Flat spots in endgrain hollowing

[Henry C. Gernhardt, III]

Folks---

I need opinions from all ye box and goblet turners, or anyone who has hollowed endgrain with a straight-shaft tool.

As you know, I've been playing with goblets. I've been trying each time to make the curvature of the inner wall more even, and match well with the outer curvature, including slight undercutting. Although I've come close, I can't seem to keep from getting facets on the inner surface (diagramatic example in attached image). Is this just a situation of needing more practice? I am trying to make smooth, sweeping motions with each cut.

Thanks!

[Andy Hoyt]

Hank - when I attempt what you're doing, my final shaping and finessing passes on the interior will often be with a small irish grind bowl gouge. Super sharp and light sweeping pulling cuts from the bottom to the rim.

One continuous motion. And if I think I'm messing up (regardless of whether I am or not - although I usually am) I continue the cut through to the rim. Why? Because otherwise it won't be a practice cut for the next pass.

Your facets suggest that you're cutting towards the bottom of the vessel which would be against the grain and likely causing you to apply to much pressure with the tool which in turn results in what you're getting.

Why the bowl gouge with an irish? Because for me, it puts the cutting edge in the correct orientation for the motion I prefer.

[Henry C. Gernhardt, III]

Andy---

Thanks for the info. I am hollowing from the base to the rim, as demonstrated in the Sorby video on Woodcraft.com. I guess my movements just aren't flowing enough yet...

Would you happen to have or know where I could find a diagram of an irish grind bowl gouge? Is it fingernail or flat ground?

Thanks again!

[Andy Hoyt]

Here's my version:
41163

[Raymond Overman]

I'm not going to discount Andy's suggestion because I've used it as well but a nice sharp round nose scraper can also help even out the curve. The key is to hone the edge then raise another burr on the end when sharpening it. I have a little pocket diamond hone that I use to do this with. Just remember to take light cuts. It works great.

It's really the same concept as the bowl gouge scraper but you have more mass to reduce the vibration. Good luck.