CNC bowl turning...part 3

[Doug Rasmussen]

I had some time this afternoon so I finished the inside of the bowl.

The bowl wall thickness is about 3/64" (.050"). The thickness is consistent in the curved portion, the thickness does not increase toward the bottom.

The moisture content measured on the inside just off the lathe was 22%. The outside was a little less since it dried a bit overnight after turning 24 hours ago.

According to an article in the archives this should dry without cracking given its thin section. Two five second runs in the microwave brought the moisture content down to 16%.

Picture shows after the final turning using a carbide tipped boring bar. A 1-1/8" collet is holding it on the spud on the bottom.

 

[Jamie Straw]

I had some time this afternoon so I finished the inside of the bowl.

The bowl wall thickness is about 3/64" (.050"). The thickness is consistent in the curved portion, the thickness does not increase toward the bottom.

The moisture content measured on the inside just off the lathe was 22%. The outside was a little less since it dried a bit overnight after turning 24 hours ago.

According to an article in the archives this should dry without cracking given its thin section. Two five second runs in the microwave brought the moisture content down to 16%.

Picture shows after the final turning using a carbide tipped boring bar. A 1-1/8" collet is holding it on the spud on the bottom.

Handsome bowl. Wishing you luck. If it warps, it'll be art!

 

[Doug Rasmussen]

Thanks for the interest Jamie. I was impatient and gave it a few more short bursts in the microwave to get it down to 8% moisture content. It did warp, the top rim is no longer flat and no longer round, but that just adds character to the piece.

My interest in woodturning goes back to my first business where we had a couple automatic wood lathes. As the business changed focus we got more into metal working, hence the CNC machines. In retirement I kept a couple of CNC's for my hobby use. They work well for woodturning.

With CNC's more emphasis is on design than needing the eye-hand skills to do difficult pieces. The bowl could as well have been done in ebony with no more effort on my part.

CNC is definitely coming to the arts and crafts. In my business we "built" wood, metal and glass art for several nationally known artists. The artist supplied a sketch, from there we made the pieces which probably 99% of the public assumed the artist did himself. Well known artists like Wendell Castle whose work may sell in the hundreds of thousand$, are they hand carved? No, Wendell has a very expensive CNC robot to do the carving. Sculptors from all over the world use WallaWalla Foundry to do their work, they have some of the most exotic CNC technology available anywhere.

 

[Bill Boehme]

Wendell Castle certainly isn't a slave to mainstream fashion. Even if I ever became recognized as an artist, I don't think that I could wear a high-water suit with orange pinstripes and matching orange shoe laces.

 

[Richard Coers]

Must be a pretty small bowl, the wall thickness looks way thicker than 1/16" in the picture. Curious what kind of surface finish you got with that cutter.

 

[Doug Rasmussen]

Must be a pretty small bowl, the wall thickness looks way thicker than 1/16" in the picture. Curious what kind of surface finish you got with that cutter.

Richard, yes, it is a small bowl. When I started with the blank it had a potential to be 5" diameter. After cutting away the cracked areas it ended up at 3-1/4" inch. There's a rim around the top which you can see in my second post making the wall thickness appear greater.

The cutter gives an okay finish. What you see in the picture is the back or underside of the cutting edge. Ideally, it has a too large a radius hand ground at about 1/16", also more back rake would be better. The insert used on the outside was freer cutting with an .008" radius.

This piece of madrone had a high moisture content with a bit of spalting making it a little punky for getting the best surface finish.

 

[Doug Rasmussen]

Wendell Castle certainly isn't a slave to mainstream fashion. Even if I ever became recognized as an artist, I don't think that I could wear a high-water suit with orange pinstripes and matching orange shoe laces.

Bill, he does have his own fashion sense.