I'm in the process of assembling my bench base and was clamping up this morning. I used dowels (via Jessem jig) for the joinery and planned to use a parallel clamp to tighten the joint flush. The joint is a 5"x1.75" stretcher to a leg which has 8 dowels in it. I began applying glue and things were going okay, but I couldn't pull the joint tight.
I reach for another parallel clamp and tried that, didn't really help much. I start getting antsy and nervous. So I reach for another and still nothing! Now I'm in panic mode. Did I mention my 10 month old was beginning to stir and fuss on the video monitor? So I had three parallel clamps (jet and bessey) and I was turning those pesky handles with all my might and it wasn't going anywhere! Thoughts of having to trash a couple weeks of work and explain it to the LOML are going through my head now. It would have been comical to watch I'm sure, and only my fellow ww'ers would understand what it's like!
Looking for yet more force, I grab one if my Rockler aluminum bar clamps and try that. The joint pulls together right away, and all three of my expensive clamps crash to the bench top. Happiness and relief set in and the rest of the glue up goes smooth.
But how is one cheap bar clamp putting more force on the joint than 3 of my parallel clamps? It's a lot easier to get grip on the handles of the bar clamp and they are longer so I can generate more force I suppose. The negative of the bar clamp is they tend to pull the joint out if square so you have to balance it with another clamp on the other side.
So the lesson here for me is that parallel clamps are not the be all and end all of clamps. Maybe the next time any of you get into a similar situation, try some other types of clamps.