Green Goblet Turning

[Don Wattenhofer]

This is a technique that I was initially introduced to at a Demo by Del Stubs in about 1990 and I am guessing that I have turned well over 1000 goblet forms ranging in size from about 2" tall by 1 1/2" diameter to 18" tall by 10" diameter. The goblets are turned from the full round of a tree trunk or branch and it is best using fresh cut live trees cut in the dormant stage, which is the best way to guarantee that the bark will stay on. The reference to shear scraping is as it was at the time, which I still believe is the best and most efficient way to get a smooth finish on green wood. The picture below will show how out of practice I am in this case the wood is an upper branch of an Iron Wood or American Hornbeam cut down on Sunday the 4th of April. The problem is the heart wood is very dry and darker than the sap wood so very little light came through at the transition so when I got down to about 10thou" it fell off as shown. The 3rd one has a knot that caused a problem. The 4th one I sprayed water plus stopped regularly the measure the thickness so I knew what the light getting through meant.


The photo below is the first one when things were going according to plan, the thickness at the bark is about 60thou" and down to 20thou"at about 1/8" before the point of separation.

 

[Jim Reynolds]

Thank you for documenting your process. As you stated, a lot of what we know is learned from others.

 

[Al Chavez]

Yes thank you Don,
Great pdf and your photos really provide a fantastic introduction to someone like myself who has not seen these types of turnings.

 

[Don Wattenhofer]

Thanks for the interest and if you have any specific questions I would be glad to try to answer.

One of the main reasons I posted this is the recent infatuation with the so called NRS, which I think is an inferior application of the burred scraper but is easier to teach. The burred scrapers used in the turning of these thin walled goblets is mostly applying the burr at a negative rake shearing angle whether it is inside or outside. The NRS per accepted dogma is used flat on the tool rest, which is cutting at 90 degrees to the wood grain where as if you rotate the tool to between 45 and 60 Degrees it will make a shearing cut that would be an advantage in an area like the concave lip of the goblet.

 

[Al Chavez]

I've just rounded the bottom edges on my scrapers using my 80# CBN wheel today. I've found that I've been rotating the scrapers and that the sharp edges were marking up my rest and even starting to put slight grooves into it. I started rotating the scrapers on the last few bowls I've turned trying to find that sweet spot. Its very reaffirming to read your last reply Don.
Al

 

[Don Wattenhofer]

I've just rounded the bottom edges on my scrapers using my 80# CBN wheel today. I've found that I've been rotating the scrapers and that the sharp edges were marking up my rest and even starting to put slight grooves into it. I started rotating the scrapers on the last few bowls I've turned trying to find that sweet spot. Its very reaffirming to read your last reply Don.
Al

Been there don that. Those sharpe corners definitely can cut into the tool rest especially a cast iron rest.

 

[Don Wattenhofer]

I just sprayed a bunch of goblets mostly in black cherry, 1 in boxelder and 3 in red oak plus 4 bark edge bowls in cherry and 1 in white oak. The bark on is an advantage for spraying because you can hold them touching the bark only and no visible finger prints.

 

[robo hippy]

A NRS can work very well on end grain. They do a good job on the bottom of a bowl, but not as good of a job on the transition or on bowl walls. Interestingly, if you take a standard scraper and hone the burr off, leaving a polished surface, you can get very nice surfaces on harder woods. I do like a shear scrape with a burnished burr for my clean up cuts....

robo hippy

 

[Don Wattenhofer]

A NRS can work very well on end grain. They do a good job on the bottom of a bowl, but not as good of a job on the transition or on bowl walls. Interestingly, if you take a standard scraper and hone the burr off, leaving a polished surface, you can get very nice surfaces on harder woods. I do like a shear scrape with a burnished burr for my clean up cuts....

robo hippy

The NRS as you call it will work great flat on the tool rest on the bottom of these goblets only because it presents the burr properly for that portion of the turning and shear scraping is non existent on pure end grain. The conventional round nose scraper with burr can do the same plus it can transition to shear as you move from the center to the side walls, but of coarse it does not stay flat on the tool rest.
Note: The NRS without a burr does not work right? but if it has a burr it cuts great so think about it the burr is not negative rake. The burr can only cut as deep as the burr is so therefore it is more about presenting the burr at the necessary angle to each particular surface. In the case of these goblets the bottom is rounded so by turning the single angle scraper on edge and starting in the center in the 12 o'clock position and moving out while gradually moving the cut to the 11-10 o'clock positions does work but it does take practice.

 

[robo hippy]

Don, there are now carbide NRSs available, and they cut. Not sure how, but apparently they do work. I haven't tried anything but feather light cuts with my NRSs because that is what they are supposed to do, they are not for stock removal, only very gentle cuts, and if you have to push at all to get a cut, then your tool is dull. With my boxes, I can get a 220 to 400 grit surface from the NRS, and it is my preferred inside and top and bottom finish tool. I also use them to clean up the in sides of my boxes. I do use a skew or gouge for the outsides. Most of the time, there is not enough room on the inside of boxes for the shear scrape.

Funny thing about the standard scrapers. I tried one with the burr totally honed off, and it cut great. I can take off shavings when roughing green bowls that are far thicker than the burr. I understand the concept that you should not be able to take off a shaving thicker than your burr, but it doesn't seem to hold true, especially in light of the scraper which has no burr. I am told that the carbide scrapers can not be burnished to raise a burr, yet they still cut fine.

robo hippy

 

[Don Wattenhofer]

Don, there are now carbide NRSs available, and they cut. Not sure how, but apparently they do work. I haven't tried anything but feather light cuts with my NRSs because that is what they are supposed to do, they are not for stock removal, only very gentle cuts, and if you have to push at all to get a cut, then your tool is dull. With my boxes, I can get a 220 to 400 grit surface from the NRS, and it is my preferred inside and top and bottom finish tool. I also use them to clean up the in sides of my boxes. I do use a skew or gouge for the outsides. Most of the time, there is not enough room on the inside of boxes for the shear scrape.

Funny thing about the standard scrapers. I tried one with the burr totally honed off, and it cut great. I can take off shavings when roughing green bowls that are far thicker than the burr. I understand the concept that you should not be able to take off a shaving thicker than your burr, but it doesn't seem to hold true, especially in light of the scraper which has no burr. I am told that the carbide scrapers can not be burnished to raise a burr, yet they still cut fine.

robo hippy

Yes I have seen advertisements for carbide NRS but I have not seen any videos of them in use. I have seen round or square carbide insert used as a shear scraper by rotating the shaft, which would be similar to the long wing of a bowl gouge. The lack of a burr is a limiting factor such that controlled cut that the burr provides can not be accomplished with carbide.
The honed round nose scraper I believe in the past was referred to as a fluteless gouge and of coarse it was not used flat on the tool rest.