Tolerance Guidelines
Tolerance Rules of Thumb by Material
| Material Specified | Rule of Thumb Tolerances |
| Polypropylene | (+/-) 0.003 base plus .002 per inch specified |
| No-Break Polypropylene | (+/-) 0.003 base plus .002 per inch specified |
| Glass-filled Polypropylene | (+/-) 0.003 base plus .002 per inch specified |
| Talc-filled Polypropylene | (+/-) 0.003 base plus .002 per inch specified |
| HD Polyethylene | (+/-) 0.005 base plus .0025 per inch specified |
| LD Polyethylene | (+/-) 0.004 base plus .002 per inch specified |
| Polystyrene | (+/-) 0.002 base plus .001 per inch specified |
| SB (Styrolux/K-resin | (+/-) 0.003 base plus .001 per inch specified |
| ABS | (+/-) 0.003 base plus .001 per inch specified |
| PC/ABS Blend | (+/-) 0.002 base plus .001 per inch specified |
| PC (Polycarbonate) | (+/-) 0.002 base plus .001 per inch specified |
| Nylon | (+/-) 0.002 base plus .0015 per inch specified |
| Glass-filled Nylon | (+/-) 0.002 base plus .0015 per inch specified |
| Acetal | (+/-) 0.002 base plus .0015 per inch specified |
| Glass-filled Acetal | (+/-) 0.002 base plus .0015 per inch specified |
| PBT | (+/-) 0.002 base plus .002 per inch specified |
| Glass-filled PBT | (+/-) 0.002 base plus .0015 per inch specified |
| PUR (Rigid Polyurethane) | (+/-) 0.002 base plus .0015 per inch specified |
| TPE Santoprene | (+/-) 0.003 base plus .002 per inch specified |
| TPE SEBS | (+/-) 0.003 base plus .002 per inch specified |
| Acrylic | (+/-) 0.003 base plus .001 per inch specified |
Tolerance guidelines are expressed as a base (minimum) tolerance plus added tolerance based on linear inch of a given product feature, and represent typical variation from part to part once molded. By means of example, a 2 inch feature on a prduct molded from ABS will likely consume a tolerance of +/- .005 inches (Base of +/- .003 plus .001 X 2 inches). The same feature on a part molded from Polypropylene might consume a tolerance of +/- .007 inches (Base of +/- .003 plus .002 X 2 inches).
We urge caution in the application of these guidelines. Part geometry can have a dramatic impact of dimensional stability. In some cases, the guidelines provided are insufficient to cover actual variation, but in many more cases, these same guidelines suggest far more variation than is actually seen in the parts. The only reliable way to assess dimensional stability is to mold and analyze the product. At Guttenberg Industries, every project involves trial samplings and statistical analysis that compares actual variation to your print requirements. This process insures that every dimension identified as key to quality is realistic as documented on the print.
