minimizing chatter

[Runner4404spd]

hey guys, i need some tips on minimizing the chatter on a machined surface. i am using a r-25 clone and trying to countersink a hole. the countersink part has a lot of chatter on the surface. any tips?

[Karl_T]

For chatter on something like this, try changing feeds and speeds. I'd first try more feed, less speed. Once chatter begins on a part its hard to stop it.

It would help if you could tell us which material and what tool. For example, if you're using a counterbore, I'd look to see if the pilot hole is too large. If the material is AL, it most deffinitely needs hi feed and low speed on something like this.

Karl

[RJSheets]

By chatter of the countersink, do you mean that the c'sink is not round.
You can try to adjust speed and feed of the c'sink to reduce the chatter. The other thing to try is a different type of c'sink, I am assuming that you are using a 3-flute c'sink right now. I have had good luck with an "O" flute countersink giving a good round finish. (search McMaster.com for countersink)

[Geof]

If working in aluminum do the countersink first then the hole. This way the center of the countersink is just rubbing and stabilizes the cutter. If the countersink will not penetrate, drill the smallest hole possible that will allow it to enter.

[NC Cams]

Lock the table (both X & Y) direction before cutting. THis is critical, especially if you do NOT have preloaded ball screw drive. Clearance/movement potential in the part allows chatter.

Put a bit of drag on the spindle with the lock. This prevents possible spindle chatter from spindle movement.

Suggest drilling reaming hole with locked table, then follow with countersink. Don't leave and come back unless you have real accurate screw drive - almost impossible to perfectly recenter if you move.

If the c'sink is coaxial with the hole you're trying to c'sink, you have a hard part of the battle won.... namely, even cutter loading when you put c'sink into the hole.

Ditto re: speeds and feeds above.

[mxtras]

Good stuff so far - but what about the cutter? Was it made in 'AC' (another country) out of recycled pallet banding? Is it three flute? Is it sharp? Is it TOO sharp? Too many unknowns here to really even speculate.

90% of the time when chatter is present, reducing the speed is the most beneficial change you can make.

Scott

[gar]

060124-1221 EST USA

Runner4404spd:

I like Geof's method. Use a starter drill with the angle you want for your countersink. Starter drills are very rigid.

.

[Geof]

Originally Posted by mxtras Good stuff so far - but what about the cutter? Was it made in 'AC' (another country) out of recycled pallet banding? Scott

I can answer this question: No. If it was it would have turned into a blob of squished distorted metal with no cutting edge; it would not chatter.

[mxtras]

Yeah - good point.

But it could squeal like a stuck pig!

Scott

[Runner4404spd]

ok, guys heres what i'm using. its an aluminum block with and i'm trying to countersink with a carbide cutter and its a 6 flute. now, my machine speeds aren't infinitely adjustable, i have belts. i am planning on going to a variable speed drive but i haven't gotten there yet.

thanks for the help so far

Jerry

[Geof]

Originally Posted by Runner4404spd ... i'm trying to countersink with a carbide cutter and its a 6 flute...Jerry

My approach of trying to do without any hole will probably not work; The multi flute countersinks I have used have a flat end so they will not enter without a pilot hole. Use a pilot hole about the diameter, or very slightly smaller than the flat on the end in this case.

[fpworks]

Carboloy Minimaster

Use it for spot drilling, countersinking, and chamfering. You can run it much harder than a spot drill and it will not chatter.