Scraping

[wheelie]

Im trying out scraping at the moment, which i have always done it, but with lots of sanding due to tear out,

when scraping a bowl with either round nose or Robert Sorby multi tool/tear drop, no matter how i do it, whether it be

- Shear scraping
-Tool flat on tool rest, and scraping on center line
-Tool rest higher than center line

I always get bad tear out in the following red areas, resulting in lots of 120 grit sanding. But the thing is that the rest of the bowl is perfectly smooth, thats why its so annoying.

i know that its due to the grain, but i was wondering when you guys scrap your bowls do you get tear out and sand it, or dont you get tear out at all,

please post your thoughts and ideas on this, :D

[Skew ChiDAMN!!]

i know that its due to the grain, but i was wondering when you guys scrap your bowls do you get tear out and sand it, or dont you get tear out at all,

If any turner tells you they don't have problems with tear-out they're either lying or only work with "easy" timbers. :rolleyes:

Some woods are absolute mongrels for tearout, while others are very forgiving. Many of the mongrel woods turn easily when green though, which is one reason (among many) some turners turn green and then cure. :)

It can be a problem with all tools, but using a scraper flat on the tool-rest exaggerates the problem... which is why it's most often noticed when scraping. The solution? Sharp tools and shear-scraping so that it slices the grain instead of scraping. It won't prevent tearout but it'll minimise it... also reducing sanding time.

BTW, if you're getting significant tearout with a properly used bowl gouge, or a spindle gouge on the outside, don't even bother taking a scraper off the rack. Either reach for the sandpaper instead or change woods. :D

[RETIRED]

or get some lessons.;)

[TTIT]

That's the problem with Skew :( - doesn't leave much else to say on a topic. Well fielded Skew! :D

[rsser]

.. well I'm game!

Wheelie, on all kinds of wood?

Some are more prone than others to tear-out, and a tip I got from Len Smith who'se one of our leading turners down under: a scraper with a burr is good for medium density timbers but get rid of the burr for hard and soft woods.

Also take fine cuts and stop the moment you hear a high pitched thrumming noise - that's bowl flex and you can't do anything more. And you do know that you can't come right up to the rim on the inside don't you? And that you only want less than half the scraper edge in contact with the wood?

[wheelie]

Well im using the 3/4 round nose scraper and it is taken straight from the grinder,(120grit) and the edge is perfect no multibevels of bluing or anything, and when i aproach it to the wood at 45 degrees it shear cuts, and im not pushing, im just gently touching the tool against the wood.

And the outcome is fine shavings, so i stop the lathe, and theres just huge tearout, as in the picture above, the non red bits are perfect, very very smooth and nice finish, but the red... well that looks really bad,

so far i have tried it on Oak, and a few other woods that i dont know the name of, i think one was Lime, and maybe another was Chesnut,

anyway I'll post some pics hopefully today or tomorrow,

[Auzzie turner]

I hardly ever get tear out. I use a 3/4" bowl gouge on just about everything. I get 0% tear out with it. The only time I ever get tear out, is when I am turning a bowl with an overhanging rim, and you have to reach right in, and dig into the endgrain. If you have a bowl gouge, hold it the right way, so you can get those light feathery shavings, which give you a mirror finish. I usually start sanding at 240-320, and continue up to 2500, 2 coats of shellawax, and you've got a winner. Try and master the bowl gouge techniques, and you should improve rapidly.

Have fun, but remember safety first.

Happy turning,
Regards..........Joash

[rsser]

Well im using the 3/4 round nose scraper and it is taken straight from the grinder,(120grit) and the edge is perfect no multibevels of bluing or anything, and when i aproach it to the wood at 45 degrees it shear cuts, and im not pushing, im just gently touching the tool against the wood.

And the outcome is fine shavings, so i stop the lathe, and theres just huge tearout, as in the picture above, the non red bits are perfect, very very smooth and nice finish, but the red... well that looks really bad,

so far i have tried it on Oak, and a few other woods that i dont know the name of, i think one was Lime, and maybe another was Chesnut,

anyway I'll post some pics hopefully today or tomorrow,

Hmm, fine shavings sounds right ... but Oak is pretty coarse grained anyway. You could try taking the burr off after grinding.

You're coming from the bottom up?

You've got the tool rest as close to the wood as possible?

[Jim Carroll]

One way to help eliminate some tearout is to do your finishing cuts with a smaller bowl gouge about 10mm.

The reason for this is that you have a smaller cutting surface so you are not cutting large chunks out like you do with the larger gouge.

The other thing you do not mention is toolrest height. For scraping the toolrest should be above centre height with the tool slightly angled downwards so that you are still cutting above the centre of the bowl.

If your toolrest is on centre height and the gouge is angled down wards then all sorts of tear out can occur.