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Hartwig knowledge for the soul Retention knobs and pull studs are not intended to last forever. Your Safety Program must include inspections. Pull studs must be visually inspected for damage and checked for tightness every time the tool in the holder is changed.
Before installing a new retention knob or pull stud in a tool holder, clean both items with solvent and blow them off with an air hose. Inspect both items to make sure that there are no nicks or scratches on joining surfaces.
Always tighten retention knobs and pull studs with a torque wrench. The force required is very hard to judge without a torque wrench. A retention knob or pull stud that is too loose or too tight is dangerous.
Retention knobs or pull studs are designed to be the weakest link between the spindle and the tool holder. For this reason they are not intended to last forever. Monitor their condition and be sure to include retention knobs and pull studs in your Safety Program.
KEEP A MAINTENANCE SCHEDULE
Every 2-3 years, depending on use, knobs should be removed from the holder and magnetic particle inspected. Any retention knobs or pull studs showing indications of cracking must be discarded.
If your machine is in a crash, or releases a tool prematurely, this is an indication that either the Retention Knob fingers, finger guide, belleville washers in the spindle, or the Retention Knob is damaged.
The machine tool should not be used until inspected by maintenance personnel. In this case, all the retention knobs in the machine should be checked for cracks or damage immediately.
TORQUE
30 taper pull studs 10-12 ft lbs, no more, with loctite
40 taper pull studs 12-14 ft lbs, no more, with loctite
50 taper pull studs 18-20 ft lbs, no more, with loctite
It is highly recommended you tighten your pull studs with a pull stud socket. This gives you a true torque reading and doesn't damage or side load the pull stud while tightening. If you over-tighten the pull studs they will distort the taper on the holder, causing poor contact and can hurt your spindle.
Some tool holders don't have a big enough chamfer in the back and the pull stud shoulder may not seat against the tool holder, instead it sits on the pilot radius. It is good practice to either us a .001 shim or just hold up the tool holder to the light and make sure there isn't any gap. |
