L7 Series Drill Point Dies: Flute Length, MC Style and Selection

L7 provides the longest flute range in the current ZLD catalog. It is a tooling option when the approved screw drawing calls for that geometry. The series name is not a drilling-capacity rating or permission to use the screw in a structural joint.

This guide explains the catalog dimensions, the comparison with L6 and the checks needed before ordering.

Specification overview

Parameter	L7 series
Flute length ℓ	17.8–19.0 mm, depending on Dø
Die style	MC (III)
IFI screw sizes	#12 and #14
Approximate DIN size correspondence	ST5.5 and ST6.3; confirm the specified screw standard
Dø for #12	4.3–5.1 mm, in the listed 0.1 mm increments
Dø for #14	5.3–5.7 mm, in the listed 0.1 mm increments
Die codes	L7-43–L7-51 and L7-53–L7-57; no L7-52
Die materials	HSS or carbide, selected for the forming process
Product requirements	Approved drawing, applicable standard edition and agreed test conditions

The catalog records the L7 flute range as “17.8–19.0 (19.0)”; the parenthetical 19.0 is a catalog reference value. Confirm the applicable length for the selected code on its drawing.

The table describes available tooling geometry. Confirm the actual code, mating die set and machine pocket before ordering. Nominal screw size, point diameter Dø and wire diameter are different dimensions.

How L7 differs from L6

Catalog feature	L6	L7
Flute length ℓ	15.8–17.0 mm	17.8–19.0 mm
Style	MC (III)	MC (III)
Screw sizes	#12 and #14	#12 and #14
Dø	#12: 4.3–5.1 mm; #14: 5.3–5.7 mm	#12: 4.3–5.1 mm; #14: 5.3–5.7 mm

The documented series difference is flute length. Other drawing features, such as point profile, functional radii and thread start, still need comparison. A longer flute does not by itself prove better drilling, higher forming force or greater wire consumption.

Choose the geometry that meets the drawing, then compare production results. Tool price, accepted output, rejects and changeover downtime determine manufacturing economics.

When to consider L7

A drawing requires the longer flute. Check that the requested length lies within the L7 range and that a listed Dø code and MC pocket fit the design. Agree how the finished point will be measured.

The screw must pass through several layers. Document all material grades, thicknesses, gaps and the required thread engagement. Validate the screw under those installation conditions. The sum of layer thicknesses does not automatically select an L-series die.

The joint design is changing. Replacing a through-bolt or another fastener requires a suitable engineered connection and verified fastener performance. A die code cannot authorize that change. Once the screw design is approved, assess whether L7 can form its specified point.

Material selection for the cold-forming process

The die contacts the wire blank while forming the point in the factory. The finished screw later cuts the installed substrate. Drilling heat and installation chips do not act directly on the forming die.

Evaluate the actual wire grade and delivery condition, blank volume, cavity geometry, alignment and lubrication. Separate uniform wear, adhesion and edge fracture when comparing candidate HSS or carbide grades. Supplier properties and heat treatment must suit the actual forming duty.

For an optional coating, assess adhesion, dimensional allowance and compatibility with the underlying tool material. Compare coated and uncoated trials at the same replacement criterion. Record accepted screws per matched die set and include coating, reject and changeover costs; no fixed life multiplier follows from L7.

Practical notes for running L7

Define the blank from the whole screw geometry. Confirm wire diameter, cut length and preform dimensions rather than deriving material volume from flute length alone. Inspect underfill, cracking and point symmetry during setup. The wire properties guide explains which incoming-wire information to collect.

Confirm machine fit and support. Check the actual MC die-body drawing, clamping arrangement, alignment and permitted machine load. Do not assume that a machine accepts the tool because it already makes another screw with the same nominal size.

Inspect the forming sequence. Trace uneven flutes or an off-center point through blank preparation, positioning, cavity condition and wear. Change one controlled factor at a time so the result can be attributed to that change.

Test both production and installation. First confirm formed dimensions and accepted output. Then test the finished screws in the specified material stack with defined speed, thrust and acceptance criteria. Keep these results associated with the relevant wire, tool and production batch.

First confirm L7 is what you need

Two errors are worth avoiding. An incomplete joint description can omit a layer or gap that affects screw performance. Choosing L7 before defining point geometry can also result in an unsuitable tool, even if its nominal size matches.

Send the screw drawing or sample, IFI size, Dø, required flute length, machine-pocket drawing and actual wire condition. Include the intended joint and test requirements as separate finished-product information.

The die selector lists catalog candidates from screw size and Dø. It does not certify drilling capacity or choose a material from plate thickness. Compare each candidate's flute and style with the drawing before requesting a quote.

Summary

L7 offers 17.8–19.0 mm flute geometry in MC style for #12 and #14, with separate Dø ranges of 4.3–5.1 and 5.3–5.7 mm. Selection depends on the approved drawing, machine fit and forming trial; finished-screw performance requires its own validation.

ZLD supplies HSS and carbide options. Standard die samples typically take 3–4 working days after the specification is confirmed, and trial orders start at one matched set. View the specification table or send your drawing.

Further reading

• L6 series: geometry and production selection
• Selecting drill point dies
• IFI and DIN screw-size comparison
• Carbide and HSS comparison