Updated December 21, 2025 · ~4 min read
The numbers .001, .003, and .006 describe the straightness of a carbon arrow shaft, measured in thousandths of an inch. This article explains how this straightness is determined at the factory, why it cannot be certified in a store, and how a spinner can give a misleading impression depending on the tool, technique, and components.
Understanding the straightness of arrows
In archery, we often talk about .001, .003 or .006 arrows. These numbers are used to describe the straightness of a carbon shaft, therefore its maximum defect when it rotates on itself.
Straightness is expressed in thousandths of an inch: the lower the number, the straighter the tube.
- .001" → maximum deviation of 0.001 inch
- .003" → maximum deviation of 0.003 inch
- .006" → maximum deviation of 0.006 inch
What determines straightness
The straightness of a shaft is a direct consequence of the manufacturing process. It depends in particular on the orientation of the carbon fibers, the tension applied during winding, the resin and the curing process.
Once the tube is manufactured, its straightness is permanent.
How straightness is measured in the factory
The stated straightness (.001, .003, etc.) is defined in an industrial environment using a numerical, repeatable and calibrated measurement.
Tools needed
In manufacturing, measurement relies on tools designed to read very small deviations consistently.
- a motorized measuring bench with constant rotation;
- perfectly aligned precision supports;
- a digital comparator with a minimum resolution of 0.0001";
- certified calibration standards;
- bare shafts, uncut, without insert or notch.
What is measured, specifically
The shaft is rotated, then the comparator measures the maximum radial runout over several areas of the tube. The maximum value observed is used to classify the tube into a category (.001, .003, .006).
Why can't we certify straightness in stores?
In a store, one can observe an obvious defect, but one cannot certify an industrial tolerance such as .001, .003 or .006.
An archery range typically lacks a calibrated motorized alignment bench, a comparator accurate to 0.0001", certified reference standards, and industrial measurement procedures. Without this set of tools and conditions, it is impossible to reliably confirm straightness.
The spinner: uses and limitations
The most common tool in stores is the hand spinner. This is an observation tool that allows you to roll the arrow to see if anything is visually "off".
What a spinner allows
- detect a seriously defective arrow;
- see a significant veil;
- identify an obvious problem.
What the spinner cannot do
- measure a numerical value of straightness;
- visually distinguish a .001 from a .003;
- to confirm or refute an industrial tolerance.
At a scale of 0.001 inches, the human eye cannot judge accurately. In practice, a spinner doesn't measure : it gives a visual impression.
Why a spinner can skew the evaluation
Even when used in good faith, a spinner can give a false perception of straightness. The visual impression depends as much on the tool as on how it is used, and on the components installed on the shaft.
1) The quality of the spinner
Not all spinners are created equal. Certain details can create "false beat," even if the shaft is straight.
- Rollers : ovalized rollers, irregular surface, wear over time.
- Bearings : uneven friction, non-concentric bearings, variable resistance to rotation.
- Chassis alignment : base not perfectly flat, supports not parallel.
2) The pressure exerted on the arrow
Excessive pressure on the rollers, a poorly centered arrow, or a variable support angle can distort the rotation.
At this level of precision, minimal pressure can be enough to create a visual wobble effect, without the tube actually being out of tolerance.
3) The components mounted on the boom
One often overlooked point is the influence of the components. Even with a straight shaft, the movement of the point or nock can give the impression that the arrow is crooked.
- slightly off-center insert;
- imperfectly machined point;
- Misaligned notch.
This is one of the reasons why, in the factory, straightness is measured on the bare shaft.
Measured straightness vs. perceived straightness
Many misunderstandings stem from this: measured rectitude and perceived rectitude do not always tell the same story.
- Measured straightness : industrial data, numerical, calibrated.
- Perceived straightness : visual impression influenced by the tool, the eye, and the components.
What a .001 arrow means to the hunter
A .001 rated arrow aims for very high consistency between shafts, increased regularity of dynamic spine and consistent shooting behavior.
However, it's important to keep in mind a key distinction: the difference between .001 and .003 is measurable at the factory, but rarely noticeable while hunting. Bow tuning, shooter consistency, and final setup often have a greater impact than the tolerance difference.
FAQ — Frequently Asked Questions
Can a spinner in a store confirm if a dart is .001?
No. A spinner is useful for spotting an obvious problem, but it cannot certify an industrial tolerance like .001, especially without calibrated instrumentation and numerical measurement.
Why might an arrow appear crooked on the spinner even if the shaft is good?
Because the visual impression depends on the quality of the spinner, the pressure applied, and the components (insert, tip, notch). These elements can create an apparent wobble even if the tube is within its tolerance.
Why is straightness measured on a bare shaft at the factory?
Because the goal is to measure the tube itself, without the mounted components (or operations like cutting) influencing the observation and distorting the interpretation.
Conclusion
The values 0.001, 0.003, and 0.006 describe a straightness level defined by a numerical industrial measurement. In a store, a gross defect can be detected, but a tolerance like 0.001 cannot be certified. The spinner remains useful, but its result depends heavily on its quality, the method used, and the components.