#711 HIGHT GAUGE
The gauge was designed many years ago to accept a #4 coupler. Unfortunately none was developed for the #711 oldtime or 3/4 couplers, necessitating eyeballing to set these. By removing the centering pin, lowering the mounting surface and drilling two holes, a #711 can be mounted.
Snip off the center post. True the bottom surface even with the level at the rail lugs. Since the coupler will be mounted directly on the pad, file or mill the mount surface to the bottom mounting pad level .332" plus the thickness of the box bottom .020" = .352". A flat diamond file does an excellent job. Scribe a center line and using the box bottom flush with the pad end, locate the center hole distance. Drill a tap hole .060" for the #1 selftapping screw provided. Mount the box bottom temporarily right side up and mark the second hole for the lug on the coupler. Drill about the same size as that in the box. If you are planning to mount the feeler gauges covered below, now is a good time to tap the large open hole 6-32.
Remove the lugs that seat the top plate from the 711 box bottom. Assemble the coupler upside down in the box bottom, without the spring, and test by mounting in gauge. To prevent sag, file the lugs down until play is minimized but still allows coupler movement. Insert spring, screw it down and it is ready to use.
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L TO R-- STANDARD GAUGE WITH EVERGREEN FEELERS
3/4 GAUGE WITH K & S CHECKING PLATFORM HEIGHT
ADDING FEELERS GAUGES
Adding the feeler gauges is very simple. Tap the open hole in the gauge 6-32. It is larger than the recommended diameter but there will be very little stress on the threads. True up the rear gauge top lightly to allow strips to lie flat. True the bottom surface even with the level at the rail lugs. Measure the height above above the bottom. This is nominally 7/16" = .4375', which will accept most box mounting heights, except those lowered .100" as used with over-set knuckles.
Obtain some various thicknesses of 3/8" wide Evergreen or K & S strips, selected to add the desired heights above the rear gauge top. They can be mixed. Drilling a #6 clearance hole (.138") in the end is easier before cutting to length desired. Dimensions and hole location are not critical, but the hole ends should clear coupler lids to permit swinging feelers out of the way to permit use of magnet height feeler pin. Be sure to debur and remove any ridges raised by drilling.
With the desired thicknesses added, measure the height to be sure. Since the 711 knuckle height is about .117" and others are around .130 - .145" and if not corrected, coupler sag often exceeds .010"; a few thousandths will not matter very much. Scribing the thickness on each will help identify it.
Lower heights may be measured with adjustableMACHINIST'S PARALLELS used with a strip of Evergreen, mounted on a length of track.
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