Wooden Knobs: How Hard Can It Be?

[Greg Carter]

I have access to a lathe and am thinking of turning simple all-wood knobs for the V and T controls on my solid-body. Attachment is the issue. LMII and others have a brass sleeve insert with a tiny, really tiny, set screw. Not sure where to buy those inserts and no way I'm making them.

Why can't I use CA glue to attach rubber tubing to the wood knob, and size the knob hole and the tubing for a really tight compression fit on the knurled pot post? Obviously, this would not work on a smooth shaft. I think Home Depot rubber tubing would work.

what am I missing?

Greg

[Steve Senseney]

You can simply drill a slightly undersized hole, and skip the rubber (or metal) insert. If it still seems too tight, drill it a little bigger.

I have not needed a set screw for the knobs I have made. If you need a set screw, you can easily drill in the wood, and use a metal screw that would tighten with a flat blade screw driver, or a small Allen head type set screw.

[Chad McCormack]

Hi Greg. I wrap the drill bit with some painter's tape and press it snug into the hole in the center of the knob stock, chuck it into the drill press, and just work it with sandpapers. Works like a charm.

[David King]

Most pots have 6mm shafts but will measure out a bit smaller. If you drill 15/64 you will be very close. You can tighten up the fit and harden the wood with thin superglue. Alternatively you can force the split shafts open a bit with a screwdriver to get a tighter fit. I've heard of folks cutting plastic knobs apart to get the metal collars out and reusing those but that's really a sign of incipient madness. You can make nice metal inserts on a turret lathe, that's the way I do mine. Again there is nothing wrong with drilling the side setscrew hole and threading the hole with a tap right into the wood. Wood holds machine threads extremely well. I use 4-40 size setscrews which are small enough not to be noticeable. I see others using 6-32 or larger set screws which I think are overkill. Rule of thumb with threads, the finer the thread -the greater the holding capacity. It's counterintuitive but it's still true.
When tapping any holes in wood or metal that aren't "blind" holes you'll want to use a gun tap aka a spiral point tap not the hardware store variety which are pretty worthless for anything.

[David King]

Chad made mention of this earlier but what I do for a temporary spindle is to either superglue or elmers glue the knob to a steel spindle shaft (drill rod) and chuck that in the drill press or lathe for a VERY secure work holding solution. When the time comes to remove the spindle I simply heat it up the rod with a torch or a soldering iron and melt the glue. A much easier way to make the knobs is to use a plug cutter but you need the clamp down the wood and use a drill press. The trick here is to drill the shaft hole FIRST and then, without moving anything, cut the plug out around your hole. If your drill press isn't a TPOS you'll end up with a perfectly concentric knobs in a minute or two. Good luck.

[Dave Stewart]

I do much the same, in a drillpress, mainly because most knobs are way oversized for my tastes. Clamp stock securely, then I'll first just kiss the surface with a forstner bit of just the OD I'm after. Replace that with one to counterbore a pocket so the knob will fit down over the pot nut. Finally, drill for the press-fit mandrel. Rough saw/sand to shape, then fit the mandrel, & finish shaping/sanding in the drillpress. I drill up to 15/64" & have never needed to use a set screw.

[Steve Senseney]

Here are a couple of knobs I made (took me a while to find the picture)-

a small knob.JPG (13.35 KiB) Viewed 10016 times

[David King]

Dave Stewart,
I forgot all about the counterbore, thanks for bringing that up. I can't emphasize enough how much easier all of this is on a small metal lathe.

Here's a photo of some of my recent efforts:

[Patrick Hanna]

Greg,
I believe you are over-thinking the whole thing. As others have said, you can usually drill out to a nice, press fit. If not, you can drill and tap from the side of the knob for a small allan-head set screw--often a hardware store item. Or another option: If, after drilling for the shaft, you believe the fit is a little too loose, just put a dap a bee's wax on the shaft and press the knob home. The bee's wax is sticky enough to hold the knob, but will remain soft enough to easily remove the knob if that ever becomes necessary.
Patrick

[David Schwab]

Here's a photo of some of my recent efforts:

Those are very nice David. How did you do the flutes?

[David King]

Thanks David,
The flutes are done with an indexer on the milling machine using a 1/8" ball nose cutter. It's a fairly slow process to end up with a wooden wirenut.