Clippers are 50% of your cutting system, if they are not functioning properly, newly sharpened blades will not cut properly. If there is any free play in your clippers drive assembly your blades will drag. That clipper may have problems as well causing the same symptoms. Just don’t assume that your clipper is OK because blades were cutting on it before they were sharpened. General clipper maintenance is very easy and should be checked regularly. All groomers should learn simple mechanics of their clipper. On Andis clippers, check the blade drive monthly if you're doing 8 to10+ dogs a day.