Articulated Hollowing tool Question

[Gary Conklin]

When making an articulated hollowing tool, do you bore to leave the bearings slightly proud? How are they setup on the store bought units?

[Gary Conklin]

C'mon. I know a bunch of ya'll have made a a steel snake/Elbo, or Monster Style hollower.

[Steve Harder]

Not sure if this answers your question but:

I built my DIY elbo using 1 1/4 square steel solid stock.

A typical joint, from top to bottom, 3/8" machine bolt, washer, thrust bearing, washer, steel stock, washer(s)(for spacing), thrust bearing, washer, steel stock, washer, nylon locknut. No boring involved.

[Scott Crumpton]

I just finished building something that looks kinda like the Kobra design, haven't even had a chance to try it yet. Used 1x1.5" steel bar. For the bearings, I drilled a pilot hole all the way through, then drilled in for the bearings from each side using the pilot for alignment. The bearings are proud about 1/3 of their width. I then enlarged the pilot hole to 1/2" to clear the 3/8" bolt. Each joint has two bearings and is assembled like this: 3/8" G8 bolt, bearing, drilled bar, bearing, steel washer #1, nylon spacer, steel washer #2, tapped bar. Washer #1 has an OD that doesn't hit the outer race of the bearing and distributes the force on the surface of the nylon spacer. The nylon spacer is so that there's an compressible element to pre-load the bearings. Washer #2 is there because the nylon spacer wasn't long enough to give the clearance I needed. The bolt threads into the second bar and is held with a set screw.

[Thom Sturgill]

I used 6012 aluminum bar 1in square. I drilled a ~ 1/2" hole and followed that with a 7/8 in hole such that the roller blade bearings set just proud. 7/8" is just a hair large (should be 22mm) so a single layer of tape makes them a force fit. I used the sex bolts and bushings that came with the roller blades to hold the thinner sections top and bottom to the end pieces.
The bushings cause the thinner sections to set about 1/32 above/below the end bars.

The end piece mounted to the upright uses a larger screw threaded into the end of the upright as the sex bolts would not work. If I had been able to, I would have machined the upright to fit the inside diameter of the bearings (7mm) and be threaded on the end to receive a nylon cap nut. I may remake that piece over spring break as my brother has a metal lathe.

So far it works great. The one I saw at a symposium seems to be made about the same except it was anodyzed.

[Thomas Canfield]

I had a unit made from 1" square bar and used some 1" x 1/2" bars for the middle section. The bearing surfaces were not machined, but rather a hardened steel flat washer (.06") was used on each side of a needle washer to provide a good rolling surface instead of the soft steel bars. The bolting was 3/8" and a split lock washer used to provide pressure on the bearing, and then double nuts to hold the bearing stack. Check McMaster Carr for needle bearing and hardened washers or a local bearing supply.

[Richard Madden]

I used oil impregnated bushings, 5/8"OD x3/8"ID sitting flush, not proud, and thrust bearings. I believe Bill Bolen suggested this route, and I'm happy with it.

[Gary Conklin]

Thanks, all. This is on my short list of to do's and want to get it right. The FIRST time.

[Thom Sturgill]

Thanks, all. This is on my short list of to do's and want to get it right. The FIRST time.

Why? making tools is S-o-o-o much fun! (but not as much as turning)

[Gary Conklin]

Thom, I do enjoy making tools almost as much as turning esp. since I seem to struggle turning since I get limited time to these days. Getting rusty. Making tools I can work in 15-20 min increments and not worry much about putting it down, except the bug to get it done.

[Rob Cunningham]

Not sure if this answers your question but:

I built my DIY elbo using 1 1/4 square steel solid stock.

A typical joint, from top to bottom, 3/8" machine bolt, washer, thrust bearing, washer, steel stock, washer(s)(for spacing), thrust bearing, washer, steel stock, washer, nylon locknut. No boring involved.

I built mine similar to Steve except I put a bronze bushing in the steel and used a 3/8 shoulder screw. All the other parts are the same.I did ream the holes to .497" for the bushings.