bandsaw

A while back I inherited my Grandpa Hatch's old table saw. Apparently he got it when they were first married but it still works just fine. It is powered by a 3/4 hp induction motor which has a shaft extending out of both sides so I had the idea that I could use the free end to power an additional tool. Bandsaws go in the broad category of "tools that I would love to have but can't afford" so it was a natural candidate.

The first problem was that the motor rotated the wrong way. Unlike simple DC motors, you cant just trade a + and - pole to reverse direction on an induction motor. I found some vague directions on the motor itself but the wire colors didn't make sense. After staring at it for a while I realized one wire was of a different construction than the others as if it was not an original, It seems my grandpa had been doing his own modifications decades earlier. This little discovery warmed my heart and brought a little smile to my face.

Assuming his wire to be the missing color i was able to successfully rewire it so it now can be switched to rotate in either direction. I fabricated anti-bump flanges to go around the switches for some added peace of mind.

Next i added a sprocket to the free shaft to drive the chain was planning on using. To save the money I used bike chain i had lying around, which didn't quite fit. The motor made a convenient lathe so i could grind the sprocket down to a workable size

 

After doing the math I found that the original wheel sprocket would spin the bandsaw much to fast so I welded on a larger sprocket from another bike to bring the final speed down.

Free handing with angle grinders, warping metal with the sloppy mig welding process, and drawing up plans in my head is not the best recipe for precision, so to get the tighter tolerances needed for a bandsaw I had to make almost every component adjustable. The final product has 19 points of adjustment to keep it running well. One key point of adjustment is the angle of the two wheels to control how the band tracks across them. This is what i ended up with.

 Each wheel has one of these brackets on both sides. This allows me to adjust their angle with a great deal of precision and also doubles as the band tensioner.

For simplicity and cost, the original design used bike wheels. I wasted a lot of time experimenting with shoegoo, rubber, and different types of tread to try and line the wheels. The wheel well has a natural trough to it that you think would help the blade track to the low point in the center. After more research and experimenting I realized an important counter-intuitive truth, the blade will actually always try to climb to the highest point. I ended up ditching the wobbly bike wheels, ripped out their existing hubs/ bearings, and mated them to mdf wood cutouts.

Using a temporary set up I was able to spin up the wheels and then grind down the perimeter until they ran perfectly true.

Unlike the original wheels, i carved these ones so that they were slightly rounded with the high point near the center of the wheel.

For upper and lower blade guides, I pulled bearings out of an old pair of rollerblades which turned out to be a perfect size.

The frame itself was fairly simple and straight forward.

The table mount allows for the table to be set at different angles and has a lateral adjustment.

Lateral adjustment for the lower blade guide.

This mount can adjust the lateral and vertical positioning of the upper blade guide and controls the angle as well to make sure it runs parallel to the blade. The T bar coming out towards the camera tightens the back bracket allowing for quick raising and lowering of the blade guide.

Using the old wheels to cut out the new mdf wheels

Finished product

In truth the whole thing works better than i thought it would. It produces an even cut with a small clean kerf and can do really tight arcs. Switching the motor back and forth between the bandsaw and the table saw usually only takes a couple of seconds. One major drawback is that if i ever want to cut a larger piece of wood it can only go so many feet past the table saw before it hits the back of the bandsaw. It takes several minutes to unbolt the bandsaw from the bench at some point it may be worth make some kind of quick release mounting (or finding a new motor so it can be mounted independently to its own bench, any one have an old induction motor lying around?). A cover is also in the works to have less of the blade exposed.

Here is the final product in action.

http://www.youtube.com/watch?v=x0cNV1Hhu8k&feature=youtu.be