MRO Magazine

Wrench Time – How to improve maintenance productivity

April 3, 2018 | By Doc Palmer

Doc Palmer, PE, MBA, CMRP is the author of McGraw-Hill’s Maintenance Planning and Scheduling Handbook.

Doc Palmer, PE, MBA, CMRP, is the author of McGraw-Hill’s Maintenance Planning and Scheduling Handbook.

Wrench time explains why a company can get a 50 per cent boost in maintenance productivity! That means a good workforce completing 1,000 work orders each month could become a superior workforce completing 1,500 work orders per month, for free! That’s a big deal! But you don’t have to measure it. You probably should not measure it. But you might want to measure it. Decisions, decisions…

The concept of wrench time shows how a typical workforce can improve its productivity by 50 per cent or more. Wrench time is the percentage of time a person available (not on vacation or in training) typically is engaged in productive activities moving a job forward. Not counted as wrench time are “non-productive” activities, such as break, travelling to jobs, obtaining parts or other similar instances, even though they are part of doing business. Maintenance forces at good plants usually have an overall wrench time of only 35 per cent. Amazingly, this seemingly low score is typical across companies, industries, countries and even cultures. These groups have the same wrench time because at about 35 per cent productivity, people “feel busy.” Over the years, workforces around the world staff up (or staff down) in accordance with the growth (or decline) of the backlog of work at a productivity rate that keeps everyone busy and keeps the plant operating at a good capacity. The problem with this philosophy of staffing and backlog management is that it ignores the ability of the plant to move beyond merely good capacity and merely good productivity. Most plants can achieve superior capacity by completing more proactive work with the same workforce.

Consider a 30-person workforce at 35 per cent wrench time versus 55 per cent wrench time. 55%/35% = 1.57. 30 persons x 1.57 = 47 persons. The 55 per cent workforce completes work at the rate as if it had 47 persons. If the 35 per cent workforce completes 1,000 work orders per month, the 55 per cent workforce would be completing 1,570 work orders per month. The extra 570 work orders per month are free. Planning and scheduling absolutely answers the question: How can we complete more proactive work to head off failures when we have our hands full of reactive work? That’s a big deal!

But there are problems with measuring wrench time (other than just the time and effort involved). One problem is that conducting a study has great potential to upset the workforce. Another problem is that measuring wrench time does not improve wrench time. What the plant really wants anyway is to improve its work order completion rate. Why not just accept that wrench time is 35 per cent and start doing planning and scheduling properly? Plants that correct their planning and scheduling efforts should see their work order completion rates rise, which is what they really wanted anyway. They rose because of the concept of wrench time whether it was measured or not.


There is also another reason not to measure wrench time. Wrench time can be a terrible measure to begin with. A carpenter could show up at the wrong house and hammer slowly all day without taking a break. The carpenter might have 100 per cent wrench time inefficiently doing the wrong job. (But we do not consider wrench time to be the all-in-all, one and only perfect KPI. Wrench time only measures available time working. We presume that considerations of proper work selection and working efficiently stay the same at 35 per cent and 55 per cent wrench time.) The problem here is that by management focusing on wrench time, it gives a signal for everyone to look busy (and possibly leads to gaming the system).

Nevertheless, a plant might want to measure its maintenance wrench time. A plant might want to prove that it is a typical plant at 35 per cent or see whether it has an effective planning and scheduling program. If a plant does measure wrench time, there are improper and proper ways to do it.

Not all methods to measure wrench time are valid. First, productivity and delays self-reported by the personnel are generally not valid. Most such results are in the 70 per cent or higher range. It is difficult for craftspersons to recognize that a moment here or there is not actually “work.” Consider, if it is difficult for management to realize that typical wrench time is only 35 per cent, how can one expect mechanics to understand 35 per cent is “okay” and report themselves accurately? Secondly, a study in which observers follow specific craftspeople around all day is also generally not valid. Most of these studies show 50 per cent or higher wrench time. For one thing, the persons selected might not be “typical” craftspersons on “typical” days. For another, persons being followed generally do not act normally. Third, studies where observers go at statistically set times into a shop area to see what visible persons are doing is also not valid. These results are generally in the 50 per cent or higher range. These studies do not include personnel that are available, but not in the shop area. These unseen persons might have been travelling, in the storeroom, or in some other delay area.

The best method to measure wrench time is usually with a statistical sampling method where each person in the workforce has an equal chance of being observed over a sufficient period to represent the actual workforce over time.

The concept of wrench time is a big deal. It is the key to understanding the dramatic gain possible in maintenance productivity through proper planning and scheduling. But you do not have to measure it. Be cautious if you do.

Doc Palmer, PE, MBA, CMRP is the author of McGraw-Hill’s Maintenance Planning and Scheduling Handbook and as managing partner of Richard Palmer and Associates helps companies worldwide with planning and scheduling success. For more information visit or email Doc at



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