I have a Milwaukee portaband saw and noticed some unusual behavior recently. I made a plate to mount to the saw and in turn clamp to a bench vise so I could keep the saw in a vertical position. While making a cut I noticed that the top wheel (the one that can be slacked to replace a blade) was oscillating while the saw was running. The wheel oscillated about 3/16 of an inch up and down. I checked the tension lever to make sure it was tight and made another cut. Again the same oscillations.

I have never seen this before since when I am making a cut using it in the conventional manner I am not looking at the wheels. Is this oscillating motion normal? Is there some adjustment I do not know about? It was always my impression that the adjustable wheel is moved to tension the blade and remains in that position until it is slacked off.