I installed a pair of threaded inserts into my deck to re-attach the a-frame after the original screws pulled out (was a very rough day and the old fixings were 20 years old). The inserts have a coarse thread on the outside and a metric thread (M8 in mine) through the middle and are installed with an allen key. I glued them in with epoxy for good measure. The centre holes are all the way through but a blob of sika of epoxy at the end before fitting would fix that, if it is a problem. These are the ones I used and are made from 304 (A2) stainless so not quite as strong as 316/A4 but should be up to the job. Just add a few more if possible:-
SCREW IN HEADED STAINLESS STEEL WOOD INSERT M8x18MM 5pcs | eBay
I plan to make my own from 316 bar when I finally get the lathe up and running.