Simple Hollowing System

[Steve Eure]

I recently bought the Simple Hollowing System from HarrisonSpecialties. I really like the functionality, fit and finish of this product. I contemplated buying the Elbo from Tim Yoder, but was able to save some money on the Simple system. I used it a few times and really like it. I contemplated building my own, but decided to just buy one.
The only issue I have is the depth of hollowing. I have only been able to go in about 7" on an 8" form. I start to get terrible chatter unless I take extremely light cuts. Would buying the longer cutter be advantageous or is that just a pipe dream? I realize that the cutter is vibrating because it is not being supported well enough at that depth. Those of you who hollow deeper vessels, what do you do to combat this?

Thanks,
Steve

[David Walser]

Steve -- I've never used the Simple Hollowing System, but I do have and like a similar articulating system. All these systems have three potential sources of chatter: First, the bar/toolholder. The deeper you go, the thicker the bar needs to be to avoid chatter. A lot of hollowers use a rule of thumb for how deep you can reach with a given thickness of bar stock. I don't put a lot of faith in such rules because a lot depends on what you're cutting and what type of cutter you're using. However, if you're using a 1/2" thick toolholder, I would be surprised that you could go 7" without chatter. Buying a longer toolholder isn't what you need, you need a thicker toolholder.

The second source of chatter is the 'body' of the articulating tool -- the play in the bearings and the flex in the each piece of the 'arm' -- all play into chatter. With a well-made tool, this shouldn't be much of an issue. You say you're pleased with the fit and finish. (It looks well-made in the photos on the maker's webpage.) My only concern is that the tool appears to be made out of aluminium. Mine is made out of steel. Maybe aluminium is strong and stiff enough.

The third source of chatter, and one I'd not really considered until looking at the Simple Hollowing System, is the way the articulating tool is attached to the lathe. An articulating tool is supposed to absorb the rotational stresses imparted on the cutting edge of the tool as you're hollowing. If the parts of the tool -- the toolholder, the body of the tool, or the anchor point -- flex, you'll have chatter. The Simple Hollowing System uses what appears to be a rather thin rod to anchor the tool to the lathe. Again, from the pictures only, the rod would appear to be a potential source of flex. Other articulating tools attach to the banjo, the tailstock quill, or to a thicker post.

So, try a toolholder made from thicker stock and see if that works. If not, it may be the Simple Hollowing System is great as long as you don't hollow too deep.

Good luck.

[Tom Wilson66]

I do have the Simple Hollowing tool and agree with what David said. I didn't need to go over about 6" on a hollow form, so it is quite good for my use. I wouldn't use it for going any deeper than that, even with a heavier bar. If you need a deeper cut, get one of the heavier hollowing systems, or use a heavy duty boring bar freehand, just for the last few inches.

Also, another consideration is the size of the cutter used. The bigger the cutter, the more of a bite it will take and that can cause chatter, also.

Tom

[Richard Coers]

My opinion is that the cutter is way too large. Everyone pretty much settled on 3/16" HSS bar stock in the first captured bars. Your system uses a 1/2" diameter carbide scraper cutter right? That just engages too much wood. I make a lot of my own hollowing systems, but if you can do some metalworking, I suggest you find a small cutter around 1/4" or less to try.

[Reed Gray]

I have one of the old Monster articulated arm systems. They claimed you could go 12 inches deep. With my experience, I think it is well suited for depths up to 6 to 8 inches. Beyond that, you get chatter, and that chatter comes from all of the joints in the articulated arm. Having a bigger shaft on your hollowing cutters does help. When trying to go beyond that 6 to 8 inch range, I found that if I roughed it out with a heavy bar, and then did just finish cuts with a small cutter, there was not as much vibration. I used my McNaughton coring tools with it.

robo hippy