How are hammer drills different from rotary hammers?

Hammer drills and Rotary hammers are widely used in construction industry for drilling and breaking of concretes and masonry.

Even though they share some similarities there is a key difference between them. Rotary motion i.e. the spinning (mechanism) of drill bit in both the machines are same, provided the chucks used are also similar. The difference lies in the mechanism of generating hammering motion in them.

 In Hammer drills, the hammering motion of the chuck is generated by interlocking two ridged discs. When the ridged discs ride one over the other they generate hammering action to produce the required pounding force.

In Rotary hammers, to and fro piston mechanism is used to generate required hammering action of the chuck. Air is used to push the pistons, just like the engines in two wheelers and cars. Usage of air for piston movement gives this machine greater pounding force, making rotary hammers more powerful compared to hammer drills.

Hammer drills are used for small size drill holes in porous concrete and masonry; rotary hammers are used when the concrete is dense and the size of drill holes are bigger. Hammer drills can be used in 'drill only mode' and 'drill plus hammer mode'; likewise Rotary hammers can be used in 'hammer only mode' and 'hammer plus drill mode'. In other words, hammer drills can be used as a drilling machine and rotary hammers can be used as a mini jack hammer.

In conclusion, for drilling smaller holes in porous concrete and masonry hammer drills are useful. For drilling bigger holes in dense concrete and minor demolishing (like Tiles removal) rotary hammers are useful. Both these machines are very useful in Constructions industry and considered as must have power tools for civil engineering work force.