If the TTS is so awesome, why do I get horrible chatter with a 3/8 end mill?

[beanbag]

I am using the TTS ER20 collet holder. Yes, I crank down the ER collet pretty darn tight, as well as the drawbar. Yes, I jam the holder all the way up until it hits the spindle nose. Yet under certain circumstances I get horrible chatter with a 3/8" end mill. To solve the problem, I just run the end mill in a regular R8 collet and the problem goes away. Is there anything I am doing wrong, or is the TTS system not that stiff because it sticks out too much?

[txcncman]

Over-tightening collets can actually CAUSE chatter problems where there were none before. Tighter is not always better. Tight-enough should be the goal.

[DareBee]

Extra length and extra joints/connections will always grant loss of rigidity.

[RTP_Burnsville]

Are you using good quality and sharp bits? Are your speed and feeds correct? Is your work piece held correctly?

I use 3/8 inch bits most of the time and have not had any issues unless one of the above was incorrect.

Robert

[philbur]

Did you try a different TTS holder?

Phil

[TXFred]

The ER collet holder sticks out a couple of inches, whereas an end mill in an R8 collet hardly sticks out at all. So it will be more prone to chatter. But it shouldn't be that big a deal unless something else is wrong.

What's your feed, speed, depth and width of cut when you get chattering?

Have you checked the runout of the end mill in the ER collet holder? Maybe you got a bad one.

Frederic

[beanbag]

The torque spec for ER20 is 60 ft-lbs. The little stubby wrenches they give you are only like 5" long, so I have to lean on them with most of my weight.

My end mills are fine.

My speeds and feeds are ok, if anything, they are conservative for carbide. Maybe 4000 rpm or less, and .001-.002 feed per tooth. Sometimes I can get the chatter to go away by dropping the rpm way down, but not by increasing the feed.

Workholding is solid.

I didn't try checking the runout.

[TXFred]

My speeds and feeds are ok, if anything, they are conservative for carbide. Maybe 4000 rpm or less, and .001-.002 feed per tooth. Sometimes I can get the chatter to go away by dropping the rpm way down, but not by increasing the feed.

I didn't try checking the runout.

Definitely check the runout. With those chip loads, if the tool holder is putting 0.001 - 0.002" of runout into the end mill, then one flute is rubbing while the opposite one is taking twice the chipload.

G Wizard says that you should be running 5100 RPM (Maximum speed for the 1100) and 61.2 IPM on a slotting cut at 0.1875" depth. That's a chipload of 0.003 for a two flute end mill. This is assuming that you're cutting Aluminum. You didn't specify the metal.

If you're using less than 50% stepover, then the feed needs to increase even more.

Unfortunately, you haven't given much information to work with. It would be a big help if you would tell us your numbers. Just saying that your end mills are fine and approximating feeds and speeds may seem OK to you, but it doesn't give us any information to work with. Remember, some people think that Harbor Freight end mills are good end mills.

Can you tell us:
Brand of end mill.
Number of flutes.
Exact feed and speed.
Depth of cut.
Width of cut.
Type of metal you're cutting.

All of that will help us figure out the problem.

Frederic

[crawley]

you aren't taking enough material with each cut. IPT should be .003 at least, that is why you are getting rid of the chatter by lowering the speed, you are effectively increasing your IPT. I run 3/8" carbide all the time at 5100rpm .15doc 46ipm (.003ipt) with stickout of up to 1.5 in TTS and I have no chatter issues. The TTS end mill holders do seem to work better than the collet holders in my experience.

[philbur]

Did you try a different TTS holder? (and collet)


Phil

[hall6ppc]

I was having some minor problems with chatter with my as well 1100 , even with Conservative feeds and speeds . I found the problem to be that my Tormach R8 collect was a tad bit to long. My TTS holder would bottom out on the collect rather than the spindle nose when fully tighten . I re ground the end of the collect of about .015 and the chatter went away .

Rmiller

[HLF Ordnance]

I had chatter issues with a 1.5" LOC and stick out with the TTS ER20. The endmill specs: 3 flute, carbide, 45 deg helix, with ZrN coat.

I run it at 5000rpm and 20 ipm .125" depth and .1875 step. It doesn't chatter constantly but when I changed to a TTS endmill holder all chatter stopped.

My guess is it is the length of the ER20 holders. Why are they SOOO long anyway???