The fixed revolving broach toolholders for internal broaching with cylindrical shank are broach-holding devices designed to produce regular internal broached profiles on lathes, machining centers and drilling machines, using dedicated and correctly dimensioned broaches. They are used when accurate internal profiles must be produced in through holes or blind holes, such as internal hexagons, internal squares, internal slots, grooves, shaped profiles, light internal teeth and other geometries obtainable with a dedicated broach.

The operating principle is based on rotary broaching, a process in which the broach works with a slight angular offset in relation to the axis of the broach holder body. This controlled inclination allows the tool to enter the material progressively, avoiding full frontal engagement and reducing the force required compared with a direct push on the entire profile. The combination of rotation and axial feed supplied by the machine tool generates inside the hole a profile corresponding to the shape of the broach being used.

The principle remains the same even when the machine kinematics change. On a lathe, the workpiece and the broach normally rotate while the broach holder body remains stationary. On machining centers, the workpiece and the broach may remain stationary while the body of the broach holder rotates. On drilling machines or other suitable machines, use depends on system rigidity, controlled feed capability and correct alignment between spindle, broach and hole. In every case, broaching quality depends on the stability of the machine-toolholder-workpiece system and on correct parameter selection.

These toolholders are intended for internal broaching and must be used with broaches compatible with the required H dimension, as shown in the technical table. The H dimension is essential because it defines the correct geometric coupling between broach and toolholder. A broach with an incorrect H dimension may compromise the working inclination, cause abnormal wear, tool seizure, out-of-size profiles, irregular finish or overload of the internal bearings of the broach holder.

Correct workpiece preparation is essential. For internal broaching, a suitable pre-hole must be produced before the broaching operation. The pre-hole should not be selected randomly: it must reduce the amount of material to be removed, limit feed force and leave only the necessary stock for the broach to generate the final profile. For demanding internal profiles, hard materials or larger sizes, a properly dimensioned pre-hole improves tool life, reduces the risk of sticking and produces a more regular finish.

Centering is one of the most important factors for correct broaching. The broach must work as closely as possible on axis with the hole and the workpiece. Poor centering may generate eccentric profiles, out-of-size slots, poor finish, premature wear of the broach and bearings, or a helical effect, where the broached profile tends to spiral instead of remaining straight. Before machining, it is therefore advisable to check machine concentricity, workpiece clamping, toolholder rigidity and the absence of abnormal play.

Feed selection is more important than spindle speed alone. Speed can be adjusted according to the machine and material, but feed rate has a major influence on cutting force and profile quality. Softer materials such as aluminum and brass allow smoother working conditions, while steel, cast iron and tougher materials require lower load, better pre-hole preparation and proper lubrication. A rigid machine allows more stable broaching; a less rigid setup requires more cautious feed settings and greater attention to workpiece clamping.

During the initial contact phase, the broach may tend to rub against the material before reaching full engagement. Wear may be higher during this stage than during steady cutting. When the cycle allows it, it is useful to start with moderate rotation and a positive feed over a short initial stroke, so that the tool quickly enters full cutting contact. After this phase, the parameters can be adapted to the actual operation. This practical approach helps reduce localized wear and improves profile consistency.

Broaches used with these toolholders are generally made from high-hardness tool steel and must be selected according to the material and the profile required. For demanding work or repetitive production, coated broaches may be considered when available, in order to improve wear resistance, sliding behavior and tool life. The broach should always be inspected before use: damaged edges, wear, micro-chipping or residues on the cutting edges can immediately affect the accuracy of the internal profile.

In workshop applications, these broach holders are used to produce internal seats on mechanical components, bushes, rings, hubs, small shafts, turned parts, fittings, transmission elements, special tooling and maintenance components. On CNC lathes and multi-spindle machines, they allow broaching to be integrated into the production cycle, reducing machine transfers and part handling. On machining centers, they make it possible to produce internal profiles without moving the workpiece to dedicated machines, provided that alignment, rigidity and correct broach selection are respected.

For correct use, it is advisable to keep the taper, broach seat and contact surfaces clean, periodically check the condition of the broach holder bearings, verify broach compatibility with the H dimension, use lubrication suitable for the material and avoid forcing the operation when the profile is not being generated correctly. In case of tool seizure, out-of-size profile or irregular shape, pre-hole size, feed setting, centering, clamping rigidity and broach condition should be checked before increasing force or drastically changing parameters.

The fixed revolving broach toolholders for internal broaching with cylindrical shank are intended for CNC operators, turners, tool setters, CNC programmers, precision machine shops, industrial production departments, maintenance technicians, machine tool builders and setup specialists. They are an effective solution for producing internal profiles with accuracy, repeatability and good finish quality, integrating broaching directly into conventional or CNC machine tool operations.