Sunday, July 24, 2011

A Flour Sifter Repair

Kitchen gadgets can present you with some remarkably challenging repair work. The unfortunate flour sifter pictured below is a good example.

The leaf spring that gave the sifter blade's lever its self-return action fell to pieces, and re-creating that looks to be beyond me; I can't even picture how the spring might have been configured when it was whole.

Also, note the upper end of the lever -- it used to just perch on its pivot rod, held there by spring tension. It doesn't encircle the pivot rod. There's another complication.

And one more problem with the sifter that the photo doesn't reveal is that the sifter blade is loose on its spindle. This is truly an inoperative sifter.

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The Sifter Blade

I'll start with the loose sifter blade; that should be a fairly straightforward thing to correct. Here is out of the sifter. A little cotter pin was holding it to the crank mechanism in the bottom.

That's a view of its underside. That flatted spindle is free to turn to no effect.

Here it is right side up in the vise.

The factory did a nice-looking but quite ineffectual peening job on it. Here it is after a proper bit of peening with a light hammer.

That takes care of that; no more loose sifter blade. Now I have to deal with the lever's pivot.

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The Pivot

I've made a pivot sleeve and pin for it.

The sleeve was made by boring a 4mm diameter steel rod in the lathe with a 3mm drill. The pin is 3mm diameter steel rod that I've threaded at both ends. The nut that's on the pin was installed permanently with CA adhesive and a bit of peening.

Here's a photo of my method for die-threading rod. It works a lot better than the orthodox method.

The die is held stationary while the work is turned. It's much easier to keep the work presented squarely to the die this way.

Here's the lever with its new pivot sleeve soldered in place.

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The Spring

The broken leaf spring really had me racking my brain over how to restore its function. Then a light went on and I thought, "torsion spring"!

I went for a rummage in my salvaged torsion springs bin and came up with this.

One Last Detail

That's just about everything, but there was one remaining flaw that was bothering me. At the left side of the handle, the hole for the pivot rod was 3mm diameter; that's what led me to use 3mm diameter rod for a pivot pin. But at the right side of the handle, the hole for the pivot rod was oversize -- almost 4mm diameter -- to accommodate the factory's purpose-made pivot pin, I suppose. That made for a pretty sloppy fit for the pivot pin at the right side.

When I was boring the 4mm diameter rod to make the sleeve, I had bored it deeper than I needed to, so I had left the makings of a tiny bushing. With a bit of careful setting up with the aid of a dial indicator, I was able to cut a 0.024" long piece off the end of the bored rod, and I had a bushing. Here it is perched on the sifter's handle just below where it goes.

I drilled out the oversize hole a bit to a full 4mm, and the bushing goes in place and does exactly what it's supposed to do -- take up the slop so the lever pivots as it should.

So, it's done.

At final assembly, I'll put the hex nut on with blue Loctite, and oil the pivot a little with light mineral oil.

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For what it's worth, here's a view of the underside of the sifter.

Squeezing the handle lever results in that crank moving through an arc of about ninety degrees, then returning when the lever is released.

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I tried it out filled with flour, and it pretty much works ok. The torsion spring could stand to be a little bit more forceful, though. The flour piled up on the sifter blade imposes a load such that the first couple of lever strokes don't want to return all the way. After that it works fine.

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Aside from the poor peening job the factory did on the sifter blade's spindle, and the leaf spring that broke, this is a beautifully made tool. To just throw it away would be a shame. But the landfills are no doubt piled high with such things because of the difficulty of repairing them effectively. And I have no illusions about the 'economics' of what I've been up to here with this little item. Many would consider it outrageous the amount of resources I've brought to bear on repairing something that can be replaced for a few dollars, and I wouldn't try to argue the point.

Then there are those who maintain that 'business as usual' is about to get dumped in a jar and given a good shaking, and such work as I've given an account of here will be the new 'normal'.

We'll see.

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Addendum -- SUNDAY, MARCH 10, 2013

A reader pointed out to me that there's a way to sift flour without using a purpose-made flour sifter -- you put flour in a strainer and tap the strainer. (It seems that many TV chefs use the method.)

The reader had a flour sifter similar to mine fall apart on her; that got me thinking about the style of flour sifter that my mom always used. My mom's sifter was the type that you cranked, something like this one.

It takes both hands to operate it, but a sifter like the one pictured above will probably last forever. (Something to keep in mind when shopping for a flour sifter.)

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