Rebuilding Trunnions on a 14″ Steel City Band Saw

Not long ago, a friend offered to give me his old bandsaw, which he was replacing with a newer, bigger model.  The only catch: the old bandsaw had two broken parts, and because the manufacturer has gone out of business, replacement parts were not available.  I accepted the offer anyway.  This is the story of how I fabricated replacement parts out of commonly-available materials.

The bandsaw is a 14″ model, built by Steel City.  The broken parts are the trunnions, which are the curved pieces that attach the table to the base and allow the table to tilt in order to make an angled cut.  Although this bandsaw is solidly built, I understand from my internet research that it’s not uncommon for the trunnions to break.  They’re just made from pot metal.

Bandsaw Broken Trunnion 2018

This is the underside of the bandsaw table, and you can see how the curved parts have just crumbled away.

Here’s how I made my own replacements for these parts.

First, I should explain that, while the original trunnions allow the table to tilt, I really don’t need that feature. I just need the table to sit solidly on the base.  So I made replacements with  some hard maple blocks, sawed to the right radius, and attached them to the table with angle iron.

Bandsaw Trunnion Repair 2018

Probably the hardest part was making sure the radius was a match. I started by trying to trace one of the broken trunnions, but I couldn’t get the block close enough to the radius to get an accurate trace. So I just used the mating surface, like this. I went ahead and traced out the whole radius, but in reality, only about a half of the radius is in contact with the base.

I sawed out the radius on my old bandsaw (which I thankfully still have). If I hadn’t had that, I would have resorted to a coping saw.

Bandsaw Trunnion Repair 2018

I clamped the two pieces together and smoothed out the saw marks with a file. It doesn’t need to be especially smooth or pretty, but the trunnions do need to be exactly the same size.

Bandsaw Trunnion Repair 2018

After drilling through them and counter-boring the tops for the bolt head, they fit nicely onto the base! The bolt hole is drilled oversize, which provides just a bit of wiggle-room in fitting everything together. I probably should have also drilled the counter-bore a little bit oversize, too, but this worked. (I did have to buy longer bolts, too.)

Bandsaw Trunnion Repair 2018

Each trunnion is attached to the bottom of the table with three bolts.  I used the old, broken trunnion to figure out how long each piece of angle-iron should be. I attached the angle-iron to the wooden blocks with screws, and then I drilled out the oversize holes in the angle iron for the bolts that will attach the new trunnions to the underside of the table.

Bandsaw Trunnion Repair 2018

Finally, I bolted the new trunnions onto the table. I ended up putting in the bolts loosely, setting the whole thing on the base to get the trunnions positioned correctly (because of the oversize mounting holes, there’s a bit of wiggle room), and then snugging down the bolts.

Now for a confession: what you’ve just read is the streamlined version of the process I actually went through to fabricate these parts. I had to make a number of little adjustments here and there, and there were some missteps along the way. For example, when I went to bolt the trunnions to the bottom of the table, I found that I had made them just a little bit too wide, and while the mounting bolts fit okay, their washers didn’t. I think I forgot to factor in the thickness of the angle iron on both sides when cutting the blocks to thickness! So I just used a grinder to take 1/8″ off the edge of each washer. Another funny thing: I accidentally counter-bored the wrong side of the trunnions at first (visible in the picture above). But it doesn’t affect how they mate to the base, so I just left it there.

But now the table sits securely. Because the bolt holes are oversized, it is possible to adjust the table by a few degrees in either direction, which is just as well because I needed to use the set-screw to get everything leveled.

Bandsaw Trunnion Repair 2018

So now the saw is usable again.

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2 Responses to Rebuilding Trunnions on a 14″ Steel City Band Saw

  1. potomacker says:

    I think that your repair is remarkable but I must ask about your opinion of the Steel City. Frankly, if a critical piece of my machine broke, (the casting looks undersized and faulty) I would ave doubts about the rest of the parts, too. Serious doubts and concerns. Did Steel City not offer to replace the broken parts?

  2. Goes right along with your (and our) philosophy of using recycled, repurposed wood. Never throw away if it can be used or fixed, and there is usually a way to build it in wood, no matter what the original material.

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