As investors try to make sense of U.S. expansion that's better than a snail. though not yet robust, manufacturing is certainly attractive for investment, Bertelsen said. He's held Parker Hannifin for two years, Fastenal is on his buy list now and he says Grainger could be in the future. Owning stocks in this part of the industry is important for gauging the strength of the economy. Even so, production activity remains uneven. Recent sales advances -- particularly for Grainger -- could be driven more by market-share gains than a rebound in demand, Roukis said, adding that this could be misinterpreted as overall strength in the industry. 

In addition, Fastenal experienced a soft industrial market in its most recent quarter, which hasn't changed a lot, Oberton said on the call. We don't believe it getting any worse. We don't see signs that it's improving.

Eoin Treacy's view

While 2011 witnessed impressive outperformance by the consumer sector, the industrial sector has been this year's star performer. At the present moment a considerable proportion of industrial shares have become overextended relative to their respective 200-day MA so it is potentially notable that a number of wholesalers such as W.W.Grainger have returned to test the region of their respective 200-day MAs. 

W.W.Grainger was among a small number of companies to hit new all-time highs in 2009 and it has remained in a reasonably consistent medium-term uptrend since. The share has returned to test the region of the 200-day MA over the last month and will need to continue to hold above $250 if the medium-term upside is to continue to be given the benefit of the doubt. ​

Fastenal was also an early leader but accelerated to the 2012 peak and has spent almost two years ranging with a mild upward bias. It will need to continue to hold the medium-term progression of higher reaction lows, currently near $45, if potential for an eventual upward break is remain credible.