The design of these blade guides is similar to the ones on my 16" bandsaw and my 14"bandsaw. But with wider guide blocks needed for wider blades, I opted to put the screws on either side of the blocks instead of through them.
Trying to keep the design compact, I figured it was best to just cut a machine screw thread into the wood and screw the 1/4" bolts straight into that. That method worked out on my 14" bandsaw.
But I wasn't sure if this would hold adequately, so I tested various woods by tapping a thread into them, screwing a screw in and tightening until the thread in the wood stripped. But then, with some exotic wood, my bolt twisted off. At this point, I realized, the wood, even regular hardwood, would be more than strong enough.
I marked all the screw hole locations by using callipers to scratch where the holes need to go. I added countersinks to the holes in the slot using the point of a larger drill bit because there was no room for a countersink bit.
Then I put a 1/4" machine screw tap in a drill and cut threads in the holes, then checked them with a bolt.
The side of the main body for the blade guide gets a slot cut in it. I first drilled three holes next to each other, then drilled between them, moving the workpiece side-to-side to join the holes into a slot. This only works, just barely, with a brad point bit.
The slot allows the body of the blade guide to move forward and back when mounted to the guide post.
Attaching the block that holds the guide blocks to the main body of the blade guide.
The guide blocks, which I cut from lignum vitae, will form a sort of "V" shape. If you don't have lignum vitae, any other exotic hardwood should also work (I previously used Bocote, but ran out). The guide blocks on my first homemade bandsaw are made of maple, and I have not needed to replace them yet.
The guide blocks are held on with two screws and small metal plates, about 3 mm thick.
I made these from some bar stock. I used callipers to scratch lines for where the holes need to go, then punched center divots with a center punch and drilled them on the drill press. When drilling metal, it makes it is easier to drill a smaller pilot hole before drilling the hole up to full size.
After that I used an angle grinder with a thin cut-off disk to cut the plates out.
A "thrust bearing" goes above the guide blocks. The back edge of the blade pushes against it while making a cut. I'm using a ball bearing, which I mounted on a 5/16" bolt. A larger washer on either side of the bearing clamps it in place, while smaller washers, which are the size of the inside of the bearing, keep it centred.
Drilling the hole in the guide bearing to fit the nut
Then tapping a thread into it with a machine screw tap using a drill.
I also drilled a larger hole around this hole to allow for room for the nut on the back of the guide bearing.
I cut a slot in the head of the carriage bolt so I can turn it with a screwdriver to adjust how far back the bearing is.
I cut a deep slot in the body of the guide bearing so that when the screw holding the guide is tightened, it also clamps down on the screw for the thrust bearing, locking it in place.
Cutting away part of the post for where the blade guide will mount.
Another notch needs to be cut away so the blade guides can be moved further back.
After that, I placed the blade guide on the post, pushed it back as far as it would go, then put a drill in the front-most position in the slot and started drilling, drilling only about 1 mm deep.
I then finished drilling the hole on the drill press.
I drilled two shallow holes on the back to make room for the head of a T-slot bolt (I have some extra T-slot bolts). Otherwise, I would have used a carriage bolt.
The guide post needs to be mounted on the bandsaw body. But before I do that, I'll make the lower blade guide.
Two main pieces of the lower guide body cut, on thhe 1:1 printout from my plans.
Two slots need to be cut in each of these two pieces. A slot mortiser would be good for cutting these slots, but you may not have one, so I'm demonstrating cutting these on the drill press.
I start by center-punching holes on either end of the slots, plus another hole in the middle.
I drilled the three holes, then drill between the holes. This is tricky to do with a brad point bit. It would be impossible with a metal drill bit. After enough drilling and side to side movement, it turns into a slot. I used a file to clean up the sides of the slot.
The main part of the lower blade guide body needs another layer glued onto it.
The other side gets a thrust bearing mounted onto it. I put a T-nut on the back to hold it. In retrospect, I should have just screwed it straight into the wood, but by the time I thought of it, I had already drilled the hole too large for that.
This is how the two pieces fit together.
I want the blade to end up just to the left of center on the ball bearing, so if the bearing wears a groove into it, I can just flip it over.
Here marking where I want the blade to end up.
Then screwing the block that mounts the guide blocks on. The screws end up on the line that I marked. I did, of course, drill pilot holes before screwing it on.
This is how the blade will run through the blade guide.
The guide will attach to part of the table with two bolts, once I build the table. But that will have to wait for later.
I start by marking a line on the frame directly behind the blade.
The furthest back that the blade guides will need to go is when using a narrow bandsaw blade, because the front edge of the guide blocks needs to move back because the blade's front edge is further back.
With the guide moved back as far as it will go on the post, I'm checking how far back the post will have to go on the frame.
I also measured the distance from the center of the guides to the left edge of the guide post. 28 mm on my guides, so the cut-out for the guide needs to be 28 mm to the left of the blade.
I clamped a piece of plywood to the frame to act as a guide for a circular saw, then made the cut. I made a series of cuts to hog out most of the notch, then cleaned it up with a chisel.
Checking the fit with the post. Not perfect. The cut was neither straight nor square.
I'm cutting a notch in the middle of the beam so the post will only touch near the top and bottom. That way, I don't have to try to make the whole notch dead straight. After that, I carved the ends of the notch to be square.
Checking the fit, while baby Harriet came for a brief visit.
I need to make a clamp to clamp the post into the notch in the frame. I made this one out of Baltic birch plywood, like the guides.
A strip of wood with a 45° bevel clamps to the edge.
I used the 45° piece I cut off, holding it in place with C-clamps to provide a clamping surface.
I should have just glued this piece on while it was still square and then cut the bevel on it on the table saw. That would have been easier.
Drilling a hole for a threaded rod to go into the frame. I drilled this as deep as the drill would allow.
I'm holding a scrap of wood onto the end of the frame to help me guide the drill square to the surface.
I then used a thin strip of wood to work some construction adhesive into the hole. I also covered the end of the threaded rod with construction adhesive before pushing it into the hole.
Back to working on the clamp. The back of the clamp has a rabbeted piece on it to keep the clamp from sliding forward as the bevelled part pushes onto the guide post.
I wanted to make sure I got the placement of the rabbeted piece just right before gluing it on, so here test fitting it, with the rabbeted piece only held on with C-clamps.
After checking it, I glued it on and trimmed off the excess.
I figured it would be nice to have a star knob on the coupler nut. I put a 1/4" blade into my unfinished bandsaw and used it to cut out the knob, using a template shape from my plans.
I drilled a hole slightly smaller than the coupler nut into the plywood and used a chainsaw file to file it slightly hexagonal before pressing the coupler nut in with a vise.
The bandsaw is usable in its unfinished state. That means I can use it to cut out the trunnions for the tilting table.
Next: Trunnions and table