BAN503 hex bolt bulletproof 2,0mm

The upper end of the family and what follows from it

Two millimeters is where the whole scale offered ends. Above this grade the manufacturer carries nothing further, so anyone who needs an even heavier joint has to reach for another head shape or help themselves with their own modification. Within this family it is simply the ceiling.

A larger head brings two things at once, and each tips the scales a different way. The face beneath it is noticeably wider, so the joint has something to live on. At the same time, though, the head stands higher above the surface, and a knock acts on it through a longer lever that tries to prise it out. Both can be balanced by making the seat somewhat deeper.

Sinking it instead of gluing it on top

• Drill the seat deep enough for the lower rim of the head to disappear in it
• Try the depth dry until the shape sits exactly
• A sunken head transfers the force into the wall of the hole, not just into the glue
• On thin walls drill shallower instead and support the joint from underneath

The difference between a head laid on the surface and a head sunk halfway in is clearly noticeable at this dimension. The first can be prised off with a fingernail, the second will not be lifted even by careless dusting. Visually both look almost the same, though, because only the part the eye notices stands above the surface anyway.

It therefore pays to devote a few minutes to a test on an offcut of the same material before the bit is set against the finished part. The offcut gives away how the material behaves, whether it tears at the rim and how many turns are enough. Nothing is tried out on the model any more; there you only repeat the movement your hand already knows.