This is my rendition of Marc Lecuyer’s Machinist’s Hammer project. Marc has provided a thorough tutorial on how to build this hammer on his Youtube channel and drawings are available for download on his website.
I was inspired by this project as it combined a few lathe techniques which I had not previously attempted. These include: long taper turning, short taper turning, knurling, form cutting and four-jaw work holding.
I followed Marc’s videos pretty closely, the most notable deviation was that I used 20 mm round 304 stainless bar for the handle (stock which I had on hand) instead of 19 mm steel. I also used matching 20 mm 304 stainless square stock for the hammer head.
The handle comprises of a tap cut M10 thread on one end and a 12 mm deep drill on the other end. I believe the deep drill is to reduce the weight of the handle and improve the overall weight balance. The hole is later covered with a press fit cap. The handle was knurled and then the radius cutter shown above was used to cut the 5 mm radius which transitions into a 5º taper. Fortunately, one of the lathes which I have access to is equipped with a taper attachment, which was used to turn the long taper.
Even though the handle has been hollowed out I still feel that the centre of gravity is slightly too far towards the handle end of the hammer. This may be partly due to the fact I used 20 mm stock rather than 19 mm as specified. I may still drill out the pressed in end cap and deep drill the handle with a larger sized drill, possibly 13 or 14 mm, to further reduce the weight of the handle.
Dialling the 19 mm square stock in the four-jaw chuck.
Short taper turning by hand using the compound slide, taking care to result in a perfect parabolic curve where the taper surfaces meet on each flat face of the hammer head.
Completed hammer head, ready to have M10 hole drilled and tapped to accept the hammer handle.
Brass hammer tip parallel machined, drilled and M10 tapped.
Test fitting the hammer head.
All of the completed parts prior to assembly. Hammer handle, brass tip, acetal (Delrin) top, hammer head and press fit end cap.
Fully assembled Machinist’s hammer.
Overall I am happy with how this project turned out and I learnt a lot of the new turning techniques as mentioned above. I will mostly likely make the modifications to address the hammer weighting issue in the near future.
I think the knurling could be improved somewhat, the alignment is not quite right, resulting in a not quite perfect diamond knurl shape, but the finish is nice and uniform so I am happy with it for now. I was working within the constraints of the tool I had on hand. I am thinking that my next project will be to build a pinch type knurling tool, I see Hemingway has some nice kits available…
EDIT: I ended up drilling out the handle to a diameter of 13 mm and about 116 mm deep. I then reamed a short section to 14 mm and made a new press fit end cap to fit. The weight balance is now greatly improved and feels much better in the hand.