Injectors from the Hammer-Blow group lock within the drill hole
by compression and friction after being pounded into place. These
injectors are available in both metal and plastic versions in two
different diameters. The Hammer-Blow design uses the smallest drill
holes and is the least expensive of all injector types but is not
effective in "punky' concrete, layered substrates, or surfaces which
have been weakened by chemical attack.
The 3/8" hole size is one of the smallest in common
use. Small diameter drill holes are desirable because small holes
are quicker to drill and take out less concrete. Small diameter
injectors are, however, subject to depth limitations because of
bit diameter-vs-length constraints. As the bit diameter becomes
smaller, the maximum length of the bit must become shorter. Thus
short and small bits may be easier to use but somewhat more likely
to miss the targeted crack.
The QC8-HP is made from high-impact plastic and
has a long threaded shaft on the zerc for reliable retention under
pressure. The zerc and injector are shipped disassembled; the zerc
is normally inserted into the injector just prior to use. The aluminum
QC8-HA uses a barbed zerc which is installed just prior to injection
using a simple Zerc Drive Tool. This same tool is used to place
the QC9-HS. For large injectors in drilled hole sizes of 1.0" to
2.0", Strata Tech has the Twist-Lok Injector series.