There is considerable confusion about the different, commonly used methods of drilling and, particularly for remedial work, it is important that the correct tool and method is used to ensure a proper result and to avoid damage to the existing masonry.
To deal with all situations that may arise, contractors
using the Helifix Dryfix system will need both an
|
electric hammer drill (3-jaw-chuck type) and a rotary hammer (SDS type).
The 3-jaw-chuck type drill is used only for drilling whereas the SDS type drill is used with the Helifix Power Driver Attachment used to insert DryFix ties and, in special circumstances, for drilling into hard material. (see below).
|
|
This type of electric hammer drill is designed to provide a rotary drilling action, which may be amplified by a light ‘tapping’ action. This light percussion improves the drilling rate but is gentle and permits fragile masonry substrates such as brick, terracotta, mortar, hollow concrete block (C.M.U.), to be drilled without damage, particularly when the drill breaks through the material into a void or cavity This kind of drill will commonly have a chuck speed up to 2500 rpm with 10-40,000 percussive ‘taps’ per minute.
The Bosch electric hammer drill, 1194 VSR, and the Milwaukee Magnum have been found to be satisfactory but other units with a power rating of 7.0 amps and a similar specification are available.
Please note that any reference to a particular make of tool is for guidance only and Helifix takes no responsibility for the performance of any particular tool. Specific tools should be discussed with the manufacturers or their representative. |
The rotary hammer drill, SDS type, is always used to set the Helifix tie into position with either a ‘DryFix’ Power Driver Attachment for masonry stabilization, or a Helifix Power Support Tool for masonry re-facing.
The SDS hammer drilling system is only used for drilling into dense materials such as reinforced concrete, some limestone and sandstone and for blind holes in strong material. Sometimes the method may be used to drill mortar. The drilling of all holes should be tried first with the 3-jaw-chuck type drilling machine and the SDS method should be seen as a “last resort”. It should not be used into cavity masonry as significant breakout is likely to occur in the cavity. A 3-jaw-chuck adaptor fitted to an SDS machine must NEVER be used in place of an electric hammer drill.
Typically, SDS type Rotary Hammers have a chuck speed range of 600-800 r.p.m. with approx 4,000 hammer blows/minute. There are a wide variety of tools available, with Bosch, Hilti and Milwaukee tools being popular. The Bosch 1122VSR 7/8” or 11222EVS 11/8” and the Hilti TE15 are the most widely used but other units with an amperage of 6.9 to 7.8 should give adequate performance. |
