M8 threads in series production: Why this customer values more than tool life

Which threads were produced in the pipe flanges?

The task was to cut M8 through threads with a length of 10 mm in pipe flanges. The components were machined on a CNC-controlled machine with a tapping chuck.

S45C is an unalloyed steel whose properties can be altered through heat treatment. In this application, the tensile strength at the time of machining was around 800 N/mm², according to the customer's internal testing. This information is important for tool selection because the material designation alone does not describe the actual condition of the material being machined.

The decisive factor is therefore the condition of the material immediately before tapping. If a component has previously undergone heat treatment, for example, its hardness and strength may change. The original material properties cannot then simply be applied to the subsequent threading operation. Tool selection and cutting conditions must be reassessed based on the changed condition.

Machining conditions at a glance

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Why is Form B suitable for this application?

The tool used was the VÖLKEL GREEN RING machine tap DIN 371, Form B, HSSE-PM-TiN in M8 × 1.25, article number 30035. This version combines a geometry suitable for through holes with a powder-metallurgical cutting material and a TiN coating.

The spiral point of Form B directs the chips forwards in the cutting direction. In through holes, they can exit the pipe flange on the opposite side. This means that the chip flow suits the machining task. A prerequisite is that there is enough space beyond the thread for tool overtravel and the emerging chips.

Tool selection therefore depends on more than just the thread size. The path the chips need to take during machining must also suit the hole and the workholding setup.

You can find more information in the article Form B or Form C: Which tap is suitable for which hole?

What do HSSE-PM and TiN offer in series production?

HSSE-PM refers to high-speed steel produced using powder metallurgy. This manufacturing process creates a fine, uniform microstructure. The combination of toughness and wear resistance is particularly relevant to repetitive machining operations in which the cutting edges are subjected to loads over many threads.

The TiN coating complements the cutting material with a hard, wear-reducing surface. It can reduce friction and the tendency for material to adhere to the tool. The cutting material and coating therefore perform different functions: The cutting material provides the tool's load-bearing foundation, while the coating protects its surface during machining.

In the application described, a cutting fluid was also used. The emulsion had a concentrate content of 6 to 10 percent. The achieved number of threads per tool, meaning the number of threads produced before the tool reaches its defined wear or quality limit and has to be reground or replaced, must therefore always be considered in relation to this specific combination of tool, component and machining conditions.

At VÖLKEL, we therefore recommend taking a holistic approach when optimising the tapping process. Cutting material, coating, tool geometry, cutting parameters, toolholding, and cooling and lubrication must be evaluated together and matched to the actual condition of the material. Anyone changing one of these factors should also consider the effects on the other process conditions.

What result did the user achieve?

Up to 1,200 tapping operations per tool

Compared with the customer's requirement of 1,000 tapping operations, this represents up to 200 additional threads, or an increase of up to 20%.

The customer gave consistently positive feedback on both the tool life and the cutting results of our GREEN RING PM machine tap.

For series production, this combination is crucial. A high number of completed threads is only useful if their quality also meets the requirements. At the same time, the number of threads per tool affects how often a tool has to be replaced and the machining process interrupted as a result.

The number achieved relates to the M8 through threads with a length of 10 mm in the customer's S45C pipe flanges. It is therefore a specific result from this particular application. However, it does not constitute a general tool-life guarantee for other materials or thread dimensions in a different application.

Why did tool availability also matter?

In addition to the technical performance, the customer was impressed by the reliable availability of VÖLKEL taps from stock. The user had repeatedly experienced supply shortages with their previous supplier.

This aspect is part of the economic assessment of a tool for series production. Even a suitable tool must be available in time for the next production order. Supply shortages can create additional procurement work or make it necessary to switch to a different tool whose suitability must first be checked.

In this application, the GREEN RING machine tap therefore met two requirements: It achieved the required machining performance and was reliably available to cover ongoing tool demand.

Over 99% of our catalogue items are available from stock. This delivery capability is part of VÖLKEL's commitment to its customers and helps users plan their tool requirements reliably.