Screw Material Guidelines Table
BASE SCREW MATERIALS |
ACCEPTABILITY FOR RESIN WEAR CONDITIONS |
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MATERIAL DESIGNATION |
TREATMENT (1) |
Rc (2) |
FH (3) |
ABRASIVE |
CORROSIVE (7) |
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NORMAL (4) |
AVERAGE (5) |
SEVERE (6) |
MODERATE |
SEVERE |
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| ALLOY STEELS: 4140 |
Flame -hardened |
48-55 |
no |
Acceptable |
Poor |
Unacceptable |
Unacceptable |
Unacceptable |
| 4140 | Chrome-plated | 60-65 |
yes |
Good | Acceptable | Unacceptable | Good | Unacceptable |
| Nitralloy 135-M | Nitrided | 63-70 |
yes |
Good | Acceptable | Unacceptable | Poor | Unacceptable |
| TOOL STEELS: PM 9V |
Heat-treated |
54-56 |
no |
Excellent |
Excellent |
Good |
Acceptable |
Unacceptable |
| PMM4 | Heat-treated | 62-64 |
no |
Excellent | Good | Acceptable | Poor | Unacceptable |
| PM 420 | Heat-treated | 54-56 |
no |
Excellent | Excellent | Good | Excellent | Good |
| SPECIAL ALLOYS: Monel K-500 |
Age hardened |
37-39 |
opt’l |
Acceptable |
Unacceptable |
Unacceptable |
Excellent |
Good |
| Nickel 718 | Age hardened | 43-45 |
opt’l |
Acceptable | Unacceptable | Unacceptable | Excellent | Good |
| Encapsulations | Carbide coatings | 70+ |
opt’l |
Excellent | Excellent | Good | Excellent | Poor |
PM = Particle Metallurgy Process
(1) Includes chrome-plating to .003"-.005" and gas or ion nitriding for 24+ hour cycle.
(2) Rockwell C hardness.
(3) Flight hardsurfacing required.
(4) Thermoplastics with no reinforcements.
(5) Thermoplastics with up to 30% reinforcement.
(6) Thermoplastics with more than 30% reinforcement.
(7) Moderate includes cellulosics, acetals and others containing corrosive additives.