Finishing
- Processes
- 25
- Families
- 3
- Column
- Tolerances
Additive12
- AnodizingType II adds 0.0002–0.001 in (5–25 µm) total, roughly half of it outward; Type III adds 0.0005–0.004 in (13–100 µm). Budget the full coating thickness on a diameter and 4× the radial buildup on thread pitch diameter
- Black OxideAdds roughly 0.00003–0.00005 in (0.75–1.25 µm) — treated as dimensionally neutral; no allowance needed on threads, gage surfaces or press fits
- Cerakote Ceramic CoatingAdds about 0.001 in (25 µm) per coated surface; budget 2× on a bore diameter and roughly 4× on thread pitch diameter, or mask
- Chemical Conversion CoatingChem film on aluminum adds 0.00001–0.00004 in (0.25–1 µm) and needs no allowance; manganese phosphate on steel can reach 0.0002–0.0004 in (5–10 µm) and should be checked on close fits
- E-Coating (Electrophoretic Deposition)Adds 0.6–1.2 mils (15–30 µm) per surface, uniform over the whole part including recesses; budget roughly 4× the film thickness on thread pitch diameter
- ElectroplatingZinc 0.0002–0.001 in (5–25 µm), electroless nickel 0.0005–0.002 in (13–50 µm), hard chrome 0.0002–0.010 in (5–250 µm) per surface. Electrolytic deposits vary 2:1 or more between high- and low-current areas; electroless nickel holds about ±10%
- GalvanizingHot dip adds 1.8–3.9 mils (45–100 µm) per surface per ASTM A123, so holes close by 3.6–7.8 mils on diameter; electrogalvanizing adds 0.0002–0.001 in (5–25 µm) and is far more predictable
- PassivationNo measurable dimensional change; the passive film is a few nanometers thick
- Powder CoatingAdds 2–4 mils (50–100 µm) per surface; budget 2× film thickness on a bore diameter and roughly 4× on thread pitch diameter, or mask
- PVD CoatingAdds 0.5–5 µm (0.00002–0.0002 in) per surface — dimensionally negligible for most fits; thicker tooling coatings at 4–5 µm should be checked on close-fitting punch and die clearances
- Spray PaintingA complete system adds 4–6 mils (100–150 µm) per coated surface; budget 2× on a bore diameter and roughly 4× on thread pitch diameter, or mask
- Vacuum MetalizingMetal film 0.05–0.15 µm (2–6 µin) is dimensionally negligible; the base and topcoats add roughly 0.5–1.5 mils (13–38 µm) total per coated surface
Subtractive8
- Abrasive BlastingCleaning passes remove very little, but aggressive or repeated blasting removes measurable stock; mask any toleranced feature. Anchor profile is specified at 1.5–4.0 mils (38–100 µm) for coating work
- Bead BlastingRemoves under 0.0005 in (13 µm) — generally treated as dimensionally neutral, but toleranced bores, threads and sealing faces should still be masked
- CNC EngravingDepth control of ±0.001–0.002 in (±0.025–0.05 mm) is routine; stroke width with a conical tool varies directly with depth, so both must be specified together
- ElectropolishingRemoves 0.0002–0.001 in (5–25 µm) per surface, so bores grow and shafts shrink by twice that on diameter; sharp external edges break by 0.002–0.003 in (50–75 µm)
- Grinding, Sanding and PolishingSurface and cylindrical grinding ±0.0001–0.0005 in (±0.0025–0.013 mm); honing corrects bore geometry within a few tenths; lapping holds flatness to a few millionths of an inch
- Laser Marking and EngravingAnnealed marks remove no measurable material; etching removes 0.0001–0.001 in (2.5–25 µm); engraving removes 0.001–0.020 in (0.025–0.5 mm). Beam positioning within the marking field is typically within a few thousandths of an inch
- Photo Etching±10–20% of material thickness is standard; approximately ±0.001 in (±0.025 mm) achievable on thin foil. Half-etch depth is controlled to a residual thickness rather than to a depth dimension
- Vibratory Tumbling and Mass FinishingRemoves 0.0001–0.001 in (2.5–25 µm) per surface in a typical cycle and breaks exposed edges 0.002–0.010 in (0.05–0.25 mm); the edge break is not controllable to a tolerance
Printing5
- Foil Blocking and EmbossingTransferred foil layer is sub-micron and dimensionally negligible; image registration typically ±0.010–0.020 in (±0.25–0.5 mm), and exact between foil and emboss when a combination die is used
- Hydro Transfer PrintingThe complete system adds 0.003–0.006 in (75–150 µm) per surface, dominated by the base and clear coats; the printed layer itself is negligible
- Pad PrintingImage position typically within ±0.005 in (±0.13 mm); the transferred ink film is a few microns and adds nothing dimensionally
- Screen PrintingRegistration typically ±0.005–0.010 in (±0.13–0.25 mm); dried ink film 0.0004–0.002 in (10–50 µm), which is enough to matter on a stacked assembly
- UV Inkjet PrintingImage placement typically within ±0.010–0.020 in (±0.25–0.5 mm) relative to the substrate datum; printed film 0.0004–0.0008 in (10–20 µm) for a standard CMYK build
About finishing
Finishing processes change the surface rather than the bulk: appearance, corrosion resistance, hardness, friction, or dimensional fine-tuning.
Finishing is where tolerances get consumed. Plating adds thickness, anodizing both adds and eats into the substrate, and blasting rounds edges, so the finish has to be chosen before the drawing is dimensioned.