Thread: Mahr Zentimess Oil Change

No it's not the latest model Skoda. I know that a couple of forum members have similar indicators and if this helps to rescue one of those indicators down the track, then it will have been worthwhile submitting this post and wrestling with the camera and tripod.

I had eagerly been waiting for the arrival of the indicator I had bought on German Ebay. I already have a 1um Mahr Millimess indicator and I was after something a little less sensitive to use on my mill. So when I opened the package I was pretty disappointed to find that the needle didn't move. The spindle moved but not the needle.

So I partially dismantled it. The cause of the lack of movement was the dried out lubricant in the gear pivots. The needle did start to move sluggishly after repeated pumping of the spindle which suggested no mechanical damage. The screws securing the face are two different lengths.Take heed. Two small countersunk screws fasten the anodised dial face and when these are removed, I found that pushing the spindle so that the needle is in a 12 o'clock position, allows the removal of the face without the needle striking the protruding stop on the face. The gear train is sandwiched between two plates. Non of the screws on the upper plate need to be touched. On the larger rear plate, there are 3 spring loaded screws. They provide a movable mount for the large plate which is itself, spring loaded. This movement is required for the fine adjustment of the needle.

After removal of the sprung fixings and the plate tension spring from it's housing mounted pin, the gear assembly can be removed. I did this ar.. about. I used a screwdriver to lever the spring loaded plate away from the fine adjuster. This adjuster has a cross dowel that needs to be under the plate to allow the plate's removal.

I did not feel adventurous enough to dismantle this assembly. There is a fine hairspring providing tension to the needle . I could not see how I would be able to accurately reset the spring tension if I progressed further with the dismantling.

I have a book written by a fellow, Michael Yamamoto titled "Repair of Mechanical Dial Indicators and Calipers". He recommends the use of acetone or lacquer thinner as a cleaning solvent. I used acetone. I poured it into a clean sardine tin to a depth of about 6mm then sat the assembly in it making sure the needle was not immersed. Moving the rack lever in and out quickly resulted in free movement of the mechanism and the needle. Blowing it dry resulted in absolutely no movement. This was remedied with the application of a small amount of watch oil to the pivot and gear teeth. I used the fine point on my tweezers to apply the oil.

Reassembly was straightfoward. The indicator functions properly. Well worth the minor overhaul. Now I have two Mitutoyos to deal with, an altogether different species.

BT