Power Scraping a Camel Back Straight Edge using a Biax Power Scraper

[@carver3419]

Wow! What a great door prize .... That Biax Power Scraper sure streamlines things.

[@leiferickson9666]

I thinks you need a lesson or two, man a butcher you are! 🍁

[@jasen963]

Wow and I thought grinding would of got it to precision flat I did not realise that scraping takes it to a higher level of accuracy. Thank you Keith for your knowledge

[@63256325N]

Some lucky winner will be getting a nice tool. Have fun at the party. Thanks for the video.

[@ron827]

Absolutely super as usual. Having a Keith Rucker scraped straight edge would indeed be a treasure to own. I assume you will personally mark it in some way like all good artists.

[@lookcreations]

Am just setting up to scrape in half a dozen camel backs so I can scrape in my lathe bed. Good quick refresher thanks KR

[@michaelshea5427]

Great job Keith! 6 Ten-thousands out to start and probable 2 ten-thousands or better after! Awesome!

[@michaelshea5427]

The big black granite Brown and Sharp surface plate that Keith was checking his work on by using the blue dye is a precision plate that came with a calibration certificate. Its analogous to a 1" proof gauge one uses to check their calipers or micrometers. The granite plate is just a big flat version used for checking flatness. When Keith rubs the Camel Back straight edge on the plate with the blue dye it is showing high and low spots in the Tenths! The way scraping works you can not remeasure with the test indicator like Keith did in the beginning because you have hundreds if not thousands of tiny high and low spots that the test indicator would constantly be bouncing up and down on. Anyone concerned about having an amazingly precise straight edge would love to have this!

[@vajake1]

Thanks for posting this one! Great work Keith!

[@johnapel2856]

Interesting. I have never seen scraping done. It is not what I expected. I need to watch your other scraping videos. I'm starting to get a little understanding of why and how the process is done. Thanks!

[@ROBRENZ]

Nicely done Keith! ATB, Robin

[@morelenmir]

That is an absolutely fascinating technique! Somehow, despite being interested in machining and other handycrafts all my life--mainly through exposure to steam locomotive restoration and preservation--not to mention growing up in what used to be the heavy industry centre of England I have never seen this done before! The surface pattern it gives is beautiful and very hypnotic to look at. It reminds me a little of pattern-welded steel or (so-called) 'wootz steel' tool blades. Obviously totally different in composition, but the effect on the eye is similar. Were it mine I would be too afraid of spoiling the lovely edge to use it!!!

[@markkoons7488]

Thank you for this video. I find the subject exciting. I realize this craft - all craft - is rooted in utility but I'm "KZbin-investigating" the techniques of scraping for the art metals possibilities, their surface decoration value. I think scraped surfaces are beautiful and I'm considering how they might be displayed in future furniture or architectural projects. Would you or any of your viewers care to direct my attention toward scraped non-ferrous work?

[@stephenwagar2663]

A# 1 Video , You Say Not Much Detail , But I Learned More From This Video Than Any Of The Old Ones. I Have Been Watching Since The Table Saw Restoration, Thats When I Saw Adam . My World Blew Up And Now I Watch , Fenner , Mr. Pete , Richard , Don Cosset ,Steve Summers Tom Lipton , Pierre ... All Because Of You , Thank You Sir !!!!!!!!!!!!!!!!!!!!!!!!!

[@MrRustydawg]

Thank you sir. That was educational.

[@jessemancuso7837]

Great videos, Keith! Very helpful and I really appreciate them. Thanks!

[@MrShobar]

Nice work, Keith. Scraping is really an art. I enjoyed this.

[@JesusvonNazaret]

The yellow really helps to see what you did on the video

[@Musicalbullet]

Great video Keith! I love the scraping videos. Patiently waiting for the straightedges to be available

[@johntompkins147]

Thanks for the video Keith never seen this process before. Very interesting.

[@WilliamTMusil]

Looking good

[@RichardHeadGaming]

A very nice prize for some lucky attendee.

[@elsdp-4560]

THANK YOU...for sharing.

[@bcbloc02]

Good to see advice is still readily available!! lol

[@bcbloc02]

I am sure at some point I will do some scraping on video and I will go thru the "advice" I receive then. I don't want to hijack Keith's video.

[@markdawson1435]

chris0tub

[@dineshmk250]

nice and precise work mr keith

[@smurf196uk]

great video as always keith i am so looking forward to your monarch restoration to be honest i prefer your restoration videos more than any of the others for me they are more informative and enjoyable but in no way am i saying the other videos are lacking even the much older videos are a fantastic point of reference and very informative keep up the great work keith all my best wishes to you and yours

[@jcs6347]

Great video Keith video, thanks!

[@daviddominessy]

Thanks for the quality content as usual!

[@Pappaoh]

Keith, thanks for the great vid. I am crossing my fingers and hoping to win your straight edge at the bash, really sorry I won't see you there. Boy! Who knew this would be such a controversial vid;)

[@mike-carrigan]

Even though I really don’t need it, I really want one

[@frankinpattaya]

Keith I don’t completely understand, at 1 thou couldn’t you use 800, 1000 and so on wet and dry paper to finish it off. Regards Frank

[@oldschool1993]

Don't remember Keith mentioning how long the castings had been aged. But it looks like the grinding relieved some surface tension and the casting bowed a little- wonder if it will hold shape after scraping or continue to move.

[@BeachsideHank]

This has turned into a real huff contest amongst the 'experts", it's now all about who can blow the most smoke up the other guys a*s. Arguing the semantics of scraping with other people is useless, it's like playing chess with a pigeon- no matter how good you are at it, the pigeon will just knock the pieces over, sh*t on the board, and strut around like it's victorious. Keith, how you keep from having a drinking problem is beyond me, thanks for all you do.

[@BeachsideHank]

The greatest opponent of knowledge is not ignorance but it is the illusion of being knowledgeable, with the availability of Google and other technologies you would almost have to fight to stay ignorant.

[@BeachsideHank]

Knowing your history, dialogging with you is like massaging a wooden leg- nothing will happen. Over and Out!

[@BeachsideHank]

Got under your skin there, eh snake? Yea, you’re “helpful” alright, like a sharp stick to the eye helpful. Dunno what public school you went to, but your parents should demand their money back, you can’t even parse my 1st post in any proper context.

[@BeachsideHank]

Naw, I’ve got ol’ snake figured out. You misinterpret an observation about debate, and you take it personal for some unfathomable reason (probably seeing yourself in it somehow), and you reply like you are an avenging Golem. As to *“...with the aim of correcting and offering advice...”* You are making the classic blunder of the smug & arrogant, with the availability of Google and other applications one would almost have to fight to stay ignorant, so drop that “sharp stick” of yours, you’ll be the better for it.

[@BeachsideHank]

You continue to deny, deflect, and obfuscate, and you’re the one who wanted “engagement”? Be careful what you wish for, you just might get it.☺

[@tpobrienjr]

It is gratifying to see a Jorgensen handscrew (patented circa 1900) playing a central part in holding the work. It's yet another good application of that venerable tool.

[@rjkejk57]

The finish is super fine to the eye,however I wonder what it would look like under a magnifier? Is there any way to get a picture that shows the details from the final scraped piece? Just curious as to see what the scraper actually does.

[@shooter7a]

Show it floating on air! A well scraped piece should be able to float on air when you slide at across the surface plate. I learned this the hard way when I ruined a well scraped prism. I set it down, in a sliding motion and it floated right across the plate, and off the other side.

[@christopherkann6385]

Thanks Keith for another informative video. Does ambient temperature effect the flatness?

[@prodoverjeff2876]

I've done some scraping over the years, and I have a question. When scraping a camel back like this, how do you control the angle between the two surfaces? In other words, if one end of the tool is 45 degrees, how do you know it is 45 degrees at the other end? Is there some form of 3 plate method? I can understand usually an exact angle would not be needed when scraping a machine, but a constant angle on the camel back seems important. Any advice? Another video?

[@russb2945]

Good to go ..ship it...

[@MrPGT]

It won't affect me, as I can't see myself ever doing any scraping, but could you use an oscillating multi tool as a cheap power scraper? Do you think you could try one sometime and let the viewership know how it compares, or if it can even work, Keith?

[@DSCKy]

I was thinking the same thing as I have no intention of buying a power scraper, but it might be fun to give it a try with a tool I already have.

[@duobob]

That has been tried with varying levels of success, but so far nothing has shown to be rugged, long lasting, and easy and comfortable to handle and use, while also doing a consistently accurate and predictable job. If it had been, scraping fans would be copying it or buying it as a commercial item. There is a small market that it quite interested in such a tool, but the holy grail has not yet arrived. Biax scrapers cost several thousand dollars new today. Please, anyone, come up with something just as good and long lasting as the Biax scraper, or hopefully even better, and you will be able to sell many thousands of them. My Biax scraper was built in the 1970's and has been used hard since. It still works well. Build a better mouse trap and people will stand in line to buy it...

[@MrPGT]

Thanks, Bob. It is just something that has been tickling the back of my brain since I saw the first of Keith's scraping videos with the Biax scraper in it, and I thought it looked a lot like a multi tool. DSCKy, pretty much how I feel, but I have neither the space nor a real need to do any scraping. It looks like a pretty cool skill for a machinist, though.

[@ke6bnl]

heard of people buying a pneumatic gasket scraper from harbor freight to do this, not the mass that this tool has though.

[@hankus253]

Is there any concern for the age of the casting and the accuracy of the scraping for the short term? Can a iron casting be aged faster by repetitive running through heat and cold cycles?

[@shadrachmalooly9394]

Very interesting video. So what's the blade of the scraping tool made from?

[@ClipperDays]

Shadrach Malooly. Carbide edged tool steel.

[@shadrachmalooly9394]

Many thanks ClipperDays.

[@a320214]

Awesome !! At 6:55, is it paper rag or ?? ( lot of small rag-particles coming with the yellow )

[@N57RU]

Well Keith, I enjoyed your video as always But........ 1) Get rid of the paper towels for applying and use foam rollers to apply your bluing / yellowing. 2) If you want to make a precise tool, your going to have to age and or normalize those Green Castings. 3) You need a master gauge to check your 45 deg's. Just friendly suggestions....... (Wink)

[@N57RU]

Could be, but did you notice the paper flakes after he wiped on the Yellowing. Paper towel gets in the points and doesn't clean out easily. It snags the cast iron.

[@tr5317]

All the yellow compound does is allow a bit more contrast to make the blue move visible. The blue can be very hard to see against the grey of the steel. This is covered quite thoroughly in all of the videos from oxtoolco, robrenz, thisoldtony, stefan gotteswinter, etc.

[@tr5317]

Check out the oxtoolco video on "how thick is a sharpie", and maybe you'll find that the thickness of these dye materials being applied might not be as thick as you think

[@cup_and_cone]

Sorry, you might have said it in a past video: what is the stroke rate on the power scraper?

[@michaelmelrose1260]

Keith - a question.. Back when I served my apprenticeship as a Millwright in the Pattern Making Shop we all always left castings outside in all weathers to "settle down" as the Foundryman would say. Do you age your castings before working on them. Best regards Mike

[@elischultes6587]

Michael Melrose I believe the ones he got previously from Richard King he said they were aged a year. Keith hung them and rang them with a rubber mallet.

[@sblack48]

Did you do anything to get the stresses out of the casting, like whack it with a mallet etc? Or was the casting stress relieved? Nice video, cute little straight edge.

[@michaelshea5427]

For those wondering why scraping. You cant affordably buy surface plates that big to diamond lap and you can't lap lathe, mill and other large equipment ways and dovetails.

[@elchuco00]

I find sticking your tongue out to your left instead of your right while scraping, you get much better accuracy..... Grteat vid!!

[@elchuco00]

No bite....just hold it in place with your lips!

[@elchuco00]

Might get close to the same accuracy......but not quite there...lol

[@crockteerden4023]

I find it easier to scrape back toward you so your not scraping over your chips

[@agdtec]

Couldn't you program at CMC to engrave a pattern like that better accuracy and quicker

[@Bhupindersingh-rh8jt]

Vmc can't do like that.. vmc also need secreping of linear guide way fitting....

[@powaybob]

Great stuff. Did I miss the part where you checked the 45 deg. angle between bottom and side?

[@xenonram]

powaybob it's not meant to be 45°. It needs to be

[@kellerrobert80]

This measures flatness. There are better tools to precisely measure angles, eg sine gauge.

[@peterkolovos3079]

I don't get this process at all. He ground them flat then scraped them? I know nothing about machining but they were already ground flat.

[@MrSpad007]

Seasoning cast iron for about a year after casting thence machining works best.

[@jmhannnon]

I would have thought that the cast iron needs to be aged a bit before going for a precise surface.

[@Landrew0]

Why would something so small need a camel-back? Wouldn't an I-beam be sufficient?

[@scottgarloff1390]

so it was too flat?

After the scrapping how accurate is it? In the beginning you used a dial gauge to show it was 6 thousands of an inch out, what was it after the scrapping?

[@tonysplace8009]

You mean 6 10-thousands of an inch

[@ClipperDays]

After scraping it's as good as the surface plate. And Brown & Sharp is pretty dang good. Back a few videos he told us just how flat when he got it. But I don't remember.

[@lookcreations]

The degree of flatness achieved can only be as good as the reference surface used. Surface plates are made to different tolerances if flat. There are special measurement tools to check and confirm and then certify at the given time. Once the plate is used that value becomes suspect. Tom Lipton has some excellent videos on the subject Oxtools I think is his channel. As for the yellow butter 🤪

[@Phantomthecat]

lookcreations Keiths plate was calibrated not long ago to AAA so it's pretty damn flat. 👍

Yes, but then there was no point in using the dial indicator if there was none done afterwards,

[@Лишнего.нет]

А мы толкем жженую резину мешаем её с маслом далее промокаем сложенную тряпочку и наносим на плиту!! Вместо краски !! Удобней и цвет на метале лучше видно!

[@clydedecker765]

Not criticism - observation. It appears that your grinder is bowl shaping or arching (lower in the middle of the grind). Is that really true or just a happenstance of uneven hardness of the castings?

[@iteerrex8166]

yes i noticed that too and was gona say something, but u beat me to it lol

[@ClipperDays]

Could be a little of both. Now when Keith scrapes in the ways of the surface grinder, he will get better results.

[@Hoaxer51]

Clyde Decker, kinda hard to complain about a .0006 inch belly in something you’re going to hand scrape.

[@duobob]

If and when Keith uses a 'camelback straightedge' to scrape in the ways he will get better results. He is not learning and mastering scraping just for the novelty of it...

[@clydedecker765]

Actually disregarding others, I was suggesting that the problem might be in casting and materials used because he ground them inline back to back. To suggest his machining in anyway would be totally off the mark. The machine ways would have to have a "regular wave" in them of equal specs over 12 inches. Of course he always intended to scrape them as a final finish. I said it was not a criticism of him. I can see casting/moulding/timing/releasing and material mix inconsistency as possibilities but not the machining. Materials being of mixed hardness in pouring pieces of metal is outside my expertise. As suggested .. this is NOT a big problem by any means. Just suggesting he might have a need to look at the manufacturing process but its probably too small to worry about..

[@jamescampbell9533]

Wouldn’t it be easier to lap something like this? It’s not a way that needs a oiled surface.

[@PatFarrellKTM]

Interesting video, but I don't understand the process. I know nothing about this stuff, but I would have expected the surface grinder to do a better, smoother and straighter surface than the hand gouging. Clearly I'm missing something fundamental.

[@DSCKy]

The idea is that is averaged to an extremely flat surface... there are obviously hi's and lo's but the hi's are all the same.

[@chroboe]

Pat, this is one of those cases where smoother isn't actually better. These straight edges are meant to be used on sliding surfaces like the ways of a lathe and if both sliding surfaces were perfectly smooth then there would be no room for any lubricant, it would actually get squished out. So the benefit is that flatness of the straight edge is transferred to the ways of the lathe and those gouge marks from the scraping end up acting like oil "reservoirs" and do a much better job of keeping the sliding action smooth and thus minimizing wear vs a non-scraped surface. I am not a machinist but Ive been subbed to this channel for a few years and think I have the gist of it, feel free to correct.

[@royreynolds108]

My suggestion is to look up Kieth's scrapping videos and other scrapping videos to get a better explanation of the process and what is wanted. Those videos explain what you are asking.

[@mrtrizzae]

This Old Tony has some good hand scraping videos. Explains it a little more in depth.

[@bigun447]

How many darns are in a flat? Tee Hee

[@stxrynn]

I completely understand that you are flattening both surfaces, but are you at all concerned about the angle between the surfaces? That's always been a sticking point for me. Is that important at all, and if it is, how do you keep that angle? If it's no big deal, I can live with that. But based on the geometry of the camel back, I assume you want an accurate angle. Thanks in advance for the answer...

[@TJ-ed8xg]

I think he can't really understand what he is dooing ! Of course the angle needs to be checked ! I mean, for a toy you don't need, no ... And not speaking of the paralellisme !

[@xenonram]

The angle is arbitrary. He uses it to blue the underside of dovetail ways. As long as things are straight, parallel, and square, that long, acute angle that is only meant to blue the underside of dove tail ways, does not matter. (No one would ever use it to measure an angle or to set something to its angle; for many reasons.... Even if it was a really accurate, known angle.) As long as it is an angle

[@chroboe]

Why would the angle need to be checked? The purpose of this tool is to transfer flatness from the surface plate to a larger part; this has nothing to do with angles and even if it did there are better tools to measure angles than this.

[@stxrynn]

Okay, Andrew and chrobe; that totally makes sense. I can see that. Even if you have to tilt it to get it to transfer the ink, it'll be flat on it's own plane. Now, I can quit wondering. I was thinking that it had to be in good in relation to the bottom, not independent of it. Now I know. It doesn't transfer it's angle, it transfers it's flatness. Perfectly sensible. TJ: Mr. Rucker has forgotten more than I'll probably ever know about scrapping. I'll defer to his judgement.

[@lookcreations]

Chris, if the angle were critical you would be correct in much of what you say. However for its intended use as a reference straight edge the angle has be less than that of the dovetails it will be checking. I would recommend that you watch a video where such a dovetail is being refurbished and that will help show the intended use. There is one on my channel under the shaper machine tool slide rebuild.

[@carryitaround]

12

[@donaldmackinnon4621]

hi at each kieth now hi in the middle, it was only 6 inch why not use the hand scraper?

[@EnsignRho]

I still do not understand. I've posted about this a half dozen times. It takes so much effort to scrape something like this in to tolerance. It takes time, expense, equipment, etc. What does it gain you compared to a well-polished or well-machined surface? You're going to be a few ten-thousandths more accurate. How does that gain you anything when even temperature fluctuations can cause things to increase or decrease in size by more than that?

[@Sizukun1]

I think he addressed this in a really early scraping video; essentially when a part you want to be perfectly flat and level, but is too large to put onto a surface plate, you have to use these straight edges. If your straight edge is a few tenths off, it can have a dramatic effect on the part you're trying to correct/repair or tune accurately. I think Keith also identified this with another machine repair for the ways; the oil was consistently producing a few tenths of slop every time which threw off the accuracy of the machine. A few tenths on one part, plus a few tenths on another, compound to create too loose of tolerances. My understanding is for the average hobbyist they'll never notice. But an accurate tool and scraping as a skill are useful.

[@Sizukun1]

To put it in an easier perspective, a bar stool with 3 or 4 legs will be more stable and flatter to the ground versus a bar stool with a flat bottom; its more likely to wobble if you flip it upside down.

[@EnsignRho]

Wouldn't your inability to hold the tool perfectly straight also influence the final product? If you're using a 12" scraper surface across a 48" surface being scraped, it would be very easy to leave mountains and valleys across the surface. I'm really not trying to be difficult, but given the expense and effort in scraping things like this that can't be scraped on a surface plate ... I really don't see the point. Use a gasket material that can be compressed and it will fill in all of the voids. Why isn't that a better solution?

[@Sizukun1]

I'm not an expert and don't claim to be, and you're right the valleys produced by human error and scraping are just places for oil to go. The peaks all being the same height are what really matters. Its why a square inch test window is used to count 30-40 "peaks" showing there are sufficient peaks all at the same height in relation to a surface plate. The overall piece looking like blue "static" from a TV screen shows the entire straight edge is uniformly flat across the tool. The 12" straight edge is meant for smaller parts, Keith uses a 48" camel back for larger jobs.

[@EnsignRho]

I appreciate your information, and I see the points you're making. They make sense, but I still don't see the gain in all this extra effort. He was only off 0.0006" to begin with. And we don't know what he's off now, but on his previous scraping videos he says he's able to get down to a few millionths off. Those 0.0006" variations would've been spread out over 12", meaning much less than 0.0001" per inch variation when scraping with its original form from the surface grinding. I really don't see the advantage when there's so much effort involved to get there.

[@EnsignRho]

If you are concerned about scraping it in so perfectly flat, why not use some kind of mechanical assistance to lay down the hash marks? Why use a free-hand method for that? Wouldn't you want the islands of un-impacted-by-hash-marks contact areas to be uniform? If they are not uniform it will wear unevenly over time.

[@MoraFermi]

This randomness is actually a beneficial property. Imagine for a second that your straightedge's surface looked like a sawtooth in profile. It would hide any imperfections that were repeating at even multiplies of the tooth width. With random points, you get no such effect.

[@EnsignRho]

There are so many impact points across a multi-inch surface like this, with the motor running at a relatively analog speed, that using a mechanical cross-hatch pattern would still produce randomness in the islands, but the islands would be more uniform overall from the mechanical nature of the cross-hatch.

[@silasmarner7586]

again , very well put.

[@EnsignRho]

You started being 0.0006" out max across the whole surface after the surface grinding. You probably could've achieved better than that with a slower few last passes giving it time to cool and not distort under the grinding heat, but even so that 0.0006" was only on the right/left edges mostly. You've then spent how many minute (at 16:00 you say about 45 minutes, and that was before you scraped in the side, and did a final scraping on the bottom, so maybe 60-75 minutes??) scraping this surface to a flatter form, and what have you gained? You didn't show us the final movement across the surface with your 10-thousandths indicator. But suppose it was down to 0.0001" ... what surface could you scrape in with a 0.0001" variation better than you could with a 0.0006" variation when you're going to be scraping by hand across a surface? What's to prevent your mishandling of the tool (unintentionally, but simply because you're doing it by hand) to be more than 0.0006" out anyway? I honestly do not understand scraping. So much effort for seemingly so little gain. The only time I could see it being of benefit is if you were doing parts for extreme uses, like jet engines, or Space Shuttle components, etc. For a transmission / engine mating surface, or for something else where you can use a gasket ... what is the point?

[@doscucharas]

It's not for gasket sealed surfaces it's for load bearing sliding surfaces.

[@ebrewste]

The point is to be able to make a flat (measured as coplanarity across the high spots), to whatever tolerance he needs, with minimal equipment. He doesn't need the power scraper - it just make it easier. Furthermore, he is using this straight edge as an inspection device (many people want 10x accuracy in inspection equipment over the device to be measured). We can assume he wants it to be flatter than 0.0006" TIR. It's totally reasonable to grind it better and call it a day, if he can. But the time spent scraping isn't so bad. I suspect his grinding problems were fixturing issues (in addition to heat). Those last few tenths aren't always easy to chase down. In production? This wouldn't be scraped. Note the lack of scraped items for sale from large vendors. It would be worth the time getting the fixturing made and his grinding dialed in. Lastly, I think he is learning, so he is scraping more than is strictly needed. After he gets better at scraping, he will likely be 2x faster at it and will scrape more when it "needs" to be done, as opposed to scraping partly for fun.

[@EnsignRho]

ebrewste, excellent reply. Thank you.

[@DSCKy]

It would most likely be used on machinery... like mills, lathes, shapers, etc.

[@DSCKy]

I would assume he would have used coolant or mist if he hadn't intended to scrape it afterwards. I'm sure part of the reason for scraping this was for practice.

[@henryD9363]

This is amazing but I really don't understand why he's using that power tool. It seems like Ultra Overkill and would completely destroy any hopes of having a flat surface. It seems to be digging deep trenches that are multiple thousands of an inch deep, whereas you only want a fraction of a thousanth removed. ????

[@ebrewste]

It gets tiring. Scraping absolutely can be done by hand. I've done it. I got a power scraper because I didn't want to do that again. I can dig a ditch by hand, but I choose not to. Also, you really need to be thinking / doing detective work when scraping to make good decisions, and being exhausted doesn't help.

[@henryD9363]

ebrewste Thanks. I obviously don't understand the concept of scraping. I thought it was removing very thin amounts of metal over a uniform surface. But this looks to me like digging deep grooves. I'm totally ignorant!

[@sblack48]

John H no he is not digging deep grooves. Just a few 10ths. It's hard to tell from a video.

[@silasmarner7586]

www.mmsonline.com/articles/the-art-and-science-of-hand-scraping

[@kellerrobert80]

He's taking out MUCH less than a 0.001 cut. More like 0.0001 or 0.0002 or less. The light reflecting off the scraped surface exaggerates the hills and valleys.