Plate & base height-to-paper combinations in thousandths-of-an-inch
| Plate Type | Image Relief | Plate Height | Base Height | Underlay/ Bed plate/ Bed Height Adj. |
|---|---|---|---|---|
| Photopolymer standard depth, polyester-backed | 0.027 | .040 (+ .004 adhesive) | 0.875 | — |
| Photopolymer standard depth, steel-backed | 0.027 | .040 (+ .004 steel) | 0.875 | — |
| Photopolymer deep relief, polyester-backed | 0.047 | .060 (+ .004 adhesive) | 0.853 | — |
| Photopolymer deep relief, steel-backed | 0.05 | .060 (+ .004 steel) | 0.86 | — |
| 16 gauge (magnesium, copper) | .040–.045 | 0.064 | .838 .759 .668 | .016 .095 .186 |
| 80 thousandths (magnesium) | .050–.065 | 0.08 | .838 .759 .668 | — .079 .170 |
| 11 point (magnesium) | .070–.100 | 0.153 | .759 .668 | .006 .079 |
| ¼" (copper) | .070–.100 | 0.25 | 0.668 | — |
Notes
Base height column lists the ideal combination first.
Copper and magnesium are also available in 3/8” thicknesses, but are rarely used for letterpress.
Sources
Boxcar Press, JetUSA, NA Graphics, Owosso Graphic, and Sterling Toggle.
Thanks also to John Henry and Eric Holub.