Carving bits

[JWheeler]

I own a Carvewright machine and have been using the 1/16 carving bit that came with the machine for awhile now. I have made a number of Lithopanes and lately the quailty has gotten worse. I decided to get a new carving bit. I bought one from Sears for their Compucarve machine ( bit and adaptor ). It appears to be a four flute bit. I tried to use it on a Litho and it cut deep in the corian and dropped out of the QC. I loaded the old carving bit , carved with no problem. I tried 3 different patterns , same results.

[Jeff_Birt]

I have used the four flute bits for a few years with no problems. I would suspect that there is an issue with the new adapter not letting it seat in the chuck correctly.

[JWheeler]

should I try putting the new bit in the old adaptor.

[bergerud]

The QC holds the bit adapter using centrifugal force. The weak spring is not what really holds in the adapter. The two half rings inside the top of the QC are thrown out into the taper of the outer sleeve and force outer sleeve down to secure the adapter. Ingenious really. The problem is that the QC can simply let go of the adapter if the rpms drop. I have had this problem when carving both wood and cast acrylic. If the carving starts with a straight cut in the y direction, the machine plunges in and moves too fast. The rpms drop and the tapered helix of the bit, wanting to screw into the board, simply pulls the adapter out. Different bits are more helical than others. I'll bet your new bit is more has greater pitch than the old one.

A solution to your problem might be to add feather or draft to the pattern so your carving starts less aggressively.

For cast acrylic, the pull out was so bad, I had to use a non tapered bit.

I consider this a programming bug and would have reported it except I was too scared to experiment and confirm. Maybe LHR should adjust the program to start carves more gently. Better safe than sorry.

[Jeff_Birt]

Actually the detent balls hold the QC in place. I've had one bit fall out when I first got the machine. Two + years later and it never happens no matter what material I use. If your bit is falling out you either did not put it in right or your have a QC/adapter problem.

[bergerud]

I am not a fool Jeff. Of course it is the balls which hold the adapter. I am describing the mechanism which applies the force to the balls. The outer sleeve is tapered on the inside and forces the balls in when it is pushed down. There is a weak spring which pushes the sleeve down. The spring is what you push the sleeve up against when you insert the adapter. If the adapter is pulled down hard, the sleeve can move up against the spring and release the adapter. The half rings prevent this from happening when the QC is spinning. The half rings fly out against the tapered top of the outer sleeve and actually push it down.
Under heavy load, the rpms drop and only the spring holds the balls. With the vibration, side load, and pull down from the helix, the adapters do pull out.
I have had this happen to me as have many others. In my case, the adapter and QC were new and undamaged (even after the event).

[Digitalwoodshop]

I see you are new on the forum. The QC is fussy and you must be sure you have it locked in place or the bit will come flying out. I have had it myself.

There is much posted about the QC... Some leave it dry, others like me use lots of 3 in 1 oil to keep it loose so it will hold the bit holders.

Your machine is most likely still in warranty but at some time I would plan on buying a after market ROCK chuck to replace the QC. Not sure what LHR's policy is about using a ROCK while in Warranty???

Every new QC you buy is money that you could have put toward a ROCK chuck.

Good Luck,

Don't forget to read Tips and Tricks too,

AL

[bergerud]

Sorry for the diversion JWheeler. Could you give us a sample or describe the carving? Also give the version of designer you are using. When I experienced this problem, my carving started with a straight edge about 1/4 inch deep and 8 inches wide in cast acrylic. Carving on best if I remember. The machine made a light pass first and then dug in, nearly stalled the motor; the bit pulled out, drilled over 1/2 inch into the work and broke.

[JWheeler]

I am using ver 1.134 . I was carving 1/4" corian 5"x8". What you described in your post sounds exactly like what happened. As far as the adaptor being seated in the QC , the old bit and adaptor worked fine on the same patterns that the new bit and adaptor would not work on. Hope this helps.

[unitedcases]

I had this happen a while back and strangely enough it was the encoder in the back of the z motor? The one on the back of the truck itself, it is what actually controls the up and down motion. Anyway there is a "photocell" that will get a little bit of dust in it. I had to remove three screws carefully and just give it a quick shot of air. I had a board that really got chewed up and that is what it was. I could probably look at the machine and describe it better if you want. But that is just my two cents.

[bergerud]

I need to know more. When you say old adapter and new adapter do you mean bits or adapters? Was the carving being carved on normal, best, or optimal?
I believe that the problem is caused by too fast a cut rate and I want to reproduce the situation.

[JWheeler]

I have the original carving bit and adaptor that carves fine except for the quailty. I bought a new bit and adaptor set from Sears. That new bit and adaptor are the ones causing the trouble. I was carving in best mode. The original bit is 3 flute , the new bit looks to be 4 flute.

[bergerud]

I could not get the "plunge in and cut too fast" behavior using ver 1.150 so I when back to ver 1.134 where I did witness the behavior. (I used soft fiber board and a collet chuck for the test.) I simply cut a 1/8" slot 6" wide at 1/4" depth on best. Version 1.134 makes some shallow passes and then two fast passes on the way down to the 1/4". These fast passes are the ones which I have seen cause y axis stall and bit pullout. During these passes, the bit has to cut in front and on both sides at once. (Brutal when carving plastic.)

Version 1.150 behaved differently: fast shallow pass, slow passes to get down and then faster passes when down.

The good news (I hope) is that if you upgrade to ver 1.150 your problem could be over.

This seems to be a bug that has been fixed. Let us know how it goes.
(Keep your finger on the stop button!)

[JWheeler]

Thank you and I will give it a try and let you know the results.

[bergerud]

Maybe I am wrong. There is now another tread (http://forum.carvewright.com/showthread.php?t=12079) going on the same problem with 1.150.