Anchor Spacing ( center to center spacing )
To obtain the maximum tension and shear load, a spacing, S = 12 anchor diameters (12d) should be used. When using the minimum recommended anchor spacing,
S = 6 anchor diameters (6d) the load should be reduced by 50%. The following table lists the load reduction factor for each anchor diameter (d), based on the
center to center anchor spacing
| Anchor Spacing(s) in inches |
| dla = d |
12d |
11d |
10d |
9d |
8d |
7d |
6d |
| 1/4" |
3" |
2-3/4" |
2-1/1" |
2-1/4" |
2" |
1-3/4" |
1-1/2" |
| 5/16" |
3-3/4" |
3-3/8" |
3-1/8" |
2-7/8" |
2-1/2" |
2-1/4" |
1-7/8" |
| 3/8" |
4-1/2" |
4-1/6" |
3-3/4" |
3-3/8" |
3" |
2-5/6" |
2-1/4" |
| 1/2" |
6" |
5-1/2" |
5" |
4-1/2" |
4" |
3-1/2" |
3" |
| 5/8" |
7-1/2" |
6-7/8" |
6-1/4" |
5-5/8" |
5" |
4-3/8" |
3-3/4" |
| 3/4" |
9" |
8-1/4" |
7-1/2" |
6-3/4" |
6" |
5-1/4" |
4-1/2" |
| 7/8" |
10-1/2" |
9-5/8" |
8-3/4" |
7-7/8" |
7" |
6-1/8" |
5-1/4" |
| 1" |
12" |
11" |
10" |
9" |
8" |
7" |
6" |
| 1-1/4" |
15" |
13-3/4" |
12-1/2" |
11-1/4" |
10" |
8-3/4" |
7-1/2" |
| Reduction Factor - Anchor Capacity |
| Tension/Shear |
1.00 |
0.91 |
0.83 |
0.75 |
0.65 |
0.55 |
0.50 |
EDGE DISTANCE (Center to Edge Spacing)
To obtain the maximum tension and shear load, an edge distance, E=12 anchor diameters (12d) should be used. When using the minimum recommended edge distance,
E=6 anchor diameters (6d), the tension load should be reduced by 50% and the shear load by 20%. The following table lists the load reduction factor for each
anchor diameter (d) based on the anchor center to edge distance
| Edge Distance ( E ) in inches |
| dla = d |
12d |
11d |
10d |
9d |
8d |
7d |
6d |
| 1/4" |
3" |
2-3/4" |
2-1/1" |
2-1/4" |
2" |
1-3/4" |
1-1/2" |
| 5/16" |
3-3/4" |
3-3/8" |
3-1/8" |
2-7/8" |
2-1/2" |
2-1/4" |
1-7/8" |
| 3/8" |
4-1/2" |
4-1/6" |
3-3/4" |
3-3/8" |
3" |
2-5/6" |
2-1/4" |
| 1/2" |
6" |
5-1/2" |
5" |
4-1/2" |
4" |
3-1/2" |
3" |
| 5/8" |
7-1/2" |
6-7/8" |
6-1/4" |
5-5/8" |
5" |
4-3/8" |
3-3/4" |
| 3/4" |
9" |
8-1/4" |
7-1/2" |
6-3/4" |
6" |
5-1/4" |
4-1/2" |
| 7/8" |
10-1/2" |
9-5/8" |
8-3/4" |
7-7/8" |
7" |
6-1/8" |
5-1/4" |
| 1" |
12" |
11" |
10" |
9" |
8" |
7" |
6" |
| 1-1/4" |
15" |
13-3/4" |
12-1/2" |
11-1/4" |
10" |
8-3/4" |
7-1/2" |
| Reduction Factor - Anchor Capacity |
| Tension |
1.00 |
0.91 |
0.83 |
0.75 |
0.65 |
0.55 |
0.50 |
| Shear |
1.00 |
0.91 |
0.83 |
0.75 |
0.65 |
0.55 |
0.50 |
Drilled Holes
The Cobra's line of expansion and specialty fasteners requires a hole to be drilled in the substrate. Our products are designed to function in holes drilled
using carbide tipped bits that conform to ANSI B94.12 standards. A properly drilled hole is a critical factor both for ease of installation and optimum
anchor performance. The anchors selected and the drill bits to be used should be specified as part of the total anchoring system. The following table lists
the nominal drill bit diameter along with the tolerance range established by ANSI for the carbide tip.
| Nominal Drill Diameter |
Tolerance Band |
Nominal Drill Diameter |
Tolerance Band |
| 3/16" |
.208-.198 |
5/8" |
.660-.650 |
| 1/4" |
.268-.260 |
11/16" |
.723-.713 |
| 5/16" |
.335-.327 |
3/4" |
.787-.775 |
| 3/8" |
.398-.390 |
7/8" |
.917-.905 |
| 7/16" |
.468-.458 |
1" |
1.041-1.030 |
Anchor holes depth is based on the anchor style. The recommended drilling depth is listed in the installation instructions for the individual products.
For one-step style anchors such as the Split Drive, the depth of the hole should be at least 1/2" or one anchor diameter deeper than the embedment depth to
which the anchor will be installed. For example, the drilled depth for a 3/4" diameter Parawedge anchor installed at a 4" embedment should be at least 4-3/4" deep.
Anchor holes should be thoroughly cleaned prior to installation of the anchor. This procedure is easily accomplished using compressed air or a vacuum. Dust
and other debris must be removed from the hole to allow an anchor to be installed to the required embedment and to insure that the expansion mechanism can
be properly actuated.
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