Welders cut beams for the substructure of a new oil and gas drilling rig at the Orion Drilling Co. manufacturing and fabrication facility in Corpus Christi, Texas.

President Trump says he is a champion of manufacturing, but his steel and aluminum tariff plan is driving a big sell-off in the industry's shares.

Multiple Wall Street banks cautioned clients against investing in the American manufacturing industry Friday as some of the nation's largest machinery companies are dropping.

Crane machinery and equipment manufacturer Manitowoc's shares declined by nearly 10 percent since Wednesday's close, while rival Terex fell by more than 7 percent in the same time period.

"Tariffs may limit President Trump's quest to be 'the greatest jobs president that God ever created,' at least within the U.S. counties that rely on machinery," Barclays analyst Adam Seiden quipped. "The Peterson Institute projects job losses in many key areas of Trump's political base that happens to align with areas of outsized machinery manufacturing assets."

Trump announced his plans to impose a 25 percent tariff on imported steel and a 10 percent tariff on imported aluminum Thursday, sending the Dow Jones industrial average tumbling more than 500 points since Wednesday.

Based on Barclays' analysis, cranes and aerial work platforms could have the toughest time dealing with higher steel prices. Agriculture equipment, though, could offset raw material headwinds with pricing of their own.

Source: Barclays

But Barclays wasn't alone in sounding the alarm on manufacturing companies in light of Trump's tariff decision. Baird analysts were also on edge Friday.

"Tariffs are a broad negative for big steel users in the Machinery space, [and] yesterday's announcement turned a potential negative into reality," wrote Baird analyst Mircea Dobre. "Longer term, companies will find ways to cope yet for the next few quarters this action will further strain supply chains and pressure margins at a point in the cycle where profit ramp is key."

Dobre downgraded a host of manufacturers to a neutral rating – including Terex, Oshkosh and Hyster-Yale – while also cutting his price targets for the companies.

Terex's stock declined 4 percent Friday. Vehicle body-maker Oshkosh shares dropped 2 percent Friday and are down nearly 8 percent for the week.

"Imports have played a growing role in meeting U.S. steel demand in spite of repeated attempts by the U.S. Government to limit import penetration," added Dobre. "The reason for this is simple: foreign steel is cheaper and we're not just talking about China, we're talking about everyone."