articulated hollowing system chatter ??

[Bill Bolen]

I use a homemade articulated hollowing system (pics posted months ago) and have a question about chatter. When I get down to 7 1/2" to 8" I start getting a bit of chatter. I think it may have to do with the size of the boring bar bit holder as much as length over the tool rest. I use a 5/8" bit holder and am wondering if the chatter could be eliminated by going up to a 3/4" bar for that long reach? any insights are appreciated....Bill..

[David Walser]

Bill,

The reason people use bigger bars is so they can reach farther over the tool rest without getting chatter. So, without using your system to know for sure (in other words, I'm about to make a wild guess), I'd think using a thicker bar would enable to reach deeper without chatter. Note: Reaching farther over the tool rest increases the forces your hollowing system must absorb. It may be 8" over the tool rest just generates too much leverage for you set up. (In other words, even though I disclaimed everything I was about to say by pointing out I was making a wild guess, I still felt the need to waffle. I've been paying too much attention to politics lately.)

[Dick Strauss]

Bill,
You may be able to use a box tool rest that extends into the HF to extend the support for your rig. That way, you might only have 5" of overhang from the tool rest instead of 8" (assuming the rest extends 3" into the HF).Here is an example of what I'm talking about...
http://www.woodturnerscatalog.com/store/Lathe_Accessories___Tool_Rests___Universal_Box_Too l_Rest___universal_rest?Args=
Obviously you could make your own version quite easily! Most of these are 1"+ wide so it may not be useful for your purposes.

A bigger bar usually means less vibration unless your captive system is the weak link. A 5/8" bar extended 8" is likely the weak link IMHO. Try to have the tool bit extended as little as possible since it is likely a 1/4" bit that can vibrate a lot if extended.

[Bernie Weishapl]

You are right that the smallish bar is probably the cause of your chatter. I use a 1" bar when going deeper than 8" or more. You must also make note if the rest of the unit can take the forces that a 1" bar is likely to give. I use the monster tool made for my 16" lathe and even with the 1" bar wouldn't go much deeper than 12".

[Reed Gray]

When I put my big Kelton blades (3/4 inch) in my Monster system, I get chatter. I figure the leverage arm is just too long for this articulated system. If there is any slop at all in your system, that is a contributer as well. The shorter blades are no problem. They aren't made to go deep. For forms over about 8 inches deep, I use my captures system.
robo hippy

[Wayne Bower]

Bill, as you know I to use a home made rig. I have just resently went to a 1" diameter bar. I also built a tool rest with 2 legs instead of just one. I have not taken any photos of the rig since I remodeled it. I will take some photos and post. BTW my rig works well and I have hollowed to about 8" deep without the chatter being a problem.

Good Turning

[john taliaferro]

i hang every thing heavy i can find between the tool rest and gate, it gets me another bit . i got 22 inches small cuts though, hackberry nice wood. practice duuk un cover first. john t

[Bill Bolen]

thanks all...I found some 1" round stock and will make a bit holder for my attempt. I need to get down to 9 1/2" and stay in some form of a comfort zone. I have some pretty long arms on this rig and it is very solid with zero slop. I'll post when done. Appreciate all the help...Bill..