Carbide Button Dies and Punches: Headed or Straight, Scrap-Retention or Non-Clogging, and What to Specify
· Vanguard Carbide
The standard forms of carbide button dies and punches, what each is for, the tolerances catalogues publish for them, and the checklist to send when you order the carbide part or its blank.
The Short Answer
Carbide button dies (die buttons, matrices) and carbide punches come in a small number of standard forms: headed or straight, and for button dies, plain, scrap-retention or non-clogging. The form decides which dimensions are tight, which features have to be machined into the carbide, and how the part sits in the die.
If you are ordering the carbide part, whether a finished button or a blank to finish yourself, the supplier needs to know the form as well as the size. This article explains the forms, using published catalogue data and two die-making articles as references, and ends with a checklist of what to specify.
Headed And Straight Button Dies
ISO 8977:2003 sets the basic dimensions and tolerances for headless and headed matrixes (button dies) with outside diameters from 5 to 50 mm. Its dimensions are matched to punches made to ISO 8020. It was last reviewed and confirmed in 2025.
A headed button has a collar at the top, which usually sits in a counterbore of the die plate. A straight (headless) button is a plain cylinder pressed into the plate. In both cases the outside diameter is a press fit and is ground to a few microns.
For example, one large catalogue supplier lists its carbide button dies with a shank tolerance of m5 for headed types and n5 for straight types, or a plus-only tolerance of 0 to +0.005 mm, in a HIP carbide grade of 87–88 HRA. In the same catalogue the standard full-length tolerance is +0.2 to +0.4 mm, with tighter length tolerances available as options. Headed buttons can be ordered with one or two key flats on the head. A shaped (non-round) hole has to line up with the punch, and a flat on the head is one way to orient the button.
| Shank diameter | m5 (headed) | n5 (straight) |
|---|---|---|
| 3 mm | +0.002 to +0.006 mm | +0.004 to +0.008 mm |
| 4 and 5 mm | +0.004 to +0.009 mm | +0.008 to +0.013 mm |
| 8 and 10 mm | +0.006 to +0.012 mm | +0.010 to +0.016 mm |
The point for ordering: the outside diameter, the hole and the length are the dimensions that carry tolerances. If you buy a blank to finish yourself, say which of them you will grind, so that the blank leaves stock on those surfaces.
Plain, scrap-retention and non-clogging buttons:
The different button types exist mainly because of slug pulling. As Art Hedrick explains in The Fabricator, slug pulling is when the scrap piece (the slug) sticks to the punch face on withdrawal and comes back up out of the button. A pulled slug can damage parts and dies, and trapped air that forms a vacuum pocket under the punch face is a major cause.
Remedies described in that article include air vents and spring-loaded ejector pins in the punch, a smaller punch-to-die clearance (which helps but shortens punch and button life), and buttons designed to hold the slug:
- Slug-control buttons: two small slots machined at an angle in the matrix raise a burr on the slug that wedges it in place.
- Slug-hugger buttons: barbs in the matrix dig into the slug.
- Reverse-taper (bell-mouth) buttons: the hole narrows slightly so the slug is held in compression. For most piercing, 0.0005 to 0.001 inch of taper is more than enough, and too much can split the matrix.
- Vacuum units that pull slugs down into the matrix.
Catalogue scrap-retention buttons work on the same idea and come with published limits. The catalogue cited above gives them as:
| Limit | Value |
|---|---|
| Hole diameter | 1.0 to 16 mm |
| Workpiece tensile strength | Up to 1177 N/mm² |
| Workpiece thickness | At least 0.15 mm |
| Clearance per side | Less than 20% of the workpiece thickness; with more clearance the retention effect cannot be expected |
Because these buttons work by forming small projections on the slug, the catalogue says they are not suitable for precision holes, or where the punched-out piece is the product.
Non-clogging buttons work the other way: they help the slug leave. In the catalogue's non-clogging type, an air inlet hole near the shaped hole lets a vacuum device draw air through the button, and the airflow carries scrap out better than vacuum alone. The same catalogue writes button relief as a taper of 1/50, 1/100 or 1/150: a 1/50 taper grows 1 mm in diameter over 50 mm of length, about 1.15°.
Punches And Pilot Punches
The same supplier's carbide pilot punch range shows how punch variants are usually described. The families come with a round (R), tapered or sharp-angle tip, most of them in standard, lapped or TiCN-coated versions, all in a HIP carbide grade:
- Standard punches, shank tolerance m5
- Punches with key grooves, headed or straight
- Straight punches without a head
- Punches for fixing to the stripper plate, headed or straight
- Movable punches with a g6 shank, which is below nominal size so the punch can slide: −0.002 to −0.008 mm for 1.6 to 3 mm shanks, down to −0.006 to −0.017 mm for 13 and 16 mm shanks
When you order a carbide punch or punch blank, the shank fit (press fit or sliding), whether there is a head, the tip shape and the finish all change how the part is ground. Name them on the inquiry, or send the catalogue-style designation you are replacing together with your drawing.
Choosing The Grade For Punches And Buttons
In Carbide in tool and die (The Fabricator), the main levers are grain size and cobalt content: finer grain is harder, more wear-resistant and more brittle; more cobalt is softer and tougher. The article also stresses two properties that matter in stamping: corrosion resistance, because the cobalt binder can be leached out during wire EDM in dielectric, grinding with emulsion, or by corrosive lubricants; and edge stability.
The article reports a test blanking 0.065-inch stainless steel with a wire-EDM punch:
| Grade tried | Result |
|---|---|
| 15% cobalt, submicron grain | Chipped on pullback after 500 hits; poor surface quality and corrosion caused galling at the edge |
| 15% cobalt, coarse grain | Excessive wear after 5,000 hits |
| 12% cobalt, medium grain, corrosion-resistant | 50,000 hits; 80,000 after lubrication was improved |
These are results from one application, not general life figures. What they show is that the cheapest-looking change, a tougher grade, is not always the fix. The same article notes that a chip on top of the punch can point to poor surface finish, galling or too much clearance, while a chip down the side can point to too little clearance or insufficient shock resistance.
Our carbide blocks page lists the grade classes we use for stamping. Tell us what you stamp, its thickness and stroke rate, and whether the part will be wire-EDM cut, and we propose a grade with its data sheet.
What To Specify When You Order The Carbide Part
| Item | Why it matters |
|---|---|
| Type: headed or straight; plain, scrap-retention or non-clogging | Decides which features are machined into the carbide |
| Outside or shank diameter and its fit (m5, n5, g6 or a plus-only tolerance) | Press fit or sliding fit; ground to microns |
| Full length, head diameter and head thickness, with tolerances | Catalogue standard length tolerances are loose unless you ask for tighter |
| Hole size and shape, land length and relief taper | The working part of the button |
| Key flats or other orientation features | Needed for shaped holes |
| Material stamped, its thickness and the stroke rate | Drives the grade |
| Finished part, or blank with grinding stock; grinding or wire EDM | Changes the blank size and favours a corrosion-resistant grade for EDM |
| Quantity, and whether it repeats | Price and how the part is made |
For round punch and button blanks, as-sintered or ground, see our punch and die blanks page.
FAQ
What do m5, n5 and g6 mean on a punch or button die?
They are ISO tolerance classes for the shank diameter. m5 and n5 put the diameter slightly above nominal for a press fit in the die plate; g6 puts it slightly below nominal so a movable punch can slide. For a 4 or 5 mm shank in the catalogue cited below, m5 is +0.004 to +0.009 mm and n5 is +0.008 to +0.013 mm.
What is the difference between scrap-retention and non-clogging button dies?
Scrap-retention buttons hold the slug in the button so it cannot be pulled back up with the punch. Non-clogging buttons help the slug fall or be drawn out, for example with an air inlet and a vacuum device. Catalogue scrap-retention buttons are not recommended for precision holes or where the punched-out piece is the product.
Can carbide button die blanks be cut by wire EDM?
Yes, wire EDM is a common way to cut shaped holes and punch profiles in carbide. The cobalt binder can be leached during EDM in dielectric, so tell the supplier the part will be EDM cut; a corrosion-resistant grade may be the better choice.
Do you supply finished button dies or only blanks?
We supply round punch and die button blanks and carbide blocks, as-sintered or ground, made to your drawing. Send the drawing and we confirm in the quotation which features and tolerances are included.
Sources
- ISO 8977:2003, Tools for pressing — Matrixes, ISO catalogue page (abstract and status)
- MISUMI, Carbide button dies: types, shank tolerances, scrap-retention limits, relief tapers
- MISUMI, Non-clogging carbide button dies (catalogue pages 585–586, PDF): tolerances, alterations, air inlet design
- MISUMI, Carbide pilot punches: punch families and shank tolerances
- Art Hedrick, Die Basics 101: Resolving slug pulling problems, The Fabricator
- Carbide in tool and die, The Fabricator: grade properties and the stainless blanking test