Thursday, November 27, 2014

Forceful Fridge Magnets


Lee Valley has a nice 50-piece sampler of rare-earth magnets; I've posted about it before.

The eight 1/4" diameter x 1/4" long rod magnets in the sampler make great fridge magnets, but their small size makes them difficult to manipulate -- it's not easy to get a grip on them to pull them off the fridge once they're on. Here's a way to add a 'handle' to the magnets.

Take a common 3/16" thick, 1/4"-20 hex nut, and bore out its threads to 1/4" diameter about one-third to half-way through.[1]


Set a magnet into the nut's bore, and apply CA adhesive to the interface from the back, so the runny adhesive can wick in and secure the two pieces together.


You end up with a strong little fridge magnet that's substantial enough to be easily manipulated. Here's a view of one holding an entire calendar to the nose of my vise.



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The magnets are just as good at more orthodox tasks like 'pinning' notes to any ferrous metal surface.

I keep a lot of notes on my progress on various projects in the workshop, and the magnets work fine on overhead HVAC ducts, like so.


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Addendum -- FRIDAY, NOVEMBER 28, 2014

The sampler also has 3/8" and 1/2" diameter disc magnets, and those can be adapted in a similar fashion to the 1/4" rod magnets; use 3/8" and 1/2" hex nuts, but bore the nuts very shallowly. Here's a view of the whole lineup of 'handle'-fitted magnets.


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Note:

[1] Boring out a nut's threads is best done on a drill press, with the aid of a drill press vise, like so.


It's also helpful to employ the drill press's depth stop, so the boring depth is positively limited. If you don't use the depth stop, the operation can easily get away from you and go too deep.

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Wednesday, November 26, 2014

Obscure Fasteners -- Exploding Rivets


When I was a boy, my dad's basement workshop had in it a big soldering iron. My dad told me that it was for installing exploding rivets. I don't recall him ever having given me a demonstration.

Anyway, he left me a small supply of the rivets.


(Those are 3/16" diameter x 3/8" long truss head rivets.)

Those are not what passes for 'exploding' rivets today -- hollow rivets that peel back broadly as they're clinched. The rivets pictured above have an actual explosive charge inside them. When the head of one of those rivets is heated by a soldering iron, the charge goes off and swells the rivet's shank, clinching the rivet. Here's a demonstration.




I scrounged up two aluminum brackets that already have 3/16" holes in them, and arranged them in the vise with a rivet in place.

It takes but a few seconds for the rivet to go off once a hot soldering iron is pressed against its head. There's quite a BANG, the explosive charge blows out the end of the rivet and swells the rivet's shank, like so.


The resulting join is quite secure.

I've googled 'exploding rivets', and all I come up with is the hollow peeling/folding types. These are way more fun, but some prissy safety agency probably outlawed them long ago. I'll have to make judicious use of the small supply that I have.

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Tuesday, November 25, 2014

Lexicon -- Bolt/Screw


In case you've ever wondered, "What is the difference between a bolt and a screw?", here's the answer, courtesy of Machinery's Handbook, Twenty-First Edition, Page 1131:

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"Differentiation between Bolt and Screw. --

A bolt is an externally threaded fastener designed for insertion through holes in assembled parts, and is normally intended to be tightened or released by torquing a nut.

A screw is an externally threaded fastener capable of being inserted into holes in assembled parts, of mating with a preformed internal thread or forming its own thread and of being tightened or released by torquing the head."

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So, by that, all the fasteners holding this cylinder head in place are screws, not bolts.


And the two fasteners holding this pulley together are bolts, not screws.


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Tuesday, November 18, 2014

Loosening Off Seized Screws


Some screws, you just have to look at them to know that they're likely to be seized in their threads; e.g. those two 1/4" - 20 screws holding the muffler on a Tecumseh lawn mower engine.


Don't go directly to trying to unscrew them. Instead, try to first tighten them a tiny bit. If you can get a seized screw to budge at all in the tightening direction, you're much more likely to get the screw out without breaking it, like so.


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Sunday, November 16, 2014

A New Challenge From The Roadside


My son found this out by the side of the road earlier today.


It's a propane patio heater.

It appears to be more-or-less in working order, but the big heat reflector on top can't be fastened in place as it ought to be; the part that it should fasten to (the burner shroud's lid) is badly rusted-out.


Repairing that will take a challenging bit of fabrication work.

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Here's a view of the burner shroud off on its own.


That sheet metal on top is well and truly done for. I can't re-create it exactly, but it should be possible to come up with a functional equivalent that the heat reflector can fasten to.

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Here's a view of the heat reflector.


It's quite large; it's 32 1/2" in diameter. Broken-out remnants of the burner shroud's top are still attached to it by three rusty standoffs and wingnuts. I'll get those removed, and then I'll have a hole-drilling 'template' to guide me in re-creating the top of the burner shroud.

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A New Lid For The Burner Shroud -- FRIDAY, NOVEMBER 28, 2014

I've torn away all the oxidized remnants of the original burner shroud lid, and installed three 3/4" steel corner braces, like so.


Those corner braces will be the attachment points for the new lid, which I'll fabricate from 22 gauge (0.028" thick) sheet steel.

Here's my blank for the new lid, laid out and ready to be cut.


That green sheet metal cutter will handle the 0.028" steel easily enough, but it's not really meant for curved cuts. We'll see how this goes.

Here's the cutter at work, having gotten a good start on one corner of the blank.


As expected, the cutter tends to jam as the size of a corner-waste piece increases. At intervals, I had to lop off corner-waste pieces, and restart the cut. That method went better than I expected it to, and got me a pretty good approximation of a disc.


I ground the cut perimeter reasonably true on the belt sander/grinder, and drilled holes for the corner brace fastenings and the reflector standoffs. That got me to here.


Not a bad outcome at all. Here it is with the centre piece of the reflector attached by its wingnuts.


I'm quite pleased with that -- I've got a functional equivalent of the original burner shroud. The plain steel lid and corner braces may only last a season or two before they need replacement again, but that's ok. So long as the stainless steel perforated shroud portion holds up, I can keep it in service fairly easily.

Next up is to deal with the heater's weighted base; that's a bit of a mess that wants correcting.

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The Weighted Base -- MONDAY, DECEMBER 1, 2014

The heater's base contains and conceals a black plastic container that's meant to be filled with sand, so the heater is weighted down and isn't tippy when the wind blows.


There's nothing provided to seal the opening in the top of the sand container. The container, as I got it, was full of a filthy mixture of sand, gravel and water. I got the container emptied and dried out; now I need to refill it with clean sand, but I don't want it to get wet again. I'll fabricate a cover-disc for the container's opening, to be installed with screws and silicone gasket-maker. That should be the last that I'll ever have to attend to the weighted base in any way.

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And here's an aluminum cover disc, trial-fitted to the container's opening.


Now I just need to get a bag of sand, fill and seal the container and I can be done with it.

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Container Filled -- MONDAY, DECEMBER 8, 2014

Filling the base-weight container with sand was a chore -- it could only be done little-by-little with the aid of a funnel. Anyway, that's over with, the container is sealed and back in the base.

Trying It Out

I reassembled the heater far enough that I could try to light the pilot light, and that was no go. It turned out that the pilot light's fuel supply orifice was clogged. Clearing the tiny orifice was all it took to get the heater going. See this post for information on dealing with an inoperative pilot light.

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Sunday, November 2, 2014

Tecumseh 1099 Carburetor -- Repair Kit 632347


I have a Noma Gran Prix snow blower with a Tecumseh HM80 engine that's misbehaving. The engine runs fine at governed speed, so the machine is still useable, but it will not idle. If I try to idle it down, the engine surges (hunts). If I close down the idle mixture screw completely while it's surging, there's no effect whatsoever. It appears that the carburetor's idle circuit is inoperative.

I've had the carburetor apart, and cleaned it more than once, to no avail. So, I've obtained the repair kit that has replacement welch plugs in it. Now I can open up the carburetor completely, and hopefully resolve the problem. If this doesn't work, I'll be left somewhere on the distant side of mystification.

Here's a view of the carburetor and the repair kit.


Here's the kit spread out so you can see better what's in it.


There's also a note detailing the installation procedure for the inlet valve seat.

Teardown

Teardown of the carburetor is straightforward. You readily get to here.


To dislodge and extract the float valve seat, blow compressed air into the fuel inlet. Keep a finger over where the valve seat will emerge. The valve seat is a light, tiny thing that's liable to fly off for parts unknown if it's not restrained. Here's the float valve seat shown by the carburetor.


Aside from removing the two welch plugs, I've nothing to gain by dismantling the carburetor any further, so I'll leave the throttle and choke butterflies alone.

The Welch Plugs

The large welch plug in the 'roof' of the float chamber can be pried out fairly easily. All it covers is the passageway from the primer tube's nipple to the float chamber. Here's a view of that opened up.


There's really nothing that could ever go wrong in there.

The smaller welch plug on the side of the carburetor is the cover for the idle mixture well. That's the area that's of particular interest to me here, given the symptom that I'm looking to cure.

I punctured and pried out the plug per the advice that's invariably given by the small engines 'literature'. That method worked for me, after a fashion, but I found it clumsy and difficult.[1]

Here's a view of the side of the carburetor with the idle mixture well exposed. (Down below is the demolished welch plug.)


The exposed orifices are all clear.

What remains unexposed and inaccessible is the fuel passageway from the main well to the idle mixture well. All you can do to check that is to force solvent up into the main well, and observe that it emerges into the mixture well. I tried that using the spray nozzle of my parts washer's pump, and the passageway appears to be passing fluid.

All of that leaves one more item that may be at fault -- the main jet nut. And lo and behold, look at this.


Note the very tiny upper orifice in the new nut on the right. In the old nut on the left, that orifice is completely blocked. That tiny orifice is what passes fuel from the main jet's well to the idle mixture well's supply passageway. That blockage may explain a lot; we'll see.

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Reassembly -- SUNDAY, NOVEMBER 2, 2014

Welch Plugs

For a flat-ended punch to install the welch plugs with, I squared off an end of a suitable length of 10mm diameter steel rod on the lathe. That worked well for the large plug underneath.


And it worked equally well for the smaller plug on the side. The key to getting that one installed was to solidly support the carburetor while I hammered on the welch plug. A socket wrench served nicely, like so.


Tecumseh advises to seal the edges of welch plugs with nail polish after installation. I'm not sure that should be necessary if the plug is truly seated, but I took their advice anyway to play it safe. I didn't have any nail polish, so I used CA adhesive.

The Float Valve Seat

The little instruction sheet that comes with the kit makes it clear how the float valve seat is to be oriented (grooved side up -- away from the needle). The seat goes in more easily if it's lubricated with WD-40. Press the seat into place with a suitable punch, or the shank end of a 5/32" twist drill.

Float Height Adjustment

I'm not convinced that this adjustment is as critical as it's made out to be. If the float is roughly parallel to the seating rim for the bowl when the carburetor is held upside down, you're probably close enough. For what it's worth, Tecumseh calls for 11/64" between the bowl's seating rim, and the top of the float, with the carburetor held upside down. Use the shank end of a twist drill for a gauge.

Final Assembly

The rest of it is straightforward. Everything goes together better and more easily if it's lubricated with WD-40.

And The Outcome

The engine now idles correctly; the surging is gone. That plugged orifice in the main jet nut was the source of the idle problem.

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Note:

[1] If I ever have to remove a welch plug again, I'll try a different method. That punch/puncture/pry method looks to me like orthodox hogwash that keeps getting recycled for no reason other than that it's become orthodoxy by virtue of having been recycled so often.

On the drill press, I'll carefully drill just barely through the centre of the plug, with a drill that's about 1/2 to 2/3 of the plug's diameter. That should leave me a 'ring' that can be easily pried out, and avoid the hammering/punching/puncturing nonsense. We'll see.

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