I have a belt driven cnc mill spindle. It is a CAT40, 10000 RPM spindle. I am told it is a 10K spindle with 16K bearing. It is oil chilled. I have had it rebuilt twice and both times it comes back to me with .0003" play at the spindle nose. It takes some pulling or pushing by hand, no pry bars, and I can get the movement. I move it and it stays. I spin the spindle a few rotations and it goes back to running true. It runs so true I can not get a reading. The spindle sound great and has very little expansion when warmed up. Around .0005 in Z and I run it 10K all the time. Here is the story of the rebuild. 1. Sent spindle off because it was going out. Making noise and cutting horrible. I called out a machine tool repair guy to do the exchange. Sent the spindle to a re-builder, they said the spindle was full of oil so this is why it went out. I got the spindle back and had it installed by the tech. We were not able to fire the machine because I changed the straight tooth belt to a Conitech Silentsync belt and I had to make a new motor plate to adjust for new belt size. He left and I fired the machine the next day. All went great getting it to turn. Started cutting metal and it had a bad finish when side milling. Found .0003" Called the re-builder and he said send it back. 2. When I got time I sent it back ( I removed the spindle this time) and it was full of oil again. The warranty was void. I get it but I am not happy. The tech that changed the spindle the first time never checked to see if the air bleed for the spindle was working. It was not so that cost me $6000 more. Got the spindle back and the spindle had the same .0003" play and of course it cut bad. I am now getting told IT IS OK THE HAVE PLAY IN YOUR SPINDLE. That makes no sense to me. None of my other machine have any play in the spindle. any thoughts????? This is driving me crazy. Before this it was almost impossible to get a bad finish on this machine.
I have attached a photo of where I am measuring. Manga base on the spindle housing and the tip in the spindle shaft. I am not measuring slack in the table or tool holder.
just rebuilt a cat40 spindle /now it is loose
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