Impossible Nail in Wooden Block

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Introduction: Impossible Nail in Wooden Block

About: I got an old sewing machine when I was just a kid, and I've been hooked on making stuff ever since. My name is Sam and I'm a community manager here at Instructables.

This is my take on a classic puzzling object that woodworkers have been making for years. If you've never seen the impossible nail-through-block-of-wood trick, check out Steve Ramsey's great video here.

My version and approach is very different than Steve's, however.

The nail is solid and has not been bent, cut, glued, or modified in any way. It slides back and forth within the block of wood, and the total length of the nail is longer than 2x the diameter of each hole.

The wood has not been boiled and squished or bent, as some people may suggest.

I made this because I love little objects that seem to defy physics and logic. They intrigue people and encourage them to think and reason, and I find it very interesting to observe how people respond when confronted with things like this.

If you're interested in making something similar, read on. Thanks for taking a look.

p.s. If you like this, check out my Cards in Bottles and Tennis Balls in Bottles instructables too!

Step 1: Materials

I used a piece of hardwood and a large 60d nail (which is 6 inches long). A smaller piece of scrap wood (like a piece of a 2x4) and a smaller nail (like a 20d nail) could be used just as easily.

You could use a large variety of tools to reach the same result I did, depending on what you have access to.

Here are the tools I used (links are to specific models I own and happily recommend):

Step 2: Flatten Board

The piece of wood I was using was cupped, so I used an electric planer to get it fairly flat.

The finished thickness was about 2 inches.

I used my table saw to trim the board to the final size of 5 inches by 10 inches.

Step 3: Mark, Punch, and Drill

I used a 2 1/2 inch hole saw to cut out the two large holes.

I began by marking the center point for each hole at a distance of 2 3/4" in from each end of the block. Then I used a nail set to punch a hole on each mark to help keep the drill bit centered.

A 1/4 inch bit was used in a drill press to drill through the board on these center points. These 1/4 inch holes will act as guides to help align the hole saw in the next step, so I can use it from both sides of the board to cut out the holes.

Step 4: Hole Saw

I positioned the guide holes under the hole saw and clamped the board in place. I very slowly made the cuts, raising the saw occasionally to clear the dust.

Each hole was drilled halfway on one side. Then the board was flipped over to complete the holes from the other side.

Step 5: Clean Up Holes

I used a spindle sander to clean up the insides of the holes. I've had this oscillating spindle/belt sander from Home Depot for many years. Highly recommended!

A rotary tool with a small sanding drum could be used for this step as well.

Step 6: Now What?!

Okay, now what?

Have you got an idea of what comes next?

It's not magic, I'll tell you that! :)

Step 7: Break It!

The trick here is to break the board clean in half. Then you create a channel for the nail to rest in, and glue the board back together. Pretty simple!

I clamped it into my vise, and gave the top half a hard wack with a mallet. This resulted in a nice, clean break right through the weak middle section of the board.

Step 8: Broken Board

Depending on the type of wood you use, you might experience some splintering.

I used a hardwood specifically to avoid this and it worked very well.

Step 9: Create Channel for Nail

I used a carving burr in my rotary tool to carefully carve a channel for the nail to rest in, in the middle section of the wood.

Care was taken to make sure that both sides of the channel lined up neatly and created a clean looking hole when the board halves were placed together.

Step 10: Glue and Clamp

Wood glue was spread over all the surfaces of the break on both halves of the board. You don't want to put too much, especially near the channel where the nail is. In this area, I wiped most of the glue away so only a thin film was present.

The board halves were placed together with the nail in place, and clamped. I used a wet rag to wipe away any glue that squeezed out.

Step 11: Clean Up

I wanted this to look really nice and well-finished, which to me adds to the mystery.

I used my electric planer to remove a little more material from both faces, and ran the ends through my table saw (using a sled) to trim the ends. These efforts removed any traces of the glue joint from the outside of the block.

On the insides of the holes, I used a drum sander on my rotary tool to gently sand down the glue joints.

Using a router table I rounded over all the edges of the block.

Step 12: Sand

Now I sanded the entire block with 220 grit sandpaper using an orbital sander.

The routed edges and interiors of the holes I sanded by hand with the same grit.

Step 13: Finish

To finish the block, I sprayed it with several coats of lacquer, buffing between coats with superfine steel wool.

After the final coat of lacquer was dry and buffed, I wiped on and buffed off a coating of paste wax.

Step 14: Done

It's a great little conversation piece, and holds up perfectly to intense examination.

I hope you'll make something similar! If you do, please share a photo in the comments; I'd love to see your take on this.

I always love feedback, so questions and comments are encouraged. Thanks again for reading.

3 People Made This Project!

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96 Discussions

0
user
don57

1 year ago

Very clever puzzle, by breaking the wood along the grain you avoid tell-tale unnatural lines. BTW: I would like to challenge any of the "cut and glue the nail" people to actually cut a nail in half and seamlessly glue it back together. Wood is porous and glues easily and can be sanded to hide glue seams, steel does not take glue well and even if you could get glue to hold there would be a visible seam.

3 replies

Although I have never built a puzzle like this one I would like to comment on cutting the nail.
The center portion of the wood which the nail passes through is large enough that you would never see the repair. Simply cut the nail dead center and use JB Weld to reattach the two halves....

How do you get each nail half into the center hole? Each nail half is longer than the diameter of the two large holes.

Thirds, but you'd have to restrict the movement of the nail to hide the joint.

My dad had a load of small puzzles like this that kept a small boy out of mischief for many hours. (and they still puzzle me 40yrs on!)

Awesome! This is such a great article to have on your desk and show people!

Really clever! I need to make one ;)

A great puzzle mind blower and well done, sir.

The species of wood is poplar, a typically used paint grade hardwood and very versatile in its uses for interior trim, furniture and model or prototype projects. The slight green tint, grain pattern, and clarity of the piece you used were the tells and the cambium layer remnant you planed off was also typical of poplar. Poplar is a wonderful and inexpensive wood to work with. Again, kudos, on your project.

1 reply

Thank you for your nice comment and for the insight on the wood, I appreciate it!

0
user
DriesV

1 year ago

Very clever

Sam's emporium of brainbusters and oddities keeps growing!

Good ;-)

Nicely done. As a retired shop teacher, I also appreciate the use of clamps. Better safe than sorry. I didn't think of breaking the board but what a great idea. I also like that you took the time to sand, round over and finish the project to give it a professional look. Great conversation piece. I will be trying this!

0
user
avayan

1 year ago

WOW! I am blown away on how the wood was spliced and then put back together without a seam being visible. Before reading the tutorial, I though that perhaps the nail was a two part threaded piece with the threading being hidden inside the wood. This is way easier to make for sure!

Well done and really pretty and convincing!!

Interesting take on this puzzle!

Waooo.............impossible made easy......Very nice work indeed.