What's the diff? Articulated vs captive?

[Steve Busey]

Saw this on another thread, and rather than hijack that one, decided to start anew.


I used the articulated for this one, I am still waiting for the captive system to be shipped.

Can someone help a newb and explain the difference, and maybe give a couple examples of one vs the other?

Thanks!

[Jon McElwain]

An articulated system is one where the rear of the tools is integral to a tool post which holds the rear of the tool to the bed of the lathe by a mechanical joint - usually with a bearing. It has articulations along the tool allowing it to move about horizontally in order to achieve the best cutting angle.

A captive system is a straight bar with no articulations that is held "captive" from vertical movement with bars above and below the rear of the tool. This helps control the tool when the cutting edge is deep in a vessel.

Both system utilize the lathe's tool rest which is positioned near the opening of a hollow form. A captive system is generally more robust, but more limited in movement. An articulated system is able to move more smoothly, but it may not have as much reach over the tool rest as a captive system does.

Here are two photos, the first is an articulated hollowing system, the second is a captive system.


221016


221017

Hope that helps!

[Scott Hackler]

Steve,

Articulated means that there is an attachment where the tail stock would be normally (except for the elbo system which uses the tail stock) and a "hinged" set of arms (hinged using thrust bearings) and the boring bar sticking out from this "arm". The forces are held at bay by the solid attachment at the tail stock area. (see Monster Hollowing System)

Captured means that there (usually) is a set of parallel pieces of steal with a post (goes into the banjo) and the boring bar rides in between this "captured" area with an extra bar that is attached firmly to the boring bar, running parallel. This principal stops any, or most, twisting while hollowing. (see Lyle Jameson's setup or a variation Carter's Hollow Roller)

[Russell Eaton]

Hey Steve just drop by the house in a couple of weeks and you can play with both.

[Steve Busey]

Thanks Jon & Scott! Descriptions and pics helped a bunch. Russell, you gonna let me see how thin I can go on that big chunk o' burl you had last month? ;^}

[Steve Harder]

Sometimes shop layout can dictate a system choice. In my small shop space, the articulated was the only way to go. I don't have room off the tailstock end of my lathe for a captured arm to swing around.

[Russell Eaton]

Steve the articulated lets you go into the hollow form at a much sharper angle. It also saves on space as Steve stated.

[Steve Busey]

So, the Sorby RS2000 is the manual equivalent to these mechanical systems? Found a set of the Sorby hollowing tools this weekend in one of the boxes we got out of dad's shop. Might have to look into how those work (easy to do when you're on a tight budget!).

[Jon McElwain]

Steve the articulated lets you go into the hollow form at a much sharper angle. It also saves on space as Steve stated.

I can go in at nearly a 90 degree angle (perpendicular to the lathe bed) with my captive system. It just requires extra fiddling with the back rest to adjust it at an angle closer to the work piece.

[David E Keller]

...Can someone help a newb and explain the difference...

bearings!!!!

[Steve Busey]

bearings!!!! Thanks David, that's why I hang around here - to get my "bearings" in this vortex from quality folks like you!

[Bill Wyko]

I use a captive system but |I rarely get to use it. I'm wondering, which is more prone to chatter or catches?

[Wally Dickerman]

I use a captive system but |I rarely get to use it. I'm wondering, which is more prone to chatter or catches?

Bill, chatter is usually a result of reaching too far off the rest for the size of the tool. If a 5/8 in bar chatters than a 3/4 in bar would be a better size to use.

Catches? Bill, you don't get catches do you?