i'm planning to attach a stretcher into a leg with a dovetailed half-lap joint, like this:

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this joint needs to be disassemblable, so i'm thinking of holding it in with either a lag screw or a bolt + threaded insert, through the face of the stretcher into the leg. i think the dovetail should keep it together well mechanically, it'll just need the hardware in that one axis?

i probably wanna recess the bolt head and washer so they sit below the surface, but, between the recess and the half-lap, i'm rapidly running out of material thickness...

let's suppose i'm using a 1"-ish washer under an M10 bolt. with this kinda wood (untreated mgp10 from bunnings), how much thickness do i need to keep under the bolt head/washer to stop it just pulling through? (my gut says about 1/2" should be adequate? but my gut is entirely untrained so i have no reason to trust it)

if i know how much thickness i need to keep, then i can work out what i've got left to play with

(i'm trying to avoid just using a shallow m/t + bed-bolt style joint here, even though it seems obvious, because i don't have a drill press, and i'm not yet comfortable/accurate enough with a cordless to get the perpendicular holes to line up)