I’m working on a new woodworking project that involved cutting through-slots for bolts in a couple of boards. The two boards will act as adjustable arms to hold a dowel handle for a garden cart.
I have cut shorter and narrower slots using a table-mounted router for a coin bank. These bolt slots were considerably longer and 1/4' wide so I was reluctant to use the same technique. I don’t have a plunge router – which would probably be the fastest and easiest way to do this.
For a single vertical slot, make sure it's centered side-to-side and located on the upper half of the project. Next, decide where to plunge the entry hole for each slot. For a keyhole slot that will be on a vertical element of your project, make sure to locate the entry hole at the bottom of the slot. Keyhole slots are a great way to hang a picture or plaque on a wall and are cut using a router and a keyhole bit. Learn how to set up your router and cut a keyhole slot. As Paul asked, the length of the slot makes a difference. For less than 5 or 6' my choice might be a backsaw filed for a rip cut. If the work is cross grain, then scoring the edges would be done first. If it is going cross grain, being so close to the edge you may find the wood between the slot and the edge breaks away fairly easy. Drill a hole through your lumber in one corner of your slot. If possible, use a drill bit that matches the width of your slot. For wide slots, you may want to start with a narrower bit and work your way up to avoid splitting the wood. Drill a second hole in the opposite corner of your slot. Use the same drill bits you did for the first hole.
After checking a couple of woodworking forums for ideas – including one where someone trying this on a router table said the board 'shattered' (yikes!) – the general consensus seemed to be todrill out most of the material and clean up the slot later with a coping saw.
That sounded good (and safe) to me.
Since my slot was only 1/4' wide, I decided best approach was to use a 1/4' Forstner bit in a drill press to define the slot and remove most of the material, then clean up the slot with a file and sandpaper.
The shaft on the 1/4' bit was larger than the bit itself so I had to flip the board over to drill all the way through the 3/4' material. It’s probably a good idea to do this anyway to avoid tear-out unless you have a backer board underneath when you’re drilling.
A COUPLE OF NOTES:
If the slots were 1/2” wide or more, I probably would have used a jigsaw and straightedge to clean up the slots before sanding.