YAAAHS - Yet Another Articulated Arm Hollowing System

[Eric Holmquist]

Just got this home-made articulated arm hollowing system to the point where I can try it out. Combined with basic design of the Elbo Tool with a Kobra base. Still have to make a Laser guide for it, but will fool around with it a bit first. Have the parts from Digi-Key to make my own Laser guide, but have had enough metal working for a few days.

Made my own boring bar, still need to make one of those adjustable tool holders that lets me mount the cutter at an angle.

Experimented with a different type of thrust bearing. Used Super-Oilite. They have much higher load capacity than the ball bearing type, and only cost around $0.60 apiece. They are sintered iron impregnated with oil. They can handle lots of pressure, but not much speed. Even if only rated for a few hundred RPM, moving the arm by hand, we don't get more than a few RPM out of the joints.

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[charlie knighton]

congratulations, looks good, let us know how your thrust bearings hold up

[Thomas Canfield]

Nice looking system. You might look at adding spring washers (Bellville or beveled washer) to keep pressure on the thrust bearings. That will also allow you to make adjustmens as wear takes place. I also used some thin hardened flat washers on my homemade to provide a harder surface than the mild steel bar.

[Steve Vaughan]

That's a nice-looking rig there! Congratulations! Just wait till you get the laser up and running!

[Jeff Fagen]

I like it. Is the square stock 3/4?

[Bill Bolen]

Great looking rig. I'm looking forward to some nice hf's from you now!

[Eric Holmquist]

Thanks!

The bar stock is 1" x 1 1/4"

This way I can use a 3/4" boring bar. The hole is offset to allow enough metal for adequate thread engagement of the set screws. I used M8-1.25 set screws which need at least 1/4" of metal to ensure you don't strip the threads. With a 3/4" boring bar offset in that bar, I have 5/16" of metal for thread engagement. Went with M8 set screws since they use the same 4mm hex drive as the set screws on my Talon Chuck.

I am making some bushings to allow me to use smaller boring bars

I set a goal for 2012 to learn to make hollow forms. I have struggled with hand held hollowing, and after visiting an Open Shop on making these rigs while on vacation out in California I came home determined to make one.