Wood Bandsaw Conversion - Car Craft Magazine

The beauty of this column is that we’re not limited to stories emanating from automotive boneyards. If there’s a cheap way to convert something like an inexpensive, wood-cutting bandsaw into a pricey metal saw, we will print it here. And that’s exactly what our machinist pal Lucki Candoff did many years ago when he got a great deal on a wood bandsaw. The problem with wood saws is that they spin too fast, typically with blade speeds of 600 to 2,600 feet per minute (fpm). Cutting metal demands much slower speeds in the neighborhood of 100 to 300 fpm. Since Candoff is a machinist, it wasn’t much trouble for him to work out a speed reduction solution by adding a second set of pulleys.

Perhaps the most difficult part of this conversion is working out the proper blade speed reduction. Reducing the pulley speed demands a second set of pulleys. This requires placing an independent jackshaft between the first set that will mount a second small pulley to drive the larger pulley to again reduce the speed. It sounds complicated, but it’s actually pretty simple. Candoff’s Rockwell wood saw uses one pair of pulleys to connect the electric motor to a second set of the 1:1 pulleys used for the blade. Since the second set of pulleys had no adjustment for belt tension, Candoff added a third small pulley on an adjustable slide to be used as a tensioner. As far as building the system, Candoff says the hardest part was cutting the saw’s base to open up enough area to allow placement of the second large pulley. Fitting everything to line up properly also required a little forethought. Here’s how he did it.

This may look like an expensive metal bandsaw, but it’s actually a 40-year-old wood saw that Candoff converted to a metal saw by adding a second set of speed-reduction pulleys. This is one place where slower is better.
This may look like an expensive metal bandsaw, but it’s actually a 40-year-old wood saw th
This is the front side of Candoff’s converted wood saw. These pulleys help to establish blade speed and also maintain blade tension.
This is the front side of Candoff’s converted wood saw. These pulleys help to establish bl
Here’s where the fun begins. Starting at the bottom, the electric motor reduces motor speed by using a small pulley (1) to drive a larger one (2). This isn’t enough, so Candoff devised a jackshaft system to use a second small-drive pulley (3, hidden in this photo) to drive a second large pulley (4). Candoff also added an idler pulley (5) that does not affect the ratio but is necessary to maintain belt tension.
Here’s where the fun begins. Starting at the bottom, the electric motor reduces motor spee

Arrow 1 points to the adjustment plate that positions the idler pulley. Arrow 2 indicates the position of the second small-drive pulley mounted on the jackshaft. Arrow 3 indicates the plate Candoff made out of scrap steel that mounts the jackshaft. He used sealed bearings for the jackshaft, so no lubrication is necessary. Arrow 4 indicates where the base of the Rockwell machine had to be modified to clear the first large-driven pulley.
Arrow 1 points to the adjustment plate that positions the idler pulley. Arrow 2 indicates
The model No. 14 of this Rockwell machine refers to a throat depth of 14 inches, which is the distance from the saw blade to the back of the machine. More throat depth allows for cutting larger pieces.
The model No. 14 of this Rockwell machine refers to a throat depth of 14 inches, which is
Above: Setting band tension is a story all to itself. A tight tension assures a more accurate cut, but you might consider relieving the tension if the saw will sit unattended for long periods. The top adjustment knob on this machine is to set the tension; the smaller adjustment is to set the angle of the top wheel to align the band. Left: This is a new wood bandsaw from Harbor Freight in John McGann’s warehome. The four-speed Central Machine saw (PN 67595) sells for a reasonable $349.99, but its slowest blade speed is 600 fpm and its highest is 2,670 fpm. The company tells us it’s about to release an affordably priced metal bandsaw, so it might be worth it to wait a bit longer. Harbor Freight also offers a larger horizontal/vertical bandsaw for $229.99 (PN 93762) that will cut up to 41⁄2-inch round pieces with three speeds of 80, 120, and 200 fpm.
Above: Setting band tension is a story all to itself. A tight tension assures a more accur

Setting band tension is a story all to itself. A tight tension assures a more accurate cut, but you might consider relieving the tension if the saw will sit unattended for long periods. The top adjustment knob on this machine is to set the tension; the smaller adjustment is to set the angle of the top wheel to align the band. Left: This is a new wood bandsaw from Harbor Freight in John McGann’s warehome. The four-speed Central Machine saw (PN 67595) sells for a reasonable $349.99, but its slowest blade speed is 600 fpm and its highest is 2,670 fpm. The company tells us it’s about to release an affordably priced metal bandsaw, so it might be worth it to wait a bit longer. Harbor Freight also offers a larger horizontal/vertical bandsaw for $229.99 (PN 93762) that will cut up to 41⁄2-inch round pieces with three speeds of 80, 120, and 200 fpm.
Setting band tension is a story all to itself. A tight tension assures a more accurate cut
If you are thinking of purchasing a used wood bandsaw, look for one that will accommodate a large-diameter workpiece. Candoff says he’s cut a 6-inch-thick piece of stainless steel with his converted saw, “but you have to keep the blade clean and cool with oil.”
If you are thinking of purchasing a used wood bandsaw, look for one that will accommodate
Candoff uses a Diemaster 1⁄2-inch wide, bimetal 10-14 blade on his bandsaw. Wider blades (like 3⁄4-inch) are more stable, but thinner blades (like 1⁄2-inch) offer a tighter cutting radius.
Candoff uses a Diemaster 1⁄2-inch wide, bimetal 10-14 blade on his bandsaw. Wider blades (

Blade Speed

Here’s how the math works out on the underdrive ratios. This system is set up much like an accessory drive on your engine. Think of each drive pulley as a small crank pulley and the driven pulley as the larger-alternator pulley intended to slow the speed of the alternator. A smaller-drive pulley reduces overall speed.

Primary Pulley System	Secondary Pulley System
Drive pulley diameter: 2 inches	Drive pulley diameter: 3.5
Driven pulley diameter: 12 inches	Driven pulley diameter: 13.5
Primary underdrive ratio: 6:1	Secondary underdrive ratio: 3.85:1
Motor speed: 1,800 rpm	Motor speed: 300 rpm
Primary driven pulley shaft speed: 1,800 / 6 = 300 rpm	Secondary driven pulley shaft speed: 300 / 3.85:1 = 78 rpm

We also measured the diameter of the pulley that drives the blade. This allows us to calculate the actual blade speed. The math is easy: Merely multiply the shaft speed by the pulley diameter by pi. With both wheel diameters at 13.75 inches and an input shaft speed of 78 rpm, we used this formula:

78 x 13.75 x 3.1417 (pi) = 3,369 inches per minute of belt speed

To convert to feet per minute: 3,369 / 12 = 280 fpm

Blade Running

When cutting metal, you have several options that will affect both the speed and quality of the cut. Both blade material and teeth-per-inch (TPI) are critical variables. We found this chart on SupercutBandsaw.com. The Raker refers to a specific style of blade, and the company recommends between 2 and 10 teeth in contact with the material at all times. Fewer TPI is for thicker materials, while thinner metals will cut better with more TPI. While carbon tool steel blades are the least expensive, the costlier bimetal blades last much longer, especially if lubricants are used when cutting thick material. End

Carbon Tool Steel(TPI)	Material Thickness(Inches)	Bimetal
24 Raker	1⁄16-1⁄4	20-24
18 Raker	1⁄8-3⁄8	14-18
14 Raker	3⁄16-7⁄16	10-14
10 Raker	1⁄4-1⁄2	8-12

SOURCES
Harbor Freight 3491 Mission Oaks Blvd Camarillo CA 93011 800-444-3353 www.harborfreight.com	Lucki's Engineering Services Granada Hills CA 818-366-1200 www.granadaengineering.com