Instruct: Classify the given review into positive or negative sentiment.
Query: problems with flow control knob

I've used this unit for several months and dozens of times and have had good results with the exception of the material adjustment knob. Like other reviewers I too have had trouble threading it after cleaning, and once attached, there have been times I've been unable to turn it without the use of pliers. Given how frequently you use this knob it is really frustrating and a pain in the neck...I would not purchase this gun again.