# Gilbert Erector set part number CO lamp socket



## BGHansen (Jan 12, 2019)

Another Erector set reproduction part string.  This one is for part number ‘CO’ lamp socket which was included in the largest sets from 1924 – 1932.  Being used in just the largest sets means not a lot of sales volume, but the few I’ve made in the past have sold for $10 - $15 each.

The “CO” has a fiber material base with a brass contact strip at the center and a coil of copper wire that the bulb screws into.  The base is made from a pair of the fiber disks, probably to make it a little more substantial as the fiber material is pretty brittle.

The fiber disk has an arc 90 deg. long cut into it for an anti-rotation feature of the copper wire socket.  I’ve made this before by hand drilling a series of holes, then filed down the peaks.  Also drilled the end holes, mounted the disk on an arbor in the mill vise and manually rotated the disk to cut the arc.  I planned on making a dozen or so of them so came up with some new fixturing.

Started by punching out the disk blanks (1 ¼” diameter) on the Roper Whitney #218 punch press.  Then used a fixture to transfer punch the location of 4 holes.  The “CO” have holes at 3, 6, 9 and 12 o’clock, opposite sides are 1/8” and 11/64”.  The 1/8” holes are used for 4-40 screws, the 11/64” screw for 8-32 screws to fasten the base to a model.  Punched the holes with a pair of RW No. 5 hand punches.








Made a holding fixture for my Bridgeport CNC mill for cutting the arc.  Spot drilled, drilled and undersize reamed holes for a pair of 1/8” dowel pins.  Drilled and tapped a 5-40 hole in the center for a hold down screw.  In use I found the 1/8” pins held the disk down well, so didn’t end up using the screw.








Then made a mandrel on the lathe to wind the wire around.  Measured the ID of a commercial E10 lamp socket with drill bits and went with that diameter minus a few thousandths for spring back after winding the coil of copper wire.




Made a holding block for the copper wire and mandrel.  Used a piece of hex stock, center drilled and drilled holes for the copper wire end to slip into.  I figured as long as the mill was set up I’d drill extra holes around the perimeter just in case I broke off the copper wire in one of the holes.  After the mill work, went to the lathe to drill a center hole in the hex block that the mandrel would slip into.








In use, I strip a length of #14 copper wire and bend a 90 on the end.  The end is slipped into one of the holes in the hex block and 4 winds are made around the mandrel.  Mandrel is pulled from the hex block and a couple of bends are made using Vise Grips to hold the copper wire.  Hard to see but I hand-scribed an arrow on the top of the block as a reminder for the wind direction.  Yup, made a few LH thread sockets in the past . . .








I didn’t take photos of the brass contacts, but made those from 0.015” brass.  Cut strips of brass on my shear and scribed in the hole location and length.  The center tip has a tab bent up to contact the center of the bulb.  Used a nibbler and Pexto flange bender to cut/bend up the center of the contact.




Again, not a big volume part, but gave me a chance to get in the shop and improve throughput should I need to make more.  Thanks for looking.

Bruce


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## RJSakowski (Jan 12, 2019)

Nice work, Bruce.  I would imagine that it is getting difficult to find the formerly common incandescent lamps for those sockets.


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## BGHansen (Jan 12, 2019)

RJSakowski said:


> Nice work, Bruce.  I would imagine that it is getting difficult to find the formerly common incandescent lamps for those sockets.


Hi RJ,

Thanks and yes, they are a bit tough to find.  Gilbert used brass lamp bases which are virtually impossible to find.  Go figure, they're now mostly made from brass, but then nickel-plated.  Muriatic acid strips the nickel in a flash.  

They still are available on eBay as E10 lamps which have a 10 mm diameter with a 2 mm pitch thread.  I think the old standard must have been 3/8"-13 tpi.  The fit is so sloppy and they're only a few threads so the mis-match isn't a problem.

Bruce


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## RJSakowski (Jan 12, 2019)

BGHansen said:


> Hi RJ,
> 
> Thanks and yes, they are a bit tough to find.  Gilbert used brass lamp bases which are virtually impossible to find.  Go figure, they're now mostly made from brass, but then nickel-plated.  Muriatic acid strips the nickel in a flash.
> 
> ...



I see that Newark still carries the brass base lamps.  https://www.newark.com/w/c/lighting...ults/2?lamp-base-type=e10-mes&st=incandescent


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## Mark Needham (Jan 12, 2019)

E10 is about 20 thou larger..????? technically 10mm, must be closer to the 3/8" than we think?


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## BGHansen (Jan 13, 2019)

Mark Needham said:


> E10 is about 20 thou larger..????? technically 10mm, must be closer to the 3/8" than we think?


Hi Mark,

Yup, close enough for these parts.  The incandescent sockets and bulbs have a pretty loose fit to each other.

Bruce


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## BGHansen (Jan 13, 2019)

RJSakowski said:


> I see that Newark still carries the brass base lamps.  https://www.newark.com/w/c/lighting...ults/2?lamp-base-type=e10-mes&st=incandescent


Hi RJ,

Thanks!  The original bulbs were 2.5 V (give or take).  I see they that Newark is out of stock, but I'll check when they expect to get more.

Bruce


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## Eddyde (Jan 13, 2019)

McMaster Carr stocks many of those oddball miniature and other sized lamps.


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