= Gear marking-layer gap threshold
A \b[gear marking-layer gap threshold] is an effective separation below which a stated marking process produces a visible transfer or removal of material. It is a model of the observation in a <gear contact marking test>, rather than a universal thickness or a material constant. Layer thickness, pressure, rolling history and the marking material can all matter; a visible <gear contact pattern> does not directly give local operating pressure.
For an original idealization, let the unloaded separation across a face be
$$
g(z)=g_0+a|z-z_0|,
$$
and stipulate a visible mark where $g(z)\le h$. Here $h$ is the effective threshold, $g_0$ the minimum gap and $a>0$ its slope magnitude. For a centered pattern on face width $b$, the predicted marked width is
$$
W(h)=\min\!\left[b,\frac{2\max(h-g_0,0)}a\right].
$$
Choose $b=20\,\mathrm{mm}$, $g_0=0.5\,\mathrm{\mu m}$ and $a=0.4\,\mathrm{\mu m/mm}$. Thresholds $h=1.5$ and $2.5\,\mathrm{\mu m}$ give marked widths $5$ and $10\,\mathrm{mm}$. The geometry has not changed; the observation threshold has.
Away from the onset and saturation corners,
$$
\frac{dW}{dh}=\frac2a.
$$
Here a threshold change $0.2\,\mathrm{\mu m}$ changes the indicated width by $1\,\mathrm{mm}$. In the shallow-gap limit, small changes of the marking process can therefore cause conspicuous changes in the visible pattern.
A controlled comparison should hold the coating method, applied <torque> and number/direction of roll-throughs fixed, then vary one geometric setting. A separate fixture with known separations can test whether a proposed threshold model describes the marking process, without treating nominal coating thickness as an exact gap measurement.
Manufacturer contact guidance describes patterns as evidence about assembled tooth surfaces, and the historical rating standard limits the load information inferred from a bearing pattern.<Elements of Metric Gear Technology by SDP-SI>[Section 19.1, surface contact of spur and helical meshes, printed T-221]{ref}<ISO 6336-1:2006>[Section 7.3.1, loaded contact assessment and bearing-pattern interpretation]{ref} The threshold equation is a deliberately specified illustrative model; actual <deformation> and transfer behavior need validation before converting a mark into a quantitative gap or <gear face load distribution>.
Back to article page
