screw scraper?

[mobrien]

Hi everyone,

I finally had some time in the shed today, and got to play with my new (secondhand) lathe and new supernova2 chuck.

Obviously it makes sense to start with a lump of jarrah burl. What else would I remind myself what turning is like with?!

I screwed the blank to small faceplate, and turned the outside. This went really well, and I even pulled the skew out to remind myself just how easy it is to catch! All sanded and finished with shelawax, time for the inside.

In the supernova 2 manual, it says to cut the hole in the base with a scew scraper (15 degrees). I don't have one, so just guessed using a parting tool and round nosed scraper. I have a feeling that maybe I should get what it says!

I switched the bowl around and started in the inside. A nice catch on some of the burl and bowl went flying across the room. Glad I was wearing my face mask, as it just bounced off.

On inspection, the base sheared off, I think because the angle was wrong and all the pressure was on one point. That and I should have turned a tennon, as the burl was very curly!

Anyway - I want to find the right scraper for this, as I want to make quite a few bowls - but I can't find a 15 degree skew scraper anywhere. Do I just get a square nose and recut it to be 15?

Thanks for any suggestions!

Matt

[rsser]

You don't really need a skew for this Matt.

Do the plunge cut as you did with the parting tool, and you can if you like remove much of the rest with it as well.

Straightening out the bottom can be done with a scraper. In my experience it does a cleaner job than a skew.

You can imagine the shape. Fancy name is dovetail. Ground on the left and then at the tip less than 90 degrees with a bit of a curve to the right after a straight bit.

How deep was the recess? And how big the blank?

For wood holding, with a good enough recess I've rarely found it worse than a tenon. Tho there are other reasons to go for a tenon.

[DJ’s Timber]

Matt have a look at my reply in this thread at post #14

[mobrien]

Thanks for the suggestions - looks like I might be able to make do.

I just took a photo of the offending piece - looking carefully, I think it may be more to do with the burl than the groove I cut. That and the nasty catch the other side that caused it - maybe some more patience and care with such a piece would go a long way!

M

[powderpost]

Matt, for this sort of project I would suggest you screw a waste block to a face plate, and turn it to match the bottom of the bowl. Turn the middle out of the waste block, the same as the bottom of the bowl and glue the two together. Don't use paper in the joint and cut through the waste block with a handsaw to separate the bowl when finished. Clean off the remnants of the waste block by hand with a plane or sand it off. Much safer and definately more rewarding than losing a bowl after lots of work.
Jim

[Skew ChiDAMN!!]

I'd say you're right, Matt.

That's one of the shortcomings of using the chuck in expansion mode... it's not as secure as using it in contraction mode around a tenon. You're not the first (and won't be the last) who has had the timber fail like that. The main advantage is it makes it easier to create a concealed foot.

Ya just gotta learn to tell when it's an appropriate choice of mounting. (I very, very rarely mount that way anymore. )

[Cliff Rogers]

.... Do I just get a square nose and recut it to be 15?....

That is what I did.

The shiny one on the right in this pic.

[joe greiner]

Even without knowing the dimensions, that socket looks way too shallow for a reliable purchase. Also, any tendency to crack is made worse in expansion mode; note timber isn't very strong in tension across the grain, and it doesn't matter whether you're turning faceplate style or spindle. With heavy spalting or punky wood, compression mode on a tenon also has problems. I dribble some CA on such tenons before chucking and it seems to help.

Joe

[rsser]

Raffan recommends a recess of around 4mm, and with sound wood in your case Matt, and the burl clearly isn't, and modest hollowing forces, it should've worked. For years that's what I did and only had a few problems.

I prefer a tenon these days though it's more work as it allows an even bowl thickness running down to the foot, and hey, I'm a foot man

[rodent]

skew scraper one scrape out the cavity two present your skew chisel as a scraper to the wood . three with the cutting edge of the skew paralel or flush what ever ,to the face of the timber ,you will notice the long point of the tool is now at approx 15 deg .three now recess that bloody foot im running out of words .
OH i for got silly me 6-8 mm at least for cutting out the center of hard bowls and recesses .you can go down to 3 mm but no wood butchering gently does it .