M2 is a widely used HSS grade offering a practical balance of wear resistance, toughness, grindability and cost. It can suit general press-tool applications when the block profile, work material, clearance and impact are moderate. Final suitability depends on the heat treatment and die conditions.
Cobalt-bearing M35 and M42 may be considered where hot hardness and wear demands exceed those of general-purpose M2. Complex corners, impact and side loading still require adequate toughness. The higher-performance grade should be selected from actual work material, thickness, production rate and failure mode.
A diameter range is appropriate mainly for round features. Square, rectangular and custom block punches require width, length, diagonal or gauge dimensions, corner radii and orientation. Vardhman should clarify whether 0.2–50 mm refers to shank, equivalent size or only certain round-ended block variants.
The live page states 64 ± 2 HRC. This is a common hardness range for M2 HSS punches, but actual hardness should be matched to the grade, profile geometry and work material. High-impact or thin-corner profiles may require lower hardness or higher tempering to prevent chipping.
The cutting profile requires full working hardness for wear resistance, but heads or flanges are sometimes drawn back (annealed/tempered) to 40–50 HRC to prevent head cracking or mushrooming under cyclic press impact.
That range represents Ra surface roughness in micrometres. Precision ground and polished land surfaces lower friction, reduce galling, ease slug passage and lower stripping forces during production.
Specify width (W), length (P or L), corner radii (R), overall length, shank/head details and orientation references (keyways or flats) relative to the press centerline.
Sharp internal or external corners create severe stress concentrations where cracks initiate. Adding even a small corner radius (e.g. 0.2–0.5 mm) significantly increases punch toughness and edge life.
Orientation is controlled using precision key flats, dowel pin slots, flanged mounting blocks, or rectangular shanks. Correct keying prevents the punch from rotating in the retainer and damaging the die.
Options include straight shanks with orientation flats, shoulder-headed blocks, ball-lock retainers, bolt-through flange mounts, and custom dovetail or block holders.
Heavy-load designs feature thicker shanks, generous transition radii, backed-up support plates, and tougher HSS grades for piercing thick or high-tensile sheet metal.
Non-uniform clearance causes uneven cutting loads, burrs on one side, side thrust on the punch, accelerated corner wear and premature punch-to-die contact.
Total per-side clearance is calculated as a percentage of stock thickness (typically 5% to 12% per side depending on material tensile strength and edge-quality requirements).
Excessive secondary shear occurs, cutting forces increase, stripping friction rises, corners heat up and chip, and punch life drops dramatically.
Large burrs form along the pierced edge, part rollover increases, pierced dimensions distort, and slug pulling becomes more frequent.
Rounded or worn punch corners, excessive corner clearance, punch deflection, or improper die wire-EDM relief lead to heavy burrs and poor corner crispness.
Punch tilt, un-parallel press ram stroke, uneven clearance across the profile, or unequal stripper plate clamping pressure cause dimensional variation across the hole.
Rectangular or asymmetrical slugs can tilt and jam in the die land if die relief is improper, vacuum suction occurs, or lubricant creates adhesive surface tension.
Yes. Flat-faced block punches working with light lubricants often pull slugs up. Spring-loaded ejector pins, rooftop shear angles, or vacuum-relief holes prevent slug pickup.
Block punches have large surface contact perimeters. Material elasticity grips the punch walls tightly after piercing. Polished land faces and proper clearance lower stripping loads.
Breakage stems from misfeeds, double-blanking, extreme misalignment, unguided side thrust, sharp internal shoulders, improper heat treatment, or excessive press speed.
Corners carry peak cutting stress. Sharp zero-radius corners, tight die clearance, excessive hardness, grinding micro-cracks, or vibration cause micro-chipping.
Inadequate orientation keying, loose retainer clamping, or off-center shear forces allow the punch body to shift, striking the die land and causing catastrophic damage.
Off-center entry, misaligned guide posts, uneven clearance, or localized lubricant starvation cause one side or corner to dull much faster than the rest.
High sliding friction when piercing soft, adhesive metals (aluminium, copper, soft stainless) causes metal transfer. Lapping, PVD coatings, and specialized lubricants prevent galling.
While the physical punch can enter different materials, punch-to-die clearance, shear geometry, surface coating, and lubrication must be tailored to each specific material.
Use tough HSS grades (M2/M35), increase corner radii, apply rooftop or valley shear, widen die clearance (10–15%), and specify TiALN/AlTiN PVD coating.
Yes. Rooftop, concave, or bevel shear angles distribute the cutting stroke, reducing peak tonnage and dampening snap-through shock on the press.
Punching Force = Cut Perimeter × Stock Thickness × Material Shear Strength. For a rectangular profile, Cut Perimeter = 2 × (Width + Length).
Sharpen as soon as a 0.05–0.10 mm corner wear land or increased part burr appears. Timely regrinding removes minimal stock and prevents deep corner cracking.
Regrind only the flat front face using a CBN or diamond wheel with flood coolant. Never grind the side profile land faces, as doing so alters profile dimensions and clearance.
