Articulated hollowing arm (WIP)

[Nate Davey]

As I'm on a hiatus from turning, I needed something to keep my ADD at bay. So my local Community College was offering a machining class and I signed up. Here is the first part of the upright for my hollowing arm. I'll try and get a pic of the plan in a bit. The upright will center the bar at 12.5" for the ways.

photo.JPG

Here's a pic of the Solid Works plan my buddy drew up for me. Mine differs from most in that, where the hollowing bar is inserted into the arm, that receiver has a 7/8" hole in one end and if you rotate it 180 degrees, there is a 3/4 hole in the opposite end, eliminating the need for inserts. Not sure that really made sense.

Arm Plan.jpg

Updates to follow. Comments and criticism appreciate.....preferably before I make the part.

[Eric Holmquist]

Keep up the good work!

[Eric Gourieux]

Looks good, Nate. I like the double ended arm/insert idea.

[Eric Holmquist]

One thing I tend to be curious about is why all the extra holes? Monster does the same, and I don't understand the function of all the extra holes.

[Nate Davey]

I did it to reduce some of the weight as I'm using 2" square stock. Plus it looks neat. .

[Doug W Swanson]

Looks nice so far.

I think the one reason that many articulated tools have a longer arm is to use it for a handle. Depending on the length of the tool, how deep you are hollowing, etc, the longer arm will give you something to grab. JMO....

[Bernie Weishapl]

Looking pretty good Nate. Looks like you have it well planned.

[Bill Bolen]

Great start to a good plan Nate. You have to be dying to get back to spinning.

[Baxter Smith]

Looking good Nate. Enjoy the build!

[John Keeton]

Nate, there might be several areas I would consider modifying, and the first would be the ability to change height for the arm. I use mine at dead center only to smooth the bottom of a form and get rid of the nub - all other times, I hollow with it slightly above center, sometimes higher than others depending on the wood, form, cutter used, and size of the opening.

The other suggestion would be to weld the upright support to the base for rigidity. Ultimately, all the force ends up at that joint. I am just not sure a bolt/washer will be sufficient. At least, that is how it appears you anticipate making that connection.

Looks like a nice diversion for you while you are stranded from the lathe!

[Steve Campbell]

One other comment on the base. If you make your base a little bigger and weld the upright off center you can swivel it off to the side and get a better angle for hollowing.
The rest sure looks good.

Steve

[Nate Davey]

Here is the completed upright. The hole tapped in the bottom is 1/2"x13.

John, I talked with my engineer friend who helped me draw it up and he felt it should be robust enough to take the torque, if not I can weld it at a later date. There is a little adjustability in height but not a significant amount.

Steve, I have adjusted the base plate plan so I can use the arm centerline or offset it to the back of he lathe for steeper shoulders.he plate will be 1/2" 1018 steel so should be pretty robust. Thanks John and Steve for the design input.

Thanks all for the comments, the base plate is next.
Upright.jpg