Saturday, May 21, 2016

Roadside Find -- A Pole Lamp With No Base

This pole lamp looks pretty decent, but it has no base, and the line cord has been snipped off. On the plus side, the switches and sockets all appear to be in operable condition.

There's no maker's name on it, but it does say "Made in China" on the wattage labels inside the reflectors. (Surprise, surprise.)

I can fabricate a new base for it, but there's a little challenge presented where the base attaches to the pole. Here's a view of that.

The jam nut that's needed to secure a base is missing, and that's an odd size of threaded nipple. It's M12 x 1.0mm pitch. I'm unlikely to ever find a nut to fit that. What I may do is remove that brass ring nut from its current location, Loctite the nipple in place at the end of the pole and use the brass ring nut as a jam nut underneath my fabricated replacement base.

A New Base

It would be nice if I could faceplate-turn a wooden disk for a base, but my woodlathe's swing is only 10", and it doesn't have outboard-turning capability. I'd like the base to be about 12" in diameter, so the lamp won't be at all tippy. I'll have to bandsaw a disk, and disk-sand its edges to smooth roundness on a tablesaw disk-sanding jig.

Here's what I have on hand for a base blank.

It's pretty wretched. It's a salvaged motor/grinder mount from an antique grinder that outlived its usefulness. But its thickness is good at 1 1/8", and it's nice and flat. It will have to do.

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And here's my bandsawn blank.

Now I have to rig a circle-sanding jig on my table saw so I can more-or-less 'perfect' the blank's edges.

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And here's a view of the just-completed edge sanding job on my tablesaw.

That's a rude, crude arrangement if ever there was one, but it did the job.

Remaining to be done are the following:
  • Round over the upper edge of the disc to 3/8" radius.
  • Round over the lower edge of the disc to 1/4" radius.
  • Bore through the centre of the disc 15/32" to accept the 12mm nipple.
  • Fill all the holes and surface defects and sand the thing.
  • Come up with a set of 'feet' to elevate the bottom face of the disc up off the floor. That will provide clearance for the bottom end of the nipple, and the emergence of the line cord.
  • Prime and paint the disc flat black. 
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And here we are with some progress made.

Here's a view of the fastening underneath.

(Note the oversize flat washers both top and bottom. Those are absolutely essential to achieving a firm, reliable wood-to-metal attachment of the pole to the base.)

Next up is to make a set of eight feet for it. I was hoping that Canadian Tire might have suitable ones made of black plastic, but I came up empty there. Making plastic feet would be an ideal job for a 3D printer, but I don't have one of those. I'll have to fabricate feet out of hardwood on the lathe.

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This won't be easy. As a trial effort, I made one sample of what I'm after, like so.

That was turned from a short length of 3/4" dowel held in a chuck on the wood lathe. After turning the taper, I bored it through and counter-bored it for a fastening screw. Then I parted it off. And that's where a snag arises.

Parting off multiple pieces to an exact, consistent length is not easy. I could make eight feet by the same method, but I'd be unlikely to succeed at getting them all parted off to exactly the same 5/8" length. A different approach is called for. Here's how it'll have to go:
  • Set up a length registration jig on the table saw to cut eight pieces of dowel to the same length.
  • Bore through each dowel piece on the metal lathe 9/64" -- clearance diameter for a No. 6 fastening screw.
  • Counterbore each dowel piece on the metal lathe 5/16" for the heads of the fastening screws.
  • Fabricate a mandrel that will allow me to mount each dowel piece on the wood lathe for turning the taper.
Here's my length registration setup.

It's just a scrap board clamped to the saw's table the right distance from the blade. Note that the board is positioned so that the work leaves the board before it enters the saw blade. The board must not be positioned so that the work could get pinched between the board and the blade.

And here are my equal-length foot blanks.

I cut one extra one in case I happen to botch one.

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And here they are bored and counterbored.

Next up is the challenging part -- to create a suitable mandrel so I can turn a taper on those feet between centres.

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Here's my mandrel.

Now we'll see what sort of result I can wring out of this.

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And here we are.

Eight tapered feet, all the same length.

I can't say that I did a superb job of that. My mandrel fixture left a bit to be desired, and I wasn't trying all that hard for perfection, but the result is acceptable for the purpose.

I'll do a trial installation of those feet on the lamp's base. Then I'll attend to the lamp's line cord, and complete a trial assembly of the entire lamp. Once all that has been done, I can dismantle the thing and carry on with sanding the base, and priming and painting it.

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And here's the completed lamp, ready for service.

That's not exactly its natural habitat, but it was the best place I could find to photograph it.

Here's a close-up view of the base.

The base is not absolutely flawless; if you look closely enough, its 'chunk-of-wood' origin does show through a little. But from the distance it's normally seen from, it's a perfectly acceptable lamp base -- a good example of what can be wrought from some pretty wretched salvaged material.

And here's a view of the finished underside, with the feet attached, and the line cord's emergence dealt with

Note the following:
  • The feet are attached with No. 6 x 1" round-head wood screws. It's a very firm attachment that's not going to work loose.
  • The M12 jam nut is very firmly tightened.
  • The line cord is sleeved with some tough, clear plastic sleeving where it exits the nipple.
  • The line cord is secured to the base by a cable clamp for strain-relief.
  •  The 5/8" height of the feet provides more-than-enough clearance for the nipple attachment, and the line cord's emergence and strain-relief.
All-in-all, I appear to have done a pretty decent job of getting this discard back into useable, reliable condition.


The labels inside the reflectors call for 60 watt maximum R20 bulbs. At the dollar store, I found 50 watt halogen PAR20s for $2.00 each. (By the way, here's a good explanation of what 'R20' and 'PAR20' are all about.)

LED equivalents are now widely available, and the prices, though still rather high, are within reason. The halogen bulbs do have the advantage of being dimmable; that could be a very attractive feature, depending on how this lamp ends up being put to use.

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