Bandsaw blade guides

Design considerations

This is the upper blade guide design for my new bandsaw. Note that I have the thrust bearing oriented so that the blade runs along the end face of it like most bandsaws do, as opposed to running the blade on the outside edge of the bearing like the Carter blade guides do.

I have been going back and forth over which method is better for the thrust bearing. Nearly all manufactured bandsaws have the thrust bearing oriented this way, but Carter products claims that it's better to roll on the outside edge of the bearing.

It's no harder to mount the bearing one way or the other, so why would the bandsaw manufacturers do it all "wrong"?

Well, on my 16" bandsaw I was getting tired of how loud this bearing always ran. I experimented with replacing it with just a small block of bocote hardwood, so that I had wooden blocks on three sides of the blade. This worked out well and, surprisingly, wasn't much of a wear issue. But it robbed some power. So I eventually made a blade guide like the one pictured above. Although it wasn't as quiet as the wooden thrust block, it's much less noisy than my original design.

This is probably why bandsaw manufacturers put the bearing on this way - it works just as well, but runs much quieter.

Making the guides

The body of the upper guide is quite simple. I used a piece of exotic hardwood for the cross member that the guide blocks attach to.

If you don't have any exotic hardwood handy, use the hardest hardwood you have, and soak some oil into it.

I had previously used T-nuts to get threads into this block. But not everybody knows where to get T-nuts. So this time around, instead of T-nuts, I just tapped a machine screw thread straight into the hardwood. Going cross-grain like this, a machine screw thread holds quite well in hardwood.

The thrust bearing mount is just a carriage bolt. The square part of the bolt didn't quite fit in the bearing's hole, so I filed the corners down just a little to make it fit. A nut is then used to push the bearing against the bolt's head.

I also cut a slot into the head of the bolt with a hacksaw so it can be turned with a screwdriver (you can't see the slot in this picture).

The bolt fits into a threaded hold in the guide body. That hole has a slot cut through it so that when the guide body is clamped to the guide post, the bolt gets squeezed, so it can't turn.

I kept the lower thrust bearing in the same orientation as on my previous saw. I always adjust the guides so that the top thrust bearing is just a hair further forward than the one on the bottom. My rationale for this is that the top guide, at the end of the frame and the guide post, has a bit more flex to it. So when pushing a large piece of wood hard against it, it will flex back and both guides become engaged.

So when the saw is idling, the blade doesn't touch the lower thrust bearing, so it doesn't make noise. During a cut, the blade itself makes so much noise that the noise from the lower thrust bearing can't be heard anyway.

I used another carriage bolt to hold the lower bearing against a slot. Loosening the bolt allows the bearing to be moved forwards and back. I also hacksawed a slot into this bolt head to make it easier to turn with a screwdriver.

On the other side of the bolt is a T-nut with all but one of the prongs bent flat. The one remaining prong protrudes into the slot so that the nut won't spin when the bolt is turned.

This is the only T-nut I used in the entire bandsaw. If you don't know where to get T-nuts, you could substitute a wing nut for this one, although that means having to reach around the guide to hold it while tightening the bolt.

Mounting the lower guide

With a blade mounted and tensioned in the saw, I can now use the blade as a reference to check where the guide needs to be mounted. Here's checking my mark for where to cut. (a bit hard to see, but you can click the image to enlarge it).

With my green square clamped to the frame as a saw guide, I'm cutting the frame where I marked it.

Next I put the frame on its side and cut the bottom side of this cutout.

The saw didn't quite reach deep enough for the bottom side so I had to clean out the rest of it with a chisel.

With the blade guide positioned where it needs to be, I'm punching through one of the slots to mark where to drill into the frame.

The guide body has two slots so that I can mount it in one of two vertical positions. For the upper position, I need to put a spacer under the guide. The upper position will be for regular cuts. The lower position is for some experiments that I still want to do with this saw. I'll leave that for a future article.

Here's inserting a threaded insert into the hole I had just drilled.

Because this is going into the wood end grain, this might not hold all that well. If it ever comes loose, I'll just glue it in. Even wood glue should do for gluing it in. The glue doesn't need to stick to the metal to hold it - the prongs on the insert should be more than enough to engage the glue.

Next a long screw and washer hold the guide body in place.

Mounting the upper guide

The upper blade guide mount is much more complicated.

I started by gluing an extra block of hardwood to the frame to give the guide post a bit more support.

I measured the distance from the middle of the guide blocks to the left edge of the guide post on the upper bearings I had just built.

Next I marked a line that same distance left of the blade. I had to use a square to transfer the blade position back to the frame and a ruler to measure how far over. Three hands would have been handy to have for this step.

Here's my measured cut. Getting this cut to be exactly vertical on the saw is important. Otherwise, the blade guides will not move parallel to the blade and will need adjustments every time the vertical position is changed.

I jigged something up with a board and a fence on it for making this cutout.

But as it turned out, the board I used was a bit too thick, so I couldn't reach deep enough. I also couldn't set the saw to its full depth because the motor would have hit the rail that I ran the left side of the saw against.

If I had used a thinner board, and a ruler instead of another board for the left fence, it would have worked out.

So then I had the idea of just putting the whole frame on the table saw. With a good size table saw, and only a 14" bandsaw frame, this is still practical.

Next I needed to put some sort of threaded insert next to the notch I had cut.

On my last saw, I used a table leg bolt that I screwed into the frame. But I wanted this saw to be easy to move, and I didn't want that bolt sticking out of the frame when the guide is removed. So this time around, I wanted the bolt to screw into the frame.

I couldn't find a threaded insert that large, so I used a "coupler nut" - essentially, a nut that is about 4 cm long - as an insert.

I roughened up the outside edges of it with a hacksaw. I also applied glue to the hole before hammering it into the hole.

I screwed two drywall screws next to the insert to hold it in there. The glue was actually more of an afterthought.

The clamp for holding the guide post is a bit of a complicated piece of wood. The tricky part is gluing the beveled piece on one edge. I temporarily clamped another beveled piece to the block just for clamping.

Unfortunately, I didn't get that beveled piece on quite straight. But with the table saw tilted to 45 degrees, I was able to trim it straight.

Test fitting the guide post.

Next I made a bar handle for the bolt. I just chiselled a hole the shape of the head into the wood to hold it. A square head bolt worked out really well, though I'm sure a hex head bolt would hold well enough as well.

Next: Building the enclosure

Back to the 14" bandsaw build page