My desk chair here at Roseholme Cottage's ground floor Retrotechnologist HQ (as opposed to the basement ham shack and workbench) is a fair match to my big old oak desk: it's an old-fashioned wooden desk chair, assembled from a kit over a decade ago.
As the years have passed, it has picked up both "character" and damage, the latter being a broken screw holding a stabilizing metal piece to one of the legs of the "truck," and subsequent damage to the 3/8" hanger bolt that fastens that leg to the hollow central post. The result was a rolling chair that tended to go caterwampus without constant attention.
Last week, the lagscrew half of the hanger bolt chewed up the last of the wood it was screwed into -- which meant that tightening the nut and bolt half just pulled the thing loose.
It was time to take action. The stabilizing piece problem, which I had long attributed to the screw bottoming out against the hanger bolt, turned out to be a broken-off part of the original screw. Since it was at 90 degrees to the hanger bolt, that meant there was a fairly simple fix. Here's what it looks like:The fix is hidden: I drilled out the broken screw and glued in a section of dowel, right under the tab on the circled portion; it was more than long enough to intersect and replace the wood worn away where the hanger bolt had been chewing at it, and since I used a 3/4 dowel, wide enough for that job too.
You can see where I scratched up the wood finish on the underside of the leg, trimming the dowel with a flush-cutting saw.
Since there was a little bit of chewed-out hanger-bolt hole left, I drilled it out, too, just enough to have a flat-bottomed hole in which to glue in another short dowel to fill it.
(There's a trick to getting a better bond with smooth dowels: take a pair of slip-joint pliers with nice teeth and notch up the dowel so it will have a rougher surface. Of course, always clamp it it in place while the glue dries).
Twelve hours later, once the glue had dried, I trimmed the dowels flush, held the leg in place and marked it for the stabilizing screw, drilled and installed that screw and then used a pencil stub to mark the bigger hole for the hanger bolt. Drilled that square (by eye), screwed the hanger bolt in, reassembled and hooray, I had a chair again.
But there's one trick here that I didn't tell you. Did you notice? Hint: it just about requires one of these: Remember that broken-off screw? How'd I drill that out of much softer wood -- making a 3/4" hole, yet -- without some kind of damage to the drill "bit,"* the wood or myself, hey?
I cheated. I dodged it. If you have a drill press, you can clamp the work to the table, take the centering drill out of a hole saw of the proper size, and zzipp! drill around the offending bit of metal. The plug broke off at the level of the worn-out hole for the hanger bolt and a sharp 1/2" wood chisel made short work of the remainder.
The little centering drill is there on a hole saw for a reason. Unless you have amazing upper body strength, you can't hold the thing steady while it cuts without it. But a drill press and a good clamp will do the job and make it seem easy.
On the subject of hole saws, shop tricks and "making it look easy," Starrett makes a hole saw arbor (that's the part that holds the cylindrical saw) that replaces the centering drill and allows the assembly to hold two hole saws concentrically. It's an "oops" arbor, for when you holesawed too small a hole; it centers the new size on the mistaken size. They're inexpensive, too -- I figure mine paid for itself the first time I needed it and had it.
(For the observant: yes, my tabletop press has some surface rust. It was a little that way when I bought it. I'm working it over with oil and brass brushes but I haven't got it all yet. I got the table, the base, the chuck and made a start on the column -- need a bigger brush, I was using a worn-out bore brush).
* If it has a square or hex cross-section shank and goes in a brace, you call it a bit. Otherwise, those hole-making spun-around thingies you chuck up in press or a hand drill are themselves drills. "Drill bit" is a horrid neologism.