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Sharpening question?

B

Barry Larson

Joined
Jan 23, 2023
Messages
194
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316
Location
Calgary, AB
When sharpening a scraper, do you use the tool right off the grinder or do you hone and then turn a burr similar to a card scraper for flat work?
Thanks,
Barry W. Larson
Calgary, Alberta, Canada eh!
 
Typically since the burr doesn't last that long, most will work with burr off the grinder, though some do hone and raise a burr , and still others will do BOTH. (like me - Use the burr right off the grinder, then when it needs refreshed, run it through a homemade jig with a carbon steel rod to raise a fresh burr... It works until the cutting edge gets too rounded over at which time, re-grinding is needed)
 
For stock removal, I use the grinder burr, then use a burnishing tool to form a new burr. I can usually get three or four burrs before heading back to the grinder.
For end grain boxes, hardwoods and especially exotics, I hone off the grinder burr (hone held flat to the top of the tool) then form a fine hook with a burnisher. Same idea as before, I can usually get three to four hooks before I have to regrind. Wispy shavings from exotics, leaving an incredibly clean cut.
As Brian stated carbon steel works, I'm using the same burnishing tool I use for my card scrapers with no issues.

Ps. Welcome to the forum...
 
Barry Larson said:
When sharpening a scraper, do you use the tool right off the grinder or do you hone and then turn a burr similar to a card scraper for flat work?
Click to expand...

my first step is to polish the top with the flat of a gouge slip.
then i sharpen with a 180 CBN wheel. I often use the burr off the grinder if I’m using the scraper flat on the tool rest.
if I’m using it to shear scrape I use a diamond hone to first polish the top removing the grinder burr then use the diamond hone to strike a fine burr
i can restrike the burr 3-4 times with the diamond hone between trips to the grinder.
 
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Thanks guys. Sounds like I'm thinking along the right lines. I'm trying to brush up on long forgotten sharpening skills for lathe work. Next time I'll post in the general area as I believe that I'm a bit offside here! Oh, and thanks for the welcome to the forum
Be safe and stay well.
Barry W. Larson
Calgary, Alberta, Canada eh!
 
When you do use a ground bur, it's a little more useful when you do a slow arc at the grinding wheel. I suspect it's because the bur is built up as a single piece of slag, rather than a "layered" slag that is more apt to form from a faster arc while forming the bur. Note: I have no scrapers where the edge is exactly straight....even those that appear to be straight at first glance, do actually have a slight arc to them.

( ^^^^^ Not sure the term "slag" is appropriate here.....but, I believe the ground bur is formed by heated metal that is pushed upward by the grinding process....not really a "molten" metal that might be indicated by the term "slag".)

As for burnished burs, they are a much more refined cutting edge, and capable of a more refined cut. I have seen both of these types of burs under a cheap-o handheld microscope, and the ground bur is definitely a more ragged edge than a burnished bur. Just how refined of an edge the burnished bur can be, is entirely dependent on how fine the stone or diamond hone is used to remove the ground bur prior to shaping the burnished bur. I typically use a 600gt diamond hone for this purpose, and seems to do quite well for my needs.

-----odie-----
 
I sharpen mine using a 600-grit diamond wheel on a Tormek. I immediately use it afterwards.
 
I use them both ways. For a finishing cut, always with a burnished burr. For other cuts I’ll use a grinder burr, then hone (600 gr dia) and burnish. A burnished burr not only provides a cleaner cut it also lasts significantly longer.
 
@Barry Larson , I grind my scrapers face down so the burr gets pulled down in the same direction my CBN grinding wheel spins. Is that what you’re doing?

@odie , What kind of wheels are you using that’s getting the metal that hot? I would expect a burr to be created by slight pressure of grinding and not by heat.
 
Karl Loeblein said:
@Barry Larson , I grind my scrapers face down so the burr gets pulled down in the same direction my CBN grinding wheel spins. Is that what you’re doing?

@odie , What kind of wheels are you using that’s getting the metal that hot? I would expect a burr to be created by slight pressure of grinding and not by heat.
Click to expand...

Karl.....I suspect the metal that remains in the shank isn't getting nearly as hot as the metal that's being removed. The metal that is being removed is very hot, and we see this as the sparks. Isn't it obvious to you that the sparks you see while grinding, are actually red hot metal fragments? IMHO, this is what partially creates the slag that comprises the ground bur at the top of the shank. Just how much this slag is comprised of the red hot metal being deposited at the top of the scraper shank.....plus the metal still part of the shank itself, is up for speculation.

BTW: I'm using a 1st gen 80gt Norton SG wheel. This is the wheel that was first available prior to the matrix formula being offered now. Since I haven't used the new version, I have no way to compare the two.....because of that, I have no way to formulate an opinion of any differences, but I can tell you for sure that I'm very happy with my 1st gen wheels.

I'm curious, and find it interesting about your upside-down grinding technique. I'm not doing that, but I've never felt burs being left on the bottoms of my scrapers that are ground in a more traditional upside-up way. If there was a bur there, I'm pretty sure I would have felt it on the bottom side of my scrapers over the years. You can definitely feel the very apparent bur on both my traditional upside-up ground burs, and manually raised burs, though......

I'm now wondering if grinding scrapers upside down is a common practice with other turners.....and, inviting others who do this, to comment about this grinding technique here in this discussion.

-----odie-----
 
As for the upside down scraper burr, Jimmy Clewes is one who prefers it, saying that it is sharper. I tried it only once or twice, and couldn't tell any difference. For me, I do hone and burnish the burrs on the scrapers that I am using for shear scraping. For general roughing work, I use a 180 grit CBN wheel to raise the burr. Oh, I generally hit the top side of the scraper with a diamond hone that sits in front of the grinder. A pass or two, and I have a burr that is ready for heavy roughing. On the M42, and V10 metals, that burr is fine for at least one 12 inch bowl. With my Big Ugly tool, with tantung or stellite for the cutting material, it is good for several bowls. Check out my Scary Scrapers and Shear Scraping videos. For end grain, for finish cuts, I will use NRSs. I do turn a burr on them, most of the time. You can get glass smooth surfaces with a NRS.

robo hippy
 
Thanks again guys. All good information. Sounds like using the burrboff the grinder for rough work and a honed burnished burr for finer, finish cuts (especially end grain and shear cuts) is the way to proceed. I'm in the process of getting CBN grinding wheels and a low speed grinder as I currently have high speed 8 inch grinders with conventional abrasive wheels.
Be safe and stay well.
Barry W. Larson
Calgary, Alberta, Canada eh!
 
I hear you. I just want to give the CBN wheels a go and see if they are truly better than the matrix wheels. One advantage I can see is the wheel diameter doesn't change with use and dressing, which may or may not make a difference. I'll need to try to find out!
Be safe and stay well.
Barry W. Larson
Calgary, Alberta, Canada eh!
 
odie said:
I'm curious, and find it interesting about your upside-down grinding technique. I'm not doing that, but I've never felt burs being left on the bottoms of my scrapers that are ground in a more traditional upside-up way. If there was a bur there, I'm pretty sure I would have felt it on the bottom side of my scrapers over the years. You can definitely feel the very apparent bur on both my traditional upside-up ground burs, and manually raised burs, though......

I'm now wondering if grinding scrapers upside down is a common practice with other turners.....and, inviting others who do this, to comment about this grinding technique here in this discussion.
Click to expand...
I grind top up. There is a slight burr on the bottom. I have an AL platform I use for sharpening, and it drags a bit. The <100 deg angle at the bottom, when grinding top up, limits the size of the burr. Reducing that angle to <80 will form more of a burr. I piddled with it a time or 2 and didn’t really see any advantage, but it was not much of an evaluation.
 
odie said:
Karl.....I suspect the metal that remains in the shank isn't getting nearly as hot as the metal that's being removed. The metal that is being removed is very hot, and we see this as the sparks. Isn't it obvious to you that the sparks you see while grinding, are actually red hot metal fragments? IMHO, this is what partially creates the slag that comprises the ground bur at the top of the shank. Just how much this slag is comprised of the red hot metal being deposited at the top of the scraper shank.....plus the metal still part of the shank itself, is up for speculation.

BTW: I'm using a 1st gen 80gt Norton SG wheel. This is the wheel that was first available prior to the matrix formula being offered now. Since I haven't used the new version, I have no way to compare the two.....because of that, I have no way to formulate an opinion of any differences, but I can tell you for sure that I'm very happy with my 1st gen wheels.

I'm curious, and find it interesting about your upside-down grinding technique. I'm not doing that, but I've never felt burs being left on the bottoms of my scrapers that are ground in a more traditional upside-up way. If there was a bur there, I'm pretty sure I would have felt it on the bottom side of my scrapers over the years. You can definitely feel the very apparent bur on both my traditional upside-up ground burs, and manually raised burs, though......

I'm now wondering if grinding scrapers upside down is a common practice with other turners.....and, inviting others who do this, to comment about this grinding technique here in this discussion.

-----odie-----
Click to expand...
My CBN grinding wheels produces very little if any sparks so it’s not heating up the bar itself. If you scraper is getting hot enough to create any amount of slag then you’d probably see more blue at the tip. Regardless it’s the results that count and nobody can argue about the quality of your results.

@Barry, Few other good reasons for using CBN wheels: most find a lot less metal gets removed each sharpening so tools last longer; little to no sparks means less fire hazard; no harmful dust from the grinding wheel; lot less worry about overheating tools. Although you should still find ways lower your risk to the dangerous metal dust so wear a good mask and put some strong magnets on the grinder. Clean off the magnets regularly to avoid metal dust from catching fire from a spark.
 
Karl highlights many of the advantages of CBN wheels, and also mentions something that is a disadvantage, in a way. When you sharpen on a stone wheel, you look for the sparks coming over the top of the tool to tell you when you're sharp. With CBN wheels, you lose this key indicator that you've been relying on.

Also, as mentioned, the CBN wheels sharpen faster and with less apparent steel loss, UNLESS you're standing there like a dodo (DAMHIK) waiting for sparks or otherwise not knowing when you're done. In that case, you're taking off MORE steel than necessary. Here's a suggestion to speed your learning on the CBN: Make 1 (one) pass, not even back and forth, and check. If you're not sharp, make a second pass and check. Usually 1-2 is all you need.
 
Thanks Dean. I'm quite proficient at standing like a dodo, so I'm taking your warning to heart. I believe there might be some value to blackening the bevel with a marker - the better to see where you are grinding and how much. Thoughts?
Be safe and stay well.
Barry W. Larson
Calgary, Alberta, Canada eh!
 
Dean Center said:
Also, as mentioned, the CBN wheels sharpen faster and with less apparent steel loss, UNLESS you're standing there like a dodo (DAMHIK) waiting for sparks or otherwise not knowing when you're done. In that case, you're taking off MORE steel than necessary. Here's a suggestion to speed your learning on the CBN: Make 1 (one) pass, not even back and forth, and check. If you're not sharp, make a second pass and check. Usually 1-2 is all you need.
Click to expand...
Or, just use black felt tip marker along the edge of the gouge, sharpen until you can't see any of the marker (or in a strong light you can see the facets of the old bevel and the new, until it has been fully sharpened) Edit: Heh, O.P had the idea at the same time as my post I see.
 
Barry Larson said:
Thanks Dean. I'm quite proficient at standing like a dodo, so I'm taking your warning to heart. I believe there might be some value to blackening the bevel with a marker - the better to see where you are grinding and how much. Thoughts?
Be safe and stay well.
Barry W. Larson
Calgary, Alberta, Canada eh!
Click to expand...
That’s why they are called Sharpies!
 
(Attn: @Karl Loeblein) I never get any bluing on my scrapers.....it's a matter of developing a technique that prevents that possibility.....Which includes having some water handy......if it starts to heat up, cool it down.....simple! However, I do occasionally get a little minor bluing on my gouges, but only on the surface. The bluing is gone with the next pass, and is not present below the surface. One thing I feel is important, is I'm a honer, and never rely on an edge straight from the grinder for this purpose. With a CBN wheel, the edge these wheels are capable of, won't be as sharp as my gouges are.....that is, unless they also hone. Even at that, honing is from multiple directions, and a wheel produces an edge from a single direction, which in my opinion makes a big difference in the fineness of the edge that can be created. Even with an 80gt wheel, the edge it provides will be sharp enough to cut, straight from the grinder.....but, the real question is: How well does it cut?.....and, can it cut better by honing? The same questions can be asked of a CBN wheel.

For me, the only purpose of a grinding wheel with the intent of creating a fine cutting edge, is to remove metal......nothing more.

(Attn: @Doug Freeman) I'm just coming in from the shop now, and while I was out there, I checked for a bur on the bottom of my scrapers.....and, lo and behold, there is one.....very small and almost undetectable. What makes it even less detectable, is I polish the bottoms of my scrapers, and round the corners at the same time with a deburring wheel What little bur there was, is gone with the deburring wheel......probably why I never really noticed it.

-----odie-----
 
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Grind and use, may only hone on lathe with the edge is fading. Most of my scrapers are HSS cut from old coldsaw blades, no idea of the grade, but it does hold an edge extremely well as most saw makers have their own propriety steels recipes
 
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