Padlock With Screw Key

Introduction: Padlock With Screw Key

This is a example of a screw type lock that as far as I could tell has been around since the 18th century and I came across some examples of this type of lock on eBay that were made in the 20th century. Lots of 19th century prison shackles use this design.

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Step 1: Sample Lock #2

After putting together my previous Instructable I had another simple lock I wanted to try building.

My build criteria was pretty simple:

#1 Had to be able to be made with the tools I owned.

#2 I had to be able to finish it in a couple of evenings over a week.

#3 as much as possible use materials I had or were inexpensive.

List of materials:

#1 1 1/4" .250 wall DOM pipe - about 4 inches for the body of the lock

#2 7/8" steel bar stock for the two end pieces and the latch

#3 3/4" .125 thick steel flat stock for the shackle bracket

#4 1/2" square steel stock - about 6-7 inches for the shackle

#5 5/16-20 long nut & 1" .035 tubing for the key

#5 5/16-18 bolt, 1/4-20 bolts, a spring & some misc screws, etc.

Not a big materials list-

Tools needed:

Misc files, hack saw (man I used this a lot) drill, taps, hammers, screwdrivers, etc. and a torch (for bending the shackle & shackle bracket) and a vice that is really bolted down to the table.

Step 2: How It Works

The free end of the shackle with the notch in it fits into the lock body. That notch matches the latch that is inside the lock body. When the key is removed the spring is fully extended the latch is pressed into the shackle's notch locking the lock.

When the key is inserted (the key is a long 5/16 nut) and threaded onto the back of the latch which has a 5/16" bolt sticking out of it and turned, it pulls the latch back, compressing the spring and out of the slot in the shackle allowing the shackle to be pulled out - unlocking the lock.

Step 3: Design

So when selecting materials I kept it simple. If you want to make one of these you can easily change any of the materials to fit your needs, make it bigger or smaller, etc. etc.

A Couple of Things -

I chose a 1/2" square stock for the shackle. No particular reason. There are example of these locks with very small (like 1/8") shackles.

The 1/2 square steel I used happened to be from something that was used to build a decorative staircase. If you note it has scallops cut into it. I just happen to find a pile of it at the materials yard and decided to use it.

The lock body and the latch. This is important. The latch and end pieces need to slide easily inside of the lock body. So the diameter should be just a little smaller than the inside diameter of the body. I used this ridiculously thick .250 wall tubing for my project because the inside diameter of the tubing was about .020 of an inch smaller diameter than the 7/8" rod. I used a belt sander to sand the rod diameter down so it would slide in easily. If I did this again I wouldn't of used that thick of tubing. I would of went with a .100 wall tube and found something else. Cutting the notch for the latch in that tubing was a pain in the butt.

Step 4: Making the Shackle & Shackle Hinge

I decided I wanted to pretend to be a blacksmith and do as much work on the shackle & bracket using heat, the vice and a hammer.

Bending the Shackle - poor mans bending

I put a 2" diameter pipe in the vice to use as the diameter for the shackle. With lots of heat I managed to bend a kind of crappy 180 deg bend for the shackle. I heated and bent it some more in the vice to get something that looked decent.

For the pivot end of the shackle I heated the heck out of one of the ends, put it on the end of the vice and attempted to hammered it flat. I re-heating & pounded on it until I had something that was about 1/4" of an inch thick. You'll also find out that the square rod will twist and you'll have to heat it and twist and turn it back. Note - when flattening the bar end I pounded some on one side then the other, This allowed me to try to keep it centered in the bar.

At this time I didn't do the other end of the shackle - the one with the latch notch cut in it.

The Shackle Hinge

I did basically the same thing as the shackle. First I bent about 1" long 90 deg bend into the 3/4" stock for one end of the hinge. Then using pliers, channel locks, vice grips, screwdrivers & a hammer and a lot of heat I managed to bend the hinge around the lock body and come up with something that kinda looked ok. I was looking for that hand made look and basically got what I was looking for. I heated this piece up a dozen times and beat on it before I got what I was looking for.

Note - don't buy just enough material for the shackle hinge. Buy 2x or 3x extra. You'll need the extra length so you can hold on and wrap the material around the body and not burn yourself and of course if you trash the first or 2nd one you've got extra material.

When the shackle hinge was complete, I rounded the end of the shackle so it would be able to pivot in the hinge. Then I drilled a 1/4 inch hole in both of them, temporally bolted them together and tried to fit them on the body of the lock. This is in preparation for cutting the shackle down to the proper length and identifying where the slot in the lock body belongs.

Attaching the Shackle Hinge to the Body

When I made the bracket it would easily slide on and off the lock body. So initially I tack welded the hinge to the lock body so that I could continue to size up where things were going to end up. I didn't like the look of something that was supposed to be old welded together so what I ended up doing is at the bottom of the hinge I drilled & tapped a 1/4-20 inch hole in the lock body and a clearance hole in the bracket and bolted the two together. I know this isn't 'old school' but I decided I wanted to be able to disassemble the lock and the rounded hex head screw kinda looks like a rivet. Also I wanted to not have to use a welder (electric welder) for this project :-)

Step 5: Cutting the Slot in the Body and Cutting Down the Schackle

So In this step I need to do the following:

1. Cut down the non hinge end of the shackle

2. Cut the slot in the lock body

3. Flatten & curve the shackle so it fits into the slot in the lock body

Note - measure twice, then measure again and cut once.

So I wanted my shackle when this was all done to just touch the inside of the lock body when its inserted into the lock body. That was my original idea.

I guestimated where I needed to cut the shackle and cut it with a hacksaw.

Creating the Latch end of the Shackle

I was going for old school here so I decided to heat and hammer the end thinner and wider.If you don't want to go that way you can just grind say an 1/8" of an inch off each side of the shackle to narrow it down or not do anything and use it as is. All of 19th century prison shackle examples I found all had both ends hammered down so that's what I decided to do.

This is a repeat of the opposite end of the shackle. Heat and hammer. Make sure you hammer both sides evenly so that it narrows down evenly on both side. I didn't have 100% success here but it was close enough for me to use.

Don't trim or clean up this end just yet. Cut your initial slot then determine how much of the latch end to grind down vs extending the slot in the body.

Once narrowed, depending on where the shackle lands on the body I marked where I need to cut a slot into the body. the slot will be longer than the shackle end because the shackle is moving around its pivit point so It will go out further towards the end of the lock and end up a little closer than where it initially touches the body - i.e. basically a longer slot than you might think.

Cutting the Slot in the Lock Body

I used a drill size one bigger than the width of the hammer flat portion of the shackle. I wanted the slot/shackle to be as precise as possible fit so I knew I was going to drill less and file more. You don't want a sloppy too big slot in your lock. You don't want to be able to slide a screwdriver into the slot and push the latch back and open it. Less is more for now no matter how painful filing the slot becomes.

On the line I marked for the slot. began to drill holes as close as I could next to each other in a straight line.

Then - I got out my best chisel, sharpened it and chiseled out what I could of the slot to avoid as much as humanly possible having to file. You'll know very quickly how good a chisel you own while doing this.

When the chiseling was done, them came attempting to file the slot wider. I actually had to buy a file that would fit my requirements for this. BTW - Don't hesitate to add to your tools collection or avoid taking on the project because you don't want to add a new tool to your collection.

This is where the 1/4" thick wall tubing came back to bite me. There is little or no room to file the slot because the file bangs into the inside of the tube. It took me forever to get the slot opened up to a hole that was cleaned up. I suppose using a dremel here would of came in handy but I don't own one.

Now you have an initial slot and a shackle end flattened. grind, file, cut & fit these two until you have the shackle end moving in and out of the body.

Step 6: Making the Latch Mechanism & Key

The Key

My key consists of a 1" .065 wall piece of tubing brazed onto a 5/16-18 long nut.

I ground the hex off the nut so that I ended up with a round body vs the hex and brazed the tubing onto the top of the long nut - key done!

To make it a little fancier, I added a bit of scroll work inside the key by taking a strip of 18ga sheet metal that I wrapped around a 1/4" bolt with some pliers. It only took a few minutes to do this and 2-3 tries before I ended up with something that looked kinda cool and old. Then I every so gently brazed it into the ring on the key.

Pretty straight forward.

The Latch

The latch consists of a 5/16" bolt, a spring & two pieces of 7/8" round stock (The latch & end piece).

For the end piece I cut a 5/8" slice of the bar stock off and drilled a hole in the center of it big enough so the key would fit through the hole. I had previously ground down the diameter of the material so that it would fit into the lock body. Not too sloppy, not to tight so you have to hammer it in.

For the latch cut about a 1 1/4" inch length of the bar stock. On one end in the center I drilled & tapped a hole for the 5/16" bolt. On the other end I marked a line in the middle of the stock and cut a notch out of it with a hacksaw. On the opposite end I ground a 45 deg bevel in it.


Make sure that you drill in the EXACT center of the end piece and latch and drill and tap the hole for the bolt perpendicular to the latch face. If you don't when you assemble the pieces and try to use them the key may not be aligned with the bolt or if the hole it tapped crooked, you'll try to pull the latch sideways in the lock body and it may bind.

The spring. Not to stiff, not too weak either and it of course it has to fit inside of the lock body and be able to have the key fit through it. I initially had a spring that was WAY to stiff & when I found another spring I melted two of them attaching them to latch and end piece :-(

So -

How long is the bolt - well you'll have to work that out depending on the materials you used. Start with it too long and cut it down until its going to work. Don't lock tight it in just yet.

Why did you braze the spring to the latch and end piece? Because when I tried to screw & unscrew the key in, the latch wanted to turn (rotate) which put it out of alignment with the end of the shackle. Having the spring attached to the end piece and latch prevents the latch from rotating when the key is screwed in.

Assembly of the Latch

So you will have to have the end piece fit into the body and not rotate. You can either tack weld it (Which you won't be happy with) or what I did and you can't see in the pictures is I drilled a 6-32 hole through the body and just slightly into the end piece so that I could screw/hold the two together with a counter sink head screw. You can't see it in the pictures because the shackle hinge is covering it. This only took a few minutes and worked out really.

Brazing the Spring to the Latch and End Piece

I didn't actually do this until I was satisfied with how everything was working. You may have to shorten or stretch the spring for it to work, or maybe make another latch - longer or shorter to work.

To shorten the spring you can do two things - cut it, or bend it so its shorter. I would suggest you bend it vs cutting it. The spring is probably ground flat on both ends so it sits nicely on the latch and end pieces. And if you bend it you will probably have to bend it twice to keep it aligned so it will fit in the hole.

To weld the spring - If you don't have a torch you can probably use a propane torch for soldering copper pipes together. Don't put too much heat on the spring or it will just melt in half. If you try to use a mig welder be careful, just touching the rod to the spring even on the welder's lowest setting will melt the spring.

Step 7: Notching the Latch

Now you have the latch built and the shackle slot cut and the shackle fitting in the slot you now can cut the notch in the shackle end and smooth/grind it to where it looks good and will work.

I marked the shackle end with a felt pin and slid the latch in and tapped on it to mark where it was touching. Make sure the latch its perpendicular to shackle end.

From there I measured twice, then again and then begin to file the notch into the shackle. I took my time because I wanted it to have a precise tight fit when it was locked up.

Step 8: Fitting & Final Assembly

So now you should probably have a lock that is working to some extent.

What's remaining -

Making & fitting the other end piece

Riveting the shackle to the bracket

'Aging' the lock

Making & Fitting the End Piece

I cut another piece of the 7/8 stock, fitted it into the other end of the lock. To have the piece stay in the end - I did the same thing I did for the other end piece. I drilled & tapped a 6-32 hole in the lock body and inserted a screw. I used a counter sunk screw head and to counter sink the hole I used a 1/4" drill. then once screwed in I belt sanded the remaining screw head to it so it matched the rounded body. I could of just as easily made the end press fit into the body and tapped it into place.

Riveting the shackle to the shackle bracket.

I used this technique in my previous lock instructable and it looked cool so I went with it again.

I used a 1/4-20 bolt, sanded the hex head round to resemble a rivet head. then I cut the length of the bolt so that it was sticking out of the bracket about 3/16 of an inch. I heated the end of the bolt up until it was orange hot and peened the end over. Careful here - you can peen it shut so much the latch may not be able to rotate in the bracket anymore.

'Aging' the Lock

So I didn't want the lock to look new so I tried a couple of different things here to give it that 'antique' look.

1. Hot vinegar I saw something on YouTube about putting metal in hot vinegar to etch the metal. This only works on certain types of metal. Mild steel doesn't appear to be one of them.

2. Ferric chloride - There are some references to etching knife blades on this site that you can have a look at.

2. Bluing the metal. Lookup 'Birchwood Casey Super Blue Liquid Gun Blue' for more details. You can get this at any store that sells firearms. Big Five has it. Basically it etches the metal a nice dark blue. I did this on the key for the lock but decided not to do the lock You can kinda tell in the picture if you look at the key closely.

3. Paint, powder coat, leave it in the rain etc. etc. etc. Up to you. By the time I was done putting this together it had some rust, tarnish & a worked look so I left it like it was.

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    5 Discussions


    2 years ago

    nice build


    5 years ago

    If you don't mind me asking, what was the approximate cost for this project? I'm looking into making one for my brother.


    Reply 5 years ago on Introduction

    Materials wise, I believe you could find everything at Home Depot to make it for around 20 bucks. If you have a materials place around you and you find pieces of what you need maybe less.


    5 years ago on Introduction

    This thing is seriously cool. If I were still riding a bicycle for a living I'd make one.