Burr formation on the thread! - What can we do about it?

Many people are familiar with the annoying issue of burr formation on the thread inlet. But where does this burr come from and what can we do about it?

First of all, a burr can occur in several places. This often includes the minor diameter of the thread. Time and again, we find that this tends to be produced at the largest dimension during pre-machining. In principle, this assumption is not wrong, but it often tends to lead to the thread core not being milled to full profile. This usually results in a thin burr at the transition from the milled flank to the core diameter. Conversely, this means that this problem can be solved relatively easily by reducing the pre-machined core diameter.

But what can be done if the burr occurs at the thread inlet, where changing the core diameter has no effect?

When thread milling, the tool usually penetrates the material slowly through a so-called entry loop. This creates an incomplete thread in the area from the beginning to the end of the entry loop. This often results in burrs that can lead to a safety risk in components such as hydraulic units, brake systems etc. and must therefore be removed.
This can be solved by modifying some standard tools or, in the case of special tools, by attaching a deburring edge.
This cylindrical cutting edge at the end of the threaded part on the tool is positioned in such a way that during circular milling of the thread this cutting edge removes the first incomplete thread. As a rule, this does not lead to any problems, as this incomplete thread does not have any relevant load-bearing capacity.