August 17, 2011

Replacing a Snapped Bolt

If you use and work on machines enough, it will eventually happen to you. Metal bolts fatigue and eventually break. This is a common occurrence when working on old exhaust parts, but sometimes it happens unexpectedly. I was mowing the grass today, and the mower blade retaining bolt suddenly broke. It was immediately obvious that the blade was no longer attached to the shaft because the engine was suddenly turning freely. If I had kept moving, it would have become even more obvious because it was no longer cutting grass. I turned off the mower and closed the fuel line valve, and I tipped it up to investigate. The blade and spacer were lying on the ground together. After digging around for a minute through the half-mown grass, I found the head of the blade bolt as well.

The procedure for replacing a broken bolt is straightforward in principle, but it can be a little tricky in practice. First, extract the part of the bolt that is lodged in the shaft (or whatever it's lodged in). Next, find a suitable replacement. Finally, reassemble whatever it is that the bolt held together.

The first step is the tricky part. There's almost never enough of a broken bolt left protruding so that you can turn it with the usual tools. My preferred method in this case is to drill a hole in the center of the bolt, then drill out to both sides and extract it with a flat screwdriver. This method worked well for me in this case.

When drilling metal, it's important to have the right drill bit. There are two major types suitable for drilling through steel: cobalt and titanium. In my experience, the cobalt bits tend to work much better. This may be because I bought a set of cheap titanium coated bits from an auto parts store, but I buy individual DeWalt brand cobalt bits. Both are made of high-speed steel (HSS), but cobalt bits are so named because the steel used to make the bits has a higher cobalt content, whereas the titanium bits have a titanium coating over regular HSS. This means that the cobalt bits can be sharpened, and they are more resistant to high temperatures as there is no coating to wear off.

Regardless of your drill bit choice, there is a proper method for drilling metal to get proper penetration without overheating the bit. The trick is to 'pulse' the drill, applying constant pressure. If you do it right, you will probably get a few long, twisted strings of metal out of the material you're drilling.

Chances are your bolt didn't snap off cleanly and there's some odd slope to the surface that's left behind. Start off in the middle of the bolt, and drill perpendicular to the surface to start out. Once you have an indentation that will keep the bit from 'walking', straighten out and drill straight into the bolt. Once you have a good primary hole, drill at a steep angle to one side, then the other. You want to make sure you use a bit that's small enough to keep all of this action away from the very edges. Here's how mine turned out.

It doesn't have to be perfect. It just has to be long enough to fit the blade of your screwdriver and narrow enough that the screwdriver has something to catch on and turn the bolt.

 This is a fairly new lawnmower, so the bolt came right out with a screwdriver.

My original plan was to measure the bolt and pick one up at a hardware store, but once I got the whole thing out, I saw the flaw in that plan. Troy-Bilt apparently likes to use weird, double-threaded, proprietary bolts.

Note how the thread closer to the head has a wider spacing than the thread toward the tip. Odds are you won't find that bolt at your ordinary hardware store. So, it looks like I'm done cutting the grass for the day. I had to order a new bolt online. The first site I went to wanted approximately one arm and one leg for shipping, so I tried another. The first site I came across with my part and cheap shipping was, so I ordered from them. Shipping was still considerably more than the cost of the part itself, but it's at least a fair price, keeping the total under $10.

Repairclinic also guarantees same-day shipping on in-stock merchandise, so it should be on its way later today and arrive early next week, and then I can finish mowing my grass.

August 10, 2011

Rear Window Defroster

I'm not quite sure how this happens, but when I bought my car, some pieces of the rear defroster grid were missing. As a result, only about half of the rear window would defrost, limiting rear visibility. In Virginia, it's legal to have your rear-center view obstructed, so long as you can see out of both side mirrors, but I prefer to be able to see as much as possible.

I set out to find a suitable kit. You can pay a lot of money for these things if you want to, but Advance Auto Parts had a reasonably-priced kit for $12.49 online. I think it was actually a dollar or so more in the store. A similar deal is available on Amazon. All I really ended up needing was the conductive paint and the applicator.

Permatex Complete Rear Window Defogger Repair Kit

The kit comes with everything you need to get your defogger working if you have a broken grid or detached tabs. My tabs were fine, so I only needed part of the kit.

Instructions are pretty simple and straightforward. Clean the glass with the included alcohol pad, stick the template to the glass in the appropriate place, and brush on the conductive paint.

I started using the kit by the instructions included, and it ended up looking horrible. The included template is too wide and not long enough, so it makes a wider-than-necessary mark on the glass and has to be moved multiple times. After realizing this, I decided to make my own.

 The tools I used: a strip of masking tape, a smooth cutting board, and a sharp knife. Not pictured: a good straight-edge (steel ruler). It might be better to use a box cutter with a fresh blade than a pocket knife, but this worked fine for me.
 I just eyeballed the width. I had the template from the kit (upper left) for a scale reference. It worked out well. Masking tape is cheap enough that you can make multiple attempts if you need to. If it hadn't worked out right the first time, I would have measured and done it the precise way.
 My custom template on the glass. It took a few attempts to get it aligned properly. Sedans make for an awkward angle for this project. Just be patient and you'll get it.
 This picture shows one of the lines I made with my custom masking tape template. You can see how it bled under a little bit. I scraped the excess off with a knife.
 The entire project area. You can see in the top half how wide the original template is compared to the grid lines.

Overall, the results were good. I haven't had an opportunity to use it yet, so I can't be sure if it works. Testing with an ohmmeter doesn't help. There are practically 0 ohms between lines on the grid, so there's no real chance of finding a break on one line. The best I could do was to stick a probe at a few points on each repair to ensure that current would at least flow from those points to one side or the other. That testing failed to find any problems, so I'll assume the fix was successful until proven otherwise and report back when I know for sure. There's still some cleaning up to do after using the standard template, but at least it should afford me some rearward visibility.

August 7, 2011

Cleaning Car Windows

If you're like me, you probably don't clean glass very often. Clean glass in your car can save your life, though, so break out the glass cleaner and paper towels and let's do some wiping.

The camera sees it worse than my eyes did. No camera tricks here. It was set to automatic the whole time. This window was apparently so hazy that it made my camera think it was dusk at 10 AM. The glass definitely needed cleaning, but it certainly wasn't the worst I'd seen.

First, spray your window down with window cleaner. Go ahead and wet the whole surface, but don't soak it. More than a light spray is just going to make a mess on surrounding surfaces. It doesn't matter what kind of cleaner you use unless you have tinted windows. They'll all streak if you don't use them well, and none of them will streak if you do. If you have tint, be sure to use an ammonia-free window cleaner, unless you want your windows to turn purple.

I tried to take more pictures in here, but apparently my camera went on strike. Wipe the window down once with a paper towel. Be sure to wipe everything that you want clean. If you're trying to do a really thorough job, you may want to roll the window down to get the top half-inch or so. You want the window cleaner to have a chance to work on every square millimeter of the glass. This wipe will also remove most of the cleaner. This is a good thing. If your windows are filthy like mine, your paper towel will come out looking like this:

Finally, grab a clean rag or paper towel and make another pass. You want to remove everything, so don't hesitate to rub vigorously. The streaks from the window cleaner should disappear as you wipe. It will probably take a few passes to get a section of the window clean. Once all the streaks are gone, it's clean.

Other tips: 

I wrote this after I had already done the windshield, which is the most important and most difficult piece of glass in any vehicle. You'll probably want to treat the windshield as two separate pieces of glass, and sit in the passenger's seat to clean that side. Otherwise, you'll bump your mirror a lot and end up cursing your lack of strategy. If you have an E-ZPass, remove it to clean around it, but leave the Velcro pads on.

The outside of the glass is just as important as the inside, but it usually gets cleaned pretty well by rain. I frequently give it a good wipe with a gas station squeegee if it starts to get too dirty (due to lack of rain, usually). I'm also a proponent of Rain-X, which is a product you apply to the outside glass on your car to make rain slide off. As a result, I typically only use my wipers when I'm not on the highway. Some like it, some don't. You can get it at Walmart or just about any auto parts store.

If you smoke, try to avoid doing it in your car. In addition to making your car more difficult to sell when the time comes, cigarette smoke causes a film to build up on any surface it touches, including your nice, clean glass. I clean my glass once every couple of years. If you smoke and maintain clean auto glass, you'll probably find yourself cleaning it once a month.

To maintain clean glass, avoid touching it. No matter how clean you are, you're still greasy and dirty compared to clean glass. If you drive around with children or pets in your car, they're probably going to touch it and make you clean it more often anyway. Of course, smudges on back windows are more tolerable than the front ones.

Good luck, and enjoy your clean windows.