Image of scraper burr

[Patrick Chase]

Posting this as a followup to the scraper-plane thread, and to answer Stewie's question about how I obtained plane-like shavings from my 112.

I prepared a piece of 0.042" blue-hard (Rc50) 1095 as though it were a scraping plane blade, as for an 80, 112, or 212. Bevel angle was 45 deg. I burnished at 15 deg below horizontal (30 deg above the bevel) with a carbide rod. I used a bit more pressure than usual (though still fairly light) to try to improve the visibility of the resulting burr.

I then cut a "sawtooth" into the edge with a needle file, wasted the metal between the vertical face of the tooth and the scraper edge with a file, and imaged the burr profile at 5:1 magnification (Canon MP-E 65 lens on 1Dx II body). Each pixel in the image is ~1.3 microns.

scraper_burr_1.jpg

As I've said several times in the other thread, the profile is remarkably similar to and has similar cutting mechanics to a plane blade with a tightly set cap iron. The effective cap-iron setback (horizontal distance from the tip to the scraper's face) is 60 pix, or about 0.003".

[Warren Mickley]

The big difference between a scraper burr and a double iron is how much consistency and control you have over the geometry.

[Pat Barry]

Can you please show a picture of this same edge engaged in some wood creating a shaving? That would be more informative because the thing you are showing, while interesting, isn't telling the whole story.

[Pete Taran]

Patrick,

While you are at it, can you please also post a picture of the D orbital electrons of the steel in that blade? Heisenberg says it's impossible, but I think he was just lazy.

[Brian Holcombe]

Also, can you dress in 18th century attire and show proper technique on various forms.

[Patrick Chase]

The big difference between a scraper burr and a double iron is how much consistency and control you have over the geometry.

Yes, exactly.

That's why I prefer planes to scrapers (and scraping planes) at this point.

[Stewie Simpson]

The big difference between a scraper burr and a double iron is how much consistency and control you have over the geometry.

Doesn't controlling the geometry have more to do with the length of planes sole.!!

[Patrick Chase]

Doesn't controlling the geometry have more to do with the length of planes sole.!!

He was referring to the cutting and chip-breaking geometry, as was I in my reply. It's a lot easier to change the tip angle of a cap iron than it is to create a burr with some desired angle between the cutting edge and scraper face (these two parameters have roughly equivalent impacts on chip-breaking mechanics). Likewise it's easier to adjust cap-iron setback than it is to change the size of a burr (another pair of equivalent parameters).

[Ron Bontz]

Well you guys are definitely over my head on that one.

[Patrick Chase]

Well you guys are definitely over my head on that one.

Probably because I'm making it more complicated than it is.

Look at the 10:50 mark in the Kato-Kawai cap-iron video. This is the celebrated "money shot" that shows a vertical cap-iron face set back 4 mils completely preventing tearout.

Now look back at the picture in the first post of this thread, and imagine it flipped vertically. The burred tip of the scraper has basically the same geometry and almost exactly the same scale (distance from edge to vertical face) as the iron/cap-iron combo in the video. The only real difference is that the transition from the lower-angle "iron" to the vertical "cap iron" is curved rather than sudden.

Once you recognize that fundamental similarity, it becomes evident that the size of the scaper's "hook" is equivalent to the cap-iron's setback, and the steepness of the hook determines how much the angle changes between the cutting edge and the "cap iron" face. That was really all I was saying.

[John Stankus]

Patrick,

While you are at it, can you please also post a picture of the D orbital electrons of the steel in that blade? Heisenberg says it's impossible, but I think he was just lazy.

Pete - Heisenberg wasn't lazy, he was just uncertain.

John (physical chemist by day)

[Stewie Simpson]

I then cut a "sawtooth" into the edge with a needle file, wasted the metal between the vertical face of the tooth and the scraper edge with a file

Patrick; is there a chance you could provide a similar photo without the latter intervention. It would provide a clearer indication of what the turned hook looks like prior to use.

regards Stewie

[Patrick Chase]

Pete - Heisenberg wasn't lazy, he was just uncertain.

John (physical chemist by day)

More to the point, what he really said is that if you somehow obtained a picture of said electrons then you couldn't also determine their momentum.

I was gonna let that one lie, but since somebody else went there first....

[Patrick Chase]

Patrick; is there a chance you could provide a similar photo without the latter intervention. It would provide a clearer indication of what the turned hook looks like prior to use.

regards Stewie

The iron was never used. The reason I filed it was so that I could get a picture of the edge in cross-section. I've never been able to get a reasonable image of a scraper burr without doing that first (and I've tried). The problem is that you have to shoot it from an oblique angle to do that, and the depth-of-focus is only about 0.002" (seriously) which makes oblique views impossible to interpret. That's also why you can't just take a picture edge-on without sectioning.

As it was I had to mount the camera+lens on a micrometer-driven stage to focus that shot.

[Stewie Simpson]

Appreciate the feedback Patrick.

regards Stewie;