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Refrigerator went to beauty salon

Well sort of.

Here is why I broke the trim on the refrigerator. Or rather, here is what I was doing when I broke the trim on the refrigerator. Why I broke it is, well, ok, where was I?

The white trim on the white fridge had yellowed over the last 10 years. I happened to have read in the past about people restoring old ABS computer cases and video game consoles with some sort of bleaching process involving a “RetroBright” glop product, or a hydrogen peroxide and who-knows-what lethal concoction you can make in your own science lab at home. (You know those nerds and their projects! Heh heh! Ahem.) Which of course I could do, but I was feeling lazy and I wanted instant gratification.

Fortunately, Dr. Youtube quickly educated me that in these modern times all I really need is some hair bleaching peroxide cream and UV light. I already had my UV light source ready at hand, powered by my fusion reactor conveniently stored at a safe distance of 93 million miles, readily available now that IT’S FINALLY FREAKIN’ AUGUST ALREADY!! ABOUT TIME WE GOT SOME SUNSHINE!! GOSH!! Sorry, a little Seasonal Affective Disorder lag in the Pacific Northwest; now back to the story.

A short trip to Sally Beauty Supply store and $3 got me a bottle of “40 volume peroxide cream 12%” and now I’m beautiful! Er, I mean, now the trim on the fridge is beautiful again.

Slop on the peroxide cream with a brush, put it in a clear plastic bag, and sit it in the sun for a few hours. Et voila! It worked. One of the pieces was ABS, and one was polypropylene. The bleaching process worked best on the ABS, but the polypropylene worked pretty well also.

One theory is that the bromine added as a flame retardant is what turns the plastic yellow. Something sure was retardant. But regardless of the cause, the bleaching worked and it looks much better now. Just a few more trim pieces to break off, I mean remove carefully, and the fridge will look good as new. And stylin’ with its new ‘do !

I just won’t use the hammer and block of wood to remove the other trim pieces like I did the first ones. Hey, Dr. Youtube showed me how to easily slide them off. Mine was just a little stuck. Where’s that bigger hammer? The doc just didn’t clarify it was for a different model. Hmmph!

Anyways, if you have any white plastic that has yellowed over time, this really did work well to restore it; give it a try!

Oh, and the broken trim pieces? Fixed with spin welding!

Plastic spin welding fixed fridge

I took a piece of plastic trim off of the refrigerator door, and the snap tabs broke right off. Dang it!

The piece was marked PP, polypropylene, which just can’t be glued. So I used spin welding to reattach them.

I cut a thin strip from a plastic lid marked PP and chucked it in the Dremel. Spun it up and worked it into the fillets. Friction melted it right in there, welding the tabs back on.

I put it back on the door and the tabs are holding on tight. Perfect!

Tablesaw dust collection with shop vac

Many woodworkers have dust collection systems, which use suction and large pipes and hoses to collect sawdust and other particles from power tools. For the hobbyist, these systems can be affordable, below $1000 for a decent system. Naturally, I therefore wondered what I could accomplish with my old shop vacuum, some junk from the garbage can, and about 20 bucks.

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The basic premise is to collect sawdust, trimmings, and other particles as close to the source of production as possible. Many power tools come with dust collection ports built in to them these days. My 1950s PowrKraft table saw did not, so I set out to create a dust collector for it.

The Tablesaw

Common plastic bucket and my assistant Stanley

My tablesaw was not designed for vacuum collection of sawdust, so it has quite a few openings which needed to be covered. The underside of the saw is open, with a sheet-metal rim around the inside. This made a good place to attach a collection hood. I fabricated one from a rectangular plastic bucket made from HDPE (high-density polyethylene) plastic, the most common type used in common buckets and consumer packaging.

Since the bucket had a hinged snap-on lid, I turned the bucket upside down and used the lid as the bottom of the dust hood. The lid then became an access door to the underside of the saw. I used the heat gun to bend the sides of the bucket and weld on extra corner tabs, creating flanges to sit on the rim of the saw opening.

Tubing

For the dust-collection tubing, I took the cheap route. I used 3-inch water drainage tubing and 1.5-inch sump pump tubing, both from the local home improvement warehouse store.

Neither one of the tubing sizes I used matches the hose of my shop vac at 2.5 inches, so I needed some adaptors. Several different plastic jars from peanut butter and applesauce turned out to be very close to the correct size. The opening on the applesauce jar was just a little too small, so I made a spreader jig with some wooden wedges between some nuts and washers. When one of the nuts is tightened, the washers squeeze the wedges, forcing them outward. I wrapped the wooden wedges in a piece of sheet metal from a tin vegetable can, and placed the mouth of the jar over it. By softening the jar mouth with the heat gun, and tightening the nut, I was able to expand the jar to fit the vacuum hose just right. I attached the 3-inch tubing to a hole I cut in the bottom of the jar on the other end, making a nice hose adaptor.

Front view

What’s That Noise?!

I put two dust collection points into the tablesaw collector: the large main 3-inch hose in the collector hood, and a second 1.5-inch hose to pick up stray sawdust from the top of the table. I attached them together with a Y-connection made from a plastic peanut butter jar. The 1.5-inch hose came out of the side of the jar, but I heated and warped the jar to make a Y connector for better airflow through the smaller hose.

The first time I turned on the shop vacuum with this setup, I got a big surprise. In addition to the usual loud shop vac whine, I got an additional loud piercing whistle noise from the 1.5-inch hose. Some Internet research told me this was a “standing wave” harmonic vibration, caused by the uniform ridges in the hose. The factory did an accurate job of creating all of the ridges in the hose the same. When air passes through the hose, the ridges cause the air to vibrate at the same frequency all along the hose, causing a single tone to come out. It’s one big whistle.

Ironically, my web search efforts revealed much about how to produce such a noise, but not how to surpress it. However, some thought and experimentation led to a simple answer: If the uniform ridges make the whistling noise, making them non-uniform should eliminate it. I heated the hose with the heat gun, and stretched it by different amounts at different points along the hose. It didn’t take much stretching to disrupt the harmonic effect, eliminating the shriek and producing quieter air flow.

Particle Separator

I use the tablesaw to cut both wood and plastic at different times. I want to keep the two separated so the wood sawdust can be used for composting, without being contaminated by plastic pieces.

I made a pre-separator to collect the wood sawdust using a 5-gallon paint bucket. The separator bucket sits between the tablesaw and the shop vac. Scraps and larger sawdust particles settle to the bottom of the bucket, while the air and fine dust pass through to the vacuum. It is patterened after professional cyclone separators, where the incoming airflow is directed towards the side of the cylinder and the air exit is in the center. As the particles are blown towards the sides, they lose velocity and swirl down to the bottom.

There are just a few parts to the separator. The vacuum port (air exit) has a tube going down the center of the cylinder, which I made from a clear plastic applesauce jar with a mouth sized to the 2.5-inch vacuum hose, screwed into the bucket lid . The intake port goes to a deflector which sends the air towards the inside wall of the bucket. The intake port is a snap-on connector for the drain tubing, and the deflector is a scrap of plastic. Since the tube connector, deflector, and bucket lid are all HDPE plastic, I welded them together with the heat gun. I also cut a window into the side of the bucket, to indicate how full it is.

Now when I cut wood, I plug the vacuum in to the separator, and my wood cuttings are collected in the bucket. If I want to cut plastic, I bypass the separator and suck the plastic scraps right into the shop vac.

Airborne dust filter

To reduce airborne free-floating dust, I employed a trick which I saw recently in a home improvement magazine. I took a normal household box fan, and attached a furnace filter onto the intake side of the fan. I took the plastic grill off the intake side of the fan and reattached it with spacers and longer screws, allowing me to simply slide the furnace filter into the slot. It works quite effectively, producing a nice brown circle on the filter in no time at all. This is good, showing dust that is not getting inhaled or settling on everything else.

Welding plastic with a heat gun

Common plastic bucket and my assistant Stanley As a handyman and hobbyist, I find there are many everyday plastic objects that can be used to make interesting things. Some of the most common useful plastics, such as high-density polyethylene (HDPE) and polypropylene (PP) just cannot be glued. But they can be welded with hot air. You may be surprised at what you can make with an old plastic bucket and a heat gun from the discount tool store.

There are tools designed specifically for proper welding of plastics, for production of plastic water tanks, piping, and many other industrial purposes. Many of these tools are somewhat expensive and require compressed air or other gasses. I’m focusing instead on a cheap, hobby substitute for the proper tools.

This method works well for HDPE and PP plastics, which won’t accept glue. If a type of plastic accepts glue well, such as polystyrene, acrylic or polycarbonate, use glue instead.

These plastics melt at a temperature around 500 degrees Farenheit. Needless to say, this will burn you. Wear gloves such as leather welding gloves, or at least heavy leather gardening gloves.

The Project

Pattern for rim I set out to create a dust collection hood for the underside of my tablesaw. I used the top section of a rectangular HDPE plastic bucket with a snap-on hinged lid. Using an angled cross-section gave me a built-in slope for dust collection at the bottom. The lid of the bucket provides an access door to the underside of the saw, for reaching in to change the belt.

The first step is to create a pattern for the rim of the underside of the saw. I measured and cut a template out of cardboard, and made sure it fit the saw. Then I could start cutting the bucket to match the template.

Welding tabs I heated and bent the sides to create the main part of the rim. I slit the curved corner sections to make tabs. Then I added flat corner pieces and welded them to the tabs.

Clamping while cooling The best method I found to weld plastic pieces like this is to heat the two faces of the tabs or overlapping pieces until they are soft, and then press them together and let them cool. The plastic will fuse, creating a single piece. It is a little tricky to heat the plastic just enough, but not too much. If you heat it too much it will simply melt and fall apart. The main thing is to try it on a number of test pieces first, and practice.

I found that the best way to press the two parts of plastic together is between two pieces of sheet metal. The metal will not bond to the plastic after it has cooled for thirty seconds or so, and will lift right off.

Modifying Tools

First attempt at focused nozzle There are many times when the tool you have available does not quite fit the task, and you need to adapt it. This was the case in using the basic heat gun to weld plastic tabs. The provided nozzle of the heat gun produced a fairly broad current of hot air, melting around a larger area than I wanted for welding the plastic tabs together.

Result: burned-out heat gun I created a funnel for the heat gun, which focused the hot air down a narrow 3/8″ tube. This produced excellent results in focusing the heat for welding. It also produced a significant side-effect: it choked the air output, so the inside of the heat gun overheated and melted in part. Result: destroyed tool. Good thing it wasn’t expensive.

The lesson from this is that when you modify or adapt a tool, be careful. Every power tool should be treated with respect as a potential source of danger, and some are more dangerous than others. It would have been easy to start a fire and perhaps burn the house down with a tool modification like this. Be cautious in experimenting, and have safety equiment like a fire extinguisher available.

Second nozzle design In my revised design for my replacement heat gun, I used a piece of aluminum curtain rod, with a cross-section shaped like the letter “C”. By having a slit down the side, much of the heat goes to the tip, but the full airflow can still pass out of the heat gun nozzle so the inside of the gun does not overheat. This did not provide as narrow a focus as the original nozzle, but it should at least save the tool from destruction. I made up for it by simply holding another piece of sheet metal in front of areas I did not want to heat.

Spot welding attempts

Spot welding with soldering gun and screw head One other approach I tried was spot-welding the tabs together, but I did not come up with a satisfactory technique. The heat gun is too broad to use for this, so I tried a soldering gun instead. You cannot simply stick the tip of the soldering gun into the plastic and melt it, because the plastic will burn and/or make a stringy mess when you pull the soldering gun out. Like the heat gun method, you need a piece of metal to cool with the plastic, which can be removed after a minute.

I tried heating through a piece of sheet metal with the soldering gun, but didn’t have success. It spread the heat too broadly, melting the top tab but not the bottom tab.

The best result came from heating the head of a screw with the soldering gun until it sunk into the plastic, through the top tab down to face of the bottom tab. It did manage to melt the two tabs together, but only in a small ring around the head of the screw, with poor mechanical strength. Based on that, I gave up on spot welding and returned to the heat gun.

Stinky PETE

In the movie Toy Story 2, Stinky Pete appeared to be a nice guy but turned out to be trouble. In the world of common plastics, PETE is trouble too. PETE, polyethylene terephthalate, is the very common plastic used for all sorts of uses. Nearly all transparent food containers and bottles, such as the 2-liter soda bottle, are made of PETE.

Like the other polyethylene plastics, PETE cannot be glued satisfactorily with any readily available glue or solvent. It cannot be welded with a heat gun or soldering iron either. The thin walls of common PETE packaging will shrink and warp before melting with a heat gun. They will melt with the soldering gun, but don’t seem to fuse to other melted pieces with any strength. Apparently PETE can be welded with industrial plastic welding equipment, but that is beyond the scope of my attempts. I’ve read that PETE can be glued with a hot-melt glue gun, and supposedly that’s how most retail labels are attached to PETE containers. But I didn’t have any success with it; the glue just peeled off. Contact cement and silicone sealer/caulking will hold slightly, but with poor strength, and will peel also.

The only success I have had with PETE has been with various forms of mechanical fastening. Screws and nuts will work if large washers are used to spread any stress. Rivets will work also. You can use epoxy glue through a hole, with a blob on each side. When it hardens it is essentially a rivet. One technique I like is to cut slots and tabs, like you would with a paper model. Fit the parts together, and then use clear packing tape on each side to hold the tabs in place. It works fairly well.

Submitted by amillar on Thu, 2006-04-06 11:10

Tablesaw belt guard

After I repaired the electrical wiring on my garage-sale table saw, I inspected the mechanical workings. It appeared to be in good working condition. There were, however, no modern safety controls. I later found that this table saw was made somewhere around 1956, when blade guards were optional and belt guards weren’t even offered.

I decided to make a belt guard using a piece of Lexan shatter-resistant polycarbonate plastic, to prevent dropped items from hitting the moving belt. Don’t use acrylic plexiglass for safety features like this, since acrylic will shatter with a hard impact.

Belt guard
This saw presented one small challenge, in that the motor is not stationary. It actually slides sideways along a rail when the blade is tilted, and pivots forward and backward when the blade height is changed. Therefore I had to decide whether to mount the guard to the motor or to the table. I decided to mount it to the motor, since that gave the most consistent coverage of the belt in the various motor positions.

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First I made a template using cardboard and fit it to shape. I moved the motor to its various limits of blade tilt and height, ensuring I still had reasonable coverage of the belt. I made sure to leave room for the ventilation holes in the motor case around the shaft, and room around the pulley to change the belt.

Then I transferred the cardboard template onto the plastic. I cut out the plastic with a saber saw and drilled the mounting holes. Then I had to bend the sides.

Lexan can be bent by brute force, but it leaves a weak joint. (Don’t even try to bend acrylic by brute force, it shatters into nasty shards.) The best way to bend it is with heat. I used a propane torch, since I had one readily available. I covered the plastic with wood pieces, leaving just a small strip where I wanted the fold. I heated it slowly, moving the flame along the line. When it softened enough, I bent it and held it in place for a minute while it cooled. This worked fairly well, although I did bubble and scorch the plastic in a few places.

After making all the bends, I screwed the end tabs together with simple nuts and screws. It could probably be glued also, but I did not investigate proper gluing for Lexan. I mounted it on the motor bolts, and declared it a success.

Submitted by amillar on Thu, 2006-01-12 12:57