Introduction: How to Make Giant Halloween Spiders

About: I'm just a guy that likes to make stuff.

This is how I made some basic giant spiders for Halloween decor.

This project requires old bowling balls and some rebar, and a little bit of welding.

I've made several of these over the years, and they're great for sticking in the yard, on a roof, hanging from trees . . etc.

If you make one, please be sure to share a photo or two in the comments at the end!

Step 1: Design Thoughts

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

  • should look sort of like a black widow spider
  • easy to make
  • not necessarily anatomically correct
  • 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?

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 mix gas tank
  • Homemade Welding Cart
  • welder's pliers

For cutting and grinding metal, I have:

  • angle grinders
  • 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 vise. My vise is attached to a heavy stump so I can drag it around my shop and use it where I need it.

Wear gloves, 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.

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 found some cheap LED glow sticks to use for glowing eyes, and the washers worked well to hold the front tips of the glow sticks to create the effect.

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.

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.

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 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: Done!

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

Thanks for reading!

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