How to Make Giant Halloween Spiders




Introduction: How to Make Giant Halloween Spiders

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

This is how to make giant black-widow-looking spiders for Halloween decor.

They're great for sticking in the yard, on a roof, hanging from trees . . you name it!

I've made a few of these, and along the way have worked out a few kinks and settled on a design that's pretty easy to reproduce and makes efficient use of materials.

I really hope to see other people making these - if you do, please be sure to share photos in the comments at the end!

- - - -


The abdomen portion is made from old bowling balls. Depending on the pitch of your roof, your own workmanship, and various other factors . . obviously you might not want to put something like this on your roof and would be better to leave it on the ground.

Step 1: Design Thoughts

I had been kicking around the idea of making some large (but portable) lawn/roof spiders for several years, but wasn't sure exactly how I would make them.

While trying to come up with a plan, these were the points I had in mind:

  • needed to look enough like a real black widow spider to be notably creepy, especially in low light
  • big . . but not TOO big
  • self contained/no assembly needed once completed
  • easy to move around, lift onto and off of roofs, etc.
  • durable and weatherproof
  • cheap!
  • maybe have glowing eyes?

My initial thought was to use large rocks for the spider abdomens (the back bulbous part), but quickly realized that old bowling balls were a much better option.

I'm happy with the final product, and quite proud of how they look!

Step 2: Supplies

Here is what is needed to make one spider:

  • an old bowling ball. My local thrift stores seem to always have them for about $5 each.
  • 20 feet of 3/8" thick rebar (reinforcing bar for concrete)
  • two large metal washers and two large screws for the eyes and fangs
  • roll of black electrical tape
  • black spray paint
  • miscellaneous things like 2-part epoxy, masking tape

Where I live I can buy rebar in 20-foot lengths for under $5, and the place I got mine actually has large bolt cutters available so you can cut it up to transport it more easily.

Larger home stores (like Home Depot, Lowes, etc.) sell rebar in pre-cut 10-foot and shorter lengths, but at a higher cost per foot.

For the fang-eye bits on my spiders, I just used whatever hardware I had on hand. Common hardware items like nuts and bolts are typically zinc-plated, so in order to make these safely weldable I put them in vinegar overnight which dissolves the zinc plating. (Welding zinc-plated items creates toxic smoke that is extremely bad for you.)

All in, I can make one spider for under $20 in supplies.

Step 3: Tools Required

This is a very basic metalworking project, but it does require the ability to cut, bend, and weld metal.

Rebar can be cut in a number of ways . . from using large bolt cutters to an angle grinder, to using a metal cutting bandsaw.

The required bends are very simple and can be accomplished with the help of a vice.

The basics of my welding setup:

  • 140 mig welder
  • welding helmet
  • welding jacket
  • basic welding gloves
  • Argon/Oxygen mix gas tank
  • Homemade Welding Cart
  • welder's pliers

For cutting and grinding metal, I have:

  • a few Makita angle grinders
  • Dewalt portable bandsaw

Step 4: Cut the Rebar

Here is the cut list for the rebar:

  • 8 pieces 27 inches each
  • 4 pieces 3 inches each
  • 2 pieces 6 inches each

This adds up to 240 inches total, or 20 feet.

I'm in the US where building supplies come in foot-lengths, so this project is shared using feet and inches.

My apologies for all my metric-using friends; if you're a maker-type, surely you can convert measurements or just eyeball it! ; )

Step 5: Measure and Mark for Leg Bends

Each of the 8 legs will get two bends.

Mark the 27-inch rebar pieces 9 inches in from each end. Each bend should be made at these 9-inch marks, to create legs with 3 equal segments.

I made four legs with approximately 120-degree bends, and four legs with about 135-degree bends, as shown in the photo.

The more stretched-looking legs were used for the front and back pairs of legs, which to me seemed to make for a more spider-y looking creation.

Step 6: Bend Leg Pieces

This rebar is relatively thin so simple bends like this can be done by hand with the help of a vice.

Wear gloves though, and don't be afraid to put some muscle into it!

For the best results, I would actually over-bend each angle and then bend it back into the desired position, in a sort of 1-2 motion.

Step 7: Create Cephalothorax

The core of this spider sculpture is a metal head/body ("cephalothorax" - but I'm going to just call it the "body") onto which the legs, eye-fangs, and bowling ball abdomen connect.

The body is made from the two 6-inch pieces of rebar and the four 3-inch pieces, laid out as shown.

I put my welder on the settings shown, and tacked the rectangular body together. The "tail" piece that holds the bowling ball is added in the next step.

- - - -


I guess I should point out that this is just a representative sculpture, with no intent of being perfectly anatomically correct.

As noted before, I was just aiming for large, creepy and black-widow-like.

Hence that hybrid two-eye-fang-palp thingy on the front end, and the misplacement and miscoloration of abdomen markings.

This is the internet of course, and someone might have been inclined to point out these incorrect aspects . . so I figured I'd just mention them myself. HA!

Step 8: Add the Tail

The tail piece is added now at a 45-degree angle.

All of the welds were reinforced at this point.

- - - -


There's some debate about the weldability of rebar.

For what it's worth, the stuff I used was stamped "NU3560".

From what I understand, rebar is made of recycled metals and the exact composition can vary.

For sculptural creations (non-structural, and not critical for safety), it seems common to weld it just like I'm doing here.

In practice, I found that working a bit slower and allowing a large weld pool to form and overlapping beads around the joints seemed to get the job done for me. My welds aren't the prettiest, but I don't think they're going to fall apart any time soon.

Step 9: Prepare the Bowling Ball

It might seem counter-intuitive to drill a new hole to mount the ball onto the tail of the body, but that's what I did.

On the first spider I created, I used the existing thumb hole. But that required copious amounts of 2-part epoxy putty to fill all the extra space.

So on the spider being shown in these steps, I drilled a 1/2-inch hole just above the existing thumb hole, 2 inches deep.

This allows a better fit and requires less adhesive to make the union to the body.

If needed, the pair of finger holes can be enlarged at this point. These make perfect carrying holes for the completed sculpture, which I thought was pretty slick.

JEANNE apparently had very small fingers.

Step 10: Add Back and Front Legs

I used a stack of barbell weights to prop up the body and bowling ball abdomen about 4 inches off the ground.

The bowling ball was not attached permanently at this point, but just used to help position the rear legs.

I tacked the rear and front pairs of legs in place first, and then removed the bowling ball and set it aside.

Note that these pairs of legs are the "stretched out" pairs and they are positioned with a slight outward angle, which creates what I thought was a more elongated and spider-y pose.

Step 11: Add Mid-Legs and Reinforce Welds

The two pairs of mid legs were added now, tacked in place evenly spaced between the front and back legs. These were positioned perpendicular to the ground, but angled away from the body as shown.

Reinforcing welds were now added all around the leg-to-body joints.

Step 12: Create the Eye-Fangs

I used two lag screws and two large washers to create the eye-fangs. The washers have an inside diameter of 5/8".

As mentioned before, all of these parts were soaked in vinegar until the zinc plating was gone so I could safely weld them together. Alternately you could grind off the zinc coating, but vinegar gets it ALL with very little effort.

I cut the heads off of the lag screws and used a larger washer to prop the smaller ones into position for welding to the lag screws.

If the welds are especially ugly (as one of mine was), you can always grind them down to make them more pretty.

- - - -


The eye-fangs were created this way just to be efficient.

I needed a way to prop up the front of the LED glow sticks and I also wanted some dangly fangy bits, so this just seemed like a good way to achieve both.

When the glow sticks are attached later on, they also help create a non-2-dimensional spidery body, so it all worked out nicely.

Step 13: Complete Metal Body

The eye-fangs were welded to the front of the body as shown, with a very slight backwards angle.

This completes the metal body for the spider!

Step 14: Attach Bowling Ball Abdomen

I used a bit of 5-minute, 2-part epoxy to glue the ball to the tail part of the metal body.

- - - -


The bowling ball was not attached permanently earlier simply because it would make maneuvering the body around to complete all the welds much more tricky.

But now that the body is done, we can glue the bowling ball in place. This part is exciting because for the first time the sculpture definitely looks spider-like.

Step 15: Mask for Markings

I masked off the backside of the abdomen with blue painter's tape, and drew out an hourglass shape. The shape was cut out with an x-acto knife and the surrounding tape was removed.

- - - -


I know this isn't where real black widow spiders have their hourglass shape, but what's the point of putting it on the bottom where nobody can see it?

Step 16: Paint It Black

The whole thing was then painted with gloss black spray paint.

It helps to prop up the spider on a pair of sawhorses.

Step 17: Unmask

The tape was removed to reveal a purply hourglass shape. In full sunlight it really pops, but in dim light you can hardly see it.

Since the bowling ball plastic is fairly soft, when I cut out the hourglass shape this made little grooves in the plastic that prevented the paint from bleeding under. This made for some very clean paint lines without a lot of fuss.

Step 18: Body and Glowing Eyes

Real spiders do not have two glowing eyes.

They don't have bodies made of electrical tape, either.

This isn't the most elegant way to create a spider body or add glowing eyes, but it was the fastest, cheapest, and easiest solution I could find. The following steps outline the details.

Step 19: Make the Eyes

Electrical tape was used to wrap up two LED glowsticks so the only part that glowed would be the very tips.

Step 20: Attach the Eyes and Make the Body Shape

The glowsticks are placed with the glowing tips into the eye-fang washers.

Electrical tape is then wrapped all around the body and glowsticks to create a body shape.

Ironically, this creates a great place for REAL spiders to hide, as do the finger holes in the bowling ball . . so uh, be sure to do a quick check for real spiders and pick this up with caution!

Step 21: Add Spinneret

I added a screw-eye to the back of the bowling ball by drilling an undersized hole and simply threading it in place.

This is helpful if I decide to hang one of these from a tree, or I could tether various spiders to each other across the ridge of my roof.

Plus it looks like a spinneret of sorts.

A couple quick shots of black spray paint made the screw-eye match the rest of the spider.

Step 22: Make a Bunch!

The first spider I made had larger diameter rebar for the segment of the legs closest to the body, which was more work than it was worth and made for some clunky-looking legs. So after that I started making the legs with single pieces of thinner rebar as outlined in these steps.

The two spiders shown here have not been painted yet, and I kind of like the bare metal look with the unpainted bowling balls.

What do you think?

Step 23: Stick Them on the Roof and Make a Sign

After making a handful of spiders and sticking them on my roof, I decided to make this wooden sign to put in the yard to complete the setup.

I'd love to hear your thoughts, tips, suggestions . . and if you make your own be sure to share some photos.

Thanks for reading!

Halloween Contest 2018

Participated in the
Halloween Contest 2018

1 Person Made This Project!


  • Stone, Concrete, Cement Challenge

    Stone, Concrete, Cement Challenge
  • DIY Summer Camp Contest

    DIY Summer Camp Contest
  • Water Speed Challenge

    Water Speed Challenge



1 year ago

Added pedipalps, some extra washers for eyes and glow in the dark powder.


Reply 1 year ago

Very nice! I like the angular segments on yours much better than the bent legs I did on mine. It ramps up the realism and creepiness so much.

If I were to make more at some point, I would do likewise. And I love the glowing effect! : )


1 year ago on Step 2

Depending on the rebar you use it might snap instead of bending. In my case I had to segment the legs.


2 years ago

Oh, this is just too cool!

I've been using rebar with bowling balls on top to mark tree stumps to avoid damaging the lawnmower, so when I saw your Instructable, I knew it was right up my alley. Ha!

Seriously, though, this is a very neat project, and you did a great job! Thanks for sharing this way cool Instructable.


Reply 2 years ago

Thank you! They turned out to be a pretty good hit where I live - I ended up selling all of them : D

Tsu Dho Nimh
Tsu Dho Nimh

2 years ago

Black widows might not have the hourglass on their back, but the equally venomous Australian red back spider does. So not only do you have large horrible spiders on your roof, but you have an INVASIVE SPECIES!

As a fairly easy project for an industrial arts class or a newbie welder, this is a winner.


2 years ago

Love this! I don't know how to weld, but think I can make something similar out of old bowling balls and PVC. Along those lines, I'd love to find one of those giant 4' balls and have a large spider surrounded by smaller spiders in my yard and around the front door. Thank you so much for this!


Reply 2 years ago

Cool! Glad you found this useful!


2 years ago on Step 23

Inspired by your spider I've made a rebar leg similar. My supplier only had 12mm rebar and I couldn't bend it so I half cut and welded but it gives a great sharp angle , the legs are more anatomically correct and the abdomen roughly sized ok. Love the idea of rebar for the legs gives a hairy appearance. Ordered six red cats eyes for the head. . Am considering having it on a pullcord towards my front door for halloween .


Reply 2 years ago

Excellent! I have to say, that looks so much better than mine. That's awesome. I love the improvements, and the leg bottoms especially with that added segment really make a difference. Nicely done!


2 years ago

LOL creepy factor 10 out of 10 shivver. Thanks for sharing your wonderfully executed spider project.


2 years ago on Step 23

Absolutely LOVE ur spiders, imma have to make a bunch now ...


2 years ago

Inspired I have made 8 x 12mm rebar legs , I cut half way through to get a very sharp bend and will weld the open cut up. made 60cm legs , 20,20,15,5 , trochanter, femur,tibia,tarsus. thought of using road cats eyes but cant believe the price, thought they would be cheap. need alternative


Reply 2 years ago

Fantastic!! I'd love to see pictures when you're done. I'm thrilled that you're making some, and it sounds like you're going to improve on what I've done quite nicely. Very cool to hear.


2 years ago

Cool looking but hardly "easy to place on a roof" given the amount of rebar as well as the bowling ball weight! And, if someone doesn't have the skills or tools to weld, this is pretty useless. I admit I do like your design though. I believe I can get the same results from PVC and a kids cheap ball! You do have me thinking! Keep it up and inspire as many as you can! Kids these days need to learn trades!


Reply 2 years ago

We all have different capacities. I had no trouble climbing a ladder and sticking these on my roof but I can see how many could not do that.

Before I had welding tools, I was inspired by projects like this. So I saved up, got the tools, and am learning to use them and sharing my results.

Perhaps some better word choices could be inspirational, motivational, educational . . rather than "useless." ;)


2 years ago on Step 23

This looks really good.( I wish someone would do one that doesn't require welding!)