Oh SAE, can you see?

Today, I did something that I should have done a long time ago, and something that anybody who works on bikes (or cars, for that matter) in North America should probably do. I took M5 (metric) and 10-32 (SAE*) bolts and compared them side-by-side. The thread shapes and angles are the same. The M5 has pitch diameter of 4.48mm and pitch of 0.8mm. The 10-32 has pitch diameter of 4.31mm and pitch of 0.79mm. The SAE bolt is less than 5% smaller with pitch less than 1% tighter. See for your self in the picture to the right. (M5 on the bottom.)

An M5 bolt will thread into a 10-32 nut, and then bind, resulting in an insecure fastening and probably ruined fasteners. A 10-32 bolt will thread into an M5 nut, but won't hold. A 10-24 bolt's threads are obviously too coarse, especially if you have an M5 to compare, but it's still nearly the right size. If you use a bit of force, a 10-24 bolt will thread into an M5 nut a few turns, and then seize. If you keep forcing, you'll probably strip the nut. Most bike bosses are M5, so forcing a 10-24 bolt into a bike boss is a quick way to banjax a bike frame. Don't ask me how I know this. (The simple solutions are to either drill and tap the boss out to M6 or use a nut on the back side forever.)

In the second picture, from top to bottom: 12-24, M6, 1/4"-20. The M6 is the only one that I should let anywhere near my bike. The 12-24 will thread loose into an M6 hole, such as some bike rack bosses, but it won't hold. An M6 will thread a few turns into a 12-24 nut, but additional turns ruin the threads. Same with a 1/4"-20 and an M6.

A metric/SAE screw gauge costs $4. That's a one-beer tool. A metric thread gauge is $7, a beer-and-a-half tool. So I have these, and if I'm at all doubtful of the path by which a fastener came to be headed towards my bike, out come the gauges. It's much faster than half breaking a boss and then having to half-fix it.

And I keep my bike fasteners well separate from anything that might be SAE. Harder to do at home than it would be in a bike shop, but it's not that big a deal to buy a $10 plastic bin tray to hold just my bike fasteners, nothing else allowed. SAEs who? SAEs me!

*Yeah, yeah, I know there are no "SAE" fasteners since, 1949, when UTS superseded SAE. Go ahead and try to buy a "UTS" fastener in a hardware store. Thought so.


Squirrel Eating Sunflower

The squirrels, or at least one squirrel in particular, have really taken a liking to Sven's sunflower.

There's a chill in the air. All the squirrels seem to be in a hurry.


Front Fender

This is a setup I've had for about 5,000 miles. It broke, so I made it again, but stronger, so hopefully it lasts longer.

I wanted a front fender that extended in front of the brake, and I wanted to mount a light low. It all came together as a DiNotte 1200+, a piece of ABS, and a rack bracket bent over the brake as shown in the picture, to be fixed by the brake bolt.

It worked great for 5,000 miles, and then it broke, near the bolted end. Vibration-induced fatigue, obviously. So this time, two pieces of steel, together about 20% thicker than the original, deliberately separated a bit to damp vibration. Hopefully good for more than 5,000 miles.

I'm sure someone will complain that that fender is too high, and should be closer to better block spray. But it actually blocks a lot of water. By the time water is shedding off of the top of the tire, it's in a pretty thin line along the center most of the time.


Parking: it's a skill.

September 13: SDOT SUV parked northbound in a no parking zone on Dexter Ave, blocking both a bike lane and a general traffic lane, right after a bus stop. This is downhill in a 30 MPH zone. (Just south of where Dexter passes under Aurora.) There are more dangerous places to park, but this one is pretty dangerous.

As soon as the driver saw me, she drove off. I didn't see whether she put down her cell phone first or not.

Update: I got this message from SDOT:

This is not an SDOT vehicle. It is a standard city vehicle used by all city departments. SDOT vehicles have our logos on them in blue. I would need a license plate to have facilities folks identify the city department using the vehicle. Perhaps there was an emergency situation that the driver had to respond to a phone call; it’s hard to know the circumstances.

Thank you for contacting SDOT