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Hard Scrapers
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Author:  Pegasusguitars [ Sat Dec 31, 2016 1:55 am ]
Post subject:  Hard Scrapers
Well another year has gone by and I still can't sharpen the 1/8" hard scrapers made by Alan. I learned to sharpen card scrapers years ago, but Alan's hard scrapers are a real joy to use for most work compared to the card style. I have all the shapes of the hard ones. They work so good when they are new that I'd just replace them every month if I was wealthy. If anyone has had success sharpening them with an edge like they come with, I'd appreciate hearing your process. Things like grinding wheel size and grit that works for you would be useful info. Or, if you have found an alternative to the grinding wheel, that would be interesting too. I can get a bit of a burred edge with a diamond stone, but not that incredibly aggressive edge they come with. Enjoy your building in 2017!--Bob
Author:  ernie [ Sat Dec 31, 2016 9:20 am ]
Post subject:  Re: Hard Scrapers
Hi bob , I/ve got many scrapers comm ones an home made from old spatulas /saw blades . There are so many videos on youtube describing in great detail , how to sharpen an ordinary card scraper . I have 4 burnishers ,the commercial stationary one from LV and a triangular one plus a ovoid sided one and a straight carbide one all from LV. Depending on the thickness of the scraper, and the type of cut I/m after I will use one or the other, make sure your burnisher is nice and polished with no scratches green or red rouge helps with buffing. One has to think of the edge as a polished bevel as on a plane blade. It takes a lot of practice to get the right motion while creating / feeling the burr to get a scraping action. If you are getting dust, go back and try again . I have had good luck using diamond stones initially and waterstones for the final polish. I don/t own a carruth scraper so can/t comment. I also own about 5 scraper planes which also require a burr. Practice ,practice , till you make shavings . Bahco and sandvik supposedly have the best steel for scrapers, cheers Ernie
Author:  SteveSmith [ Sat Dec 31, 2016 10:06 am ]
Post subject:  Re: Hard Scrapers
Bob, the StewMac instructions are pretty good and that's basically what I do. Here's how I do it.

1. I like the flat edge to be flat (for scraping bindings and rosettes) so if necessary, I will flatten the edge on a coarse diamond stone before I start sharpening.

2. Next I stone the sides finishing up on an extra fine diamond stone. The sides just need to be flat. The finer the grit you use for the sides and edge, the finer the cut.

3. The StewMac directions say to grind the edge at the exact center. This is pretty darn hard to do without taking a bunch of time to set up something on the grinder so I do it a bit differently. I use a low-speed Rikon grinder I got on sale from Woodcraft. I set up a tool rest on the fine wheel so it is as well centered as I can get it (straight edge from axle to tool rest gives a decent reference). Then I mark the edge with sharpie. Lay the scraper flat on the tool rest and very lightly grind the edge until the sharpie mark is gone - on one side. Flip the scraper over and repeat.

4. I like to take the scraper back to the very fine diamond stone and re-hone the flats to make sure the edge is nice and clean. And that's it.

5. They'll stay sharp for quite a while. You can tune them up by re-honing the flats.

Here's how mine works on some Brazillian cherry. This one is actually about ready to resharpen, in my opinion.
Image
Author:  Glen H [ Sat Dec 31, 2016 11:27 am ]
Post subject:  Re: Hard Scrapers
Steve, thanks, I had the same question Bob did. One thing I can't seem to find out - what grit grinding wheel is "fine"? 120? 320?
Author:  SteveSmith [ Sat Dec 31, 2016 11:36 am ]
Post subject:  Re: Hard Scrapers
Glen, according to the Woodcraft ad the fine wheel on the Rikon slow speed grinder is 120 grit.

edit: make sure to keep the wheel dressed.
Author:  Glen H [ Sat Dec 31, 2016 12:32 pm ]
Post subject:  Re: Hard Scrapers
OK, thanks again
Author:  Mark Fogleman [ Sat Dec 31, 2016 2:23 pm ]
Post subject:  Re: Hard Scrapers
Allen makes it look easy in his YT.:[youtube]https://www.youtube.com/watch?v=a7XRbfbpXiE[/youtube]
Author:  Pegasusguitars [ Sat Dec 31, 2016 7:39 pm ]
Post subject:  Re: Hard Scrapers
Thanks for all the replies. I've sharpened a lot of card scrapers over the last 40+ years of luthierie. I've no problem with that, but the hard scrapers have continued to be elusive. I'll keep trying!--Bob
Author:  Imbler [ Sat Dec 31, 2016 8:49 pm ]
Post subject:  Re: Hard Scrapers
I'm with you Bob. I've had some success by just flattening the sides and essentially flattening the narrow edge as well using very fine grits on both edges. Of course that is easier on the straight sections.
Mike
Author:  printer2 [ Sun Jan 01, 2017 9:45 am ]
Post subject:  Re: Hard Scrapers
Maybe try sharpening on a belt sander?
Author:  jfmckenna [ Sun Jan 01, 2017 10:25 am ]
Post subject:  Re: Hard Scrapers
I got an AC scrapper a couple years ago, used it till it got dull, tried to sharpen it, and threw it back in the tool box for good. I guess I just don't see whats so great about them. I can put an edge on a regular scraper in 60 seconds and get right to work scrapping shavings off. I guess if I ever do an arch top the AC scraper might come in handy for it's rigid curves.
Author:  SteveSmith [ Sun Jan 01, 2017 11:39 am ]
Post subject:  Re: Hard Scrapers
Funny how that works. I got my AC scrapers several years ago and since then my regular scrapers have been unused. Different strokes.
Author:  Mike_P [ Sun Jan 01, 2017 12:50 pm ]
Post subject:  Re: Hard Scrapers
Alan makes it look easy because of lots of practice at it and also a grinder that's pretty much perfectly set up for it already.

I disagree with his drawing on the chalk board as it doesn't make sense considering how scrapers work, and that is by a burr.

Point being, I think the Carruth Scraper should be very slightly off center so that the wheel is pulling a burr on one edge only...if it is off center in the wrong direction it will be pulling the burr off as it were...this would be why one needs to flip it over to get a pulled burr on both edges...if you are DEAD center one edge will be having a burr created and the other will have it being pulled off.

Lapping the scraper is done before the sharpening process to give a nice clean edge of metal to create the burr upon...lapping it after sharpening will damage the burr.

As far as to why it's so great of a scraper, it's being used totally flat...a card scraper is used with a slight bend in it, therefore it is not creating a totally flat surface.
Author:  DennisK [ Sun Jan 01, 2017 1:46 pm ]
Post subject:  Re: Hard Scrapers
jfmckenna wrote:
I got an AC scrapper a couple years ago, used it till it got dull, tried to sharpen it, and threw it back in the tool box for good. I guess I just don't see whats so great about them. I can put an edge on a regular scraper in 60 seconds and get right to work scrapping shavings off. I guess if I ever do an arch top the AC scraper might come in handy for it's rigid curves.

Same here. Never did work as good as a card scraper, and I don't have a grinder so I can't sharpen it the recommended way. Thought about selling it, so I didn't want to modify it in an attempt to find a way to sharpen by hand, but never got around to that either. It's probably a bit rusty to sell by now, so I guess I'll dig it up and have a go at it :)
Author:  Alan Carruth [ Sun Jan 01, 2017 3:24 pm ]
Post subject:  Re: Hard Scrapers
Sorry that folks are having so much trouble. As far as I'm concerned, if I made it look easy to sharpen it's because it is easy; far easier than sharpening a card scraper.

These scapers work just like any other scraper, it's just that the edge is the one that's left by the grinder or whatever, rather than a burr you raise with a burnisher. The big advantage of the right angle edge is that it leaves you with two workable faces that cut pretty much the same.

The most popular question I get is what grit wheel to use. I don't know. I just used the fine wheel that came with my Baldor grinder, figuring that I'd get a better cut that way than in if I used the coarse wheel. It seems to work. I did spend some time setting up the tool rest to get just the right angle. Once you've done that DON'T CHANGE IT. I do all my other grinding on the coarse wheel except for freehand sharpening of small drill bits.

There's no reason you couldn't use a belt sander; the hollow grind is not necessary. Another thing that should work would be a hand skate sharpener. I've got one, any eye it from time to time, but it makes a much tighter radius than my grinder, so it would be a lot of effort excavating the edges to the point where it would actually work.

The essentials are to:
1) always start by leveling the surfaces, to get rid of the old, dull burr,
2) grind the edge by whatever means until you get a new burr of the size you like, and
3) level up the side on a flat stone once in a while to keep it flat.

Everybody likes different tools. I used card scrapers for a long time, and can still get a good edge on one without thinking much about it. It toook me a long time to gain that skill, and most of my students have had the same experience. Once I started to use the hard scraper I pretty much left the cards alone, and the students all gravitated to it as well. That was why we used to make them in class, and why I was so happy when one of the students offered to get his brother in law to make them in his machine shop.
Author:  truckjohn [ Sun Jan 01, 2017 10:14 pm ]
Post subject:  Re: Hard Scrapers
Lol... This sounds like an instance where Al could show you in about 1 minute how to do it in person and you would instantly see what you are missing... But whatever that one single bit is - it doesn't translate well to "instructions page"...
Author:  Pegasusguitars [ Mon Jan 02, 2017 1:19 am ]
Post subject:  Re: Hard Scrapers
Like I said before, I'll keep trying. I know that quite a few things in the "skill" category look hopeless until you "get it". I've yet to meet anyone in person who has figured this out so that I could get a live demo. From the replies on this forum, which only involve only a very small percentage of the owners of these scrapers, that there might be quite a few out there that go unused once dull. They really can be great tools, but-----------
Author:  Clinchriver [ Mon Jan 02, 2017 6:46 am ]
Post subject:  Re: Hard Scrapers
Pegasusguitars wrote:
Like I said before, I'll keep trying. I know that quite a few things in the "skill" category look hopeless until you "get it". I've yet to meet anyone in person who has figured this out so that I could get a live demo. From the replies on this forum, which only involve only a very small percentage of the owners of these scrapers, that there might be quite a few out there that go unused once dull. They really can be great tools, but-----------


Lets see a pic of your scrapers after sharpening?
Author:  truckjohn [ Mon Jan 02, 2017 12:54 pm ]
Post subject:  Re: Hard Scrapers
Pegasusguitars wrote:
there might be quite a few out there that go unused once dull. They really can be great tools, but-----------


No doubt the same for chisels, planes, and regular card scrapers. I have bought many of these tools for a song because they were just dull and the previous owner lost interest and gave up.

Thanks
Author:  rlrhett [ Mon Jan 02, 2017 3:46 pm ]
Post subject:  Re: Hard Scrapers
I love card scrapers. They are one of my go to hand tools. I even use a putty knife scraper for hard to reach areas. One of the best woodworking "tricks" I know.

But ten years ago card scrapers were useless to me. I probably would have bought a hard scraper in a millisecond.

Then I was wasting time on woodworking YouTube videos when one popped up on proper "sharpening" and use of card scrapers. "Sharpening"? What the heck did that mean?

Now ye without woodworking sin can cast the first stone. But how was I to know you could "sharpen" or hone a scraper?

So I got my scrapers polished to a mirror surface and give it a quick hone on the wet stone before each use. Birds sang, unicorns pranced, the sky became one big rainbow.

My point is that card scraper or hard scraper (or plane, or chisel, or saw) is 90% how well it is sharpened. Sharpening is probably the most important hand skill a luthier can have. It's worth taking the time to learn how to do it right. Keep sharpening and re sharpening that hard scraper until you too see unicorns
Author:  SteveSmith [ Mon Jan 02, 2017 4:24 pm ]
Post subject:  Re: Hard Scrapers
rlrhett wrote:
...My point is that card scraper or hard scraper (or plane, or chisel, or saw) is 90% how well it is sharpened. Sharpening is probably the most important hand skill a luthier can have. It's worth taking the time to learn how to do it right. Keep sharpening and re sharpening that hard scraper until you too see unicorns


Yep
Author:  Mike OMelia [ Wed Jan 04, 2017 11:47 pm ]
Post subject:  Re: Hard Scrapers
I bought one of those soft (white) grinding wheels (320 grit??). And as mentioned above, I never move the table set. Mark edge with magic marker, and "grind" that off. I do need a good flattening so that's upcoming. But, these scrapers are SO useful.
Author:  Jonny [ Sun Jan 21, 2018 5:08 pm ]
Post subject:  Re: Hard Scrapers
Sorry about the bump folks but I have to ask if anyone has found a way to sharpen these without the use of a grinder?
I don't have a grinder so my stewmac scraper has sat in the tool chest for some time now
Author:  dofthesea [ Sun Jan 21, 2018 5:25 pm ]
Post subject:  Re: Hard Scrapers
Following as well. I love these AC scrapers one of the best tools when new. but Ive tried over and over again to get a nice edge on these and they never work out. I would be tempted to drive out to Allan Carruths shop and pay him to show me if he wasn't so far away. maybe someone will step up and provide a sharpening service for these. I would happily buy 10 of these and have them sharpened once a year. they last an incredibly long time when they were new.
Author:  Barry Daniels [ Sun Jan 21, 2018 7:25 pm ]
Post subject:  Re: Hard Scrapers
I looked for a long time to find a true fine grit grinding wheel. With this 150 grit wheel I can sharpen my hard scrapers easily. The thickness of this wheel also helps to keep the edge of the scraper smooth.

https://www.amazon.com/gp/product/B001DSZ35U/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
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