EST 150/3 sanding pad

[therogdoc]

Hopefully this is an easy one.
I have an ETS 150/3 that I have used for about 2 years with the soft sanding pad - has worked great and love the thing. I recently got a hard pad to use with it. Is the pad supposed to be keyed. I just cannot get the pad to sit down properly on the sander. IT tightens up just fine but when you turn it on there just seems to be excessive wobble. Any help? Thanks in advance
Roger

 

[ScotF]

All the pads fit on the machine the same way -- there are two flat sides and two round side that lock the pad onto the bottom of the sander.  The hex tightens it all down.

Scot