I'm getting to the point where I will need to drill mortises for my seat, and most every chairmaker I have seen, Mike Dunbar, Curtis Buchanan, Greg Pennington, Elia Bizzari, Chris Schwarz, all drill from the bottom to the top of the seat. The stick chair book also recommends adding a backer block to minimize spelching. But they never specifically detail why they only go from the bottom of the seat
But then I found a video on YouTube that shows an old Irish woodworker who uses his t auger to drill from the top to the bottom of the seat.
And the more I think about it, I can see this being an advantage because if there is spelching that will get cleaned up with my tapered reamer anyway, and if the reamer doesn't clean it up its the bottom of the seat any way.
Maybe it's being able to see sight lines drawn on the bottom of the chair, but if you set the bevel gauge on the line and keep it from touching I guess theoretically it would work.
I'm not about to question the validity of methods from people who have built lots of chairs, I guess I'm just wondering what if?
Is there a reason everyone drills from the bottom?