He demanded money from the till before threatening and assaulting her in the frightening incident in the Fartown area of Huddersfield.
Police have released a CCTV image of a man they would like to trace in connection with the attempted robbery on Spaines Road at around 12.20pm today (Friday).
The victim, a woman in her 20s, needed hospital treatment after the incident for a minor hand injury.
The suspect, a white male in his 20s who was wearing grey joggers, a black puffer jacket, white trainers and a deer stalker-style hat, left empty handed.
Detective Inspector Damian Simpson, of Kirklees CID, said: “This was obviously a very frightening incident for the woman involved and thankfully she wasn’t more seriously injured.
“I would appeal for anyone who recognizes the man pictured in the CCTV image to get in contact with officers are he may have information valuable to the investigation.
“I would also appeal for anyone who saw a man matching the description in the area at the time of the incident or saw anyone acting suspiciously to contact police.”