How can the length of a bolt to be used in drop-in anchors be determined?
Two factors will determine their length
- If they are too short it may mean that the bolt thread does not grip enough of the female thread of the sleeve, causing the male thread of the bolt or the female thread of the sleeve to fail.
- If the bolt is too long, its point may come into contact with the anchor’s expansion cone before the head of the bolt reaches the material to be fastened. In such a case, the bolt is unable to move any further, meaning that further torque may break the anchor’s sleeve due to the traction that the bolt thread exercises on the sleeve.
In order to calculate the correct length of the bolt, follow the indications in the Index technical documentation, as well as European Technical Assessment ETA 14/0068 and 14/0135:
- Minimum bolt length = tfix + ls,min
- Maximum bolt length = tfix + ls,max
where:
- tfix: thickness of the fixture
- ls,min, ls,max: values depending on approval assessment
For example, in the case an M8 drop-in anchor (Code no. HEHOM08), where the thickness of the material to be attached: tfix = 9 mm
Table C1: Installation parameters for HECHO / HECLO anchor
| Installation parameters | Properties | |||||||
|---|---|---|---|---|---|---|---|---|
| M6 | M8 | M10 | M12 | M16 | M20 | |||
| do | Nominal drilling diameter | [mm] | 8 | 10 | 12 | 15 | 20 | 25 |
| D | Thread diameter | [mm] | M6 | M8 | M10 | M12 | M16 | M20 |
| df | Fixture clearance hole diameter | [mm] | 7 | 9 | 12 | 14 | 18 | 22 |
| Tinst | Max. installation torque ≤ | [mm] | 4 | 11 | 17 | 38 | 60 | 100 |
| ls,min | Min. thread length | [mm] | 6 | 8 | 10 | 12 | 16 | 20 |
| ls,max | Max. thread length | [mm] | 10 | 13 | 17 | 21 | 27 | 34 |
| hmin | Min. concrete thickness | [mm] | 100 | 100 | 100 | 100 | 130 | 160 |
| h1 | Bore hole depth | [mm] | 27 | 33 | 43 | 54 | 70 | 86 |
| hnom | Embedment depth in the concrete | [mm] | 25 | 30 | 40 | 50 | 65 | 80 |
| hef | Effective embedment depth | [mm] | 25 | 30 | 40 | 50 | 65 | 80 |
| smin | Minimum allowable spacing | [mm] | 60 | 60 | 80 | 100 | 130 | 160 |
| cmin | Minimum edge distance | [mm] | 105 | 105 | 140 | 175 | 230 | 280 |
- Minimum bolt length: 9 mm + 8 mm = 17 mm
- Maximum bolt length: 9 mm + 13 mm = 22 mm
Therefore an M8 x 20 should be used
For other installation parameters, follow the values indicated in in the Index technical documentation, as well as in the European Technical Assessment.
For the installation process, consult applicable documentation and FAQ XXXXX
h1 : Bore hole depth
hnom : Embedment depth in the concrete
hmin : Min. concrete thickness
tfix : Fixture thickness
do : Nominal drilling diameter
df : Fixture clearance hole diameter
Latest revision: FAQ4 rev0
