Build - Lead Hammer Mold

I started by making the two handle pieces from 1/4" aluminum plate. With the two pieces held in the mill vise, I used a center finder "wiggler" to locate the junction of the two plates.

After drilling the four mounting holes and a center hole, I used a boring head to enlarge the center hole to fit the hammer handle.

The completed handle holders.

The next step was to sqaure up the aluminum block which will become the two halves of the mold.

After the block is square up and cut to the combined length of the two halves (plus 0.2" to allow for the futue step of cutting in half and cleaning up the cut faces), the holes for the dowel pins are drilled.

The drilled holes are reamed to 3/16". Noted I had to hold the reamer in a collet to get sufficient clearance on my small mill.

The center holes is then drilled and reamed to 1/2". It would have been more efficient for me to drill the center hole while I was drilling the dowel pin holes, but only a bit more work doing it last. The center hole is drilled to a depth a bit short of the final required depth.

The primary purpose of the center holes at this stage is to proved a reference surface for next steps on the lathe.

The block is now cut into the two required halves.

The cut faces of the two halves are cleaned up and squared up with a face mill. The photo shows the cleaned up halves with the dowel pins inserted for a test fit.

Test fitting the two halves - they fit together cleanly and firmly.

The top block is set up on the lathe in the 4-jaw chuck (with copper shims to protect the block), and initially centered using a dead center in the tailstock to press the block against the chuck face. The chuck jaws are tightened just enough to hold the shims in place.

A dial indicator is used to center the hole in the chuck.

The top block is bored out to 0.75".

For the next boring bar step (the large diameter of the hammer head), the compound rest is set to an angle of 2 degrees; this angle will provide draft to aid with removal of the hammer head from the mold.

I set the angle using a 2 degree angle standard clamped to the lathe chuck. The I adjusted the compound rest angle until I got near zero deflection when I swept the angle standard with an indicator.

With the compound rest set at the correct 2 degree angle, an indicator is used to bore to the determined depth. The boring is repeated until the outer diameter is 1.0". Since the internal bore is tapered, measuring the ID at the opening is difficult; I used both a caliper and an inside micrometer to make the measurements.

For the bottom half, I came up with a better method for calibrating the opening dimension (see below).

The bottom half was set up in the same way as the top half. However, before starting the boring operation, I first made a shallow cut ( a few thou) in the surface to establish the final opening dimension. It was relatively easy to measure the ID of this cut, which then served as a marker for the following boring in depth.

After completing the boring for the large ID for the bottom half, the angle was reset and the smaller ID was completed.

The "cylindrical" part of the mold was now complete.

With the two locating pins inserted, the two halves of the mold were clamped in the mill vise to drill and tap the holes for the handle holding plates.

The four holes for the handle holding plates are blind holes, and care must be taken not to drill into the mold hollow. Each of the four holes was tapped first with a plug tap, and then with a bottoming tap.

The final step was to drill and mill the hole for the handle. An initial 1/4" hole was drilled, and this was followed with a 9/16" diameter mill making a plunge cut. This was followed by a final plunge cut with 0.75" diameter end mill, taking care not to plunge past the half way point and into the internal mold face.

The two mold halves were then removed from the vise, separated, and de-burred.

Here are the two halves of the mold, ready for testing (not! -forgot one step)..

Oops! Almost forgot one more operation : Two small slots to enable prying the mold halves apart with a screwdriver blade. It didn't take long to complete that operation.

For testing purposes, I made a "stub handle" to use for an initial test pour. The stub has an internal 7/16"-14 thread on the outside end, so I can add a handle later if I get a successful pour.

Getting ready for a first test pour : I used a laboratory hotplate to melt lead in an old stainless steel pan. I "painted" the inside of the mold with oil to act as a mold release; the mold is propped up on and between some fire bricks.

A successful pour. Note how the lead "sinks" as it cools. The mold has extra length on top to compensate for this.

And here is the un-molded hammer head. The mold halves separated easily, and the hammer head pretty much just fell out of the mold. The somewhat wrinkly looking finish may be due to the mold release oil evaporating during the pour, or perhaps because the mold was not pre-warmed before the pour.

The final step is to cut off the excess head length. Just needs a handle added to make a hammer!

The first test pour got a good result, but I thought it could be improved. I decided to re-melt the lead and try casting it again in a heated mold.

I tried heating up the mold in the molten lead - bad idea! The cold mold caused the molten lead to solidify around it, and I had to use a propane torch to melt it out. The better method was to simply place the assembled mold on the hot plate next to the melting pot (even better would be a second hot plate, but unfortunately I only have one).

Pouring the head into the heated mold gave an improved result. In addition, I used the propane torch to re-melt the solidified lead in the top of the mold to remove the "sink;" this worked so well that I decided there was no need to cut off the excess.

Now it was time to re-cast the head on my well worn lead hammer. I melted off the existing head by dipping it in the melting pot, and also heating it with a propane torch.

I also used the propane torch to heat up the assembled mold. This worked, but not as well as heating the mold on the hot plate - I should have been more patient, but . . .

. . . in spite of my impatience, I still got a decent re-cast hammer head. I once again used the propane torch to re-melt the top end. I now have a "new" hammer, and with the mold I can easily re-cast the head when it gets worn again.