Bandsaw Tune-upComments (0)
The bandsaw may be the most versatile player in the woodshop.
It can rip, resaw, crosscut, and execute all kinds of curved work, including
cabriole legs, circles, arcs, and serpentine drawer fronts. Outfitted with an
appropriate blade, it can chew through thick stock to rough-out parts, fine-saw
joinery like tenons and dovetails, and even do detailed scrollwork. Finding
this machine equally desirable for fine and rough work, I made room in my shop
for two saws: a 30-year-old 14" Rockwell, set up with a narrow blade for
curve-cutting, and a newer 14" Delta, outfitted with a wide blade and
riser block, for resawing.
Despite its simple appearance, a bandsaw is a precision instrument. Whether you own a giant with 20" diameter wheels or a 9" benchtop, it requires periodic maintenance to cut as well as it should.
Here’s how to give your saw a thorough once-over to ensure that the parts are all in good operating order. I’ll show you how to fix common problems and quickly dance through the steps involved in changing blades.
The way it works
The bandsaw does its business by virtue of a thin hoop of toothed steel (the blade) fitted and tensioned around two tire-covered wheels. Typically, the motor drives the lower wheel via belts and pulleys. The upper wheel rises to adjust blade tension and tilts to establish blade tracking. The table, which supports workpieces being sawn, tilts on trunnions to allow bevel-cutting. Two sets of blade guides—above and below the table—prevent the blade from twisting and shifting in use. The height-adjustable guide post provides control directly above the workpiece.
A regular checkup
First things first: Give your saw a general checkup, inspecting the wheels, tires, guides, and other parts to ensure proper alignment and good working condition. It’s wise to do this annually.
Inspect the wheels and tires
For precise tracking and smooth performance, the wheels, bearings, and tires must be in good shape. Before scrutinizing each individually, check the tracking. To do this, tension a blade according to the saw’s tension gauge, then use the tracking knob to center the blade on the wheels while slowly rotating them by hand. Once centered, the blade should not wander. If the blade tracks like it should, you’re in for a cleaning and minor tune-up; if it doesn’t, plan on spending time dealing with worn tires or wheel bearings.
After the tracking test, remove the blade and listen for any bearing noise while slowly turning each wheel. Clicking or grinding noises usually indicate that you need to replace bearings. Next, inspect the tires for grooves, cracks, or other damage that can compromise tracking. If the tires need replacement, get a fresh set from the manufacturer or upgrade to urethane wheels (see photo, page 60) because they’re tougher and are installed without adhesive.
If the tires are sound, clean them with a synthetic abrasive pad. For good tracking, keep the wheels as clean as possible. Installing a brush in the lower wheel housing, as shown in Photo A, can help a lot.
Check guide post and guides
Clean a dirty post with steel wool and mineral spirits before oiling it. Also clean dirty or gummy bearings by wiping them off with mineral spirits (don’t soak them). Reverse or replace a scarred thrust bearing.
It’s important that guide blocks (or roller bearings) are parallel to the sides of the blade. Before checking this alignment, make sure the block faces are smooth and square. (For a shop-made guide block dresser, see page 16.) Slide them against the sides of a wide blade, as shown above, to ensure that they are parallel. If necessary, rotate the guide mount (Photo B) to correct the problem.
Some bandsaws come equipped with roller bearing side guides instead of guide blocks. Both types work fi ne. Guide blocks provide closer support to the workpiece for better curve cutting, but their faces wear over time, while the edges of roller guides don’t. As with guide blocks, roller guides are set away from the blade only .003" or so. With roller guides, make certain that the thrust bearing doesn’t allow the blade to slide back far enough to suffer tooth damage from the side bearings.
Check the table and trunnions
Check the table for flatness using a straightedge. A hump or dip can cause shop-made fences and jigs to sit askew. You could have a machine shop grind the table flat, but an easier fix is to simply shim accessories as necessary. Next, use a small try square to check that the table is 90° to the blade with the table registered against its stop. If it’s not, adjust the stop as shown in Photo C. While you’re at it, clean and oil the contact surfaces of the trunnion to allow easy table tilting.
Check belt(s) and pulleys
Use a straightedge to ensure that the pulleys on the motor and drive wheel are aligned for smooth operation and long belt life. Excessive saw vibration is often due to a stiff, galloping belt. Replacing it with a link belt can help. (If your blade slips or bogs down during cutting, try increasing motor pressure on the drive belt.)
There are certain adjustments to make every time you install a different-sized blade. It’s nothing complicated; you’ll just need to readjust the blade tension, tracking, and blade guides. The switchover takes about 10 minutes. I outfitted my saw with a quick-release tension lever (see bottom photo, page 61), which makes the job even quicker.
Dismount the blade
Back off the side guides and thrust bearings and remove the throat plate and table alignment pin. Release the tension until the blade is loose enough to slide off the wheels. Then remove it, taking care not to kink it in the process.
Install the new blade
After carefully threading the blade behind the guard and into the space between the guides, hang the new blade on the top wheel. Now slip it onto the lower wheel, as shown in Photo D, and apply just enough wheel tension to create traction. While slowly rotating the wheel by hand, alternately tension and track the blade until it rides in the center of the wheels. Crank the upper wheel to the proper tension.
Set the guides
Always set the guides as close as possible to the blade without touching it while it’s freewheeling. The traditional approach is to use a dollar bill as a spacer gauge, but I have a simpler, quicker approach.
The Tension Question
My approach is to set the tension according to the saw’s tension gauge and then observe how the blade cuts. (Remember that a dull blade won’t cut well even under “perfect” tension.) If a sharp blade doesn’t easily follow the cut line or bows during a resaw cut, apply a bit more tension and check for improvement. Just don’t overdo it, because too much tension can stress saw parts and induce blade breakage. In any case, never fully compress the tension spring, which acts as a shock absorber to prevent blade damage.
Getting The Drift
When ripping or resawing using a fence, you’ll need to establish the saw’s drift angle. Because of a blade’s tendency to cut in a particular direction, it may not be perpendicular to the front of the saw table.
• Strike a line 1" from the edge of a piece of straight-sided scrap about as long as your saw table. Cut to the line freehand until the leading end of the board reaches the far end of the table (top right).
• Without shifting the board, hold it down as you shut off the saw. Then use a fine-tipped marker to scribe reference lines on the tabletop at the leading and trailing edges of the scrap piece. This represents your drift angle.
• To resaw a piece of stock, determine the cut location in the stock and measure the thickness between the intended kerf and inside (or fence side) face. Using this dimension, mark two lines at the front and back of the saw, making them parallel to the drift angle lines. Next, move the fence up to this second set of lines, angling it to match the drift angle (bottom). (You’ll actually want to add 1 /32" or so for cleanup.)
First, set the guide post about 1 /4" above the
workpiece. To adjust the thrust bearing, mark the outside perimeter, as shown
in Photo E, to easily detect rotation. While slowly turning the saw wheel,
adjust the bearing forward until the blade spins it, then back it off just
enough to stop the spin. Lock the bearing position, then take the blade through
a full rotation, checking for bearing spin throughout. Readjust if necessary.
Set the side guides next. Begin by adjusting them fore or aft, so that the front edges sit a few thousandths of an inch behind the teeth gullets. (See Figure 1, page 62.) Next, set the face of each guide about .003" from the blade sides. With guide blocks, place each against the blade without deflecting it, then back the block off just a tiny bit and lock it down. (With roller bearings, use the same “touch and retreat” technique as with the thrust bearing adjustment.)
After setting both guides, slowly turn the blade a few full rotations to detect any binding, especially at the blade weld.
Make a test cut
Test cuts are particularly important before you slice into your prime stock. Close the wheel-housing doors and turn on the saw for just a few seconds. After it stops completely, make sure that the blade is still tracking in the middle of the wheels. Make a few test cuts to ensure the blade follows the line well. If you plan to resaw, read “Getting the drift,” above, for fence-setting steps.
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