what causes hammer action

[woolyhead]

Looking inside the drill on the net doesn't explain what causes the hammer action or how it's turned on and off. Can anyone tell me, please?

[tooljoe]

From what I understand, your average hammerdrill/driver drill use a type of marry-go-round hammering. Where the top of the merry-go-round is the chuck and the mechanical toy model horses that go up and down are attached to chuck. i.e. every time a horse goes up, the chuck is pushed up...that energy is transferred to the bit and from the bit to the material.

here a pic i found on the webs hammer drill/driver...

On SDS drills, I believe it does not work this way...i could be wrong though, but I believe is more of a piston action hit.. that goes up and down. Think of a piston in a car rotated by the crank.

here is a pics a found on the webs SDS drill..

A marry-go-round action, although while doing thousands of blows a minute, is is not as direct of an impact as a piston moving up and down.

[kjones]

Tool joe is pretty much right.  A "hammer drill" or percussion hammer is essentially two ribbed "gears" hitting against each other (one stationary, the other spinning and connected to the bit)., whereas an sds+ or sds max rotary hammer uses an actual beat piece (heavy piece of metal pushed forward to interact with the bit). An sds+ bit is pneumaticly pushed by the beat piece being driven forward by the piston driven off of the motor, and an sds max hammer is driven by a beat piece actually striking the bit. The sds+ and max hammers function in a very similar manner, while the percussion style is completely different.