lotsa chatter...

[szechuanking]

i'm attempting to cut pockets in poplar and mahogany. i am taking painfully shallow passes and still ending up with a lot of chatter. does anyone have a proven feed/speed rate that i could use?

thanks in advance...

[ger21]

Feeds and speeds are only part of the equation. Tooling and machine rigidity can be at fault as well.

What kind of machine, and what bits are you using?

Can you post a pic of the problem you're seeing?

[szechuanking]

Feeds and speeds are only part of the equation. Tooling and machine rigidity can be at fault as well.

What kind of machine, and what bits are you using?

Can you post a pic of the problem you're seeing?

it was purchased from ebay. here are the specs...

6061 amuminum construction
X = 24 ¼ inch
Y = 49 inch
Z = 4 ¼ inch
X = 20mm and Y, Z 16mm Ball Screws
3 = Nema 23 270 oz stepper motors
3 = precision motor couplers
1 = 4 axis's controller 3.5 amp
1 = 24v, 14.6 amp power supply
1 = db25 cable
1 = Bosch Colt router mount or Standard round Spindle mount

im using amana solid carbide 2 fluted 1/8" and 1/4" downcut spiral bits

while the machine is rather light (under 200 lbs.) it feels very rigid.

i dont have a photo at the moment but the best way to describe it would be a wavy pattern. upon increasing the rpm the chatter marks have decreased in width but remain noticeable

[ger21]

If it looks like a rippled edge, it could be tool runout.

[EBC]

try conventional cut at say .02 to .04 larger than the vectors then use a cleanup pass at full depth with a climbcut to vector size

[szechuanking]

could the downcut spiral be to blame? maybe it is pushing the chips down forcing the bit to jump?

[szechuanking]

If it looks like a rippled edge, it could be tool runout.

i seem to only get it when i cut along the grain as as opposed to accross the grain. could it be an issue with that axis alone. the ballscrew spans 49" on that axis could that contribute to the problem? there are just so many variables im not sure where to start.

[ger21]

could the downcut spiral be to blame? maybe it is pushing the chips down forcing the bit to jump?

Not likely.

i seem to only get it when i cut along the grain as as opposed to across the grain. could it be an issue with that axis alone. the ballscrew spans 49" on that axis could that contribute to the problem?

Does it do it along the entire axis, or only in one spot?
A wobbling or whipping screw can cause that.

Try turning the board 90° and see if it does it on the other axis?

[szechuanking]

Not likely.



Does it do it along the entire axis, or only in one spot?
A wobbling or whipping screw can cause that.

Try turning the board 90° and see if it does it on the other axis?

i tried an upcut spiral and was able to rule that out. i also did as you suggested by rotating the workpiece 90 degrees and sure enough, the same chatter along the y axis. i also moved the workpiece down toward the middle of the table, same result. i'm wondering if the span of 4 feet along that particular axis is just too long to stay rigid because the cut along the cut along the 24" x axis is perfect...