This instructable is on identifying and fixing the failure prone EDGE Technology tramming tool.

The tramming tool is used to help tram (or true) the head on a milling machine to ensure it is square to the table.

Be aware these older discontinued models with the failure prone indicators are still being sold on amazon and ebay for close to, if not the same, price as the newer more reliable models.

Step 1: Identifying the Failure Prone Edge Pro Tram and Mini Tram

The older Edge Tramming tools will have the Aerospace MADE IN CHINA clearly on the front indicator.

The newer more reliable indicators will have the EDGE Technology logo across the top in blue letters. The Aerospace are the failure prone indicators and are easier to damage by exceeding upward travel limits.

Step 2: Failure Modes

The tramming tool has tool main modes of failure.

First the indicators return spring mount will break allowing the indicator to just flop around.

Second is the actual shaft the spring is connected too starts to drag between the brass anti rotation / alignment plates due to over travel, temperature changes, or dropping the tool causing the indicator to get stuck and not return to fully zero position after taking a reading.

Note the over-travel stop is actually acting upon the return spring guide bar and causing it to bend. The new models use a different method to prevent over-travel damage.

Step 3: Removing the Defective Indicators

To remove the indicators a 1.5 mm or similar size hex key / allen wrench is needed.

Remove the 4 screws from the rear of the tram body holding the indicator in place.

Step 4: Place New Indicator in Tram Body

Place the new indicator into the Tram body by reversing the steps.

I choose to use an official EDGE Technology replacements from their website and I also changed from .001 resolution to .0005 resolution while I was at it.

Any indicator that is of similar size and shape with holes in the same locations should work but as shown in the photos they must seat flush with the Tram body or they will no longer be centered in relation to the Tram mount and will make using the tool more difficult as reading may be slightly off.

Remove the 4 Phillips screws from the rear of the new indicator and REMOVE the rear cover. It may be discarded with the Phillips screws and the damaged indicators removed previously.

Be sure to remove the backing plate from the replacement indicators as the will not be on the Tram center-line and may make tramming more difficult as noted above. I have included a couple of pics showing the difference in mounting with the backing plate and with it removed as compared to the original.

Step 5: Differences Between the Old and New Indicators for Those Who Care

The first photo is of the new indicator.

The second photo compares the new and the old.

Note they both can still be over-traveled or bent if dropped but the newer indicator has a much longer guide rail machined into the case as opposed to the older which has a pair of brass plates and the guide is much shorter.

There is also a difference in the tips of the indicators. The newer indicator has a much smaller tip. I am not sure if this is just a model difference or because the newer is a .0005 vice .001 indicator.

Also note the phillips screw on the new style plunger is used as a travel stop vice the spring return post as on the older design.

So there you have it. My first instructable with pictures.

Any constructive criticism or comments are welcome.