Although my workshop is very much hand work focused, there are a couple of machines I use, and enjoy using. The drill press is one of them. I started out, nearly a decade ago, with a bench top drill press that was fine for grunt work but exhibited too much run-out for precision drilling. So towards the tail end of last year I finally upgraded to a new Jet floor standing model, which has sufficient capacity and accuracy to last me decades. The impetus for making the upgrade was the need to drill 2″ mortises through the battens of the staked work table to accept the leg tenons.
Because the mortises are drilled at an angle simply securing the battens to the drill press table will not work. And so I built the “banjo” jig Chris writes about in the Anarchist’s Design Book. Nothing fancy – just two large squares of 3/4″ ply with a pair of cheap hinges at one end to provide a pivot point. But simple is how I like my jigs, and “banjo” will provide solid service for many tables, chairs and angled holes for years to come.
To establish the correct angle for the jig, and to ensure repeatability of setting, I cut two 16 degree wedges out of some scrap pine. In doing so, I was reminded just how blindingly accurate the Bad Axe Bayonet saw is – both wedges were bang on on the right angle straight off the saw, no fettling needed. I’ve said it before, but there is some serious alchemy in this saw. Inserting the wedges between the leaves of the jig held the top leaf at exactly the right angle for the leg mortise. If I come to drill mortises using different resultant angles, then it will be easy enough to cut wedges to match.
To locate the batten on the jig, I chucked a fine brad point drill in the drill, and positioned the batten by eye so that the sight line lined up with the centre of the drill press. After loosely clamping the batten in place, I then tested the location by lowering the drill bit to the work piece. What I wanted to see was the tip of the drill bit following the sight line until it hit the centre point of the mortise. Gently tapping the batten with a mallet made very controlled adjustments until everything was lined up.
With the wedges cut, the jig clamped to the drill press table, and the batten clamped to the jig, it was game time. Drilling the mortises is straight forward, providing you take care to get the batten in exactly the right position, and are sensible about how fast you try to drill out the 2″ mortises. My own observations are as follows:
- 3/4″ plywood loves to vibrate. Bracing the workpiece with a suitable piece of scrap between the leaves of the jig and directly under where the mortise will be drilled, is essential. This will increase the stability of the jig and stop the top leaf from wobbling about when the drill bit engages. The wedges set the angle, a larger brace keeps things stable.
- Go slow. Even with a powerful drill press, drilling a 2″ mortise in hard maple is a tough job. Set the drill speed to as slow as you can, and take very small nibbles with the bit, backing off regularly.
- Clamp everything. If the batten, or the jig slips, you’re going to have a lot of clean up work to the batten, and centring the batten in exactly the right position may not be that easy
- Keep your quill and chuck spotlessly clean. Because the mortise is drilled at an angle to the work piece, for the first part of the chuck’s travel the bit will only be engaging on ine sid. Drilling a large (2″) angled mortise with a forstner bit if there is even the tiniest spot of dirt or grease on the quill will result in the chuck, and bit, wobbling when you start to make the cut, and taking to the air shortly thereafter. Ask me how I know this. Cleaning the quill and interior of the chuck will keep everything working as it should, and avoid airborne machinery. In fairness, I had wiped down the quill and chuck when I first assembled the drill press, and it has worked flawlessly on other tasks. After quickly wiping down the quill and interior of the chuck, the drill press cut the mortises without any complaint. But a good lesson is always worth learning.
All of the preparation and fussing over the set up paid off, and drilling the mortises was very straight forward. My favourite method to bore holes is still with my 1923 North Bros. brace, but on a hole of this diameter the drill press jis definitely more practical. I still need to sharpen the 2″ t-augur that arrived in November, and once I have done to I will have some experiments to see how easy it is to drill the same mortise by hand.
With the mortises drilled, it was then a matter of gluing up the leg assemblies. But for that, you will have to wait for the next post.