Hi, everybody!


I seem to have ruined my Z-truck bearings (the ones called 6000 and 6002 = upper/lower on the spindle), probably by using a bit that was too large for the machine.


I wanted to carve away 3/8 of thickness from my carving surface by using a straight 1/2" bit called "bottom cleaning" bit. The difference between this and a regular straight 1/2" bit is the bottom cutting edge that goes all the way, instead of leaving the center without cutting edge.


My pass depth was set to 0.2" which I thought was OK given the size of the bit. The shank was 1/2", which added to the rotating weight, of course. The wood was paulownia. I did maybe 4-5 projects using that bit as part of the projects, the other bits being the regular 1/16 carving, 1/8 cutting and V 90degree bits.


At some point I noticed the pitch of the sound change and I also noticed all of a sudden terribly bad carving/cutting quality, cuts smelling burnt paulownia (yuck!). When I checked the movement of the cutting bit, the bottom of the cutting bit could be moved by hand maybe 1/32# (left-right,forward-backward) and I could feel some barely noticeable movement in up-down direction. But just barely.


I still use(-d) the QC, just because I am lazy and have quite few QC adapters. I tried to remove the QC and was extremely surprised that I could unscrew it with quite a little effort, as if there was no threadlock at all. Anyway, I have the QC out and have tried it with my adapters, no movement at all. Firm as rock. I have also the Z truck out and I see that there is some very, very slight movement of the spindle in the bearings. So I guess the bearings are goners.


Now to my questions:
1. the software allows for 1/2" (diameter) straight carving bit, although none is being sold by LHR. Was that too much for the machine? What bit sizes should I use for bottom cleaning?
2. what options should I consider for the future? LHR do not have refurbishing of Z-truck what I could see, just a new truck for $200. It seems though like waste to throw away the old truck just because of two bearings that cost less than $10 apiece.


Any words of advice will be welcome...

And, btw... Yes, I have read about Rock, CT and MuscleChuck. And yes, I have just installed a brand new Z-truck with CT, just waiting for the loctite to harden. But I am still reluctant to throw away my old trusted QC, maybe because bit switching was so easy (even with the dusting system installed.)

Have a nice day, everybody!

/Z