This week, the ratings of three Machinery stocks on Portfolio Grader are down. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

Ampco-Pittsburgh (NYSE:AP) earns an F (“strong sell”) this week, moving down from last week’s grade of D (“sell”). Ampco-Pittsburgh is engaged in manufacturing and selling custom-engineered equipment in a global marketplace. The stock has a trailing PE Ratio of 27.90. To get an in-depth look at AP, get Portfolio Grader’s complete analysis of AP stock.

Kadant Inc. (NYSE:KAI) is on the decline this week, earning a D (“sell”) after receiving a C (“hold”) last week. Kadant is a supplier of equipment used in the global papermaking and paper recycling industries. The stock price has fallen 6.6% over the past month, worse than the 3.3% increase the S&P 500 has seen over the same period of time. For more information, get Portfolio Grader’s complete analysis of KAI stock.

The rating of Wabash National (NYSE:WNC) declines this week from C to a D. Wabash National designs, manufactures and markets standard and customized truck trailers and intermodal equipment. The stock also rates an F in Earnings Revisions. As of Feb. 15, 2013, 13.5% of outstanding Wabash National shares were held short. To get an in-depth look at WNC, get Portfolio Grader’s complete analysis of WNC stock.

Louis Navellier’s proprietary Portfolio Grader stock ranking system assesses roughly 5,000 companies every week based on a number of fundamental and quantitative measures. Stocks are given a letter grade based on their results — with A being “strong buy,” and F being “strong sell.” Explore the tool here.