Bandsaw blade guides
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.
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.
Upper blade guideThe block that the guide blocks screw onto has a wide slot for the mounting screws. I cut this on the table saw.
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.
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 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.
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.
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.
I also drilled a larger hole around this hole to allow for room for the nut on the back of the guide bearing.
Upper blade guide postThen I made the post for the upper guide bearing. This post has a 45° chamfer on one edge for clamping it down.
I then finished drilling the hole on the drill press.
Lower blade guideThe body of the lower blade guide needs a notch cut out of it. I'm cutting this with several cuts on my table saw sled, using callipers to set the position with respect to the blade.
Two main pieces of the lower guide body cut, here checking them against the 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 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.
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.
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.
Guide post mountI can, at this point, mount the upper blade guide.
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'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.
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.
I'm holding a scrap of wood onto the end of the frame to help me guide the drill square to the surface.
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.
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
Making wood thread taps from threaded rod orbolts