Bit size limitations?

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

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?
I use the 3/8" straight bit at around .250" per pass on soft woods and less on harder woods. This is what I found when looking up paulownia However, due to a high silica content in some trees, the wood can have a strong blunting effect on cutting edges.


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. You should be able to get replacement bearings.

I would have to agree with Floyd. The wood you are using can be hard on tooling as stated and with the number of project done with the bit, it is most likely dulled up as well, if it was all paulownia. With the weight and a dull bit, I could see heavy stress on the bearings.

Did that metal damper on the lower bearing just fall out and you did not see it in the machine?

With the Damper OUT the whole head moves within the Truck....

I think you missed seeing the Damper inside the machine....

I stuffed them back it only to have them fall out again.... It was a BATTLE with the QC...

I used a 1/2” straight cut trim bit, on a 3/16” test board, 1/16” pass each time, then I switched to 1/4” cast acrylic for the finish product, even with duct collector on , it looked like it snowed in my machine, want never use that again.

Hi again! Thanks for all the replies... I see I have some learning curve to overcome. ;-)

@AL: the damper is still in place and it seems solid against the outer ring of the bearing. I can see it very clearly (for some reason better than in the newer Z-truck with CT installed). I believe it is the bearing that has become toasted. Btw, is there a way to lay one's hands on a damper ring? Seen everybody discussing bearings, but what about the damper?

@Floyd: so it was my own stupidity/impatience that killed the truck... :-( I found one page saying that Paulownia has low silica content and another that it may have high silica content. Fo reasons I do not understand I chose to believe the latter and I see (feel, I mean) that the 1/2 bit is not as sharp on the lower part as it is on the upper part. Somehow I thought that the software would adjust speeds correctly for larger bits and specified depths. I noticed though that when I carved 0.36 depth then the last 0.06 were taken very quickly... But when I took 0.2 in one step on one of the boards I noticed the flex shaft getting warmer than usual (not hot, just very warm to the touch.)

I have read quite a lot about replacement of bearings in the truck on this forum and seems like almost everybody says it is not a process that a person like me can do without erring too many times. Maybe time to learn how to. Afraid I will have the parts and pieces flying out at high speed and damaging the machine.

@myshop: Do you use dust collector? I have the insert made of metal, the Ringneck model. :-) I do not know if that could help, but I believe one of the issues can be static buildup. I have never carved anything else than pine, oak and Paulownia, MDF on a few occasions (damned stuff), but I have noticed that static buildup can be a problem. My remedy is twofold:
1. ground properly the machine frame. This will also ground the DC itself.
2. the problem remains for the intake pipe between the insert and the sucking fan. What I have done is to measure a nice length of soft copper wire without any insulation. The length MUST be shorter than the distance between the DC insert and the fan, you don't want the wire sucked in. One end of the wire gets attached to one of the screws holding the CD insert in the machine, the other end is inserted through the sucking slit of the DC so it ends in the pipe between DC insert and sucking fan. It helps take away some of the static.

Hope my explanation was understandable.

yes I have 2 of Floyd's first versions dust collectors , and a 1500cfm dust collector system next to the CWS, the problem with cast acrylic , it flakes and is hot and stick to everything.