I was thinking about the idea of making a dead blow hammer – really just an interest in the basic physics and then the design.
I started by making the parts you can see in the photo to the left, this is for 2 off hammers.
The tubes were from one of those random boxes of steel that you buy on ebay. They are mild steel, 3/4″ diameter, an inner diameter of 1/2″ and around 2-1/4″ long – for those metric people: 19mm OD, 12.7mm ID and 57mm long.
I threaded each end 14x1mm – really just based on the fact that this was the nearest size I had that would work, the thread is a touch on the shallow side in the tube, but good enough that you can wind the ends in firmly.
I was then going to make handles, but this is not that simple based on the fact that I needed to get a good joint with the tube, hmm. This got me thinking and whilst balancing the parts in my hand I got to wondering if they would work as a hammer where you just hold the head? The benefit would be that you get great control of the hammer itself, especially with regards to angle of impact, which is really useful when using this to hammer out a shape in a thin metal.
If I’m going to hold this in my hand I needed a piece of something around the metal tube to make a nicer grip – this is where the ebony came in.
So, now we have a steel tube glued into an ebony tube with Gorilla glue, some 1mm diameter steel balls and two hammer end faces: 1 off mild steel and 1x brass.
I filled each tube with roughly 550 steel balls, this was roughly 3/4 full.
The idea is that when the hammer impacts on something the steel balls move from the end furthest away from the face – this is where they move to when you accelerate the hammer with your hand, to then impact the back of the hammer face. The result is the impact energy is spread out over a longer time, a lower peak force for the same mass and the energy under the curve will be the same.
The hammer ends were fitted with a generous amount of thread lock. I will have to see with time if this can withstand the number of impacts it will see.
The final two palm hammers, slightly different, but essentially the same.
They each weigh roughly 160g each.
The end result is a really nice hammer for working with sheet metal. I will add some images of the hammer in action and some of the resultant work.
Also, I have some thoughts about a slightly different design that would allow me to increase the loose mass and reduce the fixed mass of the main body.
Plus some ideas for reducing the cost by using the cast iron swarf that we all get from machining flywheels and cylinders.