Building the hobby sawmillThe sawmill is made from pieces of 2x4 glued together in three layers. I planed about a millimeter off each side of the 2x4s to get smooth flat surfaces for better glue joints.
The corner joints of the frame are reinforced with pieces of plywood. These are glued to the top horizontal, but screwed to the other parts of the frame. This allows the frame to be taken apart for moving or putting it away.
Drilling the bolt holes in the corners. I'm using a drill guide and an extra long drill to drill all the way through the frame. I didn't have an extra long drill of exactly the right diameter, so after drilling the hole through, I used a drill of the right size from either end to enlarge the holes.
If storage space is not an issue for you, you could improve and simplify this design by just gluing the corners together.
Here I'm gluing some blocks of wood to the end of it to allow it to be bolted to the horizontal part that will ride on the track.
This keeps the carriage aligned, and also allows sawdust to slide off the track.
The wheels are held onto this rail by bolts that are simply threaded into the slightly undersized holes. Machine screw threads hold surprisingly well in wood, though it takes a bit of effort to screw them in.
A series of holes allows the vertical position of the wheel to be adjusted to compensate whether the left side, right side, or both sides are running on a rail or on the floor.
The bracket for the left side wheel has a corner joint on it, which I cut out on the bandsaw. I have had good experience cutting box joints from paper templates on the bandsaw - it worked well for the marble machine 2.1 base and support arm. I will include these paper templates in the plans.
Conveniently, the 2x4 that I used for this had a knot right where this part hooks around. That knot acts like a reinforcing dowel, so that end of it will never split off.
Here you can see how the bracket that hooks around the post is attached to the bandsaw. Two dowels (not visible in photo) keep it aligned, and a single machine screw and threaded insert hold it in place.
I could have just used long wood screws to attach this part, but so far, I had attached all the other removable parts with machine screws. So I used some threaded inserts and machine screws to attach this bracket as well. That way, I don't wear out the threads in the wood from switching between sawmill and bandsaw mode.
I needed a dowel of a bit less than 1.5" diameter. This dowel didn't need to be super accurate, and rather than take another trip to the store, I decided to make my own. I started by cutting an octagonal rail on the table saw, then rounded the corners with a hand plane. I used a piece of wood with a hole in it to periodically check the fit.
I had initially experimented with some synthetic strands from packing crates to winch the bandsaw up and down, but then switched to steel cable. The advantage of steel cable is that it will wind up in turns side by side so that the amount of elevation per tooth on the sprocket is constant. But the steel cable is much more difficult to handle. It has a mind of its own and always wants to straighten out. So the packing crate strands may have been a better idea.
Hose clamps worked out well for holding the cable (or the strand) in place. I make sure there are at least two turns of the cable around the dowel even when the saw is in its lowest position. The friction of the cable around the dowel means that, after two turns, the hose clamp only needs a minimal amount of hold to keep the cable from slipping.
I also added some "staples" to help hold the cable in place. These staples were made by cutting the head off a finishing nail and bending it into a U-shape.
Adjusting the relative lengths of the cables turned out to be a finicky affair. The bandsaw mounts in the frame so that it easily "racks" if one cable is shorter than the other. I figured this would be a good safety feature if one of the cables should let loose for some reason. But being off by even half a centimeter on one side can be problematic.
Here's the saw, on tracks. As it turned out, the rubber wheels gripped well enough even on my painted basement floor that I could use the saw without rails. Though with the rails, the saw stays aligned. Also, sawdust can slide off the rail so that the wheels don't run on a layer of sawdust.
The tracks are also useful when operating on uneven surfaces such as grass.