I needed a small but heavy soft-headed mallet for aligning work-pieces in the chuck or vise for turning or milling operations. I made a lead-headed mallet using capillary plumbing fittings as per the attached photo. I used 15 and 22 mm fittings, which gave me a small mallet that weighs 406 g (14.3 ounces). The design could be scaled up to 28 mm (or to whatever size plumbing fittings are available in your country of residence). When the head becomes deformed the lead head can be melted down and cast anew. Mine has been in use for some years and it has not been necessary yet to recycle the mallet. Refer to the attached PDF file for construction details.