Note that if you wish to access the full sized image from my camera, click on one of the thumbnails, and when it comes up edit the contents of the locator bar to change "/smaller/" to just "/" and click to load that URL.

Exactly how large it will be depends on which camera it came from, and whether I have done any cropping and editing of the images. (Normally, I will not have, so you get what the camera got.)

This is to document some ways of dealing with a Wheatstone from the period when the button bodies were of a plastic which became brittle with time, and which eventually wind up with a number of broken buttons (and with the owner shifting in less frequently used buttons until time can be found for the fabrication of replacements.

As it turns out, parts of the most recent buttons to fail were available, but not enough to make a full set using the original caps.

• dsc_1737.jpg Date: 2005:06:09 19:39:33
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  Here are three (of the seven) cap/body pairs remaining. The plastic is one which does not accept gluing gracefully, and the point of failure is (of course) at the weakest point.

• dsc_1740.jpg Date: 2005:06:09 19:41:18
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  Here are three of the replacement bodies (which I made of black Delrin) at the first stage in their production. Turning of the guide pin on the end, followed by turning to the diameter of the failed button bodies.

  The step marks the end of the part which is to be retained, and the angle (or edge) is formed by the shape of the parting-off tool, and is not significant.

• dsc_1742.jpg Date: 2005:06:09 19:42:43
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  This photo shows similar work, except to make entire buttons to replace the missing ones. I have both natural (white) Delrin and black.

  The owner of this instrument wanted the black for all buttons, but I made a few white ones at the same time, just to compare the two.

  Both of these were made, to this point, on a small CNC lathe which handles all of the steps with a minimum of crank turning. FWIW, it is an Emco-Maier Compact-5/CNC, and is well out of production by now. (As it was when I got mine.)

• dsc_1743.jpg Date: 2005:06:10 00:11:39
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  Here, we have the caps, after the remainder of the plastic bodies has been drilled out.

  For this, I used an old Unimat SL-1000 lathe, with the watchmaker's spindle (WW-series collets). A 5.0mm collet (marked 50) is just the right size for gripping the caps.

• dsc_1747.jpg Date: 2005:06:10 21:31:04
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  Here, I have made a depth stop for the Unimat WW collet, so I can turn the body back to a diameter which will press-fit into the caps.

  I have found that a diameter of 3.80mm works well when pressed into the caps with an ID of 0.149" (3.784mm).

• dsc_1749.jpg Date: 2005:06:10 21:32:45
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  Here, we have all seven caps after having new bodies pressed into them, plus one spare body.

  The pressing was also done in the Unimat SL-1000 with the watchmaker's collet spindle. The cap was held in the collet, and the body was pressed with a drill chuck in the tailstock, adjusted for a loose grip on the guide pin at the bottom of the body.

• dsc_1758.jpg Date: 2005:06:11 18:29:49
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  Here, we see the cross-hole drilling, using a sensitive drill press, and a fixture which I made for the purpose years ago, which is bolted to the table of the drill press.

  The fixture is double-ended, with the other end being the proper dimensions for the metal Lachenal buttons.

  The button lies in the V-groove, assuring that it is centered under the drill bit, which is fed through a hole in the fixture during the clamping.

  The guide pin passes through a hole in the end plate, assuring that the hole is gauged from the base of the body, not from the length of the guide pin.

  The drill press can hold no larger than a 1/8" shank (3.0mm) bit.

• dsc_1750.jpg Date: 2005:06:11 18:22:21
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  Here, you see one example of each type (cap on body, natural, and black Delrin entire.

  The cross-hole has been drilled in all of these.

  I appear to have forgotten to take separate photos of the buttons after machining the crowns on the capless ones, so this shot will have to do.

  This was done in another lathe -- a Taig (those in the UK call it a Petol, I believe), with the watchmaker's spindle installed in that one too. (Again, a 5.0mm collet.) I used this one instead of the Unimat because it was already set up with a formed tool for crowning the screws for concertina endboxes, and the crown was right for the buttons as well.

• dsc_1761.jpg Date: 2005:06:11 19:05:55
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  Now, we see the fixture moved to a full-sized drill press to allow the use of a single-flute countersink with a 1/4" shank (too large for the sensitive drill press).

  I am considering taking one of these countersinks and turning or grinding the shank down to 1/8", so I can use it in the sensitive drill press for this purpose. It would save some setup time, and allow a more precise depth adjustment than this particular drill press allows.

• dsc_1766.jpg Date: 2005:06:11 21:57:30
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  A length of felt folded over and drawn through all of the cross-holes to serve as bushings for the lever in the concertina.

• dsc_1768.jpg Date: 2005:06:11 22:14:45
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  The completed buttons, after the felt was cut off and a small jeweler's screwdriver was used to smooth the felt into place from both sides to improve the center hole.

  This will probably be necessary again before installing the buttons, as the felt will probably swell up a bit while it is in shipping.

So -- above I have documented how I made some replacement buttons for a Wheatstone. There are other ways, and the best ones for an individual are developed for the tooling which he has available.