# Weldon end-mill holders

Side-lock clamping on Weldon flats, shank and spindle interfaces, product-specific torque and runout, and a wrench-force example.

Reviewed: 2026-11-02

Tags: tooling, interfaces, end-mills, toolholding

SCHUNK's **WELDON** manual 1561545 v01.00 lists **16 N·m screw-tightening torque** and **70 N·m transmitted torque** for a **10 mm** shank. The transmitted value applies to an **oiled shank at the h6 minimum size**. This rotational rating leaves axial pullout capacity unresolved. The screw must engage the specified Weldon flat with adequate shank insertion. [SCHUNK, manual, pp. 12–13 and 20](https://d16vz4puxlsxm1.cloudfront.net/asset/076200133045-Prod/document_kv4gl18igt5q5b3vc2fc4hdq7j/WELDON%20Operating%20Manual.pdf#page=12).

SCHUNK identifies its side-lock family with DIN 1835 B and DIN 6535 HB shanks. The lateral flat provides the driving surface for the screw. [SCHUNK, WELDON family](https://schunk.com/gb/en/tool-clamping-technology/toolholders/weldon-end-mill-holders/c/PUB_8663).

## The holder is more than its nominal bore

SCHUNK **263585, WEL SK50 Ø10×100**, is one concrete example:

| Property | Published value |
| --- | --- |
| Machine interface | SK50, DIN ISO 7388-1 AD/AF |
| Clamping diameter D1 | 10 mm |
| Projecting length L1 | 100 mm |
| Clamping-screw thread G1 | M10 |
| Listed runout | ≤0.003 mm, measured from taper to D1 |

The product page identifies G1 as the screw thread and includes a WELDON clamping screw. It also lists **G2.5 at 25,000 rpm or maximum residual unbalance below 1 g·mm**. This balance specification does not establish the allowable operating speed of an arbitrary assembled cutter and holder. [SCHUNK, product 263585](https://schunk.com/in/en/tools/toolholder-quickfinder/weldon/wel-sk-50-10x100/p/000000000000263585)

The named runout relationship is not a guarantee at every possible cutter tip. A 100 mm holder projection is also not the tool's insertion length or its cutting-edge projection from the holder nose. Those dimensions describe different parts of the assembly.

## Screw tightening and transmitted torque are different

SCHUNK's WELDON manual **1561545, version 01.00**, distinguishes these quantities:

| Clamping diameter | Maximum screw-tightening torque | Minimum transmitted torque |
| --- | --- | --- |
| 10 mm | 16 N·m | 70 N·m |
| 20 mm | 50 N·m | 420 N·m |

Its transmitted-torque table applies to an **oiled shank at the h6 minimum size**. Assembly separately requires clean surfaces, flat alignment and minimum engagement. [SCHUNK, manual, pp. 12–13 and 20](https://d16vz4puxlsxm1.cloudfront.net/asset/076200133045-Prod/document_kv4gl18igt5q5b3vc2fc4hdq7j/WELDON%20Operating%20Manual.pdf#page=12)

Screw torque establishes clamping. Transmitted torque describes rotational resistance under the stated conditions. Check axial pullout and assembly loading separately.

## Comparison with collets and other pullout protection

An ER assembly has a separate collet that engages the nut's eccentric ring before installation in the holder. This differs from a lateral screw acting on a Weldon flat. The REGO-FIX ER mounting notice also relates inadequate shank insertion to poor runout and collet deformation. A flat and a collet therefore are not interchangeable definitions of retention. [REGO-FIX, ER notice 0361.0002, pages 1–2](https://us.rego-fix.com/system/files/docs/2025-06/036100002_RFAG_Beipackzettel_d_e_f_01_2025.pdf)

HAIMER's **Safe-Lock** is another distinct design: it combines frictional clamping with a positive connection using grooves in the tool shank and corresponding holder features. Its catalog explains that high axial loads can cause gradual tool movement in frictionally clamped systems. Weldon's screw-and-flat geometry and Safe-Lock's groove connection are different constructions; neither product name qualifies a mismatched shank. [HAIMER, Tool Holders, Safe-Lock, printed page 216](https://www.haimer.com/shop/catalog/downloads/files/Tool-holders/Tool-holders_US.pdf#page=216)

These mechanisms should not be reduced to a blanket hierarchy. Cutter runout, torque transfer, axial retention, balance and accessibility of the clamping mechanism remain separate properties. In particular, an antirotation feature does not by itself supply a numerical pullout rating.

## Worked example: force at a wrench handle

**Original arithmetic:** assume **16 N·m** screw torque and a perpendicular force **0.15 m** from the axis, neglecting wrench compliance:

```text
Torque = force × perpendicular lever arm
Force = 16 N·m / 0.15 m = 106.7 N
```

This lever calculation establishes neither screw preload nor tool pullout force. The 70 N·m transmitted rating remains a different quantity, not a tightening setting.

## Coverage and source dates

The SCHUNK manual's imprint prints **21 October 2024**, version 01.00. HAIMER's catalog identifies **first edition 2020**; the REGO-FIX notice prints **01/2021**. No issue date is established for the cited SCHUNK web pages. Sources were inspected on November 2, 2026; copyright and crawl dates are not publication dates.

This reference covers the screw-and-flat interface and selected manufacturer data. It does not provide universal flat dimensions, bore clearance, tightening torque, tool projection, maximum speed, coolant pressure or axial holding force. Product drawings, shank geometry, screw condition and the actual assembly determine those limits; generic examples do not establish a shop's installed tooling or approved machining conditions.

## Related reference

[Cutting tools and tooling references](../index.md)