BIZOMAT MAKEOS · Manufacturing
Broaching Plan (Pitch, Teeth, Force, Broach Length and Time)
What tooth pitch and how many teeth does this broach need, what pull does it take, how long is the broach, and how long does each part take?
Plan of an internal or surface broaching operation: tooth pitch from chip space and machine capacity (as the broach pitch tool), teeth engaged at once, the cutting force from the rise per tooth, width of cut and specific cutting resistance, the number of cutting teeth for the stock plus finishing teeth, the toothed length and stroke, and the floor-to-floor time from cutting and return speeds.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Length of cut | mm | Length of the surface being broached in the direction of travel. |
| Total depth to remove | mm | Total depth of material removed. |
| Rise per tooth | mm | Increase in height from one cutting tooth to the next. |
| Finishing (sizing) teeth | Number of teeth at the end with no rise, for size and finish. | |
| Width of cut | mm | Width cut by each tooth. |
| Specific cutting resistance | N/mm² | Resistance per unit chip area for the material at broaching chip thicknesses (your value). |
| Chip packing factor | Ratio of gullet space to chip volume the tooth must hold (about 3–5). | |
| Machine pull capacity | t | Pull or push capacity of the broaching machine. |
| Approach and clearance travel | mm | Extra stroke for approach and clearance. |
| Machine stroke | mm | Longest stroke the machine allows. |
| Cutting speed | m/min | Cutting speed of the broach. |
| Return speed | m/min | Return speed. |
| Load and unload time | min | Time to load and unload a part. |
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: Length of cut
- What it is
- The length of the surface being broached, measured in the direction the broach travels. It decides how many teeth are in the cut at once.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 2000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 50 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A longer cut needs a larger pitch for chip room and a longer stroke.
- Get it right
- Measure along the broach travel, not across the cut; for a hole this is the hole length.
What this means: Total depth to remove
- What it is
- The total depth of material the broach must remove from the starting surface to the finished size, measured on one side of the cut.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 50 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1.5 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- More stock needs more cutting teeth and a longer broach.
- Get it right
- For a round hole, use the depth on one side (finished minus starting diameter, halved), not the diameter difference.
What this means: Rise per tooth
- What it is
- How much higher each cutting tooth stands than the one before it, which is the chip thickness each tooth takes.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.005 mm to 1 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.05 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A larger rise means fewer teeth and a shorter broach, but more force per tooth.
- Get it right
- This is per tooth, not the total stock; the tool divides the stock by it to count the cutting teeth.
What this means: Finishing (sizing) teeth
- What it is
- The teeth at the end of the broach that have no rise. They do not remove stock but size and finish the surface, and they add to the broach length.
- Units and format
- Enter a plain number with no unit. The form accepts 0 to 50. Use a whole number. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 4 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Each finishing tooth adds one pitch to the toothed length.
- Get it right
- Count only the zero-rise sizing teeth here; the cutting teeth are worked out from the stock and rise.
What this means: Width of cut
- What it is
- The width of the chip each tooth cuts, measured across the cut at right angles to the travel. For a round hole it is the cutting edge length around the hole.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 2000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 20 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The cutting force rises in direct proportion to the width.
- Get it right
- For a round internal broach, the width is the circumference of the hole (π × diameter), not the diameter.
What this means: Specific cutting resistance
- What it is
- The force needed to cut one square millimetre of chip cross-section in this material at broaching chip thicknesses. It converts chip area into cutting force.
- Units and format
- Enter a number in N/mm²: newtons per square millimetre (equal to MPa). The form accepts 0.000001 N/mm² to 10000 N/mm². Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 2000 N/mm² as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The cutting force is directly proportional to it.
- Get it right
- Use a value for thin chips like the rise per tooth; values for turning or milling at heavier chips are usually lower.
What this means: Chip packing factor
- What it is
- How many times larger the gullet between teeth must be than the solid volume of chip it collects, because curled chips take up much more room than solid metal.
- Units and format
- Enter a plain number with no unit. The form accepts 2 to 10. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 4 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A larger factor raises the smallest pitch for chip space.
- Get it right
- Use a value suited to the chip form of your material; ductile materials that form loose curls need more room.
What this means: Machine pull capacity
- What it is
- The rated pull or push force of the broaching machine, compared with the cutting force of all the teeth engaged at once.
- Units and format
- Enter a number in t: tonnes. The form accepts 0.000001 t to 1000 t. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 10 t as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A smaller capacity can force a coarser pitch so fewer teeth cut at once.
- Get it right
- Enter the rating in tonnes-force as marked on the machine; the tool converts it using 1 t = 9.81 kN.
What this means: Approach and clearance travel
- What it is
- The extra travel added to the stroke so the broach can enter the part and clear it fully, beyond the toothed length and the length of cut.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0 mm to 1000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 20 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- It adds directly to the stroke and the cycle time.
- Get it right
- Include the pull-end or follower movement your fixture needs.
What this means: Machine stroke
- What it is
- The longest stroke the broaching machine can make, compared with the stroke this broach needs.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 10000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1200 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Use the usable stroke from the machine specification, not the slide length.
What this means: Cutting speed
- What it is
- The speed of the broach during the cutting stroke, set for the tool material and workpiece.
- Units and format
- Enter a number in m/min: metres per minute. The form accepts 0.000001 m/min to 60 m/min. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 6 m/min as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A higher speed shortens the cutting part of the cycle.
- Get it right
- This is metres per minute; the tool converts the stroke from millimetres.
What this means: Return speed
- What it is
- The speed of the broach or slide on the return stroke, when no cutting takes place.
- Units and format
- Enter a number in m/min: metres per minute. The form accepts 0.000001 m/min to 100 m/min. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 20 m/min as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A faster return shortens the cycle time.
- Get it right
- Use the machine’s return speed setting, which is usually faster than the cutting speed.
What this means: Load and unload time
- What it is
- The handling time per part spent loading the workpiece, unloading it and resetting the broach, added to the stroke times.
- Units and format
- Enter a number in min: minutes. The form accepts 0 min to 60 min. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.3 min as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- It adds directly to the time per part.
- Get it right
- Enter minutes, not seconds: 30 seconds is 0.5 minutes.
Method and formulas
- Pitch from chip space p = 3√(L × rise × F_p); pitch for capacity p = rise × L × b × k_c ÷ (9810 × capacity); the larger (and at least 5 mm) is used (as the broach pitch tool).
- Teeth engaged at most = ⌈L ÷ p⌉; force = teeth engaged × rise × b × k_c.
- Cutting teeth = stock ÷ rise (rounded up); toothed length = (cutting + finishing teeth) × p; stroke = toothed length + L + approach.
- Time = stroke ÷ v + stroke ÷ v_return + load time.
- Example: a 9.4868 mm pitch keeps 6 teeth cutting at 12 kN; the broach is 322.55 mm long and a part takes 0.38505 min.
Limitations
- Constant rise per tooth; progressive and rotor-cut broaches differ.
- Cutting resistance depends strongly on material, rise and sharpness.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Lay out a broach for a keyway, spline or flat
- Check a broaching machine’s pull and stroke
- Estimate broaching cycle time
Who it is for
- Tool designers
- Process planners
- Manufacturing engineers
What you get
- Tooth pitch and teeth engaged
- Cutting force against the machine
- Broach length, stroke and time per part
Interpreting the result
- A finer pitch puts more teeth in the cut, raising force but improving guidance and finish.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 980–990. Topic reference; no source tables or recommended settings are reproduced.
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Open the Broaching Plan (Pitch, Teeth, Force, Broach Length and Time) calculator