(and how to avoid the most common mistakes before you commit to equipment)
When engineers talk about permanent assembly, the requirements usually sound like this:
“It needs to rotate smoothly, but not flop around.”
“It can’t back out, even under vibration.”
“It needs to withstand a push-out / pull-out load.”
“We need to hit a torque spec.”
These are functional requirements — what the joint must do “in the wild.”
But teams often jump straight to process targets like forming force, formed height, or formed diameter. Those can help control the process, but they aren’t always the best way to define success.
The goal is to align:
Functional requirement → part design → assembly process → monitoring method → pass/fail criteria
Start here: What does the assembly joint need to do?
Most joint requirements fall into one of three categories:
Torque/articulation
The joint must rotate within a defined range (pivots, hinges, linkages).
Retention
The joint must resist push-out or pull-out force (pins, studs, staked features).
Vibration / shear load resistance
The joint must hold position and survive loading over time.
Once you know which bucket applies, it becomes much easier to choose the right spec — and avoid targets that sound right but don’t actually control performance.
Torque specs: where “by feel” creates scrap
Torque requirements are common — and frequently mis-specified.
The goal: Smooth articulation with controlled resistance.
The problem:
“Good torque” is often defined by operator feel, which varies:
- person to person
- shift to shift
- fixture to fixture
- lot to lot
Even worse, many torque issues aren’t caused by the forming methods; they come from part design and tolerance stack-ups.
The biggest torque mistake: the part design doesn’t allow consistent movement
Here are four common torque killers:
-
No gap to allow movement
If the stack-up doesn’t allow articulation, forming can “smash” components together and lock the joint. -
Too much gap
Excess clearance can create a joint that rotates too freely, wobbles, or loses resistance. -
No measurable definition of “good”
If the process has been judged “by feel” for years, teams often don’t have numbers to define acceptable torque. -
Excessive stack-up/component variance
If the components come to the assembly process with high variability impacting the joint stack-up tolerance, it may be impossible to achieve within the required torque range, without improving the component processing upstream.
The fix:
Torque requirements should be paired with design intent:
- intentional clearance where needed
- controlled contact surfaces
- tolerance stack-ups that support consistent articulation
- materials that match the friction behavior you want
What processes work well for torque-driven assemblies?
Torque requirements can often be achieved with multiple processes, depending on your joint design and acceptable variation.
Orbital Forming
Often ideal for smaller torque ranges where smooth articulation matters.
Impact Riveting or Press Riveting
A good fit when gaps are designed into the part or shoulder rivets are used, and speed is a priority.
Pivot Joint Testing
Torque specs become far more reliable when you can validate them. An in-process torque check can be paired with orbital forming, or torque can be measured in a dedicated offline station.
Retention specs: push-out and pull-out requirements
If your joint must withstand a push-out or pull-out load, focus on retention performance — not just a final formed dimension.
The goal: Withstand a defined axial load without separating.
Common mistake:
Specifying only a formed height or formed diameter without confirming it correlates to the required load.
Retention depends on factors like:
- available rivet volume/material flow
- hole size and tolerance
- material hardness
- engagement and interference
- forming repeatability
Why process monitoring matters for retention
Retention-driven joints rely on consistency.
Monitoring forming height
Forming to the same height improves repeatability, especially since the finished diameter depends on rivet volume.
Monitoring forming force
In many applications, the forming force directly correlates with push-out strength. Once limits are established, force monitoring can validate that the parts remain within an acceptable tolerance range.
Best practice: height + force together
Height and force monitoring are often used together to validate finished form requirements and reduce variation.
Monitoring can also support simple yes/no pass/fail logic based on forming parameters.
Vibration & shear resistance: when hole fill becomes critical
If the joint must resist vibration, hold position, or survive repeated loading, one of the biggest contributors is often:
Hole fill
How completely the formed material fills the hole can impact:
- joint stability under load
- resistance to movement
- long-term durability
Best-fit processes for maximum hole fill
Press Forming
Press forming typically achieves the most hole fill of cold forming processes, making it a strong choice for vibration or shear-driven joints.
Hot Upset Forming
For hardened materials or higher performance requirements, hot upset forming can maximize hole fill beyond what cold forming can achieve.
Don’t start with force; start with function
Force is important, but it’s rarely the best primary spec.
What you should spec (functional outcomes)
- torque range (with a defined test method)
- push-out/pull-out load (with clear failure criteria)
- vibration/shear expectations (duty cycle, environment)
- acceptable articulation and resistance
What controls the process (targets we can monitor)
- forming force limits
- displacement/formed height limits
- monitoring windows and acceptance thresholds
Projects struggle when teams specify the process target but never define the functional result.
A simple framework for better assembly joint specs
- Define how the part must perform in the real world
Torque, retention, vibration/shear — what does success look like? - Align part design and stack-up to that function
If the design won’t support it, the process can’t “fix it.” - Select the best-fit assembly method
Different processes excel at different performance outcomes. - Put real numbers to the requirement
Move from “by feel” to measurable criteria. - Validate and lock in acceptance criteria
Use monitoring and/or testing so the joint stays in spec in production.
Prototype validation turns guesses into confidence
The fastest way to go from “we think this will work” to “we know it will work” is prototype testing.
Orbitform’s Solutions Lab can help validate:
- Whether your specs match your joint design intent
- Which assembly process best supports your functional requirement
- Which monitoring method (height, force, or torque testing) controls variation best
- What pass/fail limits correlate to performance
What to send Orbitform to define your spec faster
To move quickly, share:
- Component prints + models (materials and tolerances included)
- Assembly prints + models (including finished form requirements)
- Functional requirements or test parameters
- What a good part looks like
- If possible, what a bad part looks like (and how it fails)
Final takeaway
If your requirement is torque, retention, or shear resistance, don’t lead with force or a single formed dimension.
Start with the functional requirements, align the joint design, and use monitoring and validation to ensure every assembly remains consistent.
Orbitform can help you define the right specification before committing to equipment and validate it before production starts. Contact us today to discuss your next assembly application.