Police were called to Charnwood Street at around 8.35pm on Wednesday (December 11), after reports of a group of men wearing balaclavas were seen breaking into a van.
The van’s owner confronted the men and they pointed what is thought to be a gun at him, before telling him to “back away”.
The group then stole high-value tools from the van.
Detective Sergeant Matt Scott, of Nottinghamshire Police, said: “Anyone who saw anything is encouraged to get in touch with us as soon as possible.
“The robbery could have a detrimental impact on the victim’s livelihood and while we are exploring a number of lines of enquiry, you might hold a piece of information that could help catch those responsible.
“If you have any information that could aid our officers, please get in touch via 101 and quote incident number 853 of December 11, 2019.”