Real Case: Fixing a 10% Assembly Failure — Without Changing the Design
Product: Magnetic Screwdriver Bit Magnets (Taiwan)
The Problem
A Taiwanese hand tool manufacturer was using disc magnets with through holes for magnetic screwdriver bits.
On paper, everything looked fine:
Tolerance was controlled at ±0.05mm — pretty standard.
But on the assembly line, things told a different story:
👉 Magnets at the upper tolerance limit were slightly oversized
👉 Press-fit force caused cracking
👉 Rejection rate hit 10%
Not a design issue.
Not a material issue.
A tolerance stacking problem — but it was costing real money.
What Most Suppliers Would Say
“Tolerance is within spec.”
“Your housing might be too tight.”
In other words: not their problem.
What We Did Instead
We focused on the real failure point — consistency.
We added a precision grinding process after sintering and machining, and tightened control on all critical dimensions:
- Outer diameter
- Inner hole
- Thickness
New tolerance: ±0.02mm
The Result
First production run after the change:
✅ Rejection rate dropped from 10% → under 3%
✅ Cracking during press-fit basically disappeared
✅ Subsequent batches: zero reported failures
No redesign.
No tooling changes.
No extra assembly steps.
Just better control on what actually matters.
| Parameter | Previous Supplier | XHMAG |
|---|---|---|
| Shape | Disc with through hole | Disc with through hole |
| Grade | N35 | N35 |
| Dimensional tolerance | ±0.05mm | ±0.02mm |
| Inspection method | Visual / spot check | CMM, 100% critical dims |
| Assembly rejection rate | ~10% | < 3% |
| Per-shipment CMM report | Not provided | Included |
| Lead time | — | 25–30 days |
What This Means for You
If you’re seeing:
→ Cracking during press-fit
→ Inconsistent assembly results
→ “Random” failures that are hard to explain
There’s a good chance it’s not your design —
it’s your magnet tolerance.
We don’t just hit “standard spec.”
We match tolerance to your actual assembly condition —
so problems stop where they start.
