BIZOMAT MAKEOS · Manufacturing
Spade Drilling Plan (Speed, Power, Thrust, Time)
At my cutting speed and feed, what power and thrust does this spade drill need, will the machine take it, and how long is each hole?
Plan for drilling a large hole with a spade drill: spindle speed from the cutting speed held to the machine maximum, metal removal rate, cutting and motor power with a tool wear allowance and thrust (as the spade drilling power tool), drilling time for the depth plus approach, checked against the motor power and the machine’s thrust limit.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Drill diameter | mm | Diameter of the spade drill. |
| Cutting speed | m/min | Cutting speed at the drill periphery (your value for the material). |
| Feed per revolution | mm/rev | Feed per spindle revolution. |
| Hole depth | mm | Depth of the hole. |
| Approach and breakthrough | mm | Extra travel for approach and breakthrough. |
| Unit power of the material | kW per cm³/min | Unit power of the work material. |
| Machine mechanical efficiency | Mechanical efficiency of the spindle drive. | |
| Allowance for tool wear | % | Extra power and thrust for a worn drill. |
| Machine | ||
| Largest spindle speed | rpm | Highest spindle speed of the machine. |
| Motor power available | kW | Spindle motor power. |
| Largest feed thrust | N | Largest thrust the feed drive and spindle bearings take. |
What each input means
Open an input to see what it is, its units, the worked example and the common mistakes, with a small diagram.
What this means: Drill diameter
- What it is
- The diameter of the spade drill blade, which is the diameter of the hole it cuts.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 300 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 40 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Removal rate, power and thrust rise with diameter; spindle speed falls for the same cutting speed.
What this means: Cutting speed
- What it is
- The surface speed at the outer corners of the drill blade, chosen for the work and tool material from the tool maker’s data.
- Units and format
- Enter a number in m/min: metres per minute. The form accepts 0.000001 m/min to 1000 m/min. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 30 m/min as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Higher speed raises spindle rpm and power and shortens the drilling time, until the spindle speed limit is reached.
- Get it right
- Enter metres per minute, not spindle rpm; the tool converts it.
What this means: Feed per revolution
- What it is
- How far the drill advances into the hole for each spindle revolution, from the tool maker’s data.
- Units and format
- Enter a number in mm/rev: millimetres per revolution. The form accepts 0.000001 mm/rev to 5 mm/rev. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.3 mm/rev as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Power and thrust rise in proportion to feed; drilling time falls.
- Get it right
- This is per revolution, not per cutting edge or per minute.
What this means: Hole depth
- What it is
- The depth of the hole to be drilled, measured along the drill axis.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 5000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 60 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Drilling time rises in proportion to depth plus approach.
What this means: Approach and breakthrough
- What it is
- The extra drill travel beyond the hole depth for the approach to the surface and for the point to break through.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0 mm to 500 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 5 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Include the length of the drill point for a through hole.
What this means: Unit power of the material
- What it is
- The power needed to remove one cubic centimetre of the work material per minute, from machinability data for the material and its hardness.
- Units and format
- Enter a number in kW per cm³/min: kW per cm³/min. The form accepts 0.000001 kW per cm³/min to 1 kW per cm³/min. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.0359 kW per cm³/min as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Power and thrust rise in proportion to it.
- Get it right
- Check the unit: power per cm³/min, not per in³/min or per mm³/s.
What this means: Machine mechanical efficiency
- What it is
- The mechanical efficiency of the spindle drive: cutting power at the drill divided by motor power, from the machine maker or your own measurements.
- Units and format
- Enter a plain number with no unit. The form accepts 0.3 to 1. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.8 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Motor power = cutting power ÷ efficiency, so a lower efficiency needs more motor power.
- Get it right
- Enter it as a fraction (for example 0.8 for 80 %), not as a percentage.
What this means: Allowance for tool wear
- What it is
- An allowance added to the power and thrust for the extra cutting force of a worn drill compared with a sharp one.
- Units and format
- Enter a number in %: percent: the number is read as a percentage, so type 8 for 8 %. The form accepts 0% to 100%. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 25% as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Power and thrust rise by this percentage.
- Get it right
- Type the percentage on top of the sharp-tool value.
Machine
What this means: Largest spindle speed
- What it is
- The highest spindle speed the machine can run, from its specification. The tool holds the speed to this value if the cutting speed asks for more.
- Units and format
- Enter a number in rpm: revolutions per minute. The form accepts 0.000001 rpm to 100000 rpm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 3000 rpm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Motor power available
- What it is
- The power of the spindle motor available for drilling, from the machine’s specification or rating plate.
- Units and format
- Enter a number in kW: kilowatts. The form accepts 0.000001 kW to 10000 kW. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 15 kW as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Largest feed thrust
- What it is
- The largest axial thrust the machine’s feed drive and spindle bearings can take, from the machine specification.
- Units and format
- Enter a number in N: newtons. The form accepts 0.000001 N to 10000000 N. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 20000 N as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Enter newtons; a rating in kilonewtons or kilograms-force must be converted.
Method and formulas
- n = min(1000 v_c ÷ π D, n_max).
- MRR = π D² ÷ 4 × f × n; cutting power = unit power × MRR × wear allowance; motor power = cutting ÷ efficiency; thrust from the handbook relation for spade drills (as the spade drilling power tool).
- Time = (depth + approach) ÷ (f × n).
- Example: at 238.73 rpm the drill needs 5.0484 kW and 12,116 N thrust; each hole takes 54.454 s.
Limitations
- Through or blind holes with good chip removal; deep holes need pecking or coolant-fed drills.
- Unit power and wear allowance as entered.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Check a machine for large-diameter drilling
- Set feed so the thrust stays within the spindle limit
- Estimate drilling time
Who it is for
- Machinists
- Process planners
- CNC programmers
What you get
- Spindle speed and metal removal rate
- Motor power and thrust
- Drilling time
Interpreting the result
- If the thrust is too high, reduce the feed: thrust falls in proportion while the power falls too.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1077–1079. Topic reference; no source tables or recommended settings are reproduced.
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Open the Spade Drilling Plan (Speed, Power, Thrust, Time) calculator