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I have a Zojirushi BB-PAC20 two-paddle bread maker. It had been working fine for years, but recently it stopped mixing right, leaving huge chunks of unmixed flour. I found that the problem was one of the paddles; it rotated freely all the way around the post it mounts on, so when bread ingredients were there holding it in place, the post would have rotated freely within the cylinder, without rotating the paddle.

Originally the cylinder had a flat side, matching the flat side of the post it mounts on and which rotates the paddle. The paddle's cylinder had been bored completely smooth and round; no vestige of the flat side.

The other paddle had only a tiny nub remaining from the flat side; it would have failed in the same way soon.

My question is, what happened to the metal that had constituted the inner flat side of the cylinder? I'm pretty sure we didn't eat bits of metal, and I never saw bits of metal when cleaning out the pan and paddles between loaves. Where did that metal go?

UPDATE:

Tetsujin asked for pictures. Here's the paddle:

Paddle for Zojirushi BB-PAC20

This shows the posts at the bottom of the pan that the paddles mount on:

Zojirushi BB-PAC20 pan showing posts

This shows the paddles mounted on the posts:

enter image description here

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    It depends which way up the 'plug' & 'cup/socket' are. If the 'cup' faces down, you ate it. if it faces up, you probably washed it down the sink when you cleaned it. Pictures would help.
    – unlisted
    Jul 21 at 17:00
  • @Tetsujin I've added some pictures. Jul 21 at 18:04
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    It's possible the metal simply deformed rather than wore, it's hard to say as you have pictures of the originals rather than how they look now.
    – GdD
    Jul 22 at 14:16
  • @GdD I think you nailed it. I'll put more in an answer. Jul 26 at 23:32
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From my comment
It depends which way up the 'plug' & 'cup/socket' are. If the 'cup' faces down, you ate it. if it faces up, you probably washed it down the sink when you cleaned it. Pictures would help.

After pictures added

You ate it.
It's very unlikely to do you any harm.

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  • For us never to have noticed chomping down on a bit of metal, would it have come off as very finely ground bits, like powder? Jul 21 at 18:10
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    Very probably. Though I've known people break a tooth & swallow it.
    – unlisted
    Jul 21 at 18:12
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    There's still a good chance a lot got washed away. The void formed as it wears will fill with dough and the metal particles will stick, but that dough is likely to stay in there when the loaf bakes.
    – Chris H
    Jul 21 at 18:48
  • &Chris H Yes, the dough that gets down in there stays there when I remove the baked bread from the pan; it doesn't come out with the loaf. Jul 21 at 18:55
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After comparing the old paddles to new replacement paddles, all of them original OEM pieces from Zojirushi made specifically for the BB-PAC20, I believe the flat parts of the paddle cylinders deformed, spread around the inside until it was smooth and nearly round.

When I placed the new paddles on the posts, I found that they were a little looser than the old ones. Again these paddles should be exactly the same. It wasn't a big difference but it was unmistakable as I tried both old and new back and forth. Looking again inside the cylinders of the old ones, I think I see evidence that the flat part was spread around inside until it was smooth and nearly round.

I've had the old paddles around three years, averaging a loaf a day. The change in fit tightness must have been very gradual as I didn't notice it.

I think it makes sense that the paddles would be made from a softer metal than the posts, so that the paddles sacrifice themselves to avoid damaging the posts. I see no wear to the posts. It would take a lot more work to replace the posts than replacing the paddles.

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  • If both parts were steel, that interface would outlive the motor and probably the owner's grandchildren. But the shape of the paddle means it would be rather expensive to make from steel - aluminium, being softer and easier to cast, is far cheaper for a part like that. Mine is a moulinex, and the drive shaft seems to be steel; the paddle feels like aluminium from the weight but the flat in the bore, which is uncoated, looks like it's a steel insert.
    – Chris H
    Jul 27 at 5:52
  • ... The oxidised aluminium worn from the paddle can still abrade the shaft, causing the loose fit with the new paddle. As they sell spares, replacing the shaft would probably mean replacing the pan
    – Chris H
    Jul 27 at 6:28

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