Effective Date: 09/25/08 Page 4 of 9
ATS Systems
Form
Subject: Ultimate Chuck Install & Training Checklist
Doc. No. FM 9-112
Rev.C
Operator and supervisor training:
Present all words in this section not shown in italics. And, add your own words and explanations to make each
point clear.
High speed lathes and chucks are perhaps the most hazardous equipment in most machine shops. Lathes and
chucks have been designed and built with your safety in mind and have many safety features, guards and interfaces.
But, the only way to prevent accidents and possible injury is to understand the hazards and to follow all the proper
rules, recommendations, and general and specific safe shop practices. People are regularly injured and even killed
as a result of "accidents" involving chucks. 99% of the time the accident is the result of operator error or lack of
experience and training, not as a result of any failure of the equipment. Please listen carefully, ask questions and
refuse to operate this equipment if you are unsure how to operate it safely. The life you save may be your own.
The bad things that can happen and the most common causes.
1. If a jaw were to come off of a spinning chuck it will become a projectile traveling in a straight line and could
penetrate the heaviest guard. There is a high likelihood of serious injury here and fatalities are not uncommon.
Possible causes:
- Bolts too short, inadequate thread engagement, threads strip off.
- Bolts not properly torqued tight and come loose.
- Wrong grade of bolts and they break.
- Excessively tall jaws and even moderate grip forces can put severe tension on bolts and cause them to break.
- RPM way too high for an oversize jaw and the bolts actually shear. (Watch out when using constant surface feet
programming!)
- Base jaw not engaged to "Safe" zone
- Poor quality or poor design jaw actually breaks and a portion of the jaw becomes a projectile. An example would
be some types of welded jaws, cast jaws that can break, or a hard jaw that is improperly hardened (through
hardened) and becomes brittle.
2. If a part is not securely clamped it can be thrown from the chuck. Unless it is struck by a spinning jaw as it
exits it will not be traveling in a straight line and there is a good chance a heavy guard will stop it but it may
not. Fatal accidents have happened.
Possible causes:
- RPM too high for the jaw selected, loss of grip force due to centrifugal force, part is released.
- Part inadequately gripped due to lack of proper chuck lubrication and resulting low grip force.
- Part inadequately gripped and pulled from jaw by an aggressive cutting tool.
- Part inadequately gripped due to poor choice of top jaw and pulled from jaw by even light cutting tool force.
(Such as soft jaws gripping an irregular rough casting.)
- Jaw positioned incorrectly or major workpiece gripping diameter variation (castings) causes jaw stroke to reach
bottom before properly gripping the workpiece. (Some lathes with some styles of stroke control will protect from
this.)
- Part inadequately gripped because the hydraulic pressure and resulting grip force is too low for the application.
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