MAXA Technical Support
DTH Hammer Weight On Bit
A DTH hammer needs sufficient weight to keep the bit closed on the drill. Excess weight on bit will only damage the bit, hammer and drill string. However, insufficient weight will cause the bit to bounce up and down in the chuck. A quick calculation is as below, but it varies on different drilling conditions.
Air pressure below 250 PSI
Required Weight on bit (lb) = bit diameter (in) x 500
Air pressure above 250 PSI
Required Weight on bit (lb) = bit diameter (in) x 800