Introduction: Home Made U-Lock Bicycle Lock

Picture of Home Made U-Lock Bicycle Lock

Make your own bicycle lock.
It can be lighter, cheaper, and much more fun than any lock you can buy.

Here's one made of cardboard!
It's perfect for use in Japan and other nice places where people don't like to steal.

I live in the United States where lots of people steal things.
So we'll make a stainless steel one from an old stove.

Step 1: The Ancient U-Lock

Picture of The Ancient U-Lock

The "Modern" U-style lock is pretty old. Here's a patent for one from 1925.
It's designed to fit over the spoked wheel of an automobile.
Back then lots of cars didn't have locks.
As Henry Ford said "You can have any color you wanted, as long as it's black."
So people accidentally taking the wrong car must have been a problem.

Step 2: Boston Massachusetts, 1974

Picture of Boston Massachusetts, 1974

Many patents for bike locks come from the Boston area.

That's because North Korean submarines loaded with ninja spies go there to steal bicycles.
There are about fifty colleges within ten miles of each other. All those students are
1) Easy to steal bikes from, and
2) Easy to sell stolen bikes to.

When I lived in Boston I had the lock made from these patent drawings. It was great. It was a bit unusual, so the North Korean training camps didn't bother teaching people how to break them open.

This excellent but simple lock is the inspiration for this whole project. The drawings shown here explain all you need to know about how it works. To keep boltcutters from reaching the hasp of the padlock, there is a sort of box around the padlock. The crossbar has lumps to keep it from pulling through the U.

Step 3: The Japan Compatible Bicycle Lock

Picture of The Japan Compatible Bicycle Lock

My Dad never stole because my Grandfather gave him a lecture on the subject: "Stealing is easy."
He was Swedish and didn't like talking very much.
Forinstance there was the famous Anderson Family Sex Lecture: "There's not much to that."
or the one on the importance of communication: "I never talked to MY parents."

My point is that cultural differences exist. One can take them into account when designing bicycle locks.

I was just in Japan for a few weeks. I lost my bike lock so I just tied my bike to the rack with a plastic bag. Of course it was still there when I got back.

North Koreans don't steal many bikes in Japan. I hear they run Pachinko parlors instead.

Step 4: Make a Model and Gather Materials

Picture of Make a Model and Gather Materials

The cardboard lock seemed about right, so I scavenged some stainless steel to make the real one. I wanted some heavy stainless that would actually be hard to cut through, but all I could find was this stovetop. As long as the finished thing looks fairly solid that's probably enough. I bought a four-pack of padlocks all keyed the same for $15, and it's time to cut metal. I marked the cuts and folds on the metal with a permanent marker. The little rectangles in the lower right corner are the cuts and folds to make the guard box around the padlock.

Step 5: Cut Out the Parts

Picture of Cut Out the Parts

I clamped it in a vise and used a sawzall with a hacksaw blade to cut out the parts.
Stainless steel workhardens quickly and conducts heat poorly.
That means you need to use a sharp blade with a slow deep cut.
The other way is use a dull blade and just melt your way through it.

Step 6: Pound on It

Picture of Pound on It

The metal edge had some curves I didn't want so I flattened it with a hammer.

Step 7: Make the Slot for the Crossbar

Picture of Make the Slot for the Crossbar

Drill a row of holes. That's the first step to cutting the slot.

As you can see I've already done one of the bends for the hasp guard.
That's easy, just clamp it in the vise, fold it over, and pound on it to make a nice corner.

Step 8: Chisel Between the Holes

Picture of Chisel Between the Holes

I'm fortunate to have friends that grind my screwdrivers sharp so they make good chisels.
Use something like that to chop out the metal between the drill holes.
When the slot is big enough for a saw blade you can saw the slot bigger.

Step 9: File the Slot Smooth

Picture of File the Slot Smooth

There are two slots in the U part of the lock.
This is the longer one at the end away from the padlock.

Keep filing until your crossbar fits easily in the slot.

Step 10: Fold the Hasp Guard

Picture of Fold the Hasp Guard

Clamp, fold, pound. Repeat.
Repeat until it's the shape you want and your padlock goes into it easily.

Step 11: Weld the Hasp Guard and the Blob on the End of the Crossbar

Picture of Weld the Hasp Guard and the Blob on the End of the Crossbar

I used old stainless steel bicycle spokes as welding rod and a TIG welder.
I'm not showing any of the details of welding because it's hard to photograph and the info is abundantly available elsewhere.
Most people don't have a TIG welder. Use whatever you've got.
If you don't have a welder use solder, rivets, glue, string, or chewing gum.
The goal is to make it look like a bicycle lock or at least like something a normal person wouldn't want to touch.

The crossbar looks just like the cardboard one except it's metal.
The blob at the end can be welded, folded, or any combination.

Step 12: Saw Down the Hasp Guard

Picture of Saw Down the Hasp Guard

I thought I made my hasp guard too deep, so I sawed it shorter.

Step 13: Grind Slots in the Hasp Guard

Picture of Grind Slots in the Hasp Guard

Keep reshaping the hasp guard until you can get the padlock to fit in it properly.
I probably made the "ears" on mine too short because of too much coffee.
The grinder blasted lots of crap into my face, so I was glad I had safety glasses on.

Step 14: Lock Your Bike!

Picture of Lock Your Bike!

Here's the finished lock in use. It looks and acts like a real lock, at least well enough for running errands.
It's lightweight and not very strong, but there isn't any lock that would keep this particular bike safe in any American city for more than a day.

I'm scavenging materials for heavier locks that would be harder to cut.
You can never have too many bike locks.


jdorrington (author)2015-11-08

at first glance I thought you were suggesting the cardboard version!

Hazzard2theworld911 (author)2012-08-12

What a nice way to scrape the paint off of your nice cannondale...

EarlyGrayce (author)2010-12-07

"As Henry Ford said "You can have any color you wanted, as long as it's black."" is a misquote, the first few generations of Fords were not even available in black.

sk3lton (author)EarlyGrayce2011-05-26

"As Henry Ford said "You can have any color you wanted, as long as it's black." is not a misquote i can't remember what model of car it was for but he did famously say that

ilpug (author)sk3lton2012-01-19

If they weren't black, what were they?

EarlyGrayce (author)ilpug2012-01-21

Ford wrote in his autobiography that he told his management team in 1909 that in the future “Any customer can have a car painted any color that he wants so long as it is black”.
From 1908 to 1914, the Model T was not available in black but rather only grey, green, blue, and red. Green was available for the touring cars, town cars, coupes, and Landaulets. Grey was only available for the town cars, and red only for the touring cars. By 1912, all cars were being painted midnight blue with black fenders. It was only in 1914 that the "any color as long as it is black" policy was finally implemented.
The model changes were not designated by a new letter but frequently under the banner of Model-T which was also seen more recently with the VW Beetle that change dramatically over the couples of decade they were built although they kept the same name and styling. 

ilpug (author)EarlyGrayce2012-01-21

Huh. Interesting!

sk3lton (author)ilpug2012-01-21

That was the whole point you could only buy the car in black and I have since researched what model car this was and it was the Model T in 1909

Zeppelinfreak (author)2011-05-15

Chain and a padlock

stupidloginthing (author)2009-09-10

any thief with a bolt cutter could have that bike in 2 seconds flat.

nah tin snips will also do it

weldor (author)2 stroke 2010-12-30

Depending upon the thickness and type of stainless steel used it can be quite a chore to cut through with snips. Stove tops are typically a 300 series ss which is not as hard ad the 400 ss. It is typically tougher (this is what makes ss such a pain in the rear to work with). The wider the strap the more trouble it will be to get through.
The lock in the pic is a Masster Lock. Although typically a decent lock, I knopw how to destroy one in a matter of seconds. Master does make a lock that has a hex shaped shank. There are other types of locks that are harder to break as well. They typically have what is best described as a "warded" shackle. Look them up on the Maaster Lock web site. There are other companies that make good locks as well. Some of the knock offs are pretty stout as well. I would recomend using a lock that is stainless as well- no rusting and all but impossible to cut with a torch as well as a real pain in the keister to cut with a saw.

2 stroke (author)weldor2010-12-30

cordless angle grinder

bo88y (author)stupidloginthing2010-09-04

Any thief with HANDS....

sora (author)bo88y2010-09-24

unless its a stupid theif

Any thief with a bolt cutter could have most bikes in a few seconds. Most bike locks are meant to prevent the casual/semi casual thief (just walking around, and steals a bike without intending to do so that day, or similar variants). If there's a gang of thieves driving in a van with power tools or even a bolt cutter, Your bike is pretty much gone, unless you have a bunch (10+) of insane strength locks.

AnarchistKid (author)2008-02-12

if i wanted the bike bad enough, id bend it back and forth till it breaks.

weldor (author)AnarchistKid2010-12-30

Stainless steel will not break by bending it back and fot\rth as you suggest. However, it will proceed to getr hotter and hotter until you burn your fingers. JUst ask anybody who works with metal for a living.

EarlyGrayce (author)2010-12-07

Funny to see your gloved hand on the handle and the bare one near the blade.

SuperCoPilot (author)2010-10-16

i found most of the time when you buy a lock from a bike lock exclusive company, they're usually more than happy to reimburse you for the bike

onrust (author)2010-10-03

Here in the states (Tucson) I lost 3 bikes in less than a month. You have got to look at what anything is locked to. Screw the cardboard lock, a hack saw will cut the chosen post. Its not brain surgery and this is why people get robbed.

dan_o_89_rs (author)2009-08-18

looks nice. inexpensive, yet perfectly functional... looks like the edges might need a covering of sorts to protect the bike's paint. but nice..

mattyew (author)2009-04-12

i have a caad5 myself, but i prefer using name brand locks like kryptonite cause they have a reputation for being very difficult to break. nice bike!

engineerable (author)2008-11-23

Switzerland is pretty much the same. My father and I were bike touring through switzerland, and most of the bikes were never locked up. Several times I saw very expensive bikes just sitting against a wall, or stuck in a bike rack with no lock. At most they use the locks that just keep the rear wheel from rotating. Too bad it isn't like that everywhere.

Yerboogieman (author)2008-10-09

this one kid used to lock up other peoples bikes with U-Locks

3366carlos (author)2008-05-30

great idea.

quicumque (author)2006-11-29

If I was some average dude (which I am not), that thing would send me off just by the looks. I say instead of adding extra weight to deter cutting devices, just make the edges nice and sharp, add some red dye at random intervals. Great job, and very nice article!

unspecified (author)quicumque2008-02-12

I love that plan!

unspecified (author)2008-02-12

Man - I just don't know about this one at all. I mean - if you have to weld as a step it implies access to a welder and most likely some steel bar stock. I am jumping on the "way too flimsy" boat - especially since all of that work went into it. I also don't imagine that a lot of people want a sharp edge gouging their paint every time they have to lock the bike. I dunno Tim - it seems that you are into "living small", but saving on the materials will certainly not offset the price of another bike. Also, the lock in the first of the final 2 pics seems to be open to shimming, preventing which I would have thought was one of the boxes key functions.

Von Klaus (author)2008-01-03

yeah any criminal can quickly snip that lock in two. rememeber kids. always lock your bike in a well lighted area. but, it is a good idea if you live in an area that people don't steal crap.

frogmeetcog (author)2008-01-03

GOOD quality stainless steel is, as Soapy here already said, not possible to drill into, much less pound through with a hammer and screwdriver. Whatever Chinese metal that is, it's pretty soft, and thus not remotely theft resistant. I have some German stainless plates from the scrapyard, and I can barely get through them with a anglegrinder and several good grinding wheels! Nice Cannondale, though. I would ship the author some of my stainless plates just for the heck of it, but they weigh a ton!

julianwisbey (author)2007-11-25

you should cover the peices in some old inner tube cause thats gunna scratch the shit outa your poor dale

Karim (author)2006-12-04

but some one or almost anyone can break off card board!!!

CaffeineHouse (author)Karim2007-07-27

hahahahahahaa you really think so? only like, the strongest guy in the world can break cardboard!

It is SO hard for me to break cardboard. I mean, I can rip rip telephone poles in half but CARDBOARD?! Holy crap I could not do it! lol

kittyno (author)Karim2007-08-13

yes, that's why he made a metal lock.

razordu30 (author)2007-11-14

Wow....if I were you, I'd consider throwing a garbage bag or something over your bike as well, to cover the labels.

A Cannondale locked with the scrap pieces of a stove top = rich and happy thief

PKM (author)2007-10-12

Hmm.. I can't say I really see the point of this design. If you're going to carry a U lock at all you might as well make it a secure one. I know no lock prevents theft, they are only deterrents, but if your lock deters anyone except some kleptomaniac wielding a gas-axe and a chainsaw I'm happy enough, and a nice certified lock also means you can get theft insurance. What I would love to see is a small or foldable design for a reasonably strong lock I could use to secure my quick-release wheels. Locking the frame to something immovable is all well and good but unless I carry three locks at a time some scally is probably going to make off with my brake discs.

stasterisk (author)2007-08-15

For instance, here's how to TIG weld!

Nice little alternative to not having a lock. If I had a cheap bike I'd make one. If it were mine I'd make it smaller, and lock through the back wheel and rear triangle - it'd be far easier to cut through the lock than cut the wheel.

Fat_Head_Carl (author)2007-03-06

I like the ingenuity - perhaps a smaller "u" will be less vunerable (something that fits very closely to a standard-sized pole in your local town). Ive seen the "tire-irom / pipe twist the lock off" trick first hand... As a serious PSA I must advise you can NEVER lock up a bike of worth (Cannondale, Trek, etcetera), it's never safe, no matter what lock you own.

guitronics (author)2007-02-19

Nice Job,and good food - for - thought. You can always improve anything...but this is really nice.Wish I had a TIG welder!

psychoalchemy (author)2006-11-30

The whole point of using a u-style lock instead of a cable is to decrease your vulnerability to portable handtools. This design will be vulnerable to bolt-cutters at the paddlelock and to sheet metal shears at the 'U' portion. Soapy's advice is pretty good, although I don't know how you would harden the padlock area and a really good padlock is about the same price as a cheap u-lock.

_soapy_ (author)psychoalchemy2006-11-30

Hardening the padlock area is simple, just look at the picture in step 2. You can see that there is extra steel plate up around the shackle of the padlock, right up to the body, so the padlock is encased when closed. This stops crops from getting anywhere near. As for the guy on MAKE: who thinks he could beat this with bare hands (by flexing?!?! With a found stick?) I'd pay money to see him try. Well, ok, I'd laugh at the video on YouTube as he shredded his hands and ran away... Good job the bike is red!

_soapy_ (author)2006-11-29

To amp up the security, add a bit of protection around the padlock area to stop bolt croppers and hammers from getting at the shackle, or switch to a close shackle padlock. You can see that in the patent drawing in Step 2.

To stop snips, SAKs and scissors, and even steel nibblers, simply add a line of MIG weld all the way along one edge, and all the way along the other edge. This will make it very very hard, to stop cutters and saws, as well as making sure the edges aren't too sharp. The middle will still be flexible, though, so it won't shatter.

You could also make a second crossbar, further up the U, to make that part stronger, and to reduce the free space for tools to work in.

As regards materials, I'd go for a good bit of hard stainless, the nasty stuff you have to cut with a disc cutter, and try for 2.5mm thick, as that is really beyond most hand tools. Widthwise, I'd suggest 3.5", as that is more than two bolt cropper jaw depths wide, even on quite big crops they only bite 1.5" deep, and crops *hate* thin slightly soft materials.

You could also cover it in plastidip or self-amalgamating rubber tape, to protect your bikes finish, as well as further annoy anyone trying to cut it. "It might stop *some* meepeople complaining about the finish, too" ;-)

Nice bike, btw.

burdgyrl (author)2006-11-29

How about a couple of thumbs & forefingers?

theRIAA (author)2006-11-28

cool, although always carry around a cheap pair of serrated scissors that can cut through pennies... and i doo want a road bike...

leevonk (author)theRIAA2006-11-28

yeah, especially a cannondale, and if the scissors don't do it tin snips should.

About This Instructable




Bio: Tim Anderson is the author of the "Heirloom Technology" column in Make Magazine. He is co-founder of, manufacturers of "3D Printer" output ... More »
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