I did something similar recently, but in softwood. I did some experiments, and ended up with this approach.
1. I used my drill press, as I couldn't come close to keeping a hand drill still enough.
2. My press has a tilting table, but I kept it square, for several reasons:
- Firstly, these needed to be through holes, and I didn't want to destroy the bit by hiitting the table.
- Secondly, keeping the table square meant it had no tendency to tilt when pressure was applied. Fortner bits do need a bit of down pressure to work.
I built a jig on which to rest the work, and used a guide block to stop the bit wandering at the start.
3. Making the guide block: drill through a large block, square to its surface, then cut it in half at the required angle on the bandsaw (or whatever - I'm lazy!).
- before making the hole, mark and punch the centre for the hole, and take that mark round as lines square to the faces of the block. Then when you are setting out the final hole, you have guide marks to align everything nicely.
4. Making the jig: I needed a set of 1" holes equally and precisely spaced along a piece of roughly 2x1 at an angle of about 30 degrees. This needed two holes in the jig, at the correct spacing, and a removable, snug-fitting peg. The first hole in each piece was made to a mark, then dropped over the second hole aligned by the peg. It's similar to doing box joints on the router table, etc. Each time a hole is finished, that then goes over the peg, so you are lined up for the next one with a consistent gap.
I guess you might adapt the peg idea to work upside down in a movable jig on a large piece of stock. Get the 45 degree guide block right, then split up the offcuts and glue back on either end, so as to make flat surfaces for clamps to hold it to the workpieces (dowel together if necessary). Clamping is difficult, especially if you have a 45 degree angle: on the "upper" side of the hole, the clamp risks fouling the drill on top, on the "lower" side of the hole you haven't got much room to clamp because of the drill table (the table ends up a long way below the workpiece). And on the low side, the clamp can end up under the line of the drill if you're not careful. And they need to be close to the work to avoid movement.
Theoretically a guide on the surface ought to be enough to minimise tearout, but I got a small amount. It might be cleaner if you used a sacrificial piece of something between the jig and the stock, both sides of the stock.
I'm typing this on a tablet at the moment. It really needs a drawing, which I'll try to do if I get a moment.
45 is rather steep for this to be successful, as the edge of the Forstner is trying to tear wood away as it exits the surface (it should be OK once you're completely into the stock though). I'd experiment with sacrificial pieces either side ofthe stock if it's a through hole), and on top if it's blind.
Finally, if you have access to a drill press, use it! In my experience all the power tool wide bits wander terribly, including Forstners, and you're starting the hole very asymmetrically, even with a guide. Rigidity helps.
E.
