Ever since Adam Cherubini brought up nails, there have been lots of posts of projects built using nails. However there’s been little talk about the pitfalls or the things to consider when using nails, so here’s some random thoughts on using nails.
1. When using nails you still need to be aware of wood movement due to seasonal change in temperature and humidity.
Here we see two pine boards nailed to a chest with oak nails, the result would be the same with iron or steel nails. The large separation at the left is a spline joint. The chest is quite old, before 1700 so it has gone through many seasonal cycles. We can see that there is a split in the edge of the boards at each nail and in the center of the boards. The splits at the nails are probably due to a difference in the coefficient of expansion between the oak nails and the pine boards. The split in the center is due to the nails restricting the boards ability to move seasonally.
This is the top of a circa 1830 school desk made from pine. The lift top is one wide board with a bread board end nailed on with cut nails. Again we see a wide split where the nailed on edge restricts the seasonal movement.
This is the edge of a wide glued up pine board nailed on to a circa 1890 chest with wire nails and my cats foot. Again we see a split at each nail and a larger split for the same reasons. If you look closely at all 3 pictures we see that the large splits all take place near the flat sawed portion of the boards not the quarter sawed edges, this is because the flat sawed portion is trying to move more than the quarter sawed portion of the boards.
2. Nailing wide boards to the bottom of chests and the backs of chests of drawers is historically correct, there is nothing wrong with doing it on reproduction work, I do it all the time. You just need to be aware of the results and prepared for the inevitable splits.
3. Narrower boards tend to split less, first because they move less and second because nails have some give and allow for small amounts of movement.
4. Seasonal movement over time will jack the nails out of the wood loosening the joints.
5. When wood expands around an individual nail, the nail does not give, the expansion crushes the wood cells against the nail, when the wood then shrinks the nail loosens. This is why so many nailed pieces have been re-nailed, sometimes multiple times.
6. Anything you can say about nails is true about screws.
7. There are ways to use nails that allow for movement.
By using narrower tongue and grove boards and either blind or face nailing just one edge, the boards are allowed to expand and contract without restriction. If blind nailed any split caused by the nail is unseen. By using narrow boards you get enough nails in the work for strength and the boards won’t shrink enough to separate the joint.