1/3 - 2/3 Rule

[John M. Smith]

I am currently shaping the outside of a hollow form. I understand that the largest diameter is 1/3 or 2/3 from the top or bottom. What I am curious about is base size and hole size. Are they 1/3 or 2/3 of the major diameter? Also height versus diameter? Currently approximately 4.25" tall by 4" or a bit under diameter.

Also, if I am incorporating a finial and/or a pedestal, how do I incorporate the rule with those items. I have seen some really large/tall vessels with what seemed to be too short of finials or pedestals.

I am turning this for a regional arts show, so I really want to nail it.

Any knowledge would be helpful.

Thanks,
John

[Thom Sturgill]

Just my opinion, but most seem to like very small feet (many want slightly rounded bottom so the form appears to float over, rather than emerge from, the table). A small opening shows skill. As to height vs width the "golden ratio" comes in here too. 1/3, 2/3 is just an approximation, it is easy to make a set of calipers that give the exact points to aim for.

A + B is to A as A is to B. So if A represents the width A+B would be the height. Don't know if this will show up right:

_____
|____| B
| |
|____| A
A


For example, using the 1/3, 2/3 approximation - if the diameter is 6" (2/3) then the total height would be 9" and the shoulder would be at 6" from the base. Personally I would use this for the body and then compare the finial to the body at maybe half the height of the body giving another iteration or step in the 2/3 ratios.

Then it gets even more complicated with details on the finial also displaying aspects of the ratio.

[Prashun Patel]

I think the Fibonacci ratios give you more freedom:

1:2:3:5:8:13...

[Scott Hackler]

I generally turn smaller (4-5") HFs and prefer a 1/2" hole and about a 3/4-1" base, tucked under. The larger the diameter the larger hole. One of the last larger HFs I made was about 8-9" wide and I had a 3/4" hole and probably about a 1 1/2" bottom.

For finials, I make a thin finial and believe that the thinner the finial the taller you can get away with. So for my 1/16" thin finials, I will make them the width or just a hair longer than the width of the form. For a Drozda style finial I would say 3/4 of the width of the form for the finial height. Exceptions for a HF on a pedestal or a very tall and skinny HF (taller finial). Just remember that the form is the most important part and the finial is just a decoration, so as long as the two flow with each other, your have a lot of leeway.

[John Keeton]

That is a small form, and a small entry hole would be nice if you have the tools for it. Most of my forms are larger than that, and while I used to strive for smaller holes, honestly, I think turners are the only folks that care. A couple of pieces have sold to turners, but the vast majority of my sales are thru galleries and the gallery owners indicate the buyers simply appreciate the art. For them, it is about the wood and the color, though I suspect the form is the initial, yet perhaps subliminal, attraction.

I normally will make the base just a tad less than 1/3 the widest diameter, and my entry holes are normally around an inch when finished. In your case, that probably is too large.

For width vs. height, it is hard to go wrong with Fibonacci. In other words, a 3x5 form, or a 5x8 form, will normally be aesthetically pleasing. However, I have deviated from that with pleasing results. It really depends on the form and proportions.