Month: May 2009

Machine Shop

Digital Caliper Roller Repair

Broken caliper thumb roller mount
Broken caliper thumb roller mount

The thumb roller fell off my digital caliper in the heat of a project, forcing me to deploy a hot backup from the upstairs desk.

This looks like a clear-cut case of underdesign, because it broke exactly where you’d expect: at the midpoint of the arch. Having my thumb right over the spot marked X, though, meant that I had all the pieces and could, at least in principle, glue everything back together.

Glued and clamped
Glued and clamped

As with all repairs involving adhesives, the real problem is clamping the parts together while the glue cures. I clamped a stack of random plastic sheets to the back of the case to establish a plane surface behind the mount, with a small steel shim to prevent the top sheet from becoming one with the repair.

The roller shaft was about the same size as a #33 drill and the opening was about 110 mils. Some 3/32″ (actually about 96 mils) rectangular telescoping brass tubing was about the right size & shape to hold the opening in alignment. Another length of tubing kept the broken part from sliding to the left.

A dab of solvent glue (I still use Plastruct, but it’s not like it used to be before it became less toxic) on both pieces, line ’em up, apply a clamp to hold it in place, and let it cure overnight.

I have no confidence that this will stay together for very long, so I’ll probably be forced to mill a little replacement mounting doodad.

Ought to be good for a few hours of quality shop time…

Memo to Self: Don’t run the slide off the end of the body, because that rubber boot is an absolute mumble to put back in place.

Administrivia, Home Ec, PC Tweakage, Software

Why Friends Don’t Let Friends Use Windows: Torpig

For those of you still using Windows, here’s a sobering look at why you shouldn’t: an analysis of the Torpig botnet by an academic group that managed to take over its command & control structure for a few days.

The report is tech-heavy, but well worth the effort to plow through.

Here are some of the high points…

Why do the bad guys do this? It’s all about the money, honey:

In ten days, Torpig obtained the credentials of 8,310 accounts at 410 different institutions.

… we extracted 1,660 unique credit and debit card numbers from our
collected data.

Does an antivirus program help?

Torpig has been distributed to its victims as part of Mebroot. Mebroot is a rootkit that takes control of a machine by replacing the system’s Master Boot Record (MBR). This allows Mebroot to be executed at boot time, before the operating system is loaded, and to remain undetected by most anti-virus tools

In these attacks, web pages on legitimate but vulnerable web sites are modified with the inclusion of HTML tags that cause the victim’s browser to request JavaScript code from a[nother] web site under control of the attackers. This JavaScript code launches a number of exploits against the browser or some of its components, such as ActiveX controls and plugins. If any exploit is successful, an executable is downloaded from the drive-by-download server to the victim machine, and it is executed.

What happens next?

Mebroot injects these modules […] into a number of applications. These applications include the Service Control Manager (services.exe), the file manager, and 29 other popular applications, such as web browsers (e.g., Internet Explorer, Firefox, Opera), FTP clients (Leech-FTP, CuteFTP), email clients (e.g., Thunderbird, Outlook, Eudora), instant messengers (e.g., Skype, ICQ), and system programs (e.g., the command line interpreter cmd.exe). After the injection, Torpig can inspect all the data handled by these programs and identify and store interesting pieces of information, such as credentials for online accounts and stored passwords.

If you think hiding behind a firewall router will save you, you’re wrong:

By looking at the IP addresses in the Torpig headers we are able to determine that 144,236 (78.9%) of the infected machines were behind a NAT, VPN, proxy, or firewall.

If you think you’ve got a secure password, you’re wrong:

Torpig bots stole 297,962 unique credentials (i.e., username and password pairs), sent by 52,540 different Torpig-infected machines over the ten days we controlled the botnet

If you think a separate password manager will save you, you’re wrong.

It is also interesting to observe that 38% of the credentials stolen by Torpig were obtained from the password manager of browsers, rather than by intercepting an actual login session.

Somewhat more info on Mebroot from F-Secure.

Remember, the virus / worm / Trojan / botnet attacks you read about all the time only affect Windows machines. Linux isn’t invulnerable, but it’s certainly safer right now. If you’re running Windows, it’s only a matter of time until your PC is not your own, no matter how smart you think you are.

If you have one or two must-gotta-use Windows programs, set up a dedicated Token Windows Box and use it only for those programs. Network it (behind a firewall) if you like, but don’t do any email / Web browsing / messaging / VOIP on it. Just Say No!

For everything else, run some version of Linux. It’ll do what you need to get done with less hassle and far less risk. It’s free for the download, free for the installation, and includes all the functions you’re used to paying money for. Just Do It!

If you think using Linux is too much of a hassle, imagine what putting your finances back together will be like. Remember, the bad guys will steal everything you’ve ever put on your PC, destroy your identity, and never get caught.

Now you know… why are you still stalling?

Electronics Workbench, Machine Shop

There’s No Undo Key in CNC

The Axis user interface for EMC2 has a manual command entry mode, wherein you can type G-Code statements and EMC2 will do exactly what you say. That’s handy for positioning to exact coordinates, but I rarely use it for actual machining, as it’s just too easy to mis-type a command and plow a trench through the clamps.

OK, on a Sherline mini-mill, you’d maybe just snap off a carbide end mill, but you get the general idea.

I was making a simple front panel from some ancient nubbly coated aluminum sheet. The LCD and power switch rectangles went swimmingly.

Then I tried to mill an oval for the test prod wires using G42.1 cutter diameter compensation. I did a trial run 1 mm above the surface, figured out how to make it do what I wanted, then punched the cutter through the sheet at the center of the oval and entered (what I thought were) the same commands by picking them from the history list.

EMC2 now handles concave corners by automagically inserting fillets, so it must run one command behind your typing. I drove the cutter to the upper-right end of the oval (no motion) so it could engage cutter comp mode, entered the G2 right endcap arc to the lower edge (cuts straight to upper right), and then did something wrong with the next command.

Epoxy-patched front panel hole
Epoxy-patched front panel hole

The cutter carved the endcap properly, then neatly pirouetted around the end and started chewing out an arc in the other direction. Even looking at the command trace I can’t figure out what I mistyped, but as it turns out it doesn’t matter… I was using the wrong dimensions for the hole anyway.

So it’s now patched with epoxy backed up by a small square of aluminum. When it’s done curing, I’ll manually drill a pair of holes at the right coordinates, manually file out the oval, shoot a couple of coats of paint, and it’ll be OK.

Nobody will ever know!

If I recall correctly, Joe Martin of Sherline was the first person to observe that, unlike word processing programs, CNC machines lack an Undo key…

Update: Like this…

Patched panel - rear view
Patched panel - rear view

The shoot-a-couple-of-coats thing did not go well: a maple seed landed on the front panel. Ah, well, it’s close enough. Here’s a trial fit; the bellyband height extenders on the sides need a dab of epoxy and a shot of paint, too, but I may never get a round ‘tuit for that.

Front panel trial fit
Front panel trial fit

It’s the long-awaited Equivalent Series Resistance meter…

Oddities

End of an Era: Knights in Shining Armor

Armor suit with bullet hole
Armor suit with bullet hole

This suit of armor at Higgins Armory Museum in Worcester MA pretty much sums up why armor suits went out of style in a hurry. Click the pic for a bigger view.

That hole is much bigger than your (well, my) thumb and the dent above it isn’t much smaller. I don’t know if the gun fired two slugs (balls?) at once, but, given the accuracy of gunfire in that era, achieving two hits so close together seems unlikely.

A gut shot was inevitably fatal: peritonitis was not your friend.

Makes you appreciate the armor our guys wear a whole lot more…

Oddities

Gas Pump Instructions: Help For Help?

Mismatched gas pump instructions
Mismatched gas pump instructions

Challenge: given the conspicuous and obviously added-after-the-fact instruction sticker, find the HELP key on the stylin’ gray-on-black keypad.

You may want to click on the picture for a bigger version. I had to remove my sunglasses and peer at the keypad; I’m glad I didn’t need any actual help.

OK, maybe this is dynamiting fish in a barrel, but you’d sort of expect somebody would have noticed the problem along the way, what with the yellow background that required two-color sticker printing.

My guess: they have more than one version of the pump…

Oddities

Safety Principles: How Not to Guy a Tent

Tent Guy Strap
Tent Guy Strap

We were at a college graduation at a Prestigious University and this was one strap among many holding up the Big Tent over the assembled students & parents.

Pop quiz: how many safety problems can you count?

Let’s see…

  1. Frayed strap sewn to loop
  2. Strap passed around hook without thimble
  3. Knotted strap
  4. Broken hook safety latch spring
  5. General corrosion

To their credit, each perimeter pole had two straps and each strap had its own three-stake ground plate. I didn’t inspect the whole tent, but this looked like the only dodgy strap along the side I was standing at.

Note: the graduate wasn’t our daughter, so we didn’t stay for the ceremony. We gabbed it up with all the assembled relations, then split before the speechifying started. Everybody survived.

Home Ec, Oddities

Halogen Spotlights: FAIL

Exposed Halogen Spotlight Bulbs
Exposed Halogen Spotlight Bulbs

This pair of halogen outdoor spotlights has been in place for at least a decade; they don’t see much use, so the filaments haven’t burned out in all that time.

A lens fell off a few days ago, at which point I realized that it was the second lens to fall off; where the first one got to, I cannot say. I suspect they’ve never been turned on in the rain, as a single drop of water on a halogen capsule would shatter it like, uh, glass.

The right-hand bulb was evidently the first to fail, as it’s full of toasted spider silk, seed husks, and bug carapaces. The reflector aluminization doesn’t like exposure to the Great Outdoors, although it’s in surprisingly good shape for the mistreatment it’s seen.

I installed a pair of ordinary fused-glass spotlights from Ol’ Gene’s stash that Came With The House; they’ve been in the basement at least as long as those halogens have been on the side of the house. I suppose he put the good spots up there and kept the plain ones in reserve.

Maybe the “new” spots will last for another decade?

[Update: frienze reports another bulb failure…

Submitted on 2014/05/30 at 10:44
I searched for a more on topic post to stick this, but — alas! — it seems to be closed for commenting.

Before tossing out the bulb, I decided to take a few pictures.

Overview
Overview different angle
Detail of failure
Less useful detail turned the other way around

I half suspect the bulb might not actually be broken in the strict sense of the word, but I decided against actually testing that theory.

Trying to show the broken socket part is a lot harder. It doesn’t photograph well.
The broken socket
What the connector is supposed to look like (in a socket part that arrived broken just like that straight from China… and it’s not like it broke in transit; the protective top simply wasn’t there at all)
Here you can maybe see it a bit better
And here it is next to some dried garlic
]