Sheer scraping - big or little bowl gouge?

[rtyuiop]

Hi folks,

After a couple of days struggling with tearout on some soft, curly new guinea rosewood, I am thinking I'm going to embark on trying to embark on a project to improve my sheer scraping technique.

The first thing will be practice, but I'm also willing to throw some money at the problem - thinking about it, it seems like a big bowl gouge would make this easier... Is that accurate?

Cheers,

Danny

[dai sensei]

I find it easier, but mainly because it has a bigger wing to use, thus I get more sharp edge by rotating slightly. You can do with any though provided they are sharp.

[handyrn]

I use a thin card scraper and it does a really good job.

[rtyuiop]

Do you mount it on a handle or anything handyrn? Seems like it'd be a bit scary to just have the card in bare fingers next to spinning wood!

[pommyphil]

I often use a curved cabinet scraper on the bottom of bowls, down hill, with the grain, STATIONARY !

[rtyuiop]

Ah! Sure, stationary I can see it. Particularly if you are already well practiced with card scrapers!

[NeilS]

- thinking about it, it seems like a big bowl gouge would make this easier... Is that accurate?



I have big gouges (as in 1") all the way down to small gouges (as in 1/4"), but tend to just use whatever sized gouge I have been using or is sharp.

You can use any straight or fluted tool for shear scraping on the outside. In my experience, a good well swept back bowl gouge works well on the inside. The sweet spot is where the edge is at 45deg or higher angle (ie closer to the tip). A light touch and wispy shavings are what you are after.

Although unorthodox, I find that you can also cut against the grain if your shear scraping cut is light enough.


Stay sharp!

Neil

[Paul39]

I use a half round thick scraper inside and a slightly curved thick scraper outside of bowls. They are sharpened upside down at about an 80 degree angle to raise a nice burr. They are used slanting down, very, very light cut, taking off tissue paper thin curls.

Good for one or two passes, then a quick swipe on the grinder.

If there is room to slant the scraper down, I see no point of a negative rake scraper. Going to the bottom of a tall narrow vessel, yes.

With some timbers with hard and soft mixed, nothing will do but sand, sand, sand.

I have a couple of curved stainless steel blades from a scrapped food processor sharpened as above for hand scraping.

[Old Croc]

Danny, do a utube search on Negative Rake Scrapers. I watched Retired use one at the Prossie Turnout last year and I was sold on their versatility. I had a billet of McJings HSS flat bar, so I knocked one up to try it. I use a lot of Qld Maple, one of the worst furry timbers around and the NRS was so easy to use.
Rgds,
Crocy.

[george mavridis]

I have seen NRS where the grind angle is the same on top andbottom and then others where the bottom angle is the standard grind but the tophas a much smaller grind, just enough to take out a small bevel almost. Isthere a difference in operation between the two or is one better than theother?

[rtyuiop]

Yeah, I am a fan of negative rake scrapers - my go to for finishing cuts is a big hefty round hamlet scraper, sharpened with a small bevel on top.

It's absolutely brilliant for hard timbers (and acrylic pens), but isn't as good on the soft stuff, like the NGR I have been playing with this week!

[Old Croc]

Yeah, I am a fan of negative rake scrapers - my go to for finishing cuts is a big hefty round hamlet scraper, sharpened with a small bevel on top.

It's absolutely brilliant for hard timbers (and acrylic pens), but isn't as good on the soft stuff, like the NGR I have been playing with this week!
NGR???
Crocy.

[rtyuiop]

NGR???
Crocy.

Sorry - new guinea rosewood (not a real rosewood in case anyone is confused).

[rtyuiop]

Today I took some photos of the bowls which provoked this question, and decided to share!

http://rtyuiop.net/workshop/ngr-bowl-set.jpg

http://rtyuiop.net/workshop/ngr-big-bowl.jpg

Cheers,

Danny

[Paul39]

Today I took some photos of the bowls which provoked this question, and decided to share!

Cheers,

Danny

I take it the area on the right side near the bottom of the top left bowl in the group shot is what gave you the trouble.

Hand scraping with a curved cabinet scraper in the problem area and blending into the surrounding area, along with hand sanding the area with the lathe stopped is one solution.

There are many ways to get to the same place. I think we have to figure out what works best for us and keep refining and practicing.

The bowls are beautiful. Nice simple shape that shows off the figure.

[rtyuiop]

I take it the area on the right side near the bottom of the top left bowl in the group shot is what gave you the trouble.

Actually that bit wasn't so bad! Those are small clusters of some feature which looks a little like very large birdseye (unsure what the name of it is) which were all through the blank. They actually cut pretty well - I think because they might be a little harder than the rest of the wood, but that's only a guess.

Around the rim on curly/wavy grain was where I had most difficulty, having to make unsupported cuts.

Cheers,

Danny

[rtyuiop]

To answer my own question - I had my first go at sheer scraping with a shiny new bowl gouge - 3/4 inch with a fairly swept back grind, and yes, having that much blade available makes things quite a bit easier.

Having said that, it was huon, so I may as well have been turning cheese!