The drill drive time test is the one number a self-drilling screw customer actually measures. Not your die drawing, not your material certificate — a stopwatch, a steel plate, a fixed load, and a screw that either goes through inside the limit or does not. When a container of roofing screws gets rejected, the rejection letter almost always quotes a drive time, sometimes a torsional strength figure alongside it. So it is worth understanding something uncomfortable: the test conditions move that number more than the die does. A drive-time claim with no stated conditions is not a specification. It is a rumour with a decimal point.
This article is about how to state those conditions, what part of the result your drill point die is genuinely responsible for, and where the die maker's job ends and your heat-treat line's begins.
What a drill drive test actually measures
Strip the standard back and the test is simple. A screw is driven against a steel test plate under a controlled axial load at a controlled rotational speed. Someone times how long it takes to drill through the plate and reach the point where the threads start to pull the screw in. That elapsed time is the drill drive time. Below the limit, pass. Above it, fail.
The test families a buyer is likely to be quoting are ISO 10666, which covers drilling screws with tapping screw thread and their mechanical and functional properties, and IFI 113 on the inch side, which carries both a drill drive time procedure and a torsional strength procedure. Check the current edition of whichever one your contract names — the limits are tabulated by screw size and by test plate thickness, and editions change. Nothing in this article substitutes for reading the table in the standard you are actually bound by.
Where the clock starts and stops is not obvious
Here is the first place two labs get different answers from the same screws. Some operators stop the clock at breakthrough — the moment the drill point exits the far face of the plate. Others stop it when the head seats. Between those two events sits the whole thread-forming stroke, which on a thick plate can be a meaningful fraction of the total cycle and has nothing to do with your drill point.
If your customer's incoming inspection stops at head seating and your outgoing inspection stops at breakthrough, you will argue for months and both of you will be right. Write the stop condition into the test method by name. It costs one sentence and it removes an entire category of dispute.
The test conditions decide the number — so specify them
Ask any fastener plant that has chased a drive-time complaint across two continents and they will tell you the same thing: before you change the die, verify the plate. The variables below routinely shift a result by more than the difference between a good die and a worn one.
| Condition to state | Why it moves the result | How to pin it down |
|---|---|---|
| Test plate grade and hardness | Hardness is the dominant variable. A plate a few points harder on the same nominal grade lengthens drive time across every size you test. | Name the grade and state a hardness range with the scale (HRB or HV) and the test load. "Mild steel" is not a specification. |
| Plate thickness, and whether plates are stacked | Drilling time scales with the depth of cut; a stacked pair behaves differently from a single plate of the same total thickness because of the air gap and burr at the interface. | State nominal thickness plus tolerance, and state single plate or stack explicitly. |
| Axial thrust load | The drill point only cuts if you push it. Too little load and the point rubs and work-hardens the plate; too much and you can crush the point. | Take the load from the standard's table for that screw size. State it in newtons or pounds-force, and state whether it is applied by dead weight, spring or servo. |
| Driver rotational speed under load | Nameplate no-load rpm is not what the screw sees. A tool rated at one speed will sag under thrust. | State the required speed at the screw, and state how it is measured — tachometer at the socket, not the tool label. |
| Clock start and stop points | See above. This alone can change a result by a large margin on thick material. | Define both events in words. |
| Number of specimens and the pass rule | An average hides one long outlier; a max-of-n rule catches it. Standards generally require every specimen to comply, not the mean. | State sample size and whether the rule is all-pass or statistical. |
| Screw finish and any lubricant or wax | Coatings change friction at the thread and can change the seating half of the cycle. Wax is a legitimate production variable and a legitimate source of argument. | State the finish and whether the test screws are waxed as shipped. |
| Plate surface condition | Mill scale, oil film, paint and re-used plate with previous holes nearby all change entry behaviour. | Require clean, unused plate area with a minimum edge and hole-to-hole spacing. |
Two of those deserve a sentence more. First, plate hardness: if you are shipping to a customer who tests on their own stock rather than on plate cut to the standard, ask them for the certificate for that stock. It is a reasonable request and it has ended more disputes than any die change. Second, thrust load: field complaints about "slow driving" often come from an installer with an underpowered screw gun, not from a test bench at all. Field behaviour and bench drive time are different measurements and should not be compared to each other.
What the die controls, and where the die maker's job ends
A drill point die is cold-forming tooling. It shapes the drilling point of the screw — and a good die maker publishes a spec system in which every die code maps to a screw size along with drill diameter, point and wire diameters, flute length and die style. ZLD Precision Mold's L1–L7 series does exactly that across IFI #4–#14 and DIN ST2.9–ST6.3, which is the level of detail you need if you are going to argue about a drive-time result on engineering terms rather than by email tone.
But the die is not the whole screw. This table is worth putting in front of anyone who blames tooling by default.
| Variable in the result | Set by | How a problem shows up |
|---|---|---|
| Drill diameter Dø | The die | Undersize hole raises drive-in torque after breakthrough; oversize loses thread engagement and pull-out |
| Point length and flute length | The die | If the drilling portion is not longer than the total material thickness, threads engage before the hole is finished and the screw stalls or snaps |
| Flute volume and chip clearance | The die | Chips pack in the flute on thick plate; drive time climbs sharply in the last third of the stroke |
| Point style (MA, MB, MC) | The die | Entry behaviour, walking on the plate surface, suitability for thin sheet versus structural thickness |
| Point-to-wire diameter relationship | The die, plus your blank spec | Incomplete point fill, flash, asymmetric point |
| Wire grade and drawing quality | Your wire supplier | Inconsistent forming, variable point hardness before heat treatment |
| Case depth and core hardness | Your heat treatment line | Point burn-off mid-drill, and most torsional failures |
| Surface hardness after carburising | Your heat treatment line | The point rounds over instead of cutting; drive time fails while the die is still in spec |
| Plating and embrittlement relief | Your plating line | Delayed fracture in service, not usually a drive-time symptom |
| Thread form and pitch | Your thread rolling dies | Seating time, stripping, not the drilling portion |
The practical rule: if drive time fails and the point geometry measures in tolerance on the sample, look at heat treatment before you look at the die. A drill point that is dimensionally perfect but soft will not cut, and no die maker can fix that.
Drive time drifts across a die's life — sample accordingly
The insider habit that separates plants that get complaints from plants that do not: measure drive time at the start, middle and end of a die's run, not just on the first-off sample. As a die wears, the point gets shorter and the cutting edges round. Drive time creeps upward long before any dimension goes out of print. Plotted against shot count, that creep is the most useful die-life indicator you have, and it lets you retire a die on data rather than on a rejected shipment. If you are already keeping die-life records for costing, this is the same dataset — see the companion piece on die wear and failure modes for how those curves usually look.
Torsional strength: the other half of the acceptance test
Drive time gets the attention, but the same standards carry a torsional strength requirement, and the two fail for opposite reasons. Torsional testing clamps the screw and applies torque until it twists off; the measured failure torque must exceed a minimum tabulated by size. That minimum is a function of core diameter, material and heat treatment. It is essentially a metallurgy result, not a tooling result.
Where the two interact is in the transition zone between the drilling point and the first thread. A point that is too long for the application means the screw is still drilling when the threads begin to load, which stacks drilling torque on top of thread-forming torque. That is where you see the classic snapped-in-the-hole failure on a structural job, and it is genuinely a geometry decision — one that gets made when you pick the die code, not on the shop floor.
So treat the two numbers as a pair. If torsional strength is marginal and drive time is long, the screw is being asked to do both jobs at once and the point specification deserves a second look against your customer's real material stack, not the nominal one on the drawing.
Common questions
Can a die supplier guarantee a drive time?
Not honestly, and be careful with any who offer to. The die fixes geometry; the drive time depends on your wire, your heat treatment, your customer's plate and their test rig. A supplier can reasonably commit to point geometry within a stated tolerance and to trial-running the die before shipment. Everything beyond that belongs to your process.
Should I ask for the factory's own drive-time data?
Ask, but do not build your acceptance on it. A die maker's trial run confirms the die forms the point it is supposed to form and that the point drills — it is not run on your wire, your heat treat recipe or your customer's plate. Some die makers, ZLD Precision Mold among them, publish no measured drill-drive figures at all. That is more honest than a number with no test conditions attached. What you want from the factory is the trial-run evidence and the dimensional report; the performance number you generate yourself.
What if my customer will not disclose their test conditions?
Then you cannot be held to a result you cannot reproduce, and it is worth saying so early and politely. Most quality departments will share the method — it is usually a one-page internal procedure. If they will only name a standard, ask which edition and which table, then buy the standard. A copy of the document costs less than one rejected pallet.
Does die material change the drive time?
Indirectly, and mostly through consistency over time. Dies in SKH high-speed steel and in tungsten carbide can form the same nominal geometry; what differs is how long they hold it, which is why carbide and coated options are chosen for high-output lines. A fresh die of either material should produce the same point. The difference shows up ten or a hundred thousand pieces in, as the drift discussed above.
What to ask your die supplier next
Before you place a die order against a customer test you have to pass, work through this list:
- Send the screw drawing and the customer's test method, including plate grade, hardness range, thickness, thrust load, driver speed and the clock start/stop definition. A properly written spec sheet prevents most of what follows.
- Ask which die code in the supplier's series matches your size, and get the drill diameter, point diameter, wire diameter, flute length and die style for it in writing.
- Confirm the drilling portion length against your customer's maximum material thickness, not the nominal thickness.
- Ask for the pre-shipment trial-run evidence and the dimensional inspection record — what was measured, on what, and against which print. The same logic applies here as in any pre-shipment inspection.
- Ask what the supplier holds by way of quality-system documentation, and read the answer plainly. ZLD, for instance, confirms it currently holds no quality-system certificates — which means your acceptance criteria have to live in the purchase order rather than in a certificate.
- Order one set first and run your own drive-time curve on it at the start, middle and end of the trial. ZLD Precision Mold in Dongguan accepts trial orders from a single set and trial-runs dies on in-house test equipment before shipping, which makes that experiment cheap enough to be worth doing before any program commitment.
- Record the die code, the shot count and the drive time together from day one. That single table is what lets you argue about tooling with evidence — and it is the same discipline that runs through the rest of fastener sourcing in China.