Where the Tooling Budget Goes in a Machine and Press Shop: Inserts, Dies and Tool Life (₹)
How much of a machined part's cost is tooling? Sandvik Coromant's Metalworking Technical Guide (manufacturer data, checked 20 Oct 2026) puts cutting tools at an average 3–5% of production cost. In our assumed example that is ₹12.8 on a ₹256 part. The bigger money sits in tool life and in the minutes a CNC or press stands idle for tools.
Last checked: 20 Oct 2026
By the Mama Editorial Team. This page covers the tooling line itself: insert edges, die regrinds and the machine minutes they cost.
Key takeaways
- Tooling cost per part has two halves: the edge or die you consume, and the machine time spent changing, indexing and regrinding it. Most shops track only the first.
- A cheaper insert rarely moves the total much. Sandvik Coromant's Metalworking Technical Guide (manufacturer data, checked 20 Oct 2026) says a 30% cut in tool price or a 50% gain in tool life typically lowers cost per component by about 1%. That is because tooling averages 3–5% of production cost.
- Running faster is not free on the same grade. With the Taylor exponent of 0.25 for carbide on steel (IIT Kanpur handout), a 20% speed increase cuts edge life to about 48% of what it was. In our example that adds ₹3.3 per part, though it buys 9% more parts per shift.
- On a press, the die is consumed by regrinds. How much steel each regrind takes off decides how many parts the die makes in its life. Grinding late means grinding deeper.
- Measure tooling against parts, not against the month's purchase bill. Track edges per 1,000 parts and hits per regrind for each part number.
What "tooling cost per part" actually means
The machining-economics model in an IIT Kanpur machining handout (checked 20 Oct 2026) writes the cost of one turned part as: cost per part = Co×Th + Co×Tm + Co×Tt/np + Ct/np. Here Co is the cost rate of operator and machine, Tt is tool change time, Ct is the cost per cutting edge and np is the parts made in one tool life.
The last two terms are your tooling cost per part. Notice that both are divided by np. Parts per edge is the number that matters, not the price on the insert box.
Taylor's rule: why speed eats tool life
F. W. Taylor's tool life equation, around 1900, is v×T^n = C, per the IIT Kanpur handout. Here v is cutting speed, T is tool life and n and C depend on tool material, work material, feed and depth of cut.
| Tool material (steel work) | Exponent n | C (m/min) | Edge life left after +20% speed |
|---|---|---|---|
| High-speed steel | 0.125 | 70 | about 23% |
| Cemented carbide | 0.25 | 500 | about 48% |
| Ceramic | 0.6 | 3,000 | about 74% |
n and C: IIT Kanpur handout, checked 20 Oct 2026. Last column: our arithmetic, life ratio = (1/1.2)^(1/n).
A small n means life collapses quickly as speed rises: on carbide, +20% speed roughly halves edge life.
What the tool supplier says, and why it is only half the story
Sandvik Coromant's guide, the Metalworking Technical Guide introduction (manufacturer data; the edition that replaced its 2005 guide), makes three claims. A 20% increase in cutting data can reduce cost per component by over 10%. A 50% increase in tool life or a 30% cut in tool cost typically reduces cost per component by about 1% each. Tooling averages 3–5% of production cost.
That argument holds when the tool can stand the higher speed; the guide itself says to use tools that withstand high cutting data. Push the same grade 20% faster and Taylor's rule takes back much of the gain in edges, as the worked example shows.
Indian public data cannot settle the share for your plant: MoSPI's ASI 2023-24 results for NIC 2592 (treatment and coating of metals; machining) have no separate tooling or consumables indicator (ASI API, checked 20 Oct 2026). Your own stores issue register is the only source.
Worked ₹ example 1: a CNC turned steel part
Every input here is an assumption for illustration. Replace each with your own numbers.
Assume: a CNC lathe at a combined machine plus operator rate of ₹900 an hour (₹15 a minute). A forged steel part costs ₹180 in material. The cycle is 1.5 min roughing, 0.8 min finishing, 0.7 min with other tools and 1 min of loading and unloading. The roughing insert costs ₹450 with 4 edges, and each edge lasts 20 min of cutting. The finishing insert costs ₹500 with 4 edges, and each edge lasts 30 min. Drills and other tools cost ₹1 per part. Each index or change stops the spindle for 2 minutes. A shift has 450 working minutes.
| Line (per part) | Base case (₹) | Inserts 30% cheaper (₹) | Insert edge life +50% (₹) | Speed +20%, same grade (₹) | Speed +20%, better insert grade at +25% price (₹) |
|---|---|---|---|---|---|
| Material | 180.0 | 180.0 | 180.0 | 180.0 | 180.0 |
| Machine and operator time | 60.0 | 60.0 | 60.0 | 52.5 | 52.5 |
| Insert edges and other tools | 12.8 | 9.2 | 8.8 | 21.3 | 13.3 |
| Spindle stopped for tool changes | 3.1 | 3.1 | 2.0 | 5.3 | 2.5 |
| Total per part | 255.8 | 252.3 | 250.9 | 259.1 | 248.3 |
| Parts per 450-minute shift | 107 | 107 | 109 | 117 | 123 |
All inputs assumed. Edge life under +20% speed uses n = 0.25 for carbide on steel (IIT Kanpur handout). The last column assumes a grade that holds its edge life at the higher speed. Price and life changes apply to the two inserts only; other tools stay at ₹1 a part.
- Tooling is about 5% of the part (₹12.8 of ₹255.8), the top of Sandvik Coromant's 3–5% range.
- Cheaper inserts save ₹3.5 a part (1.4%), but only if they last as long.
- Speed needs the right grade. On the same grade the part costs ₹3.3 more, for 9% more parts per shift, which pays only on a bottleneck with sold output. With a grade that holds its life, the part costs ₹7.5 less and the shift makes about 15% more.
To scale it, assume 10 such lathes on two shifts for 26 days. The tooling line is then about 10 × 107 × 2 × 26 × ₹12.8, or roughly ₹7.1 lakh a month. A 50% gain in tool life on that floor saves about ₹2.2 lakh a month on the tooling line, plus fewer stopped minutes. Speed gains on a bottleneck are measured in machine-hours, which is a capacity question (see counting the hours you never sold).
Where the money goes in a press shop
A press die is not consumed per edge, like an insert. It is consumed per regrind. Every sharpening takes steel off the punch and die faces until the die runs out of grindable stock, or until shims can no longer make up the height.
Mate Precision Technologies' punch and die maintenance guidance (manufacturer data for turret punch tooling, Mate, checked 20 Oct 2026) says three things. Sharpen when the edges wear to a 0.25 mm radius. Remove only 0.03–0.05 mm per grinding pass, normally 0.13–0.25 mm in total. Frequent touch-ups work better than waiting for the punch to become very dull. The same page says to check die thickness after each sharpening and shim as needed.
The press-shop tooling line has five parts:
- Die amortisation: die cost divided by the hits it makes across all regrinds.
- Regrind and repair: grinding, fitter bench time, springs, pilots and punches.
- Press waiting for the die: often the largest part; it belongs to the changeover clock (see what a 70-minute die change costs).
- Late regrind: a dull die gives burrs, and burrs mean sorting and rejects.
- Deeper grinds: a late regrind takes more steel off and shortens die life.
Public Indian rates give a floor for the grinding hour. MSME Tool Room Ludhiana's rate sheet dated 05.05.2021 lists (CTR Ludhiana, checked 20 Oct 2026):
| Operation, MSME Tool Room Ludhiana | Others (₹/hour) | Micro enterprises (₹/hour) |
|---|---|---|
| Surface grinding | 125 | 100 |
| Surface grinding, 1500×750 mm table | 300 | 240 |
| Diaform / profile grinding | 400 | 320 |
| Tool and cutter grinding | 80 | 64 |
| Jig grinding | 600 | 540 |
| CNC wire cut, 860×860 and 750×550 mm tables | 800 | 640 |
MSME Tool Room Kolkata's rate page (no effective date shown, checked 20 Oct 2026) lists surface grinding at ₹225 an hour.
Worked ₹ example 2: one progressive die over its life
Every input is an assumption for illustration.
Assume: a progressive die for a bracket costs ₹8 lakh and makes one part per stroke. It has 3.0 mm of grindable stock and runs 50,000 hits between regrinds. Each regrind takes 6 tool-room hours at ₹225 an hour plus 4 fitter hours at ₹300 an hour, and ₹3,000 of springs and pilots.
| Regrind practice | Steel off per regrind (mm) | Regrinds in die life | Die life (lakh hits) | Die amortisation (₹/part) | Regrind cost (₹/part) | Total die cost (₹/part) |
|---|---|---|---|---|---|---|
| On time, at the wear mark | 0.15 | 20 | 10.5 | 0.76 | 0.11 | 0.87 |
| Late, run until burrs show | 0.30 | 10 | 5.5 | 1.45 | 0.10 | 1.56 |
All inputs assumed. Steel off per regrind sits within Mate's 0.13–0.25 mm normal total for the on-time case. The late case doubles it. Both cases keep 50,000 hits between regrinds; more hits before a late regrind would narrow the gap. Die life counts the first run plus each regrind.
Grinding late nearly doubles the die's cost per part, here from ₹0.87 to ₹1.56. On 30 lakh brackets a year, that is about ₹21 lakh. And this is before counting the burr rejects from the extra hits at the end of each run.
Whether the die is your money or the OEM's depends on the tooling terms in your purchase order. New or modified dies can trigger a re-PPAP. Even when the customer has paid for the die, the regrinds, the spares and the idle press are on your books.
What cameras can and cannot tell you about tooling
A camera over a CNC bay can show the spindle stopped with the door open and someone at the turret, and how long and how often that happens on each machine. On presses it can show the press idle while the die is away.
A camera cannot see flank wear, edge radius or burr height, tell a planned index from a broken insert, or judge whether an edge was changed too early. That comes from part counts, inspection and the stores register. Set the stores log (Ct/np) against the stop log (Co×Tt/np) and you have the full tooling line.
How to measure your own tooling line in two weeks
- Pick your three highest-volume part numbers on CNC and on the press.
- On CNC, record edges issued, good parts and tool change minutes per part number (edges per 1,000 parts).
- For each die, keep a regrind card: hits since the last regrind and millimetres taken off.
- Price it with the formula, then test one lever at a time and compare the total per part, not the insert bill.
For labour inside the same per-piece number, the labour cost per piece calculator uses the same per-part logic. Tooling is one of the waste lines in where an auto-component plant can spend less, next to scrap and chips (see brass chips and the scrap dealer's weight).
Where Mama fits
Mama reads the cameras a plant already has and sends the owner a short morning note on where machine hours went yesterday. That includes machines stopped for tool changes and presses waiting for a die. It watches machines and flows, not individual operators, and leaves edge counts and regrind cards to the tool room. To see what that would look like on your floor, leave an email or phone in the form below.
FAQ
What is a normal tooling cost per part on a CNC? Sandvik Coromant's technical guide (manufacturer data, checked 20 Oct 2026) gives an average of 3–5% of production cost. In our assumed example it was ₹12.8 on a ₹256 part. Your figure depends on material, cycle and parts per edge, so measure edges per 1,000 parts.
Should I switch to cheaper inserts to cut cost? Only if parts per edge stay the same. Per Sandvik Coromant's guide (manufacturer data, checked 20 Oct 2026), a 30% cheaper tool typically lowers cost per component by about 1%. If the cheaper insert gives fewer parts per edge, extra spindle stops can wipe out the saving.
Why did tool life drop so much when we increased speed? Taylor's equation v×T^n = C makes life very sensitive to speed when n is small. For carbide on steel, the IIT Kanpur handout gives n = 0.25, so +20% speed leaves about 48% of the edge life.
How often should a press die be sharpened? Mate's guidance (manufacturer data for punch tooling) is to sharpen at a 0.25 mm edge radius, and it says frequent touch-ups beat waiting until the tool is very dull. Translate that into a hit count for each die from your own regrind cards.
What does it cost to get a die reground at a government tool room? MSME Tool Room Ludhiana's rate sheet dated 05.05.2021 lists surface grinding at ₹125 an hour and profile grinding at ₹400 an hour for non-micro units. MSME Tool Room Kolkata's undated page lists surface grinding at ₹225 an hour (both checked 20 Oct 2026).