55° Whitworth/BSW/BSF/BSP inch thread end mill for threading (pitch 1.377-2.540mm) - single edge, uncoated

A solid carbide cutter for milling 55° threads on CNC machines. Its single axial thread form follows a helical tool path. Pitch is selected in the program within the range specified for the individual variant. The range also includes variants intended for one stated pitch.

Select the tool from the component drawing: check the thread standard and form angle, pitch, bore diameter and required reach. Numbers in the size code describe the cutter and its pitch range; the first number is not a nominal pipe-thread size. The selected variant card states cutting diameter, working length, shank diameter and overall length.

Construction and tool specification

The single-form designation describes one thread-forming profile along the tool axis. It does not specify the number of circumferential flutes. Working length is the dimension of the working section and reach stated on the card; it does not mean a sequence of equally spaced teeth along that entire length.

Applications and workpiece materials

The uncoated version is intended for aluminium, copper and the other specified non-ferrous materials. Applications also include selected plastics. Choose the specification for the particular material and its condition, rather than cutter diameter alone.

Do not transfer parameters from another size or surface specification without checking the machining conditions. Consider tool overhang, runout, access to the thread and space for chips. Longer overhang reduces the rigidity of the tool setup.

55° threads and pitch selection

The 55° form angle belongs to the Whitworth family. G and PF are parallel pipe-thread designations; Rc and PT are designations associated with tapered pipe threads. They are not metric M thread designations. Select BSW, BSF and BSP threads by the applicable standard, diameter and pitch.

Metric M, UNC, UNF and NPT threads use a different form angle of 60°. Do not select this cutter for those threads solely because a pitch value falls within its range. Matching pitch alone does not establish profile compatibility. For a tapered thread, the program must also account for the required taper; the 55° angle does not create it automatically.

When the drawing specifies threads per inch, pitch in millimetres is calculated as P = 25.4 / TPI. The examples below are rounded to the notation used in the variants. Obtain the programmed value and inspection requirements from the thread documentation.

How to read the size code

Example: 3.5x10x1.058x50L. The code states cutting diameter, working length, pitch or pitch range, and overall length, in that order. Linear dimensions are expressed in millimetres. A dot is the decimal separator.

The shank diameter of this example is Ø4 mm and is specified separately on the card. Do not substitute the first number in the code for shank diameter. Other sizes may show two pitch values separated by a hyphen. That range applies to the individual cutter, not to every cutter in this listing.

Dimensions and access to the thread

Cutting diameter defines the size of the cutting section. For an internal thread, the cutter must enter the prepared hole and have clearance to follow the required path. Do not confuse cutter diameter with nominal finished-thread diameter or the drill diameter used for the starting hole.

Working length helps assess the reach of the working section. Consider thread length, clearance to the bottom or other obstruction, entry and exit movements and the transition from the working section to the shank. No single card dimension is an unconditional maximum machining depth.

Shank diameter is used to select the holder, while overall length L specifies the length of the complete tool. Part of the shank remains inside the holder. A 50L, 60L or 75L designation does not mean a thread of that length. Keep overhang as short as possible while maintaining access to the machining area.

The range includes cutting diameters from Ø3.5 to Ø12 mm and working lengths from 10 to 35 mm, depending on the selected variant. The image on the card is illustrative. Read dimensions and pitch range from the labels assigned to the selected variant. The illustration is not a scale drawing and must not be used to measure tool proportions on screen.

Program and toolholding preparation

• Check the thread documentation. Identify the standard, 55° form, diameter, pitch, length and taper requirements where applicable.
• Select the correct variant. Confirm that the pitch is within its specified range and that diameter and reach suit the component.
• Prepare the holder. Clean the shank and clamping surfaces, inspect the cutting edges and check mounted tool runout.
• Verify the helical path. Check cutter diameter, movement direction, pitch, entry and exit, and clearance for the tool and holder.

A single thread form allows different pitches within the specified range because pitch is determined by the helical tool path. This does not permit exceeding the geometry limits stated for the cutter. Treat a variant with one stated pitch as intended for that value.

Operating conditions and thread inspection

Select spindle speed, feed and number of passes for the material, cutter diameter, edge load and setup rigidity. Reduce tool loading when using a long overhang. If vibration or unusual noise occurs, reduce the load and inspect toolholding and chip evacuation before continuing.

Select cooling, lubrication and chip removal for the particular metal or plastic. Keep the cutting area clear of accumulated chips and monitor edge condition during the first components.

Inspect the first finished thread using the method specified for the component, for example the appropriate GO and NO-GO gauges. Gauge selection follows the standard and tolerance of the finished thread. The tool description does not replace inspection or declare a tolerance class for every possible operation.

Frequently asked questions

Can one variant machine several pitches?
Yes, if a pitch range is specified. Select a value within that range and program the matching helical path. A variant with one pitch value is intended for that value.

Does 55° mean a metric thread?
No. It is the Whitworth family form angle. Standard metric M threads use a 60° angle.

Does single-form mean one flute?
It describes a single axial thread-forming profile in this listing. It does not specify the number of circumferential flutes.

Does overall length specify threading depth?
No. Assess usable reach together with working length, toolholding, entry and exit movements and component geometry.