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1. Prelude

(Good to know)

1.1. Paint

Steel, which your van is made of, corrodes (rust) in presence of moisture and oxygen and the damage done to its structural properties is irreversible. A multilayer coating system, aka paint (primer, basecoat, topcoat) applied on steel offers a seal against the environment and therefore prevents rust.

Any steel left “bare” (without paint) after trimming or drilling a hole is a potential starting point for rust. For example, below is a photo of our friend’s work van. You can clearly tell the paint wasn’t restored after trimming and drilling, and the rust situation is much worst on bare edges (around the fan cutout and the screws):

1.2. Sheet metal screws

Why bother with threaded inserts when sheet metal screws are a thing? Here are a few reasons why:

• Rust. The screw removes the paint protection (see above).
• Not reusable. Not meant to be reusable as removing/reinstalling a screw several times enlarges the hole.
• Thread engagement. That’s the number of threads anchored into the material. Ideally, at least 2-3 threads should be engaged in steel to provide a good grip. In thin sheet metal (e.g. 0.032″), less than 1 thread is engaged:

And at last, long term joint integrity will be compromised by rust forming around the edge of the hole (no structural properties). Add vibration into the mix, and joint may get loose over time.

2. Benefits of Threaded Inserts

Threaded inserts offer the following benefits:

• Stronger and reusable threads.
• Help prevent corrosion.
• “Blind” installation.

2.1. Stronger & Reusable threads

Threaded inserts offer stronger joints compared to sheet metal screws, because the load is distributed over a larger surface and the expansion mechanism increases the grip into the thin material.

After the threaded insert is installed into the sheet metal, a fastener can be installed/removed multiple times without damaging the integrity of the joint.

2.2. Helps prevent corrosion

A van comes from the factory with pre-drilled, unthreaded holes all over the cargo area. Threaded inserts can be used to create joints without having to drill new holes, which would expose bare metal and potentially create corrosion.

2.3. Blind Installation

Installing bolts and nuts requires access from both sides (front and back). On the other hand, cross nuts and rivet nuts only require access to a single side (front); this is called “blind access”. And as it turns out, many pre-drilled holes in our Ford Transit have blind access so that’s quite convenient.

3. Drawbacks

Threaded inserts have the following drawbacks:

• Cost more than sheet metal screws or bolts/nuts.
• Require installation tools and time. More on that in the Tools & Installation section.
• Have to deal with the location of pre-drilled holes. They might not be exactly where you want them. That being said, it’s OK to drill a few holes (outside the no-drill zones prescribed by the manufacturer) and add some corrosion protection…

4. Threaded Insert Types

There are dozen of different threaded insert types, each one of them designed for a specific application. Let’s review those that are useful for a van conversion:

• Cross nuts.
• Rivet nuts.
• Hex rivet nuts.
• Squaresert^®.

4.1. Cross Nuts

A cross nut is a threaded insert featuring a slotted body that splits into four legs during installation. The four legs grip the back of the surface as follows:

Cross nuts are available as straight body or pre-bulbed body. Pre-bulbed cross nuts require less force at installation but need a slightly larger hole than straight cross nuts:

4.2. Rivet Nuts

A rivet nut is a threaded insert featuring a shank that deforms and expands during installation. The body expansion and bulge in the back create a uniform grip around the periphery of the hole. The first rivet nut (trademark as Rivnut) was invented by BFGoodrich in the 1930s to mount de-icing boots to aircraft wings (source). The rivet nut shown below features a knurled body (ribs) that helps increase spinout resistance:

4.3. Half Hex Rivet Nuts

A half hex rivet nut is similar to a rivet nut, except that its body has a hexagonal shape that increases spinout resistance. To be effective against spinout, a half hex rivet nut must be inserted in a hex hole. It is interesting to note that the Ford Transit has several hex holes from factory:

They can be found on Amazon: Half Hex Rivet Nuts.

4.4. Square Rivet Nuts

When researching threaded fasteners, we stumbled upon “Squaresert^®” which are similar to hex rivet nuts, but with a square body. Our Ford Transit also features several “square holes”, so these would work:

We found about Squaresert^® on hansonrivet.com.

5. An experimentation on spinout resistance

Spinout is the most common issue with crossnuts and rivet nuts. When an insert spins, it is not possible to torque or remove a fastener from the insert. Spinout resistance is the capacity of a threaded insert to resist spinning, and is generally determined by:

• The type of insert (crossnut vs rivetnut).
• The installation conditions (tool used, hole size, material thickness, etc).

The “crossnut vs rivet nut” debate is very polarized on online discussion groups… it goes all the way back to 2010 and dozen of new threads are popping out to this day, but we still don’t have a consensus! Under those circumstances, we decided to take a more experimental approach to the spinout problem.

Spinout Resistance Test

Our goals

• Determine which threaded insert has a better spinout resistance: cross nuts or rivet nuts.
• Determine if spinout resistance can be increased with the following:
  • Regular washer.
  • Split washer.
  • Tooth-lock washer.
  • CA glue.
  • Red Loctite.
  • J-B Weld.

Notes

• Our goal is not to quantify the “real-world” spinout torque value. In a “real-world” application, there is a non-rotating material between the bolt and the insert (the stuff you’re trying to mount). This creates friction on the insert’s head and greatly increases the spinout torque value.
• This is NOT science 😉 We don’t have enough specimens, the holes are not all perfectly identical, we may introduce variations during installation (we’re humans not robots), etc. But that’s good enough to decide which threaded inserts we will use in our van!

Tools & Material

• Automatic Center Punch.
• Astro 1450 PlusNut and rivet nut setter.
• Neiko Digital Torque Adapter.
• Wen 4208T Drill Press.
• 23/64″ drill bit.
• 21 gauge (.032″ thick) steel sheet.
• 1/4-20 crossnut.
• M6 crossnuts.
• M6 rivet nuts.

Procedure

1. Drill a matrix of identical holes (9.25mm/0.364in).
2. Install cross nuts and rivet nuts without and with “helpers” (adhesive, washers).
3. Record spinout torque.

Results

Conclusions

• Rivet nuts have higher spinout resistance, no washer of adhesive are required. (Spinout torque is higher than the recommended tightening torque, and as a result I sheared a bolt during the test.)
• Cross nuts spinout torque is lower and is less predictable, but adding a tooth lock washer under the head completely prevented it from spinning in our test (until bolt damage). The tooth lock washer also helps the cross nut sit flush and straight with the mating surface.
• J-B weld is the most efficient adhesive and is able to completely prevent a cross nut from spinning. This is because it is capable of filling the void (as opposed to CA glue or Loctite that are too thin). All things considered using a tooth lock washer is more practical, but J-B Weld could be used to lock a spinning cross nut after the fact.

Other Observations

• We found that rivet nuts have more constant and predictable spinout torque and are less finicky to install. They always sit perfectly flush (straight) with the mating surface. In our tests a M6 (1/4-20) rivet nut spec’d for a 9mm hole worked well for a hole up to ~10mm, but didn’t work well at 11.0mm.
• Rivet nuts provides a uniform and tight grip around the hole and could probably make a waterproof joint if used in conjunction with sealant.
• Cross nuts spinout torque vary more and is less predictable.
• Because of the flange under the head, cross nuts do not sit flush with the mating surface. They often end up being angled, forming a gap between the head and the mating surface. A washer fitted between the head and the mating surface helps mitigate this.
• Overtightening fasteners should always be avoided to prevent damage to bolt/insert: recommended tightening torque.

Our thoughts on these results

We will prioritize rivet nuts over cross nuts in the new van build. That being said, we still think cross nuts paired with tooth lock washers have their place for non-standard holes (oversized hole, hex or square), or to use with softer material somewhere in our build. It’s good to have options!

If you are currently building a van and already installed cross nuts, don’t freak out! We used cross nuts exclusively for our first build, and we got only one or two spinners. They do work!

6. Understanding Specifications

Spinout and pull-out resistance drop dramatically if the insert is not installed within its intended specifications. When choosing a threaded insert, here is what to look for:

Hole Diameter

This is the diameter of the hole receiving the insert:

Grip

Grip is the thickness of the material receiving the insert:

Thread

The threads of both the insert and the bolt must be identical:

In the example above, I measured 10.01mm hole diameter and 0.81mm material thickness. According to the table below, the M6 x 1.0 cross nut is a pretty good match! The material thickness is within range. The hole is a bit out of range (0.08mm oversized), but close enough.

Metric vs Imperial Threads

Bolts, screws, threaded inserts, etc., are typically offered with metric or imperial thread:

Male threads (e.g. bolt) must always match the female threads (nut, threaded insert) in order to fit.

Just like bolts, threaded fasteners are offered with Metric or Imperial threads. For a specific hole diameter, you can generally choose between metric or imperial (“equivalent” inserts). The outside dimensions of equivalent inserts are identical, only the internal threads are different:

Below is a table of equivalent inserts (inserts with identical outside dimensions):

Choosing Metric or Imperial is a matter of personal preference. In the Ford Transit, most threaded holes are Metric, so it makes sense to choose Metric threaded inserts for consistence. That being said, if your brain is wired in Imperial, then it’s OK to choose Imperial threaded inserts!

7. Rivet Nut & Cross Nut Finder

Find Rivet Nut or Cross Nut by hole diameter:

mmin

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Rivet Nut

Click to Buy	Hole Min.	Hole Max.	Grip Min.	Grip Max.
M4 x 0.70	6.00	6.18	0.45	1.52
M5 x 0.80	7.00	7.21	0.45	1.52
M6 x 1.00	9.00	9.27	0.45	2.28
M8 x 1.25	11.00	11.33	0.45	3.04
M10 x 1.50	13.00	13.39	0.45	3.04

Click to Buy	Hole Min.	Hole Max.	Grip Min.	Grip Max.
#8-32	0.236	0.243	0.018	0.060
#10-24	0.276	0.284	0.018	0.060
1/4-20	0.354	0.365	0.018	0.090
5/16-18	0.433	0.446	0.018	0.120
3/8-16	0.512	0.527	0.018	0.120

NOTE: Hole is slightly over the recommended max. diameter. It should work none the less, but adhesive such as CA glue (SuperGlue) or J-B Weld can be used at your convenience to prevent spinout.

NOTE: Hole is over the recommended max. diameter. Consider installing the insert with adhesive such as CA glue (SuperGlue) or J-B Weld to prevent spinout.

We couldn't find a River Nut for this hole diameter.

We couldn't find any Rivet Nut, because the hole diameter entered is out of range. Consider enlarging (drilling) the hole up to the next available size (mm).

Cross Nut

Click to Buy	Hole Min.	Hole Max.	Grip Min.	Grip Max.
M5 x 0.8	7.92	8.05	0.50	4.45
M6 x 1.00	9.80	9.93	0.50	7.10
M8 x 1.25	12.29	12.42	0.50	7.10
M10 x 1.50	14.27	14.45	0.50	7.10

Click to Buy	Hole Min.	Hole Max.	Grip Min.	Grip Max.
#10-32	0.312	0.317	0.020	0.175
1/4-20	0.386	0.391	0.020	0.280
5/16-18	0.484	0.489	0.020	0.280
3/8-16	0.562	0.569	0.020	0.280

NOTE: Hole is slightly over the recommended max. diameter. It should work none the less, but adhesive such as J-B Weld can be used at your convenience to prevent spinout.

NOTE: Hole is over the recommended max. diameter. Consider installing the insert with adhesive such as J-B Weld to prevent spinout.

We couldn't find a Cross Nut for this hole diameter.

We couldn't find any Cross Nut, because the hole diameter entered is out of range. Consider enlarging (drilling) the hole up to the next available size (mm).

NOTE: Hole is slightly undersized. You will have to tap with a hammer to make it fit (the pre-bulbed portion is slightly larger).

General Note: We recommend using a Tooth Lock Washer at all times with cross nuts to prevent spinout.

* Ensure that material thickness receiving the insert is within Grip Min. / Grip Max values.

8. Threaded Inserts for your Van

8.1. Ford Transit

We collected and mapped the dimensions of ALL the holes in the Transit cargo area: Ford Transit Cargo Holes Dimensions.

Using the data gathered above, we were able to determine the type and the size of the threaded insert to use for EACH HOLE:

Ford Transit Cargo Threaded Inserts

148" Wheel Base | Extended-Length | High-Roof | 2021

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(Center/Front/Rear)

Rivet Nut: M4x0.7 or #8-32.
Cross Nut: N/A.

Rivet Nut: M5x0.8 or #10-24.
Cross Nut: M5x0.8 or #10-32 with Tooth Lock Washer.

Rivet Nut: M6x1.0 or 1/4-20.
Cross Nut: M6x1.0 or 1/4-20 with Tooth Lock Washer.

Rivet Nut: M8x1.25 or 5/16-18.
Cross Nut: M8x1.25 or 5/16-18 with Tooth Lock Washer.

Rivet Nut: M8x1.25 or 5/16-18.
Cross Nut: M6x1.0 or 1/4-20 with Tooth Lock Washer and J-B Weld.

Threaded holes (no insert needed):

M6 x 1.0

M8 x 1.25

M10 x 1.5

7/16-20

8.2. Mercedes Sprinter

We don't have access to a Sprinter so we couldn't take the actual measurement, but here are the most common Sprinter cross nuts according to the Internet:

Click to Buy	Hole Min.	Hole Max.	Grip Min.	Grip Max.
#10-32	0.312	0.317	0.020	0.175
1/4-20	0.386	0.391	0.020	0.280
5/16-18	0.484	0.489	0.020	0.280

8.3. Ram ProMaster

We don't have access to a ProMaster so we couldn't take the actual measurement, but here are the most common ProMaster cross nuts according to the Internet:

Click to Buy	Hole Min.	Hole Max.	Grip Min.	Grip Max.
#10-32	0.312	0.317	0.020	0.175
5/16-18	0.484	0.489	0.020	0.280

9. Tools & How To Install

9.1. Tools

Here are a few options that work for both cross nuts and rivet nuts:

McMaster-Carr

A low-cost tool to manually install crossnuts and rivet nuts, a bit more effort and time consuming compared to the other options. This is a "pull-type" tool, meaning the mandrel of the tool do NOT turn into the insert, minimizing potential damage. Note that this tool only does one type of threads; you will need to buy a separate tool for each type of threads (e.g., 1/4-20, M6x1.0, etc.).

Astro 1450

This is a "pull-type" tool, meaning the mandrel of the tool do NOT turn into the insert, minimizing potential damage. This tool comes with mandrels for several types of thread (10-32, 10-24, 1/4-20, 5/16-18, 3/8-16, M5, M6, M8 & M10), which is quite nice. Fast and easy to operate.

Pneumatic Tool

This is a "turn-type" pneumatic tool (the mandrel turns into the insert, so there is a slight risk of damaging the threads of the insert). A low-effort and fast option, but an air compressor is required.

DIY Tool

Dirt cheap DIY tool to install cross nuts and rivet nuts manually. This is how we install ALL our cross nuts (80+) in our first van. It worked, but we would NOT recommend it because it takes SO MUCH time and effort. The bolt and K-nut also wear out super fast and need to be changed every 5 cross nuts or so. So, make yourself a favor and invest a little in a proper tool that will give good results with little effort and time! Our 2 cents!

9.2. How To Install

10. How To Transfer a Hole Pattern

Now let's suppose you have to install a wall panel (or anything really), and it has to be attached via 4 threaded inserts (more or less). The threaded inserts form a "pattern" which must be replicated precisely to the wall panel, or else the bolts won't align into the inserts:

When the panel is still blank (no holes), how can you tell where to drill the holes, so that bolts align perfectly into the threaded inserts?

By placing transfer screws into the threaded inserts and then pushing the panel against them, you can precisely replicate the hole pattern into the panel!

Transfer screws are threaded on one end, and sharp and pointy on the other end. They easily leave a mark on the panel.

Hanger bolts can act as cheap DIY transfer screws, but because they protrude so much out of the cross nut (or rivet nut) they're not very precise. That's what we used for our fist build, and we had to enlarge the holes to compensate for the low precision. For the upcoming build, we will definitely use true transfer screws:

Hanger Bolts

Buy on Amazon

Transfer Screws

Buy on Amazon

On Second Thought...

Installing threaded fasteners such as cross nuts or rivet nuts is more time consuming than screwing directly through the metal, sure. But unless you’re converting an old rusty van for the short term only, it will protect your investment in the long run. There is nothing like knowing you did things the right way! 🙂

We used cross nuts exclusively for our first van conversion, and it honestly worked just fine! We see our second van conversion as an opportunity to improve and make things even better, so we will definitely revisit and re-evaluate topics like this as we progress in our build. We learned a lot by making this page, and we hope you learned something too while reading it! Happy build!