My Bandsaw Is Not Cutting Straight

Correctly set up and maintained, a wood-cutting band saw should cut straight for either rip cuts or crosscuts.

Don't expect straight cuts if you begin with uneven blocks of wood.Don't expect straight cuts if you begin with uneven blocks of wood.
As blades wear, the accuracy of the cut decreases. Bandsaws made for the homeowner typically run blades only 1/2-inch wide, making perfectly accurate deep cuts very tricky. Choosing the right blade for the job and adjusting the saw correctly guarantee the best results possible.

Select the right blade for the job. Use skip-tooth blades designed for ripping when cutting with the grain. Choose raker-tooth blades made for crosscutting when working across the grain. Consult the bandsaw manual for advice about the proper blades for softwood or hardwood. The harder the material, the more teeth-per-inch you'll need. Using blades with a TPI too high for the material causes clogging, according to AllBandsawBlades.com.

Unplug the bandsaw before adjusting or replacing the blade. Step to the side and flip the power on and off to be sure you disconnected the right cord.

Remove blade shields and loosen blade guides and backup bearings. Screwdrivers and Allen wrenches usually fit these parts, but procedures vary with the machine's brand. Remember to loosen blade guides both above and below the bandsaw table.

Adjust the tension of the upper bandsaw wheel to tighten the band saw blade. Use the procedure recommended by the operator's manual -- some saws require a large Allen wrench for this, and others provide tensioning controls. Tighten until the tension gauge -- a standard feature on most bandsaws -- reads correctly for the blade width. Without a tension gauge, tighten until all curve disappears from the blade's working edge and tighten an extra half turn, according to Robert Vaughan of Fine Woodworking magazine. .

Spin the bandsaw wheels carefully and adjust the tilt of the upper wheel so the blade runs with cutting teeth just off the edge of the rubber pad.

Advance guide bars and backup bearings to meet the sides and spine of the band saw blade. Guides and bearings should barely touch the blade as it turns. Blade tension, not guide pressure, holds the blade straight. The backup bearings only firmly contact the blade's spine during the back pressure of a cut. Improperly tensioned blades won't cut straight, says the Oklahoma University Extension Service.

Reinstall all safety shields and covers before applying power to the machine again.

Hold workpieces firmly against either miter gauge or ripping fence and advance the work steadily through the saw. Pushing too hard causes the blade to twist or bow, throwing the cut out of line. Sharp blades cut accurately with little feed pressure.

Things You Will Need

  • Allen wrenches
  • Screwdrivers

Tips

  • Test the bandsaw on a piece of scrap to make sure everything runs properly before trying an important cut.
  • Plane one face and one edge of the workpiece perfectly true to provide accurate surfaces to place against the bandsaw table and fence.

Warning

  • Don't overcompensate by running blades wider than the maximum your machine allows. A 3/4-inch wide blade may fit on the wheels, but the frame of a machine built for 1/2-inch blades can't tighten the larger blade enough to keep it running true.

About the Author

James Young began writing in 1969 as a military journalist combat correspondent in Vietnam. Young's articles have been published in "Tai Chi Magazine," "Seattle Post-Intelligencer," Sonar 4 ezine, "Stars & Stripes" and "Fine Woodworking." He has worked as a foundryman, woodturner, electronics technician, herb farmer and woodcarver. Young graduated from North Seattle Community College with an associate degree in applied science and electronic technology.