Plate Specs

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
.027.040
(+ .004 adhesive)

.875
Photopolymer
    standard depth, steel-backed
.027
.040
(+ .004 steel)
.875
Photopolymer
    deep relief, polyester-backed
.047.060
(+ .004 adhesive)
.853
Photopolymer
    deep relief, steel-backed
.050.060
(+ .004 steel)
.860
16 gauge (magnesium, copper).040–.045
.064.838
.759
.668
.016
.095
.186
80 thousandths (magnesium).050–.065
.080.838
.759
.668

.079
.170
11 point (magnesium)
.070–.100.153.759
.668
.006
.079
¼" (copper).070–.100
.250.668

Notes
Base height column list 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.