KEVOS® MAKEOS · Manufacturing
Cutting Insert Consumption and Reorder Plan (Tool Life, Parts per Edge, Monthly Use, Reorder Point)
At this cutting speed, how many parts does each insert edge make, how many inserts will I use each month and what do they cost per part, and is my stock above the reorder point?
Consumption plan for indexable inserts on a turning operation: spindle speed and cutting time per part (as the turning cost tool), Taylor tool life at the cutting speed (as the Taylor tool life tool), the share of life used before indexing, whole parts per edge, inserts per month and per day, insert cost per part and per month, then the safety stock for a service level and the reorder point over the supplier lead time (as the safety stock and reorder point tools), against the inserts on hand.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Cutting speed | m/min | Cutting speed used on the job. |
| Taylor exponent n | Taylor exponent for this insert grade and workpiece material, from your own tool-life tests or the tool maker. | |
| Taylor constant C (speed for 1 min life) | m/min | Taylor constant: the cutting speed that would give one minute of tool life. |
| Share of tool life used before indexing | % | Share of the Taylor life you let an edge run before indexing (below 100 % to avoid edge breakdown). |
| Cut per part | ||
| Workpiece diameter | mm | Diameter being turned. |
| Length of cut per pass | mm | Length of each pass. |
| Feed | mm/rev | Feed per revolution. |
| Passes per part | passes | Passes per part with this insert. |
| Cutting edges per insert | edges | Usable cutting edges on each insert. |
| Insert price | AUD | Price of one insert, ex GST. |
| Demand and supply | ||
| Parts per month | parts | Parts made each month. |
| Working days per month | days | Working days in a month. |
| Supplier lead time | working days | Working days from placing an order to receiving the inserts. |
| Day-to-day variation in insert use (coefficient of variation) | % | Standard deviation of daily insert use as a share of the average (from usage records). |
| Service level (chance of not running out in a lead time) | choice | Chance of not running out during a lead time. |
| Inserts on hand | inserts | Inserts in the crib and at the machines now. |
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: Cutting speed
- What it is
- The surface speed at which the insert cuts the workpiece, which sets both the spindle speed and, through the Taylor equation, how long each edge lasts.
- Units and format
- Enter a number in m/min: metres per minute. The form accepts 0.000001 m/min to 5000 m/min. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 200 m/min as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Tool life falls steeply with speed, so parts per edge drop and insert use and the reorder point rise.
- Get it right
- Use the speed actually programmed, not the catalogue starting value; operators often adjust it.
What this means: Taylor exponent n
- What it is
- The exponent in the Taylor tool-life equation V Tⁿ = C, describing how sharply tool life falls as cutting speed rises for this insert grade and workpiece material.
- Units and format
- Enter a plain number with no unit. The form accepts 0.05 to 1. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.25 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A smaller exponent makes tool life far more sensitive to the speed.
- Get it right
- Fit it from two or more tool-life tests (the Taylor tool life tool does this) rather than borrowing a value for another grade.
What this means: Taylor constant C (speed for 1 min life)
- What it is
- The constant in the Taylor tool-life equation: the cutting speed at which an edge would last one minute for this insert grade, material and wear criterion.
- Units and format
- Enter a number in m/min: metres per minute. The form accepts 0.000001 m/min to 100000 m/min. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 400 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 constant lengthens tool life at the same speed, cutting insert use.
- Get it right
- It must come from the same tests as the exponent; constants from different sources do not mix.
What this means: Share of tool life used before indexing
- What it is
- The share of the Taylor tool life an edge is allowed to run before it is indexed, kept below the full life so edges are changed before they chip or break.
- Units and format
- Enter a number in %: percent: the number is read as a percentage, so type 8 for 8 %. The form accepts 1% to 100%. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 80% as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Parts per edge rise with the share used, so insert use falls.
- Get it right
- Set it from how the operators actually index, for example by part count; 100 % means running each edge to the end of its life.
Cut per part
What this means: Workpiece diameter
- What it is
- The diameter of the work being turned, which with the cutting speed sets the spindle speed and so the cutting time per part.
- 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 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 larger diameter lowers the spindle speed, lengthening cutting time and so raising insert use.
- Get it right
- Use the average diameter cut by this insert when it works over a range of diameters.
What this means: Length of cut per pass
- What it is
- The axial length the insert travels in each cutting pass, including approach and run-out while it is in the cut.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 100000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 120 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Cutting time per part, and so insert use, rise in proportion.
- Get it right
- Include only time the insert is actually cutting; rapid moves do not wear it.
What this means: Feed
- What it is
- How far the tool advances along the work for each revolution of the spindle, which with the speed sets how long each pass takes.
- Units and format
- Enter a number in mm/rev: millimetres per revolution. The form accepts 0.000001 mm/rev to 10 mm/rev. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.25 mm/rev as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A higher feed shortens cutting time per part, so each edge makes more parts in this model.
- Get it right
- Use the programmed feed for the passes this insert makes, in millimetres per revolution.
What this means: Passes per part
- What it is
- The number of cutting passes this insert makes on each part, multiplying the time the edge spends in the cut per part.
- Units and format
- Enter a number in passes: passes. The form accepts 1 passes to 1000 passes. Use a whole number. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 2 passes as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Cutting time per part and insert use rise in proportion.
- Get it right
- Count only passes made with this insert; a separate finishing insert needs its own plan.
What this means: Cutting edges per insert
- What it is
- The number of usable cutting corners on each insert, so one insert serves this many edge lives before it is discarded.
- Units and format
- Enter a number in edges: edges. The form accepts 1 edges to 100 edges. Use a whole number. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 4 edges as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Inserts used and cost per part fall in proportion as edges rise.
- Get it right
- Count only edges you actually use; some shapes cannot use every corner in a given holder.
What this means: Insert price
- What it is
- The price paid for one insert, used to find the tooling cost per part and per month.
- Units and format
- Enter a number in AUD: Australian dollars. The form accepts 0 AUD to 100000 AUD. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 18 AUD as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Cost per part and per month rise in proportion; stock levels do not change.
- Get it right
- Use the price ex GST at your normal order quantity, including any freight per insert.
Demand and supply
What this means: Parts per month
- What it is
- The number of parts made each month with this operation, which drives the monthly and daily insert consumption.
- Units and format
- Enter a number in parts: parts. The form accepts 1 parts to 100000000 parts. Use a whole number. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 6000 parts as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Insert use, safety stock and reorder point rise in proportion.
- Get it right
- Use the forecast for the coming months, not last month’s figure if demand is changing.
What this means: Working days per month
- What it is
- The number of days in a month on which the operation actually runs, used to turn monthly insert use into daily use.
- Units and format
- Enter a number in days: days. The form accepts 1 days to 31 days. Use a whole number. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 21 days as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- More working days lower the daily use, so the reorder point falls.
- Get it right
- Use working days, consistent with the lead time, which is also counted in working days.
What this means: Supplier lead time
- What it is
- The number of working days from placing an insert order to having the inserts in the crib, the period the stock must cover while waiting.
- Units and format
- Enter a number in working days: working days. The form accepts 0 working days to 1000 working days. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 10 working days as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The reorder point rises with the lead time, and safety stock with its square root.
- Get it right
- Use the realistic lead time including order approval and delivery, not the supplier’s best case.
What this means: Day-to-day variation in insert use (coefficient…
- What it is
- The standard deviation of daily insert use expressed as a share of the average daily use, describing how unevenly inserts are consumed from day to day.
- 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 300%. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 30% as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Safety stock rises in proportion; 0 gives no safety stock.
- Get it right
- Work it out from crib issue records; breakages and job mix changes make it larger than expected.
What this means: Service level (chance of not running out in a l…
- What it is
- The chance of not running out of inserts while a replenishment order is on its way, which sets the multiplier z applied to the variation in demand.
- Units and format
- Choose one of 5 options from the list: 90%; 95%; 97.5%; 99%; 99.5%.
- Example
- The form opens with “95%” selected as a worked example. Choose the option that matches your case.
- Effect on the result
- A higher service level raises z and so the safety stock and reorder point.
- Get it right
- Higher service levels cost more stock for less gain: going from 99 % to 99.5 % adds about 11 % to the safety stock.
What this means: Inserts on hand
- What it is
- The number of inserts available now, in the crib and at the machines, compared with the reorder point to decide whether to order.
- Units and format
- Enter a number in inserts: inserts. The form accepts 0 inserts to 100000000 inserts. Use a whole number. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 60 inserts as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Only moves the order-now decision and the days of cover; the reorder point does not change.
- Get it right
- Count unopened stock only; part-used inserts at the machine are already being consumed.
Method and formulas
- N = 1000 V ÷ (π D); cutting time per part t_c = passes × L ÷ (f N) (as the turning cost tool).
- Taylor life T = (C ÷ V)^(1/n) (as the Taylor tool life tool); parts per edge = whole number of (T × share used ÷ t_c).
- Inserts per month = parts ÷ (parts per edge × edges); daily use d = monthly use ÷ working days.
- Safety stock = z × σ_d × √lead time with σ_d = cv × d; reorder point = d × lead time + safety stock (as the safety stock and reorder point tools).
- Example: 16 parts per edge and 93.75 inserts a month at A$0.28125 per part; reorder at 51.609 inserts.
Limitations
- Taylor life with constants you supply; real edge life scatters widely, so confirm parts per edge on the machine.
- Demand is treated as steady with normal day-to-day variation and a fixed lead time.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Set reorder points for inserts in the tool crib
- Budget monthly tooling cost for a new job
- See how a speed change affects insert use
Who it is for
- Production engineers
- Tool crib and purchasing staff
- Machining supervisors
What you get
- Tool life and whole parts per edge
- Inserts per month and cost per part
- Safety stock and reorder point
- Order now or stock adequate
Interpreting the result
- Tool life falls steeply with speed (with n = 0.25 a 19 % speed rise halves it), so insert use and stock both change sharply with the cutting speed.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1102–1106, 1132–1140. Topic reference; no source tables or recommended settings are reproduced.
- Silver E. A., Pyke D. F. and Thomas D. J., Inventory and Production Management in Supply Chains (CRC Press)
Learn the Concepts Behind This Tool
These KEVOS® Library readings explain the method this tool uses, with worked examples.
Method explained here · Library collection
Demand forecasting for small manufacturers: matching supply with demand without drowning in stock
In Manufacturing Operations and Design for Manufacture
What it covers: Practical forecasting and planning for small manufacturers: simple forecasting methods, measuring forecast error, safety stock, reorder points, order quantities and a monthly planning meeting.
Useful alongside · Library collection
Cutting tool materials and coatings: choosing carbide grades, inserts and coatings that pay
What it covers: How high-speed steel, carbide, cermet, ceramic, CBN and PCD tools differ, how ISO material groups and insert codes work, what coatings do, how tools wear and how to choose tools on cost per part.
KEVOS® tools are screening and decision-support utilities. Verify important financial, engineering, safety, legal or operational decisions using appropriate professional standards and your organisation’s approved data.