The hand operated jack hammer consists of two parts; a tubular steel handle and a solid steel tool bit.
The handle slides over the tool bit, so as to deliver an impact blow to the top end of the tool.
The bit is interchangeable and comes in a choice of 4 end points.
The 4 interchangeable tool bits are around 1000mm (39”) in length and weigh between 5.5kg and 7kg (12lb and 15lb).
The handle is 860mm (34”) long and weighs 6kg (13lb).
The top of the handle is ergonomically shaped so as to provide a handgrip.
The hand operated jack hammer measures 1800mm (72”) fully extended (which is the same as a conventional crowbar). The handle has a “stroke” of 620mm (24”).
Given the higher impact forces delivered by the hand operated jack hammer it is important that the tool ends are resistant to fracture and chipping.
The tool ends are made from selected high grade steel with ends subject to hardening to minimize this.
The tool steel complies with Australian Standard AS1443-1994 Carbon steels and carbon-manganese steels – Cold-finished bars or AS1444-1996 Wrought alloy steels – Standard, hardenability (H) series and hardened and tempered to designated mechanical properties.
Forging and hardening is carried out in accordance with the steel manufacturer’s specifications.
Manual Handling Risk Assessment
Conducted by ORC
The assessment is based on comparison with a conventional crowbar. Using various energy calculations I compared the two devices when used as an impact tool and in my opinion the hand operated jack hammer offers a number of benefits over the crowbar. My findings and comments follow.
The tool consists of two parts; a tubular steel handle and a solid steel tool bit. The bit is interchangeable and comes in a choice of 4 end points. The handle slides over the tool bit, so as to deliver an impact blow to the top end of the tool. The handle is 860mm (34”) long and weighs 6kg (13lb). The top of the handle is shaped to provide a handgrip. There are 4 interchangeable tool bits of around 1000mm (39”) length and weighing between 5.5kg and 7kg (12lb and 15lb). The tool measures 1800mm (72”) fully extended (which is the same as a conventional crowbar). The handle has a “stroke” of 620mm (24”). The crowbar used in the comparison measured 1800mm (72”) overall and weighed 7.75kg (17lb). A stroke of between 400mm (16”) and 620mm (24”) was assumed.
The tool requires nearly 25% less energy expenditure to operate compared to the crowbar which is an advantage from a “manual handling” viewpoint. Using the crowbar one has to lift the total weight of 7.75kg (17lb). Using the hand operated jack hammer one lifts only the slide handle which weighs 6kg (13lb). (The energy savings will be even greater when digging as withdrawal from soil will take less effort compared to a crowbar).
On average the tool delivers around twice the force at the point of impact. (This is a result of the slide handle travelling further and therefore at a greater velocity relative to the crowbar’s motion and that its total weight of 12kg (26lb) is greater than the crowbar’s 7.75kg (17lb). This makes the hand operated jack hammer a more efficient tool.
With the hand operated jack hammer, the tool maintains a constant point of contact with the object being struck thus the force is being applied more accurately and efficiently. It also reduces the risk of the operator being struck from a deflecting blow.
Given the higher impact forces delivered by the hand operated jack hammer it is important that the tool bit is resistant to fracture and chipping. I note your advice that the tool is made from selected high grade steel with ends subject to hardening to minimize this. According to the specifications supplied the tool steel complies with Australian Standard AS1443-1994 Carbon steels and carbon-manganese steels – Cold-finished bars or AS1444-1996 wrought alloy steels – Standard, hardenability (H) series and hardened and tempered to designated mechanical properties. I also note the statement from the Blacksmith confirming that forging and hardening is carried out in accordance with the steel manufacturer’s specifications.
To summarise, the hand operated jack hammer should be a safer and more efficient tool for impact use when compared to a conventional crowbar. The hand operated jack hammer is not designed to be used as a “lever”.
