Key takeaways
- A 1,050 mm blank perimeter in 1.5 mm CRCA needs about 504 kN, or 51 tonnes-force, so a 100 T press runs at 51% load and has room for a stripping force of 50 to 100 kN.
- Punch-to-die clearance is 5% to 8% of thickness per side; at 1.5 mm that is 0.075 to 0.12 mm, and a die ground beyond that clearance starts making burr instead of parts.
- Each grind removes 0.1 to 0.2 mm of die height, so twelve sharpening cycles take 1.8 mm off a 1.5 mm-thick tool and the shut height has to be shimmed or the press re-set.
- Burr height above 10% of thickness, which is 0.15 mm on 1.5 mm CRCA, is the trigger to sharpen, not the appearance of a visible edge.
- Every die needs a stroke counter and a first-off record per run; without both, a crack that starts on stroke 41,000 is found when the tool crashes at 60,000.
A progressive die that has run 300,000 strokes without a record is a tool with an unknown edge. The punch may be 0.05 mm below its original height, the die opening may have worn 0.08 mm a side, and the burr on the part may have risen from 0.03 mm to 0.12 mm over the last 20,000 strokes. None of that shows in the part dimensions until it does, usually in one shift, as a cracked flange, a slug pulled into the strip, or a tool that has to come off the press for a week.
Press tool maintenance records exist to make that progression visible. They are not a compliance file produced for an audit. They are the only way to know whether the next grind is routine or the last one the die can take, and whether a burr on a delivered part came from a worn edge or from a material change.
This guide lists the fields a die card needs, the frequencies that make them useful, and the numbers that turn the card into a decision.
What must a press tool maintenance record contain?
A die history must answer four questions at any moment: how many strokes the tool has run, how much material has been ground off it, what the cutting clearance is now, and what the last part inspection found. Everything else on the card supports those four.
The first field is identity. Die number, part number and revision, the press or presses the tool can run in, the shut height and the strip width. A die that is moved between presses without recording the shut height will eventually be set in a press where the ram does not reach the stripper plate, and the damage is done on the first stroke.
The second is the stroke count, and it has to be cumulative and per-run. A cumulative count decides the overhaul interval. A per-run count tells the tool room how many strokes since the last grind, which is the number that actually predicts wear.
The third is the grind record: date, depth removed in millimetres, punch height after grinding, clearance measured, and who did it. This is the field most plants keep badly, because the grinder knows the depth and the card is filled in afterwards from memory. A record of "sharpened" with no depth is worth nothing, because it cannot be used to work out the remaining die life.
The fourth is the inspection result: burr height, blank dimensions, and the first-off report for each run. Burr height is the leading indicator and the one that gets skipped, because it needs a profile projector or a burr gauge rather than a pair of calipers.
The numbers a die card should hold
The values below are the working limits for a CRCA progressive die in the 1 mm to 2.5 mm range. They are starting points for a card, not universal constants: the tool design, the strip material and the press stiffness all move them.
| Parameter | Typical value | Ganesh limit or note |
|---|---|---|
| Press capacity for the part | 51 tf at 1.5 mm CRCA | 20–300 T mechanical presses; 250 T punching |
| Cutting force basis | F = perimeter x thickness x shear strength | 1,050 mm x 1.5 mm x 320 MPa = 504 kN |
| Stripping force | 10–20% of cutting force | 50–100 kN on the same blank |
| Clearance per side | 5–8% of thickness | 0.075–0.12 mm at 1.5 mm; measured, not assumed |
| Sharpening interval | 30,000–80,000 strokes | condition-based; halve for stainless |
| Burr height trigger | 0.1 mm, or 10% of thickness | 0.15 mm on 1.5 mm sheet |
| Material removed per grind | 0.1–0.2 mm | 12 grinds take about 1.8 mm off die height |
| Punch penetration into die | about one third of thickness | 0.5 mm at 1.5 mm; less on thin gauge |
| Guide pillar clearance | 0.02–0.04 mm | re-bush at 0.06 mm |
| Die spring life | 500,000–1,000,000 strokes | nitrogen cylinders checked for pressure each run |
| Shut height tolerance | plus or minus 0.05 mm | record the value set, not the nominal |
| First-off inspection | every run, every restart | 5 parts, burr and 3 critical dimensions |
| Die history review | monthly, by tool number | tool room owns the review, not the press shop |
The clearance row is where most of the quality comes from and where most cards are silent. Clearance is set at tool build, and it changes in two directions as the tool wears: the punch edge rounds over, which increases effective clearance, and the die opening wears, which also increases it. A die built at 0.09 mm a side may be at 0.13 mm after 200,000 strokes. That is outside the band, and the part will show a heavier burr and a slight rollover change before it shows a dimensional problem.
The burr trigger and the clearance limit usually arrive at the same time. When the burr reaches 0.15 mm on 1.5 mm sheet, grinding the punch face restores the edge and brings the clearance back towards the design value, because grinding removes the rounded zone. The mistake is to keep running because the dimension is still good, then to grind 0.4 mm at once when the burr finally becomes unacceptable. That single deep grind removes more die life than four shallow ones.
How the cutting force decides what the card must track
The tonnage calculation is short and it sets every other parameter. For a blank with a 1,050 mm perimeter in 1.5 mm CRCA, cutting force is perimeter times thickness times shear strength: 1,050 x 1.5 x 320 MPa, or 504 kN. That is 51 tonnes-force, and on a 100 T press the tool uses half the capacity, which leaves room for the stripping force and for a slightly thicker strip without overloading the frame.
Two consequences follow. First, the press is chosen with a margin, so a rise in tonnage is a signal rather than a limit. A tool that needed 51 tf when new and needs 58 tf after 150,000 strokes is telling you that the edge has dulled and the clearance has changed. Monitoring peak tonnage is one of the cheapest wear indicators available, and most presses already have the sensor.
Second, the tonnage is not the same as the energy. A mechanical press stores energy in a flywheel, and a tool that uses most of the flywheel energy in one stroke will slow the press and produce inconsistent parts even when the force is inside the rating. That is why a 300 T press can run a 250 T punching tool comfortably but should not run it at 95% of rated force on every stroke.
Off-centre loading is the quieter problem. A progressive die with a heavy station at one end puts a moment on the ram and the slide guides, and the effect is uneven wear on the guide pillars. The card should record which station was changed or rebuilt, because a die that has had one station re-cut and not the others will load unevenly for the rest of its life.
The grind record, and why depth matters
Each grind removes 0.1 to 0.2 mm from the punch face. That seems small until it is accumulated. Twelve grinds at 0.15 mm take 1.8 mm off the punch height, and a die designed with 3 mm of regrind allowance is more than half consumed. The shut height must then be adjusted, and on some tools the punch no longer reaches the stripper, so a spacer is needed.
A card that records depth per grind lets the tool room answer three questions that otherwise arrive as a surprise:
- How much regrind allowance is left before the punches must be replaced.
- Whether the last grind was deeper than necessary, which shortens the remaining life.
- Whether the interval between grinds is shortening, which points to a material or lubrication problem rather than normal wear.
The interval shortening is the interesting one. A die that ran 70,000 strokes between grinds for a year and then needs grinding at 40,000 has not suddenly worn faster because of age. Something changed: a harder strip, a different lubricant, a press that is out of level, or a strip that is being fed at an angle. The grind record is the evidence that proves the change happened, and the date it started.
The failures a die history prevents
Four failures account for most unplanned tool downtime, and each leaves a different trace on the card.
Slug pulling
A cut slug is dragged back up through the die face and sits on the strip. On the next stroke it is pressed into the part, or it dents the die face, or it jams the strip and stops the press. The cause is usually a worn punch edge, insufficient punch penetration, or a missing slug hole. The card shows it as a run of parts with indentations that starts after a grind, when penetration was reduced and not re-checked.
Chipping at the punch corner
Small clearance on a sharp corner concentrates stress and chips the punch. A die built at 0.07 mm a side on 2 mm CRCA is at the tight end of the range, and a corner radius under 0.5 mm will chip within a few thousand strokes. The trace is a sudden change in burr height at one corner and a part that shows a small step on the cut face.
Galling in a draw station
Where a progressive die also forms, the draw punch picks up material and scores the part. The cause is lubrication, surface finish or a punch that has lost its coating. The card records the polish or re-coat, and the interval between them is a wear trend in its own right.
Guide pillar wear
A pillar at 0.06 mm clearance lets the die halves shift, and the punch and die edges no longer align. The symptom is a burr that appears on one side of the part, then a step in the cut face. Guide clearance is rarely measured because it needs the tool apart; that is why it should be checked at every scheduled grind rather than only at overhaul.
The common thread is that none of these failures announces itself with a dimension out of tolerance. They announce themselves with a burr, a tonnage or a noise, and only the card connects the symptom to the cause.
What Ganesh keeps in the tool room
Press tools, progressive dies, welding fixtures and checking fixtures are designed and built in-house, which means the die card is created at build and follows the tool for its life. The tool room holds the grind records, the punch and die clearance measurements and the rebuild history, and the press shop records strokes, tonnage and first-off inspection against the same die number. Tooling is quoted separately from the piece price, so the amortisation and the maintenance expectation are visible in the quotation rather than buried in it.
The press range runs 20 T to 300 T, with 250 T punching for the heavier blanking work, so a tool can move between machines as volumes change. That mobility is useful and it is also the reason the card records shut height, bolster height and the presses a die is cleared for. A tool that has only run in one press hides a setting error until it is moved; a tool with a card does not.
For the wear side, the progressive die maintenance guide covers the interval maths, the stamped part inspection article covers the first-off and patrol checks that feed the card, and the tool and die capability lists what is built in-house. The plant and quality hub collects the records and calibration material that sits around them.
What to put on the card, in order
- Identity: die number, part number and drawing revision, tool type, strip width, strip grade and thickness range.
- Machine: presses the die is cleared for, shut height, bolster height, and the tonnage measured at first run.
- Counters: cumulative strokes, strokes since last grind, and strokes since last overhaul.
- Grinds: date, depth removed, punch height after grinding, clearance measured on four corners, and the operator.
- Edge condition: burr height at last inspection with the method used, and the part dimensions checked.
- Wear parts: guide pillar and bush clearance, spring or nitrogen cylinder identity and pressure, and the stroke count at replacement.
- Repairs: what was welded, re-cut, polished or replaced, why, and who approved it.
- First-off: five parts per run, the critical dimensions and the burr reading, signed by inspection.
Eight fields, one page per die, reviewed monthly. A tool room that keeps this for fifty dies has a maintenance plan. One that keeps it for five hundred has a maintenance system.
When the card is not enough
A die history tells you how a tool has behaved in the plant that ran it. It says less about whether the tool will behave in yours. A transferred die arrives with a card that may be complete, partial or reconstructed, and the only reliable test is a strip trial with the tonnage, burr and first-off dimensions measured from a known strip.
Two things the record cannot cover. It cannot certify a die that has been welded and re-cut at a corner, because the heat-affected zone behaves differently from the original insert and the card only records that a repair happened. And it cannot substitute for a strip layout review: a tool that ran well on 1.2 mm CRCA may be outside its clearance band on the 1.6 mm the new part needs.
Where a customer owns the tool, the card should travel with it and a copy should stay with the moulder of the parts, so a new supplier inherits the stroke count rather than restarting it. That is the difference between a transfer and a rebuild, and it is usually decided before the first purchase order. Send the part drawing, the annual volume and any existing die record, and the quotation will state the tool assumption, the maintenance interval and what the card will contain.
Frequently asked questions
How often should a press tool be sharpened?
On condition, not on a calendar. For 1.5 mm CRCA a progressive die typically runs 30,000 to 80,000 strokes between grinds, and the trigger is burr height above 0.15 mm, a change in blank dimensions beyond the drawing tolerance, or a rise in press tonnage. Stainless wears faster and often needs half that interval.
What should a die history card contain?
Die number, part number, press and shut height, cumulative stroke count, date and depth of every grind, punch and die clearance measured after grinding, burr height at last inspection, guide pillar and bush clearance, spring or nitrogen cylinder changes, repairs with the reason, and the first-off inspection result for each production run.
Why does burr height matter more than part dimensions?
Dimensions can stay inside tolerance while the cutting edge wears, because the die opening and punch size change slowly compared with the burr. Burr height rises first and predicts the edge condition. At 10% of thickness the edge is worn enough that the next thousand strokes will start to produce slivers, cracked flanges and jams.
Can a worn die be repaired or must it be replaced?
Most cutting tools can be repaired by grinding and, when the die height has fallen, by shimming the die shoe or re-setting the shut height. Welding and re-machining an edge is possible on a small section but changes the metallurgy locally. Once clearance can no longer be restored by grinding the punch, the punch is replaced and the die insert re-cut.
Who should own the die history?
The tool room, not the press shop. The press shop reports strokes, tonnage and first-off results; the tool room owns the card, the grind records and the decision to take a tool out of service. When the press shop owns the card the tool is only examined after a failure.
Sources and further reading
- ISO 2768-1 — General tolerances for linear and angular dimensions without individual tolerance indications · reviewed 3 Nov 2026
- IS 513 — Cold reduced carbon steel sheets and strips, the grade and thickness basis for CRCA stamping · reviewed 3 Nov 2026
- ISO 9001:2015 — Quality management systems, covering control of production and monitoring of measuring equipment · reviewed 3 Nov 2026
Need the tool history before you approve a transfer?
Send the part drawing, the annual volume and the existing tool condition report. We will review the die design, the stroke history and the maintenance route before quoting tooling and piece price.
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