Fitting WIT to already fixed trackwork

Add your comments and questions about the mechanical control of model railway signals and points particularly by the WIT (wire-in-tube) method.

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Fitting WIT to already fixed trackwork

Post by modadmin »

We are sometimes asked if it is possible to fit our Point-wit mechanism to existing trackwork that has been permanently fixed.

The answer is that it usually is, although it can be a bit tricky.

Point-wit needs a hole of about 8mm (5/16") diameter directly under the operating hole in the tie-rod of the points. You can achieve this by drilling up under the points - BUT YOU NEED TO BE VERY CAUTIOUS TO AVOID DESTROYING YOUR POINTS. Here is a recommended procedure.

Firstly, you need to know exactly where to drill the hole. The most secure way of doing this is to drill a small (smaller than the hole in the tie-rod) pilot hole down through the board using the hole in the tie-rod as a guide. Ideally, you should use a pair of matchsticks or similar to wedge the points in the mid-way position. (Slide the matchsticks between the point blade and stock rail on each side.)

You can then drill the full sized hole up through the baseboard allowing the drill to follow the pilot hole. BUT YOU MUST USE A DEPTH STOP. Without a depth stop, the drill will be uncontrollable as it breaks through at the end of the hole and will almost inevitably destroy your points.

If your drill does not have a depth stop, then there are other options.

You may be able to insert the drill bit sufficiently into the chuck that the protruding length corresponds to the required drilling depth. (For normal length 8mm drill bits this is unlikely to be workable.)

Alternatively, you can use a length of tube to surround the brill bit while allowing only the required depth of drill to protrude beyond the tube. If there is no suitable tube to hand, then cardboard may be fashioned into a stop by wrapping it around the drill bit several times and securing it with tape.

Drill bits have a conical point and therefore you may need to carefully "dig out" any residual material at the top of the hole. Probably the safest way to achieve this is with a tiny chisel or "sharpish" small screw driver. DON'T WORK THE TOOL VERTICALLY otherwise you are likely to overshoot and damage your points. Rather, use a sideways scraping action levering the tool against the bottom edge of the hole.

Alternatively, if you have a suitable slot drill or end mill available, it may be possible to complete the hole using this.
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