How long does a card scraper stay sharp?
biznazion
| Posted in Power Tools and Machinery on
I’ve recently started using a card scraper instead of sanding. It took me a while to figure out exactly how to sharpen it, but I’ve now got that part down – I think. My question is, how long on averge does one stay sharp when scraping hardwood (like cherry or maple)? When I first turn the burr I get very nice fluffy shavings, but it seems that only a few minutes later, I’m back to fine dust and it’s not cutting well at all.
Replies
Biz,
They do dull fairly quickly depending on the hardness of the wood you're scraping and the quality of the steel the scraper was made from. I've found that when they start to dull, you don't have to start from scratch with the refiling, etc. You can roll the edge back on just by placing the scraper on the workbench held upright by your fingers and thumb in the web of your hand, and with the burnisher, roll the edge back. I can usually do that a few times before having to refile. D'master.
Maybe I should add that I file so that I get a burr only on one side of the edge, instead of both sides, as is usually done.
Not long, but I think that's why most seem to put all 4 edges on when they start. You can also put the burnisher in you pocket and touch it up at the work to save a few trips to the sharpening stand. I learnt the hard way, working as a part-time farrier, that most of the time is spent walking backwards and forwards from the horse to the anvil.
I hold the burnisher parallel to the flat surface of the scraper and roll the burr out and then on edge to roll it back again. It doesn't take much pressure to renew the burr this way. One can do this several times before needing to file a new edge.
BJ
biznazion,
Ditto the others comments, however, I bought the Veritas burnisher and keep it in the apron....one swipe on each of the four sides and I'm good to go. Also, I've been using the jointer and smoother in feather cut mode to achieve the non-sanded surface..and the scraper only on tearout and squirrely grain...
Thank you all for you comments. I guess now I'm wondering about the quality of the scrapers I have. They are marked 'Clifton' on the side and are about .037 thick. I have indeed been rolling the edge several times before re-filing. That small carbide burnisher does look handy - but since I'm in a small garage shop, the walk from one side to the other is all of 10 seconds.
I keep four scrapers in my apron - two thin ones, and two thick ones. I use them every day and students borrow them frequently. I tune them up once before the semester starts, and once about halfway through, using a file and coarse diamond stones to shape, and fine diamond and ceramic stones to hone.
When students ask whether their scraper has been honed sufficiently to roll a burr on the edge, I ask them to use their scraper without a burr to see if it produces shavings, or just dust. If shavings, grab your burnishing tool and go for it. If not, keep honing until you have a polished 90-degree corner that'll produce shavings before rolling a burr.
I'll use a scraper without a burr to remove delicate shavings from stock with a reversing or swirling grain, like burl veneer, especially if I'm getting tearout with a well-tuned handplane.
Two common mistakes are applying too much pressure when rolling a burr and ending up with a burr that's weak and fragile, and rolling the burr too far over, so you have to lay the scraper down at an uncomfortably extreme angle to get it to cut.
Good luck,
-Jazzdogg-
Whether you think you can, or you think you can't, you're right.
biznazion,
As jazzdog said, the problem that properly turned edges that don't last very long is usually (always?) a burr that's too big. I had to learn that the hard way. O have a drawer full of scrapers I don't use because I used to get only a pass or two before they made nothing but dust. These days I'm still astonished at how long an edge can last.
In sharpening scrapers I've learned "less is more." It doesn't take many passes and it doesn't take much pressure to get an edge that lasts. I now take no more than three swipes drawing out a burr, and no more than two swipes to turn the edge, always with much less pressure than I used to use. (In that drawer with the scrapers I also have a HSS burnisher with deep furrows in it from my "many strokes, much pressure" days.)
Alan
Alan and Jazzdogg,
I have over time been learning that 'less is more' as I was trying way to hard at first and was very frustrated by the sharpening process. All of a sudden, not sure what triggered it, but I took a much lighter stroke with the burnishing rod and wha-la, the scraper actually made shavings instead of dust. So I do believe that my technique still needs some help and perhaps I need to look at the honing phase a bit to make sure it's actually ready for a burr. Thanks to all for the tips.
Glad I could help.
By the way, I find it very helpful to annoint my burnishing rod with light machine oil or camelia oil before use. You can avoid disfiguring your burnishing rod by using its entire length - instead of holding it in one position as you burnish your scrapers.
Let us know what kind of results (shavings) you get before rolling a burr!
-Jazzdogg-
Whether you think you can, or you think you can't, you're right.
Edited 10/5/2004 10:13 pm ET by jazzdogg
biznazion,
I'm glad you learned "less is more" lots quicker than I did. I struggled along for quite a while before I caught on.
If you still think you're not getting enough use out of your scraper, and there's nothing wrong with the way you create the edge, there's little else that can go wrong. About the only other thing I can think of is the sides of a scraper have to be flattened and polished the same as the edge. But again, I'm sure you already do that.
When I first get a new scraper, I stone the flat sides up to about a 3000 or 4000 grit waterstone. That way I have to do that chore only once.
I'm sorry I couldn't be more helpful.
Alan
Well, I think I making progress. We'll see how long the new burr's last now. I spent some time today re-tuning the edge and honing it. I use float glass and sandpaper to sharpen my tools and with the scraper honed to 400 grit and the sides flattened, I can indeed make shavings without rolling a burr - they are not great, but I can 'feel' it cutting. With a light coat of oil on the burnisher - I rolled a burr and it makes some nice shavings. I'll use it for a while and see if the burr has any increase in longevity.
biznazion,
You did watch the video on the homepage here didn't you?...along with the article in FWW last month? I found that very helpful and made the jig he uses (jig=piece of wood with a slot in it to hold scraper upright)...just in case you were not aware...
You bet - I even saved it for future reference :) A while back I was so frustrated I spent an entire afternoon going back and forth between the web and the garage trying every single tip I could find on sharpening a card scraper. Yes - I hate sanding that much! Anyway - I was hit with the revelation that 'less is more' somehow and stopped killing the edge when I rolled the burr. I'm now fine tuning my sharpening skills and on this last project (a burial flag display case) I've not touched sandpaper at all execept to finalize an small ogee curve before finishing. The last project I did was a redwood umbrella stand and that saw no sandpaper at all - just hand planes and a scraper.
I never could get that burr right. I tried and tried but nothing seemed to work. One day I took a use blade from my Delta thickness planer. You know the ones; the replaceable ones that cost almost $30 a set. Well I never hard the heart ( Ok so i am frugal!) to part with them when they got nicked or dull in the planer. So I took a piece of scrap cherry and cut a kerf in it about 1/2 the depth of the blade width. the kerf was cut on my table saw with a blade that was just slightly thinner than the planer blade ( band saw blade might work here too). I broke the blade in 2 pieces and set one piece in the kerf and pounded it home with a mallet. Now this scraper works slick. As good as one that was sharpened for me by a pro. and with it set in the cherry I can get a grip on it to sharpen it on an oilstone if I want to...... or I just flip the balde over.or...........just put in another blade. Lasts a lot longer than a scraper burr I tell you.
cherryjohn,
I was just stairing at my used planner blades today....did you roll the edge in the holder or just use the blade as is straight up and scrape?
I put the blades in straight up. I have used a piece of scrap cherry about 7/8" thick for the holder with the kerf for the balde cut in the middlr of the piece of wood. When I use the scraper I rock the tool forward so that it just rides on the edge of the cherry and the blade...............works great
Hello
I can not add to what everyone here has already said on sharpening a card scraper. but I found a neat trick that may help you in a pinch.
I work at a hospital. they use glass cards, (so samples can be looked at under a microscope) they are about 5" long and 3" wide, and come in a box of 500.
the glass scraps very well. its fast and cheap. I found 4 boxes being thrown out so I figured why not try? Man I have four sides to use and then I throw the glass away. no more sharpening! ;-)C.A.G.
I have used broken glass like that. When I have a contour that a straight scraper wont work on I find a piece of glass window pane that isnt useable ( mamy around my house) and I break it and use a piece that has a similar contour. Dulls quickly though and I have always wondered about the glass left behind with the work. I generally use the glass scrapers when i have to do some refinishing ( stripping) of some old piece and I fine sand after anyway so i guess the glass left behind is no big deal
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