Jamb saws are electric or battery-operated machines designed to undercut door casings prior to the installation of hardwood and other types of flooring. This makes the process easier for the flooring installer because instead of cutting around the various types of door jambs, the installer simply can undercut them with the jamb saw and slide the flooring underneath. This not only simplifies the process, it also provides a better product because it gives the appearance that the casings were originally placed on top of the flooring.
There are two main designs for jamb saws, and both are adjustable to accommodate different flooring thicknesses. The first is an oscillating variety that uses either a straight double-sided blade or a straight blade with teeth only on the very front edge. This model is particularly good for cutting inside corners where two door casings meet. It is not as powerful as the second, rotary type of jamb saw, but its slower operating speed causes less damage to the casings during the process.
The second design resembles a circular saw placed on its side. It uses a round, fully toothed blade that rotates at a high rate of speed. This design is inherently more dangerous to the door frames and the user. The blade is round, and it cuts in a circular motion, so it is difficult to use in tighter areas. This limitation notwithstanding, it is the jamb saw of choice for professionals because of its power and the speed with which it can cut through multiple casings.
Jamb saws are produced by many manufacturers, with prices ranging from a low of $40 US Dollars (USD) to the highest of more than $300 USD. The difference between the high-end and low-end models is evident in quality and life expectancy. The cheaper models are not well suited for heavy commercial use, but they should suit the occasional installer or do-it-yourself user well.
When choosing a jamb saw, the buyer should be aware that a battery-operated model doesn't have the power or work-day longevity of the corded models. The wood pinches the blade during the process, so undercutting casings draws a lot of power. Additionally, there are nails and metal bands within some door frames that can make the saw draw even more energy during the cutting process. If the installer requires a full day's productivity, and on-demand usage, the electric variety never needs to wait for a battery charge, and it doesn't lose power as it is used.
Before the advent of the jamb saw, flooring installers would lay a piece of flooring down as a guide and then undercut the jambs with a regular handsaw. This was slow, laborious work that added to the time required to do the job. The motorized jamb saw changed this nature of the process and made it faster and more efficient.