[Minna]

Hi,

I am turning a Wood bat on a cnc hobby machine. I am New to this and finding that when my program gets near the handle of the bat to turn. My machine begins to Vibrate and make Horrible cuts, causing the bat to snap.

My Question is, why is this happening?

Does it have to do with the cut depth/feedrate/tooling/spindle speed?
And if so how do I correct this?

Any help would be great..

Thank you.

[ger21]

Any pics of the machine? What tooling are you using? Climb or conventional cut? feedrate? depth per pass? spindle speed?

[Minna]

Couple of pics,


Feedrate has been from 8in/min to 33in/min
Spindle speed 700-1150
cut depth, 1/8in - 1/4in

Can't seem to get a smooth cut over that handle area,

What do you think?

[ger21]

You may need a steady rest, but try lighter cuts. You may need a different cutter geometry as well. Looks like a metal cutting tool. You want something extremely sharp for wood.

[Minna]

Thanks, where would be the best place to look for that sharp wood cut tooling?

[cam1]

Hi:
Some observations/comments: Nice Machine

1. Cover the ways with rags when you cut wood, the dust will get under the saddle, and stick to the lubricated surfaces.

2. Use an HSS square tool, grind it really sharp with lots of rake in all directons.

3. I sometimes use a groove turn toolpath to make long slender shapes. Groove turn toolpaths plunge into the diameter leaving just a little stock, and then retract. They remove most of the material, leaving the part ready for a finish pass. In your case you may want to break up the toolpath to rough machine the portions of the bat where the most material needs to be removed, and then do many light finishing passes. Wood is tricky, as it's very elastic, and it's whipping on you at the center. Try slowing the speed and reducing the depth of cut.

regards

[Geof]

The suggestions for the cutting tool are the correct approach; wood needs something similar to a knife edge slicing the material off.

Another approach with long slender parts like that is to turn it around, and have the handle end near the chuck. It is difficult to see if you are doing it between centers, but if you turn it around and grip a bit of extra length in the chuck you will get better rigidity near the thinnest section. Also have a split metal sleeve to grip it in so the jaw pressure is spread over a larger area.

Using this approach you finish all the turning except the top end of the handle, and do this last...very carefully, until you have almost parted it off from the length gripped in the chuck. You do finish up with a small tip that has to be hand sanded.

[Art Ransom]

A common problem is too much pressure beng applied by the tail stock causing the material to bend. From the pictures it appears that the maerial is whipping/flexing. I have turned several bats on my manual lathe and whip has not been a prblem. You speed seems ok, maybe even little slow. I woul start with changing max cut depth to .1" and finish cut to .05 with 100 IPM feed. Also you might try using a bowl gouge as a cutting tool.Keep us informed with your progress.

[Minna]

Thanks,

So I will try the cut depth to .1", Feedrate is ok at 33IPM I would like it faster however it seems like it's getting caught/skip on the wood sometimes. Is that due to the spindle speed being to low? What spindle speed do you suggest?

[Art Ransom]

I use a router on my indxer which doesen't help in your case. Also when turning manually I adjust speed so it feels right. Tear out is mainly a combunation of speed, depth of cut and tool sharpness. You will have to play around with these.

[Minna]

When cutting wood, where is the best place to come in to cut?
Right at centers/Above/Below.

[cam1]

Hi Minna:
DNC (dead nuts centered) I'm assuming that you are referring to the setup of the cutter with respect to the center of rotation. On some very heavy cuts some people take the deflection of the tool into account, and set it a touch high, so that it goes to center when it deflects. I've always set my tools on center by taking a light facing cut on a piece of stock. You are on center when the "tit" on the center of the stock is removed.

regards

[Minna]

Where can I find a center piece that will attach and run with my Zaxis on my machine, and gently apply pressure to my wood billet to reduce vibration. I need one that will change in Diameter as the wood is being cut. Is there such a device?



Thanks,

Minna

[cam1]

Hi:
It's called a steady follow, unfortunately it needs to be adjusted after every cut, as it is attached to the cross slide. Here's a question to ponder: How do the factories produce bats? Find the answer to that, and adapt it to your process (es).
Sorry to hear that it's still an uphill battle, but you've come a long way minna.


regards

[cam1]

Perhaps a spring loaded "plastic" fingers?, [careful here, especially when X axis retracts and rapids.... ]
A hand or solenoid operated retractor, in conjunction with a minimum retract value on X could work. 3 adjustable fingers set at 120 degrees....

cheers

[Andre' B]

Hi:
It's called a steady follow, unfortunately it needs to be adjusted after every cut, as it is attached to the cross slide. Here's a question to ponder: How do the factories produce bats? Find the answer to that, and adapt it to your process (es).
Sorry to hear that it's still an uphill battle, but you've come a long way minna.


regards

I worked for a place turning tapered gun barrels using one of these.
http://www.smwautoblok.de/smw-en/pro...20_221_224.pdf

It's just money!


Edit:
If you are real cleaver you may get enough info from that PDF to build something good enough for turning wood.
from that PDF to build somthing good enough for tunring wood.

[Andre' B]

Here is a vid on one bat lathe.

[ame="http://www.youtube.com/watch?v=QcBP8AXgPvI&feature=related"]YouTube - Wood Bat Making Video Diablo Bats[/ame]

And another, note the steady is on the preturned blank dia. and only one pass is used.
[ame="http://www.youtube.com/watch?v=ov3awRWfVJc&feature=related"]YouTube - Wood Baseball Bat How it's Made on CNC Woodturning Lathe[/ame]

[oreos40]

for wood a steady follow is not adjusted for each pass. There is a cutting bit that is set up to cut precisely to the diameter of the bearing that is feed across the chips can be seen if you watch to the left of the follower. this particular machine has one sizing cutter and two profile cutters. some machines will use tow sizing and two profile when they go from a piece of square stock. one poster mentioned chucking on the outside diameter of the wood and turning the handle toward the headstock this will help. your biggest problem is that the insert tool you are useing is not sharp and probably has no relief. it is probably a TNXX series. you need to get something like a TCGT with a HPsuffix. it will more than likely be a C2 grade and will be up sharp with no hone and no coating. This means it will be sharp! most metal cutting bits are not dead sharp and have a honed edge to keep them from chipping the first time they come into contact with the metal. If you look closely there is a heavy relief in the grind of the knives on the bat lathe in the vids. What you are getting is the material is being scraped off andthe bat is climbing over the cutter instead of being cut. Then go back to the rules of lighter cuts I would say you could jack the speed up to about 1800 on a 3" dia turning and be just fine. The high shear of the bit will eliminate the pull on the stock if you take lighter cuts. adjust your bit to cut at center with a flat presentation many insert holders have a negative set on the bit.

[cutsall]

There are various manufacturers of wood lathes Intorex, Locatelli that turn bats. They have square steadies and round steadies. I have succesfully turned bats on a Hapfo and Intorex with no steady. The right cutter is imperitive and it often doesn't create good results without the right wood. I always place the handle at the headstock for rigidity. Just by looking I can tell your piece is whipping from severe vibration. Contrary to metal wood will often vibrate worse with a light cut than a heavy cut. A heavy cut puts the wood fibers under tension and keeps vibration to a minimum while a light cut allows the different grain densities to bounce the piece. A typical blank has face grain and edge grain both with distinct cutting characteristics. What wood are you turning? Typical bats are Ash or Hard maple preferably with a tight grain pattern typical of slow growth higher density lumber. I have turned Beech due to its cosistant grain. If you follow the cutter recommendations experiment with depths of cut, speed, and feed The last resort is a simple board say a 3' 2" by 4" with one end resting on the crosslide or in the bed between the ways applying pressure on the piece to absorb excess vibration. But I believe you will be successful once you find that magic combination of cutter geometry, depth of cut, speed and feed and machining sequence with the right material selection. Carry on young man trial and error is the foundation of success.