Threads and countersinks in sheet metal
We tap threads M3 to M16 into laser-cut tap holes and drill countersinks at 90°. The configurator checks these rules when you choose a thread or a countersink.
Why sheet thickness and distances matter
In thin sheet a thread has only a few load-bearing turns. An M8 screw in very thin sheet tends to tear out rather than hold the part. In very thick sheet, on the other hand, the tap is heavily loaded. Below 0.3 times or above 2 times the nominal diameter the check blocks the thread; in between, but outside the recommendation, it shows a note.
With countersinks it is the other way round: the countersunk head needs room. For countersinks (90° to DIN 7991): sheet thickness at least the head height of the countersunk screw + 0.5 mm remaining thickness.
Rules
- Only through holes: Every laser-cut hole goes through the whole sheet.
- Sheet thickness between 0.5 × and 1.5 × nominal diameter. With thinner sheet the thread has too few turns, with thicker sheet tapping becomes unreliable.
- Distance from hole edge to part edge at least 1 × nominal diameter.
- Distance from hole edge to bend edge as for every hole (tables per material). We tap the thread before bending, because too close to the edge it distorts.
- Stainless steel up to M12; steel, aluminium, copper and brass up to M16.
Thread sizes
| Thread | Tap drill | Sheet thickness from | Sheet thickness to | Distance to part edge |
|---|---|---|---|---|
| M3 | 2.5 mm | 1.5 mm | 4.5 mm | 3 mm |
| M4 | 3.3 mm | 2 mm | 6 mm | 4 mm |
| M5 | 4.2 mm | 2.5 mm | 7.5 mm | 5 mm |
| M6 | 5 mm | 3 mm | 9 mm | 6 mm |
| M8 | 6.8 mm | 4 mm | 12 mm | 8 mm |
| M10 | 8.5 mm | 5 mm | 15 mm | 10 mm |
| M12 | 10.2 mm | 6 mm | 18 mm | 12 mm |
| M14 | 12 mm | 7 mm | 21 mm | 14 mm |
| M16 | 14 mm | 8 mm | 24 mm | 16 mm |
Countersinks
| Countersink for | Clearance hole | Smallest sheet thickness |
|---|---|---|
| M3 | 3.4 mm | 2.2 mm |
| M4 | 4.5 mm | 2.8 mm |
| M5 | 5.5 mm | 3.3 mm |
| M6 | 6.6 mm | 3.8 mm |
| M8 | 9 mm | 4.9 mm |
The screw head should lie fully within the sheet, with some material remaining underneath. That is why every countersink needs a minimum sheet thickness.
What suits my sheet thickness?
| Sheet thickness | Thread | Threads in stainless steel | Countersinks |
|---|---|---|---|
| 1 mm | – | – | – |
| 1.5 mm | M3 | M3 | – |
| 2 mm | M3, M4 | M3, M4 | – |
| 2.5 mm | M3, M4, M5 | M3, M4, M5 | M3 |
| 3 mm | M3, M4, M5, M6 | M3, M4, M5, M6 | M3, M4 |
| 4 mm | M3, M4, M5, M6, M8 | M3, M4, M5, M6, M8 | M3, M4, M5, M6 |
| 5 mm | M4, M5, M6, M8, M10 | M4, M5, M6, M8, M10 | M3, M4, M5, M6, M8 |
| 6 mm | M4, M5, M6, M8, M10, M12 | M4, M5, M6, M8, M10, M12 | M3, M4, M5, M6, M8 |
| 8 mm | M6, M8, M10, M12, M14, M16 | M6, M8, M10, M12 | M3, M4, M5, M6, M8 |
| 10 mm | M8, M10, M12, M14, M16 | M8, M10, M12 | M3, M4, M5, M6, M8 |
How to order a thread
In the Part designer click a round hole and choose “Thread M…” or “Countersink for M…”. We set the hole diameter automatically: tap drill for the thread, clearance hole for the countersink. In your own STEP files, please draw the tap hole(e.g. M6: Ø 5 mm) or the clearance hole; we suggest matching holes as threads when you upload as threads. Metric ISO coarse threads; fine and imperial threads on request.
Checklist
- Sheet thickness suited to the thread (0.5 to 1.5 × nominal diameter)
- For countersinks: sheet at least head height + 0.5 mm
- Tap drill or clearance hole in the STEP file
- Distance to the edge and to the bend observed
Questions
Can I order an M8 thread in 3 mm sheet?
Possible, but not recommended. For M8 we recommend at least 4 mm. 3 mm lies between 0.3 and 0.5 times the nominal diameter: the check shows a note that you confirm before ordering, because only a few thread turns carry the load. Below 0.3 times it blocks.
Are threads also available on bent parts?
Yes. Threads and countersinks are made before bending. Keep the distance to the bend line (table value “Hole → bend edge” in the design guidelines); the check blocks a thread that is too close.
Do you offer press-in nuts?
No. We tap threads directly into the sheet and countersink holes for countersunk screws.
Is anything different for stainless steel?
The rules for thickness and distances are the same. In stainless steel we tap threads up to M12, because the material is considerably stronger than structural steel. A separate price per thread applies to stainless steel; it is shown on the Threads & countersinks page.
Prices and delivery time for threads and countersinks: Threads & countersinks. Calculate the tap drill: tap drill calculator. Mounting plate as a starting point: Cut-to-size in steel S235JR.