The deal sees current management Colin Palin and Patrick Walker invest with Parkin, who becomes chief executive of PTI, to acquire the business.
PTI has over 50 years experience in the manufacture of parts across a range of sectors including Formula One, medical, oil and gas and aerospace.
The group has vowed to continue recruiting and training apprentices in the region following the deal as it looks to retain high quality engineering expertise in the UK.
Finance Birmingham invested £1.2m as part of a multi-million pound funding package to support the takeover.
Ian Fairclough, investment director at Finance Birmingham, said: “PTI has an excellent reputation for producing high value components for a wide range of clients.
“The workforce is highly skilled and this, combined with the business’s ability to collaborate with its customers, allows it to design and manufacture unique components to suit a variety of needs.
“The company’s potential to strengthen its offering is evident through its plans to drive revenue, not only with its existing customers, but by entering new markets.
“The support from Finance Birmingham will accelerate this by allowing the business to invest in the additional staff and operations needed to do so.”
Parkin added: “We are keen to retain high quality engineering expertise in the UK and PTI is certainly at the cutting edge of providing specialist low volume components that are used in extremely demanding conditions.
“To maintain this service from manufacturing to the testing and inspection of products, there is a demand for an engineering expertise that can only be achieved by a dedication to apprentice training and a philosophy of continuous improvement.”