The Sawmill

Figure 1: My prototype bandsaw mill

 

 

Figure 2: My prototype bandsaw mill

 

The sawmill is a bandsaw mill of my own design and construction. The structure is built mainly from welded steel tubing. The mill rails are rectangular steel tubing and sit on 4”x 4” pine sleepers that rest on a concrete floor. I much prefer having the mill indoors, so I did not design it to be portable. The low-to-the-ground base makes rolling logs on the mill manually relatively easy without lifting equipment. The mill is powered by a 7.5 HP, 220V, single-phase, Baldor electric motor (Figures 3 & 4). Internal combustion engines are often used as mill power sources, but engine drive would require a clutch to avoid constant stop and start of the engine and would require venting of exhaust gases from an indoor environment. The electric drive is easy to start and stop electrically and is much quieter than engine drive.

 

This is not a production mill, but easily provides a surplus of lumber for my use. A good day of work at my mill will yield about 400 board feet of lumber +/- 100 BF depending on the size of the logs, the thickness of lumber, and whether I am sawing hardwood or softwood. When the overhead of storing and stacking lumber, dealing with slabs, clearing sawdust, regrinding bands, hauling logs to the mill, and doing basic mill maintenance is factored in, it would about cut that productivity number by half, but I rarely work a full day at the mill. My overall annual production is only in the 1000-2000 BF range, which is clearly in the hobby mill class.

 

The tubular steel mill rails measure 18’ long and are spaced about 6’ apart. The bandsaw rides on a carriage with cast aluminum wheels guided on the steel rails. The mill has a capacity for sawing logs up to about 15’ long x about 30” diameter. The band is a 153” x 1.25” x 0.042” x 1.3 TPI Starrett “Woodpecker” carbon steel band. The relatively small band wheels of 13.5” diameter result in a finite fatigue life for the band. My bands typically saw about 800 BF of lumber before failure. To keep the band in good cutting condition, I need to regrind the teeth about every 200-300 BF. Sharp teeth on the band are essential for good cutting performance. When the band dulls, I will notice poor tracking leading to “wavy” lumber and more force required to advance the carriage.

 

The bandsaw assembly height adjustment is accomplished using a winch (Figure 3) to lift the entire assembly vertically, guided by the vertical steel pipe column and the milled steel bracket that rides on the column. The saw assembly weighs around 300 lbs., but is easily lifted with the winch. Each click stop of the winch rachet represents about 1/8”, but this varies with the amount of cable rolled on the winch reel. I always check the lumber thickness with a tape measure before I start a cut. A planned upgrade that has been a vision for several years, but not yet realized is a simple measuring scale fixed to the mill, so I don’t have to keep checking with a tape measure.

 

Figure 3: Winch system for height adjustment. Each rachet click of the winch represents about 1/8” of vertical lift. The entire bandsaw assembly slides vertically on the pipe guided by the milled steel bracket. The winch cable is attached to a balance point on the approximately 300 lb. assembly so it lifts without a tendency to bind. It easily lowers under its own weight and is racheted down with the winch.

 

Figure 4: Band drive. The motor is a 7.5 HP Baldor 220V single-phase machine.

 

Properly guided bands are essential on a small band mill. I use sealed ball bearings mounted so as to be adjustable in/out and up/down (Figure 5). The guide mounting brackets slide on the rectangular steel tube frame member. I have a total of four such guides. The two outermost are fixed in position at maximum extension and include a bearing that backs the band preventing the cutting stresses from pushing the band off the back of the wheel.

 

Figure 5: One of the adjustable band guides. The square tube weldment holders slide vertically on the post to set the position of the ball bearing against the band. The shafts supporting the bearings can be adjusted in/out. The hold-down bolts with tee-heads clamp the entire guide assembly to the tubular steel frame.

 

Figure 6: Sawing a good size poplar log. The log is about 18” diameter x 10’. The optimal size log is in the 10” – 18” diameter range. Small ones are inefficient to saw because of the overhead of slabbing and turning the log. Big ones are more effort to manually turn and yield a surplus of wide lumber, which is less useful.

 

Figure 7: A small cedar log being finished on the mill. This eastern white cedar timber will become deck planks.

 

Figure 8: Sawing a small hardwood log. The photo shows the basic log clamping system of steel tubing blocks with a threaded shaft running through for tightening against the log. The clamp block can be positioned in any of a series of holes on the 4”x 4” sleeper supports. A visionary upgrade is a hydraulic clamping system.

 

Figure 9: Throwing sawdust from a small cedar log. An irritation is the accumulation of sawdust on the rail which interferes with smooth movement of the carriage. Another simple planned upgrade is a small brush mounted on the carriage to sweep the rail clean as I saw.

 

Figure 10: Lounging at the mill door with the new pup, “Angie”.