Sharpening (Burnishing) Scrapers

[Bernie Daniel]

This topic came up in the mandocello build thread and so that the topic does not end up hijacking a thread that many are following I start this one on the topic. Here is a link to instructions on how to burnish a cabinet scraper. The link has a video embedded and I also add that to the post.

[Bluetickhound]

I got an error message trying to upload the video on my phone but youTube is chock full of good vids on the subject.

[sunburst]

Well, that's close. I think there are several ways for him to improve his results. I'll see if I can get some pictures of how I do it to bring up the differences in what I do, and the reason for those differences. No video, that takes more computer skills than I care to maintain (Boils down to I can't remember my password to get back into Youtube. Remembering passwords is a computer skill I can't seem to master.)

[sunburst]

This one needed some work anyway, so here goes.

I have a file like the one the guy in the video used (the upper one), but I like this big one better,

and here's why. I can span the entire length of the scraper, lay it flat on the side of the scraper and remove the old burr with a few strokes. This way I don't file any irregularities into the edge from the file possibly tipping or filing more in one area than another.

With the burr filed off of both sides, once again I can lay the file on the full length of the scraper, hold it at a 90 degree angle to the edge (angle done by eye, close enough) and file a few strokes until the edge of the scraper is square.

You might notice that there is no handle on the file. Without a handle, one can lay the file flat on the scraper and stroke without interference from the handle.

I've seen burnishers with damage and wear from burnishing scrapers, as the guy in the video warned, but there are ways to avoid that.
Here, I'm oiling the edge of the scraper. I rubbed my finger on my face next to my nose, and that's enough oil to rub on the edge of the scraper so that the burnisher will slide easily and not be damaged.

I start with very light pressure, and when the scraper edge starts to burnish and and become smooth I increase the pressure gradually and the smooth burnished edge does not damage the burnisher. I stroke the burnisher straight back and forth along the edge until the top, flat edge is burnished, then tilt the burnished first one way then the other to form the hook.


In the video, the guy lets the burnisher go over the end of the scraper and roll the corner of the scraper over. Most scraper sharpening tutorials I see tell us to not worry about the corners, we won't be using them anyway. Well, I use the corners, so I want them sharp and square. I don't let the burnisher drop over the corners but instead try to roll the burr right to the corner without rolling the corner over.
In the video, the guy has a huge hook on his scarper and he has to lay it down at a low angle to get it to cut. I don't like that much of a burr so the angle of the scraper is higher, it doesn't require so much downward pressure to use, and the burr is more durable for longer use between sharpenings.
Hope that helps.

[Marty Jacobson]

Thanks, John. I've been feeling like I've lost my scraper mojo lately, and this will be helpful to get back in the game. I was taught to burnish the sides first and then roll the edge over, but I think that makes the hook too large and too brittle, at least the way I'm doing it. Not many things are as satisfying to use as a nice sharp card scraper.

[Tim W]

A good friend of mine is an inventor/ tool maker and not long ago gave a seminar on this subject for the Gwinnett Woodworkers Association who recorded it. It's a bit long but you'll dang sure know how to sharpen a scraper by the time it's over. Here's the link.

https://www.youtube.com/watch?v=TiC15vRQv_4

[CedarSlayer]

All the above advice on scrapers seems solid enough to me. Here is my method, http://toolmakingart.com/2008/08/12/...-to-tune-them/

Bob

[Doug Edwards]

That's good John. What about the curved scrapers? They are tough for me to do.

[Petrus]

I have this book from the library, it's very helpful: Sharpening: The Complete Guide, by Jim Kingshott. It's geared for woodworkers in general, not luthiers, but covers a lot of the same ground. Discusses what sharpening is, hardness vs. ductility, looking for the "candle" on a blade, beveling, stones and strops as well as machine grinding, saws, scrapers, gouges, and Japanese saws and wet stones (Japanese implements are reputed to be some of the highest quality blades you can get!)

http://www.amazon.com/Sharpening-Com.../dp/0946819483

[Bill Snyder]

Whetstone.

[sunburst]

That's good John. What about the curved scrapers? They are tough for me to do.

Curved scrapers are a little tougher to sharpen. The egg-shaped one that I was using (and was in the photo) in the mandocello thread, I sharpen like a card scraper; remove the old burr with the file laid flat on the surface, file the edge to 90 degrees by clamping the scraper in a vise and sort of rolling the file along the edge lengthwise. I have to clamp the scraper in at least 4 positions so that I can file the 90 degree edge all the way around, then once again clamp it in at least 4 positions to burnish it all the way around. I usually use wooden vise jaws so that I don't damage the burr by clamping it in the steel vise.

I usually skip the step of honing the edge of the scraper on a stone before burnishing because I'm usually using card scrapers for fast, relatively rough work. If I want a finer edge I will sometimes hone the 90 degree edge on an Arkansas stone before burnishing, but the burnishing process smooths the surface anyway, so the burr is only a little finer if the stone is used. When I do use the stone I will alternate between Honing the 90 degree edge and honing the flat surface of the scraper. That cleans up the edge and removes the file burr so the hook that is burnished has less of the roughness of a simply filed edge.

For scraping spruce, and for fine detail work, I have some thinner, smaller scrapers that I file to a 45 degree angle at the edge. I hone the edge and flat with the Arkansas stone so that the edge is pretty sharp, then turn a light burr with the burnisher. It can help to burnish the burr over, then use the burnisher to re-straighten the burr, then re-establish the burr. That work-hardens the steel and makes the burr a little more durable so that it can last longer in use. When sharpened to a 45 degree angle, those scrapers can be used with no burr at all and give us a very smooth scraped surface.

[Pete Jenner]

This is a very timely thread for me. Thanks Bernie and John.

[Petrus]

I think I was thinking of Japanese water stones.

[sebastiaan56]

Is anyone using the Alan Carruth style scraper?

[Rob Roy]

I have used the original carruth scraper and like it. The progressive radius curve is great for the recurve area of tops and backs. I particularly find it advantageous in fairing the curves on a figured maple back. It is a very different critter from a card scraper and carves out significant amounts of wood compared to a card scraper. The procedure for resharpening it on a grinding wheel seems intimidating (the scraper is so thick there is actually a concave curve between the front and back faces), but I've used it to dress 3 maple backs thus far without the edge showing any sign of wear.

[Bluetickhound]

Finally got the video to upload. That dude is Mathias Wandel and he is a woodworking/engineering genius. Check his video where he builds his own bandsaw. Very impressive!

[Mike Conner]

So, until now I have demonstrated such poor ability to sharpen scrapers that I abandoned all hope and they have sat in a drawer.

I followed John Hamlett's method above, though since the scraper was already filed I just used a medium ceramic honing stone to prepare the edge. I used the shaft of a screwdriver as a burnisher. Sharpening the scraper edge took maybe 5 minutes!

I have a walnut archtop guitar body with maple binding in progress, and just glued in the binding earlier today. Expecting another disappointment, I took a scrape at the maple binding. Imagine my amazement when a nice feathery shaving was removed instead of powder and heat that I experienced up to now.

Thank you John and others for showing us how to do this properly. I am now a scraper convert. Next is taking a shot at the curved scraper!

[Mike Conner]

I burnished a curved scraper the same way as above: Dressed the edge using a medium-fine grit ceramic stone then burnished John's way. Burnished at 90 deg to the edge, then drew out the edge using a screwdriver shaft as burnisher. Worked great on doing the recurve on the walnut back. Wish I had learned this a long time ago! Thanks again everyone...

[Champlin]

Well, this has been enlightening. I've been using and burnishing my scraper for almost 10 years without complaint. I was taught to roll the sides up first, then back down. I've just assumed rolling them up was a necessary step for getting a good edge. I just tried the way illustrated here.. whaddya know.. It works!

Thanks,
Devin