Question:
My thread is made in cast aluminium. What happens is when they do it up they over tighten it then they start threading on an angle.
Please advise.

Answer:
Clinserts are habitually installed at the side of a plate or close to the edge of a surface.
The risk exists, when installed to close that performance is influenced, and you do not achieve enough pull-out strengths.

1. Clinserts at the side of an edge
The general rule is to install with a drill distance of (0,8mm minimum + 1/2 diameter of the drilled hole)
advice to put all clins as far as possible from the edge.
Case  1: With CLM8, outside diameter = M12, drill distance can be 6,8mm.
Case 2: With CLM5, outside diameter = M8, drill distance can be 4,8mm.
Case 3: With CLHM20, outside diameter = M30, drill distance can be 15.8mm.
Tap marks may show on the flat side and the insert should be positioned with keys 45°to 90° (2 CLINS) offset from the flat side.

2. Clinsert in a boss
The general rule is to install the Clinsert in a boss with a minimum outside diameter = 1,5 x diameter of the outside thread of the Clinsert
Case  1: CLM8x1,25 with an outside diameter of M12 your boss diameter needs to be 18mm
Case  2: CLM5x0,8 with an outside diameter of M8 your boss diameter needs to be 12mm
Case  3: CLHM20x2,5 with an outside diameter of M30 your boss diameter needs to be 45mm