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Sharpening a scraper

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DrPhill

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Hi all, I have bought some flexcut profile scrapers. Out of the packet they scrape well, but the instructions say that they can be improved. So I tried on a couple and all I can do is make them worse.....
Has anyone here successfully sharpened a flexcut profile scraper from blunt? What should I be doing (except not messing with the half-sharp ones)?

Thanks in advance for any help

Phill
 

D_W

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file the profile with a fine single cut file until you get a burr. Stone just the side of the profile you want to use, and only a little (scraper steel is soft and you'll hone off the file marks very quickly, and then roll the burr.

If you're still having trouble (keep in mind, I don't know how people expect these to be used), file the scraper about 20 degrees off of 90 and then stone the edge halfway between that and 90 and then roll a burr).

If that also fails, just file them to get a fresh edge and use them to scrape, and if you want a finer finish, find a finer file.
 

DrPhill

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Thanks D_W
file the profile with a fine single cut file
Single cut file..... you expose my ignorance, sir. I had to look that up. Would a diamond file do instead? I .have a small set of files - half of them metal half of them diamond, but the metal files are all 'overcut'.
scraper steel is soft
Exposing my ignorance again.... I was assuming that it would be hard steel.
keep in mind, I don't know how people expect these to be used
Nor do I really, but I find that scraping wood with them (while they are still sharpish) really removes material fast and sort-of smoothly.
 

D_W

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do you pull the edge across wood? If so, I know what you're doing, but have different types of profiled scrapers for this kind of work (mouldings and guitars).

* the reason i said single cut file is they have teeth that you can use perpendicular or diagonal to an edge and not expose the edge itself to deep scratches. They also remove saw temper metal quickly.

* as far as hardness goes, scrapers are generally hardened, but they're hardened only to a saw temper and not to something like a chisel or razor, so they can be honed quickly where as some high hardness steels don't hone very quickly (the hardness resists abrasion).

On a scraper, this is in your favor as you want to hone an area, but not too much.

diamond files work like "double cut" files, which are sets of two different cut directions. "single cut" are like mill file pattern,but they can be very fine cutting if you get a fine file.

There's a maker (glenn drake or something?) in the US who makes a very small single cut file for scrapers, to the point that they suggest no honing. Never tried it. I like to file scrapers and then hone just near the edge on the side that will be used rather than trying to get burrs on two sides. It takes almost no time to prep the edge and roll a burr like that and more than cancels out trying to get two strong burrs on a 90 degree edge.
 

DrPhill

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Hah ... just tried again with the above suggestions ringing in my ears. I used a stone to flatten the narrow edge - which seemed to raise a better burr than the file. The burnisher did not seem to do much (but that may be me not knowing what to do or what to expect). The result was much better though. I did notice that I have to hold the scraper closer to perpendicular, but starting to get larger pieces (almost miniature shavings).

To clarify my last comment in previous post - I am not sure what these are intended for, but I am using them to remove tooling marks and to leave a smoother surface without the need for sandpaper.
 

DrPhill

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Thanks D_W, our posts crossed.
It seems odd trying to get a burr. I have spent half a century sharpening blades and learning not to raise a burr. I think that maybe I was using too coarse a file, or using it too vigorously, or both in the belief that I needed to work hard. The idea that the steel is softer than I expected was probably the key.
As I begin to understand what I need to do, then the instructions begin to make sense.
I bought a burnisher, but being cylindrical it slides off the small profiled tools. I think that a flat faced burnisher would actually be easier.
 

D_W

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So, on a scraper, you're preparing the steel and then rolling the edge into a burr (this is different than honing a burr onto something, which is just a fragment of steel remaining that hasn't let go of the main body). In this case, you're preparing a main body and then working the steel over into a burr (a very neat and orderly construct). That burr will have a sharp edge on the front and should leave a smooth surface.

However, you can forgo the burr for now and just file wear off of the edge of the scrapers you have and that will get you part of the way there. As the edge rounds, you will have to refresh it. The burr allows for a deeper and smoother cut.

This guy isn't so good at sharpening a scraper, but his pictures are just dandy:
 

D_W

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(given that these are profiled and small, I think mastering pulling the edge across a file and then using the burr that such a thing leaves is a good place to start. Even though the edge will be a bit rough, it will be square/crisp).
 

DrPhill

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Again, thanks. That article was very interesting - it shows me more of what I am trying to achieve (though not so much about how). It does sound as if I have been using too much force on the burnisher.

given that these are profiled and small, I think mastering pulling the edge across a file and then using the burr that such a thing leaves is a good place to start
Maybe reverting to a stone was a good idea, I find it easier to keep the piece vertical, and the stone should be fine enough.

And you are right - any edge that I can get on these scrapers will help me get the job done (smoothing my carvings especially in the small hard-to-access crevices. I may get a traditional rectangular scraper to practice on (I have a feeling that it will help spruce up the dining room table - old pine with stains and mottled wax finish).

Just to make sure that I understand
I like to file scrapers and then hone just near the edge on the side that will be used
'hone' means using burnisher?
 

D_W

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Again, thanks. That article was very interesting - it shows me more of what I am trying to achieve (though not so much about how). It does sound as if I have been using too much force on the burnisher.


Maybe reverting to a stone was a good idea, I find it easier to keep the piece vertical, and the stone should be fine enough.

And you are right - any edge that I can get on these scrapers will help me get the job done (smoothing my carvings especially in the small hard-to-access crevices. I may get a traditional rectangular scraper to practice on (I have a feeling that it will help spruce up the dining room table - old pine with stains and mottled wax finish).

Just to make sure that I understand

'hone' means using burnisher?
Three steps:
* file away wear and mangled steel
* hone area that was filed to create a finer edge that will roll a smooth burr
* draw the burr out and then turn it (some people only do the last part)
 

IWW

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Phil, I presume you are talking about "card" scrapers? I don't know what you are using your scrapers for (because it can make a difference), but here is some advice from my own experience, from wich you can take what you will.

To add to what DW has said & maybe help you to grasp the principles better, let's start from scratch. First up, you don't need a 'burr' in some cases; a scraper can work with clean 90 deg corners, albeit not as well in most cases. When using a scraper in a holder (a combination known as a "scratch-stock") I rarely bother turning a burr, it's usually more bother than it's worth. However, for typical "flat" work a card scraper works infinitely better with a burr. Turning the burr serves two main purposes:

1) it work-hardens the edge. As DW has pointed out, scrapers are generally tempered to a much softer level than a plane blade, so a 'raw' edge on a scraper doesn't last long on tough woods. The work-hardened edge caused by raising the burr can be quite a bit more durable. (Edit: As DW has just said, "drawing" the edge [i.e. turning it back & forth a couple of times] increases the work-hardening & makes the edge a bit more durable still, but simply raising a burr is usually enough for practical purposes).

2). The burr acts to roll the shaving as it forms, in a similar way to a chip-breaker on a plane blade and the combination of this & the fine-ness of the shaving ensures you get very little tear out. Be aware, however, that a dull or coarsely-sharpened scraper can tear fibres very effectively, especially on soft-ish woods (rule of thumb, the harder the wood, the better it scrapes!).

To knock off old paint or glue squeze-out, I generally use the scraper "off-file", i.e. no further honing after flattening the edge with a 10 inch smooth-cut mill file (the "mill" part is important, "mill files" are a much finer cut than ordinary flat files). Just turn an edge and away you go.

If you are levelling veneers or cleaning up a surface prior to finishing, you want a far more refined edge than a file leaves. To hone the edge of a scraper, you need hard stones, something like India or hard "natural" stones or the scraper cuts & gouges & will make a right mess of your stone. You may be able to use one of the harder water stones if you have a light touch & are exceedingly careful, but I wouldn't attempt it myself. I use a fine diamond plate, but for many years before I had that I used a hard Arkansas stone. I hold the scraper very slightly askew to the direction I'm moving it, just enough to prevent gouging, but not too much or I have trouble keeping it vertical to achieve a perfectly square edge. Having a square edge gives you two good corners to turn, but if you have too much trouble achieving this, make one corner just a little more acute than 90* and use that. What won't work well is an obtuse corner, you'll get no workable burr on a 100*+ corner!

Finally, the burr itself should typically be just enough to feel with your finger. I've found that beginners nearly always roll too much burr to begin with. About 3 or 4 passes with my (round) burnisher is usually plenty. If the burr is excessive, you'll find you have to lean the scraper too far forward to get it to cut, to the point where your little fingers are dragging on the wood, & they very quickly let you know they don't like that!

Some people get very passionate about what to use for a burnisher, but just about anything as hard as or harder than the scraper steel will work. When I started out 40+ years ago, the typical burnisher recommended was a screwdriver shaft. Screwdrivers are not the best for the job, they are tempered to about the same hardness as scraper steel so it generally takes more passes, the shaft also becomes worn & scratched & the resulting edge isn't as clean & straight as you'll achieve with a very hard material. Old solid-carbide bits are excellent, but the piece of 1/4" HSS I've used for many years does the job & shows not a single scratch or mark as a result.

People also have differening opinions about the ideal shape of a burnisher. After using a screwdriver for a couple of years, I ground the teeth off a 6" 3-cornered file & polished it up to 1200 grit. That worked much better, but at one time I was using curved scrapers quite a bit and found a round burnisher easier to use on curves. The smaller contact area means you get more "turn" for the same amount of pressure, which is why I say "just 3 or 4 light-ish passes" are usually sufficient. If you use a flat burnisher you have to press more heavily or make more passes to get the same amount of 'roll' on the edge because the force is distributed over a wider area. The round burnisher also gives me good "feel" of the edge and I can tell instantly if it isn't clean after honing or has become chipped from use (I typically re-turn the burr 3 or 4 times or even more between "sharpenings").

These are all things to think about when you start using card scrapers, but if you use them much, very soon it all becomes intuitive and you know just how much burr will work best for a given situation. I would say that learning to use a card scraper was one of the best lessons I ever learnt in woodworking. I live in the land of hard, gnarly woods, which scrapers take in their stride. Apart from the fine control & the quality of finish scrapers can give, they have saved me hours of sanding, for which both my arms & lungs are rather grateful...... :)
Cheers,
Ian
 

DrPhill

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Thanks Ian, that does help. It seems that I have underestimated the complexities of scrapers.
What I am using are small shaped tools that can be used, I assume, to clean machined profiles, they fit in a handle and can be used to clean recesses in my carvings. (eg: Flexcut Profile Scraper Set).

I use a fine diamond plate
Hmmm, I have some somewhere. Great shout.

I hold the scraper very slightly askew to the direction I'm moving it, just enough to prevent gouging, but not too much or I have trouble keeping it vertical to achieve a perfectly square edge.
Are you abrading along the face or across it?

Be aware, however, that a dull or coarsely-sharpened scraper can tear fibres very effectively, especially on soft-ish woods (rule of thumb, the harder the wood, the better it scrapes!).
Don't I know it! My current piece is yew. There is a marked difference in the finish between the light sapwood and the dark heartwood.

I've found that beginners nearly always roll too much burr to begin with. About 3 or 4 passes with my (round) burnisher is usually plenty.
That hits home. Almost certainly one of my mistakes.

they have saved me hours of sanding, for which both my arms & lungs are rather grateful......
And probably the environment too.
 

IWW

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What I am using are small shaped tools that can be used, I assume, to clean machined profiles, they fit in a handle and can be used to clean recesses in my carvings. (eg: Flexcut Profile Scraper Set)....
Aah, now I'm on the right page! I've not met or used those gadgets, I jumped to the conclusion you were using card scrapers (just an oblong piece of sawplate-like steel sans handles). And I have very limited experience of using scrapers on carvings, although making saw handles is a form of carving, I suppose, & I've made one or two of those & use small scrapers a lot for cleaning up after rasping to shape.

I use "scratchstocks" for cleaning up (or making) various mouldings. Like this one, made for putting a quirked bead on some chair rails:
2 beader.jpg

So my prattling on about using a diamond plate for sharpening edges isn't relevant in your case, I was talking about the straight edges of 'square' scraper blades. For making or 'sharpening' profiled scrapers I generally use cutoff wheels for roughing out & fine chainsaw files or small flat files to refine the shapes (& occasionally, metal scrapers made by grinding spent files). To get the edges "sharp" & smooth-out residual file-marks on concave or convex shapes I run the burnisher over the edges, but hold it almost square so that it produces only the tiniest of hooks, if any. The idea is to smooth the cutting edge & hopefully, create some work-hardening rather than making a palpable hook.

I've not tried scraping Yew, but in general, softwoods do not scrape well. It can be done with a very sharp edge & a fine touch, & from the little bits of Yew I've worked with it is probably one of the better softwoods to scrape, but shorter-fibred, hard hardwoods generally respond much better to scrapers - ebonies and rosewoods scrape beautifully.

So I'm not much help to you in your specific circumstances, but the basic principles should be the same, so I'm sure you'll get it sorted in time....
:)
Ian
 

DrPhill

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I'm just wondering why the carved finish is not good enough. Can you post a picture ?
Some of my shaping is done with a file - I find it easier for spherical portions. In other places I want a smoother surface than I can get carving. A quick scrape addresses both of these concerns.

It may be that the problems are a symptom of a lack of carving skill or using the wrong tools (up until a week ago I was using palm tools exclusively but struggling with larger removals).
Whatever their merits in this case I am sure that they will come in handy. I prefer the idea of scraping to sanding, but need to know how to maintain the tools.
(Hope that does not sound defensive. I appreciate all approaches to solving the problem)
 

Adam W.

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No, that's a fine answer.

You should get a nice shiny finish with carving tools, which would remove the need for either scraping or sanding. So I was just wondering if there was something I could help with on the carving tool front.

That's all.
 

DrPhill

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No, that's a fine answer.

You should get a nice shiny finish with carving tools, which would remove the need for either scraping or sanding. So I was just wondering if there was something I could help with on the carving tool front.

That's all.
A kind thought - and maybe there will be in the future. My tools will cut to leave a smooth finish - when sharp. But my skill leaves a finish that is many facets with ‘boundaries’ between them. Especially on convex surfaces. The scraper removes the boundaries to smooth one facet into another.
 

IWW

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Much depends on what you are carving, of course. I think the lightly-faceted, off-tool finish is highly appropriate for some carving, less-so for others. My 'carving' is limited in scope & done sporadically over the years as required, so I haven't acquired a high level of skill. Most of what I have done was shallow reliefs on furniture. I would like to get the results of a Grinling Gibbons by deft gouge or chisel cuts alone, but I am far from that level. So I muddle along to get the job done as best I can. I'm not above using small, shaped scraps of scraper plate to help me get there when I'm striving for a bit of anatomical 'realism', even (shudder!) a bit of sandpaper when sorely pressed...... ;)
Back detail.jpg

A couple of times I've had to carve chair knees on reproductions made to match old sets & admit to hiding behind some "distressing" to cover my lack of skill & tools that could match the original cuts. I once made a pair of armchairs to match an old set of walnut side chairs (themselves reproductions made in the early 1900s). I could see how the original carver had done it with a few selected tools & a series of single cuts. It probably took him 5 minutes to do each knee & 30 seconds to do the little curls on the back splat - took me nearly as long to do that simple carving as to build the chairs!
Walnut arm chair.jpg

I've also been asked to imitate old "pressed" chair backs a few times, to fill out partial sets or make matching kids' chairs. On these, crisp cuts are not at all desirable. I roughed out the patterns with a skew and a very small gouge or two, then rounded the shapes up with scraping, finishing off with scrunched-up sandpaper to imitate the wear & tear of the originals.

Chair match.jpg

So there's all kinds of "carving" & all kinds of ways of getting there.....
:)
Ian
 

DrPhill

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There is some nice work there. You are more versatile than me - I am just learning/playing at the moment.

Thanks for the gibbins reference. That led me off on an internet journey and revealed how much thee is left to learn.
 
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