation gives approximately 796 rpm. On a machine with fixed settings of 630 and 800 rpm, 800 rpm is close to the calculated value. If the setup is less rigid or the material is difficult to machine, 630 rpm is a more cautious starting point.
For inch units, use rpm = (cutting speed in surface feet per minute × 12) ÷ (π × drill diameter in inches). Keep the units consistent; entering a diameter in millimetres into the inch formula produces the wrong speed.
These calculations apply to the cutting diameter. When using an annular cutter, use its outside diameter, not the diameter of the pilot pin or the solid core left inside the cutter. Follow the cutter manufacturer’s starting data: an annular cutter and a solid twist drill of the same diameter do not necessarily use the same cutting speed or feed.
Select a cutting speed that fits the job
The workpiece material is the starting point, but its condition matters. Harder or work-hardened material generally requires a lower cutting speed than a softer grade in the same family. Stainless steel also requires attention to feed: allowing the drill to rub without cutting can harden the surface and make the next pass more difficult.
Tool material changes the calculation. High-speed steel and carbide drills have different operating ranges, and coatings do not make every drill suitable for every material. Use data for the actual tool wherever possible. Reduce the starting speed when the tool is worn, the machine or workpiece is less rigid, or the drill extends unusually far from the spindle. A damaged drill should be replaced or correctly sharpened rather than compensated for indefinitely by changing rpm.
Diameter has a direct effect: at the same cutting speed, doubling the drill diameter halves the calculated rpm. A setting that cuts well with a small drill can overheat a larger drill in the same material. Recalculate when the diameter changes, including when moving from a pilot hole to a larger finishing drill.
Coolant and cutting fluid can affect the cutting-speed range, but they do not substitute for a suitable speed or adequate feed. Use only a fluid and delivery method compatible with the material, tool, machine, and work area. Keep fluid away from electrical components.
Set the speed on the machine
Read the speed chart and controls on the particular machine before making an adjustment. The available rpm values, control positions, and procedure differ between belt-driven, geared, and variable-speed machines.
- Stop the spindle. Isolate power before opening a belt cover or making any adjustment that requires access to moving parts. Wait until all rotating parts have stopped.
- For a belt-driven machine, use the speed chart to select the pulley combination. Release the belt tension, move the belt to the specified pulley steps, retension it as directed, and close the guard before restoring power.
- For a geared head, select the specified lever positions according to the machine instructions. Do not force a lever; follow the stated procedure for engaging gears and changing ranges.
- On a variable-speed machine, select the appropriate mechanical range if one is fitted, then set the speed using the control or display. The machine manual determines whether its speed control is adjusted while stopped or running.
A dial position is not necessarily an exact spindle rpm, particularly when a machine uses a separate gear range. Use the calibrated display or speed chart where available. If the actual speed is uncertain and accuracy matters, measure spindle speed with a suitable tachometer using the instrument’s safe operating procedure.
Secure the workpiece in a vise or with clamps, remove the chuck key, and make sure the drill and chuck are seated correctly before starting. Keep hands and loose clothing away from rotating parts. Stop the spindle before measuring the hole or clearing chips; use an appropriate tool or brush rather than bare hands.
When the calculated rpm is outside the available range
If the calculation falls below the machine’s minimum speed, do not assume that choosing the lowest setting makes the operation suitable. The drill may still be running above its recommended cutting speed. Select a machine with a lower speed range or reconsider the tooling and process using the tool manufacturer’s guidance.
If the calculated value exceeds the maximum speed, the highest available setting will produce a lower cutting speed than the calculated target. That can be acceptable, but cutting conditions and tool guidance still need attention. Do not increase feed simply to compensate for a low rpm; excessive force can stall the spindle or damage the drill.
For a magnetic-base machine, the listed unloaded speed is a range or reference measured without cutting, not proof of the speed under load. For example, the supplied specification for the Magnetic drill VD60 lists an unloaded range of 0–600 r/min. Confirm the applicable speed-control procedure and capacity for the exact machine and cutter before setting up. Magnetic holding also requires a suitable, clean contact surface and the securing method specified in the machine instructions.
Read the cut before changing the setting
Start the test hole with controlled feed and observe the sound, chip formation, and cutting action. A steady cut with chips leaving the hole is a more useful sign than rpm alone. Feed and speed are related, but they are separate adjustments: lowering rpm without correcting an excessively light feed can leave the drill rubbing.
A squealing sound or a polished hole bottom can indicate rubbing, a dull edge, insufficient feed, or an unsuitable speed. Stop and inspect the drill before changing settings. Blueing, smoke, or rapid edge wear suggests excessive heat; possible causes include excessive cutting speed, inadequate cutting fluid where needed, or chips trapped in the hole.
Chatter and an oversized hole are not automatically signs that speed is too high. A loose workpiece, excessive tool overhang, worn spindle, or poorly sharpened drill can produce similar symptoms. Stop the machine, correct the setup, and then retest. For deeper holes, withdraw the drill as needed to clear chips, following the tool supplier’s guidance; frequent unnecessary withdrawal can interrupt cutting and leave the tool rubbing on re-entry.
Once the test hole meets the required size and finish, record the material, drill specification, rpm, feed approach, and fluid used. Those details provide a reliable starting point for the next comparable job, while leaving room to adjust for differences in material condition and setup rigidity.
