Making the wheel mounts
I tipped the frame on its side to make it easier to work on the lower wheel mount.
Lower wheel mountI drilled a 1" hole though a piece of hardwood, which will mount on the bottom of the frame. At left, checking how it will fit.
Then drilling some holes for screws. The screw heads will be well below the surface to accommodate the length of screws I had at hand. The screws are just a bit longer than the block of wood is thick.
Blade tension will push the block up against the frame, while the drive belt will push it up against the leg. So the screws are there mostly to keep it from falling off when there's no blade on the saw.
Then I needed a holder for the back end of the shaft. This one is a bit odd shaped because I just used a scrap of wood that used to be the old tension/tracking adjust of my homemade belt sander, but the shape seemed very appropriate.
I need to mount a washer to the end of the shaft to keep the wheel from sliding off. I start by punching a divot in the end of the shaft. I used a 1" washer to help me place the center punch in the middle of the shaft before hitting it with a hammer.
I put the shaft horizontally in the vise, then eyeballed the tap parallel to jaws of the vise to make sure I have it in straight.
Upper wheel mount frameI had come up with a simplified upper wheel mount for my 14" bandsaw. While this was more compact and easier to build, a frame with a pivoting block inside (like on my 16" bandsaw) is less finicky to set up, so I'm going with that approach here.
Ideally, the corners of this would be box joined. That's how I did it for my 16" bandsaw. But that would be difficult to do without a screw advance box joint jig (other styles of box joint jig aren't as suitable for cutting deep joints in hardwood). So I'll show another method - rabbet joined with splines.
Once the glue was dry, it was time to cut the slots for the splines. I used my table saw sled, with a block of wood in it to hold the workpiece at 45°. I checked that the angle was correct with a speed square.
I flipped the workpiece over and made another cut in each corner. I then repositioned the block to cut in the middle of each corner to bring the number of slots per corner up to three.
I cut some thin strips of wood for the splines. I always cut this between the blade and the fence, though you do need a zero clearance insert for this sort of cut, or the just cut off piece will get sucked into the table saw.
It takes a few test cuts to get the thickness of the splines just right.
I used a narrow board as a spacer between the fence on the table saw sled and the workpiece for the first two cuts because the splines sticking out made it impossible to square the workpiece up directly against the sled's fence.
The actual shaft (or axle) for the upper wheel gets mounted in a block of wood, which can pivot in this frame. I'm making this block out of two layers. The front is a piece of 18 mm Baltic birch plywood, with a 1" hole in it.
As I drilled this hole, for every 1 cm of depth drilled I rotated the block 180 degrees about the vertical axis. When drilling big holes, a lot of force is involved, and the drill press table tends to flex downwards. So even if the table is perfectly square when you check it, it won't be while drilling. But by rotating the piece 180 degrees for every cm of depth, this angle error cancels out.
A slight oopsie. The drill press chuck came off! It's only attached by friction. I cleaned the tapers and rammed it firmly on. I guess I hadn't rammed it on hard enough the last time I had it off when I checked if this chuck would fit
Blade tensionerI need some way to pull the upper wheel mount up to apply blade tension. A carriage bolt through the upper wheel mount will serve that purpose.
After drilling the hole, I carved the end of it square with a carving knife
Tracking adjustBut before mounting the block, I need to mount a T-nut in the block. I didn't leave enough room for this, so I had to recess it in the block. I think I'll change the dimensions in the plans to leave enough room to make recessing the T-nut unnecessary.
I drilled the pilot holes in the plywood a bit large to leave the screws a little loose so it can pivot. Once blade tension is applied, the block is pushed down against the frame, and pulled back by the tracking adjust knob, so the screws are mostly there to keep it from falling out when there is no blade tension.
Inserting the shaft. This was a very tight fit. I think the hole in the block of wood may have had a slight zigzag from my rotating the block 180 degrees every centimeter, but better zigzag than crooked. It took a lot of pounding to get the shaft in.
At least this way, I won't have to worry about keeping the shaft from sliding out.
I also tried turning the wheels backwards to see if the blade would track differently. If it tracks differently spinning backwards, then the two wheel axles are not parallel.
Standing in front of the bandsaw, if spinning it backwards (counter clockwise) makes the blade wander away from you, then the top wheels would be turned towards the right. To fix it, the "right side" of the wheel needs to be further away (it would need to yaw to the left, to use aircraft terminology).
It worked fine, but I could see the blade moving forwards and back as it went around. This happened at the same rate as the blade went round and around, so I knew it was the blade, not the wheels, causing this. This is typically caused by a misaligned weld.
I have to say though, checking it with a ruler, I got it the wrong way around, so first I thought I had to hammer near the teeth. This made it worse, so I hammered it near the back edge. It wasn't perfect after that, but much better than before.
I also cut some curves in a piece of wood. I didn't get a narrow blade, but it looks like this blade can cut a tight enough radius for the trunnions for this saw, which I will be cutting on this incomplete saw later.
Finishing upI still needed to trim the top shaft to its final length. I bought the shafts as cut-offs at the Metal Supermarket, so they were longer than I needed.
With the shaft as tight in the block as it was, I figured it was easier to cut it off while clamped in place. I'm cutting it off with a thin cut-off disk in the angle grinder. More on cutting metal with an angle grinder here
I wasn't thinking when I made this - if you are building a bandsaw, it's not unlikely that you don't already have a bandsaw. So you can either make this a straight bar knob (no bandsaw needed), or wait until the rest of your bandsaw is done and then make this knob.
I made a crank for adjusting the tension by drilling a hole just slightly smaller than a coupler nut, then pounding the coupler nut onto the (too small) hole to leave six dents where the points of the nut are. I then filed these out a bit to make a better fit for the nut...
I also added a screw and washer to the back of the shaft to keep it from sliding forward. This shaft was a bit longer than I needed, but to save the trouble of cutting it to length, I put a spacer on the end of the shaft instead.
I would have done the same for the back of the top wheel shaft, but that shaft is in the block so tight, I figured this was unnecessary.
The next step was to make some blade guides for this saw. I made a sort of mock-up (out of scrap wood) to see how my new design would look. I came up with a slightly different design to accommodate wider blades than my previous bandsaws.
Next: Blade guides