Then cutting the tenon AFTER forming the mortise was an “ah-ha” moment for me.
Hmmm... Hadn't thought of that. The tenon being easier for me, particularly as I have a Delta Tenoning Jig for my TS, that's what I started with. But I can see the advantage of doing the tenon second.
Took my time with it, and "scary sharp" chisels made the task easier. Yep! Learned a lot about sharpening chisels on YouTube, too.
Yeah, there's no doubt sub-standard chisels were a good part of my problem.
I actually tried the mortise twice. But I was using plain old dimensional SPF and tried to make a through-tenon right up close to the end. It chipped-out on the backside, then cracked. That was in part due to my chisels already losing it and poor technique on my part.
By the time I went to attack my second try the chisels were no longer capable. They were more tearing the wood out than cutting it. I could've done as well with a blunt flat-blade screwdriver
I've got a 5/8 in. Narex mortising chisel on the way. I'll try again.
Re: "Proper sequence for drilling with a Forstner bit": Have you got a reference for that? Kind of hard to see how to get that part wrong. One thing I did
learn is I think I can see the value of a fence on my DP for that purpose.