[Herb Stoops]

That's white birch that's 30 years old I'm using it on Tom so yes. Once the points enter the wood the top isn't going to move. A dedicated mortiser will set you back around $500, the attachment was $130 I think, but 25 years ago roughly. BJ used to say why have another machine taking up room when you already have a DP. That was my sentiment too but now I realize that the DP has far greater range so to me that makes the attachment an even better deal. The attachment takes 5 minutes or less to mount BTW. There is a clamp ring on the yoke that fits on the base of the quill, above the chuck. Mine was a Delta attachment for a Delta DP so no issues with fit but it came with a bushing for a different size quill and it sounds like the two sizes are pretty standard.

Are you using square tenons in the spreaders instead of round?
Herb