<p>SPI Finish Grades:</p>
<ul>
<li>A1 Mirror: Ra 0.012-0.025μm — optical parts</li>
<li>A2 High Gloss: Ra 0.025-0.05μm</li>
<li>B1 Fine: Ra 0.05-0.1μm — general appearance</li>
<li>C1 EDM: Ra 1.6-3.2μm — textured surfaces</li>
<li>D1 Sandblast: Ra 3.2-6.3μm</li>
</ul>

<p>Cost: Mirror finish costs 5-10x more than EDM finish.</p>

<p>Full guide: https://www.mfgabc.com/guides/surface-finish-standards-ra-rz.html</p>

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<p>踩过坑的来评论区说说。</p>