need tips on scraper

[Daddy3x]

I have been turning some green bowls now and even tried one that was about 17" in diameter, can't wait for it to dry out. I have been using just a 3/8 round nose scraper to smooth corners and bottoms. Well, the other day I saw a 1 inch Sorby HD bowl scraper and had to have it, thinking it would make more consistent work in larger pieces and get better overall leverage when hanging out over the toolrest. I sharpened it, it had a nice even burr on it, and I keep getting pretty big catches. Any suggestions on how to use this more effectively? I know the obvious point would be operator inexperience, but are there any good starting pointers for me to look at?

[TTIT]

I have a 1" scraper but it never gets used - come to think of it, I don't even know why I keep it on the rack??? For scraping the inside and outside of bowls ( or just about anything else!), I use a Sorby RS200 hollower with the scaper attached because with the round shaft you can roll it to 45 degress and shear scrape to get a top finish:2tsup:. Tipping a flat scraper to 45 degrees puts the cutting edge out of alignment with the fulcrum?? on the toolrest and gets too scary for me!:o and using them on the flat does exactly what you said - big catches!

[ticklingmedusa]

Try raising the toolrest just a little above centre and keep the end of your handle a wee bit above the toolrest.
This keeps the cutting edge low and if it catches it gets carried into
the space away from the piece.
Its sort of a balance and leverage game.
My big scraper is definitely grabbier than my little one.
The contour or curve of the rounded nose should be similar or better, a slightly tighter radius to that of the curve of inside the vessel. Don't scrape with the entire edge.
Light cuts are best until you find the sweet spot.

When hogging out waste at the bottom you can use a scraper to sweep to and from center but only on the bottom half of a bowl. On the upper wall this can cause catches
that in severe cases could lead to wardrobe malfunction.

[rsser]

Good advice TM.

Tho with a rough turned green bowl you can scrape right up the side, tho there's no point in doing so since you'll be coming back to finish turning when the rough-out is dry.

With dry bowls the 'old' method is to have a set of scrapers of varying widths/radii to clean the corduroy from the inside, and never to use more than a half of the cutting edge and not to come up the wall ... you'll hear the change in sound if you do ... thrumming = risk.

Shear scraping with an appropriate radius tip is the 'new' method.

An alternative is a curved rest with say a 1/4" bowl gouge with flute pointing near horizontal, and light cuts downhill. Reduces sub-surface fibre damage and tear-out and subsequent need for 60 grit gouge.

[hughie]

I often shear scrape with the handle well above the toolrest.

I pull back the toolrest 20-30mm from the work and lift the handle up 30-45' , rolling the scraper over towards the toolrest. If you get a catch here it will push the scraper out and away.

As always, light and steady scraping, sorta like patting your cat

[rsser]

yeah, you want fluff coming off, not dust.

[Daddy3x]

Thanks. I know I have used the small 3/8 round nose and had some catches while learning how to use it, but I eventually got better and now produce shavings, ribbons on green blanks. Once the thing is roughed, I have been using the small scraper to smooth the bottom, and ran it right up the side towards me. You all are saying to just make a better quality cut with the scraper and not use the scraper on the walls of the inside? I have still been using the straight tool rest that came with the lathe, would a curved one make life easier if I plan on turning many more bowls?

[rsser]

All round (ahem) curved rests make shaping the inside of a bowl easier and less damaging to the fibres. The closer the rest the less tool overhang ... so less likelihood of chatter with a small gouge and of a catch with a scraper. Check out the AAW forum for a thread on this.

On a dry wood bowl with a thinnish wall you get flex in the wall, and the scraper becomes useless and dangerous, so you can sweep from the bottom but as you come up the wall you'll hear and feel a thrumming which means time to pull out before disaster.

[NeilS]

....I use a Sorby RS200 hollower with the scaper attached because with the round shaft you can roll it to 45 degress and shear scrape to get a top finish:2tsup:.

:whs:

And, contrary to traditional wisdom, I also use oval profile skew chisels for scraping cuts. The oval profile helps with the presentation of the tool when shear scraping. A variety of elliptical edge profiles are used to work with concave curves and straight edges for convex curves. Atypically, I retain both skew bevels and grind them to a very acute angle... similar to a knife edge.

Care needs to be taken not to burn such a thin edge when grinding. To reduce the number of times I return to the grinder, I frequently touch up the burr by hand with a fine diamond card and periodically hone to a mirror finish on a felt wheel, which will quickly raise a micro burr.

I keep the tool rest as close to the job as possible (using a variety of curved rests) and at centre height.

When sharp, this scraper removes fluffy thin shavings and leaves a fine surface. I can't ever remember getting a catch, but I have carelessly cut myself a few times on the sharp edge. :rolleyes:


I'm not sure how I gradually ended up with such an unorthodox approach to scraping. If I stop and think about it, it runs counter to wood cutting theory. However, I can remember old skew turners using their skews in this way even though it was considered a no no, their skew work was supposed to not need scraping, or perhaps it was something to do with how it would dull the edge on standard carbon steel. A good quality HSS is certainly needed to keep the burr for any time at all.

Apologies for the length of this post.

Neil

[rsser]

Good stuff Neil.

But AFAIK all you're doing is using a scraper with negative rake and shaving with the burr.

[NeilS]

But AFAIK all you're doing is using a scraper with negative rake and shaving with the burr.

Yes rsser, that's about it.

Neil

[rsser]

Plenty of ways of skinning a cat.

But Neil if you were a big name you could now be hawking your new revolutionary method of getting an immaculate finish on the inside of a bowl ;-}

[rsser]

btw, re TTIT's post (I imagine) the further away laterally the scraping edge is from the support on the tool rest the more wobbly things become, which isn't good for a controlled clean finish.

I've moved away from scrapers mostly, to tips like the Sorby multi-tool, though the steel in that tear-drop is cr*p. Rodent's use of planer blades to DIY own is worth a go.

[OGYT]

I use the same technique that TM suggested, and I turn up the speed. It may be because I shake quite a bit (benign familial tremor), that the higher speed helps me make things smoother. I also use a bowl steady, to reduce the flexing of the thin sides of a bowl when finish-shear-scraping.

[rsser]

Al, did you make your own bowl steady? Or get the Oneway?

[OGYT]

Al, did you make your own bowl steady? Or get the Oneway?
Ern, I made my own using rollerblade wheels. It's not as flexible as I'd like it to be... not flexible, like bending... but flexible, like being easy to change for different sized bowls. Changing the wingnuts and bolts to different holes is time consuming.
I'm thinking of building one using T-Track, if I can figure out how to raise and lower the fulcrum. :)
The aluminum rails along the base board are for rigidity. The baseboard has a slot that runs the length of the board to move it in and out for different size bowls. The verticle piece has a small gussett, bracing it to the baseboard, that gives it more stability, also.

[rsser]

How would a pair of jointly pivoting arms like the Oneway steady go do you think, though made from ply?

[ticklingmedusa]

I use the same technique that TM suggested, and I turn up the speed. It may be because I shake quite a bit (benign familial tremor), that the higher speed helps me make things smoother. I also use a bowl steady, to reduce the flexing of the thin sides of a bowl when finish-shear-scraping.

I don't think I mentioned the effect of increased speed but
it really does seem make a difference once one gets used to it.
At 1000 or so RPM I was still getting a less than smooth finish cut.
I brought it up to 1500+ and it made a difference.
Also wanted to add that for me shear scraping is the next frontier.
My hands are not steady and I'm holding tools in a somewhat unorthodox fashion at times so I'm entering a new learning curve with that technique.
tm

[Gil Jones]

Read over this article by Joaz Hill >> http://www.maine-web.com/woodturning/shapeshifter/scaper.html <<
I made one from an old, carbon steel, bench gouge that I found at a flea market. It looks odd, but shear scrapes very well. Hardly ever have a catch with it, and the catches I get are pretty mild. I use it inside bowls, and outside too. The seldom catch thing may just be luck, but the tool seems easy to control. I'll post a pic of mine if I can find the file.

[OGYT]

I remember you telling me about these, Gil. I've never seen one anywhere I've been. Don't even know anybody that sells them.

[rsser]

Check out the double-ended shear scraper here:

http://www.johnjordanwoodturning.com/tools.htm

Couldn't be too hard to knock one up, with one curved end.

[hughie]

Gil, hmmm food for thought.

Ern,
The link is not working some thing about the page has gone.

[rsser]

Hmph, vanished overnight.

Saved a pic though.

[TTIT]

Try here (http://www.johnjordanwoodturning.com/John_Jordan_Woodturning/Turning_Tools.html) guys....

[rsser]

Dunno what's going on. I'm not getting there.

Apparently the website was revised in the last day or two.

Have done a refresh, and tried in two browsers. Pooh.

[Grumpy John]

I've made up a flat disc to sit the scraper on and find that I have much more control than with a conventional tool rest. It may upset the purists, but hey it works for me.

[rsser]

Neat idea.

When you've got foreigner's rights back again maybe machine a slot in the top to keep the scraper at 45 degrees.

Oh, and bearings in the slot so's you can easily move the scraper to and fro.

Are you taking orders? ;-}

[OGYT]

How would a pair of jointly pivoting arms like the Oneway steady go do you think, though made from ply?
Good idea, Ern... I'll have to look into it. I'm no engineer, but I would like to be able to design one that will adjust easily and simply, and lock down precisely and tight.:2tsup: