The study makes the following conclusions.

1. The current in-house wrench time study is valid and is representative of the work force at this time.

2. Current wrench time is 35.08%, or 3 1/2 hours per day with all categories summarized in Table H.1. Wrench time (Category 1) is statistically unchanged from earlier studies, but travel, work assignment, and interference time has improved. However, break and unaccountable (and to a lesser degree, waiting for materials and instructions) have become worse. Analysis of the comments and time of day for each observation suggests that concerns might be of a work scheduling or motivational nature rather than formal planning of job packages. (However, job planning might help to set job durations and work hour requirements in regard to scheduling.)

3. There are work differences among the mechanical crafts. Table H.52 summarizes the differences with respect to wrench time. In addition, on the whole, break time seems to be greater for technicians than apprentices and trainees combined (15.71 vs. 8.48%) and travel appears to be less (13.42 vs. 21.82%).

   Table H.52: Conclusion of Wrench Time Differences among Crafts

   Craft	Wrench time, %	Hours/10-hour day
   Mechanics	34.24	3 1/2
   Painters	25.69	2 1/2
   Welders	33.75	3 1/2
   Machinists	50.67	5
   Apprentices	40.21	4
   Trainees	30.80	3

4. Crews have somewhat comparable wrench times considering the study accuracy, but it appears that additional observations would make the differences statistically significant.

5. There is little difference in Monday and Friday work with only ...