A saw filer is a person who maintains and repairs saws in a saw mill. A saw filer's work area in the mill is called the filing room. Saws used in timber mills are very large. They need maintenance for safe operation. Repair of damaged saws requires a degree of skill. It takes a year of saw filing to become proficient. Automated equipment has continued to be developed and implemented to improve saw repair quality, with the end goal of operational uptime and productivity. Bandsaw filing Bandsaws in timber mills range in size from about (4" x 22ga x 10') to (16" x 11ga x 62') and can use any of the three main different saw band types: Single-cut saws have, as the name implies, teeth on one side, allowing for cutting in one direction only. Double-cut saws have teeth on both sides. These types are designed for machinery that allows the log or work piece to be cut from either the front or the back direction of travel. "Sliver tooth" saws have teeth on both sides but they have different profiles. The (usual) front side have teeth with a regular style tooth. The back of these saws have a longer style. The log is cut in a forward direction as with a single-cut but as the log returns, the saw de-burrs the cut (path where the saw passes) allowing for a cleaner finish. They are run for 4 to 24 hours then sent to the saw filer for maintenance. The saw filer inspects the saw for needed repairs then gums, fits and benches the saw as necessary. Gumming involves grinding the gullets of the saw teeth to a particular shape. The saw filer uses a semi or fully automatic grinding machine for this. Saw bands operate under high stress and heat and in the presence of wood chips. Carbon migrates into the steel from the wood. Gumming prevents case hardening and fatigue cracking of the saw band gullets. Resaw Bandsaws (teeth on one side only) may be left or right-handed, depending on which way the teeth are pointing and which way the plank falls from the log when cutting. Double cut saws (teeth on both sides) are always gummed right hand teeth first. A precise profile of the tooth (including gullet area, hook angle and top clearance angle) must be maintained for proper saw operation and wood chip removal.