Now I know why you need 3 dowels for double sided job

[mickecarlsson]

Yes, today I found out (the hard way) the reason you need three (3) dowels for a double sided job.
I was sloppy and only used two dowels, and ruined a work piece in the process

Learning by doing

[Phil]

You learn a lot from the mistakes you make, and you don't forget them.

Phil

[martin54]

Yes, today I found out (the hard way) the reason you need three (3) dowels for a double sided job.
I was sloppy and only used two dowels, and ruined a work piece in the process

Learning by doing

How did you ruin the workpiece? Flipped the wrong way maybe? if the dowels are tight then you can get away with using 2 dowels but there is still room for a little movement, with 3 there is absolutely no movement & obviously no chance of flipping the wrong way

[mickecarlsson]

Stupid mistake.
My workpiece was 140mm wide by 550mm long, one dowel at each end, and not spaced apart enough.
So, I finished side one, unscrewed the workpiece, placed it on the floor.
Set Z to the spoil board, miled the two holes.
Grabbed the workpiece, and when I handled it I managed to rotate it 180 degree
Did not notice that the piece had shifted about 10mm to the right, started the job, looked fine but about 10 minutes in I noticed the shift. And aborted the job. I managed to salvage some of the parts by rotating the workpiece and restart the job.

Lesson learned, use three dowels.