The hammer and mallet are both tools for hitting /striking others instruments. The hammer has an iron head, while the mallet is made completely of wood.
The medieval hammer used in carpentry is most often seen as a claw hammer, sometimes reinforced with long metal strips along the handle. The hammer is used for striking nails and dowels into the wood. A specialised form is used for closing rivets (riveting hammer). Metal hammers are common finds, but it can be difficult to assign the tool to a specific trade, as also smiths, stone cutters, shipwrights, among others, used hammers.
A 15th century claw-hammer. Image from 'Das Werkzeug des Schreiners und Drechslers' by Gunther Heine.
A clawhammer with a reinforced head and a wooden mallet from the Bedford Hours miniature
'Building the arc of Noah', 1433, London, British museum, Ms. 18850.
A riveting hammer in the right panel of the Merode Altar by Robert Campin, Metroploitan Museum of Art, New York.
The iron head of our medieval clawhammer is made by Deagrad. The handle is homemade from ash and secured with an wooden wedge. Ash is often used for handles as it has some flexibility
The mallet is used to secure pegs (for instance for the pole lathe), hitting chisels and gouges, hitting the holdfast, wedges and benchdogs. Medieval mallets were constructed either as a square or round block attached to a handle and as (turned) cylinders in the length of the handle.
The first type of mallet hits with the hard endgrain, and can be used with more force. Large versions of these hammers were used with wedges to split wood into planks or smaller pieces (see images below). A smaller square mallet is shown in another miniature below..Many hammers of this type with a round head are found in the miniature of Noah building the ark in the Bedford hours (see image above).
Eve uses a mallet and chisel and Adam a breast-auger.
12th century miniature from Homelie de St. Basile.
The cylinder type of mallet construction ensures that a chisel always is hit evenly with the mallet, whatever manner it is hold. However it hits with the long grain, which is more easily indented. Thus pictures often show these mallets with the cylinder hollowed out, i.e. the very worn out ones. This type is found for instance in another image of the Mendelschen Hausbuch shown below.
A cylindrical mallet used by a medieval joiner (Peter Screiner). Mendelschen Hausbuch around 1444.
A 10th century wooden mallet found in the Coppergate deposit in York, UK (no. 8188). The head is willow with a hazel handle. (Image from C.A. Morris - Wood and woodworking in Anglo-Scandinavian and medieval York)
We have two types of mallets in our toolchest, a square one (oak hammer head with an ash handle), and two turned cylinders made of acacia. (I recently discovered that this is an exotic tree; the first acacia was planted in Europe in 1579 in Castle Doorwerth, the Netherlands, so we will have to replace these mallets in time with ones made of correct wood). The tools are finished with linseed oil.