Hand Scraping for Flatness?

J. Keeton

J. Keeton

Joined
Nov 15, 2005
Messages
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So I was surfing around YouTube today and came across some videos about hand (or power) scraping surfaces to achieve extremely flat surfaces. I sat there with my jaw dropped for about 30 min... I never would of thought this was an effective method for making things flat...

It's pretty gosh darn cool... but is it applicable to knifemaking?

Has anyone attempted to flatten their work with either hand or power scraping?

I guess a major negative would be that you'd have a hard time with this method post HT. And it would probably take a significant amount of time if you're not using a power scraper. I could imagine it would help with an epoxy bond on full tang knives and maybe yield a neat texture on your flats.


Just thought this stuff was cool and wanted to share/talk about for those who haven't seen it before... like me!

Cheers,
JK

What is metal scraping:

How to hand scrape:
 
I've never heard of it being used in knife making, don't really see a reason considering surface grinding is more than adequate for knife making tasks and much faster.

Higher end vertical knee mills and some other machine tools have their ways scraped, not only is it flat but it holds the oil better than a ground surface. There are a few people who teach it in classes, otherwise you might have to go to Taiwan. Most of the better light industrial machines being produced now come from Taiwan and have scraped ways.
 
It's for cast iron, very seldom done on steel.
It's a flat reference surface, but not smooth - it gives a floating oil film

It removes .000 1" per pass

You mill or plane, then surface grind to get in the neighborhood first.

Richard King gives classes - not cheap just shy of $2,000

more videos


Stefan is more informative than nyccnc John is





Keith Rucker

The book on why
free e book
https://archive.org/download/FoundationsOfMechanicalAccuracy/Foundations_of_Mechanical_Accuracy.pdf

http://mooretool.com/publications.html

Buy the real paper copy
Foundations of Mechanical Accuracy
 
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I've heard of people scraping fullers
IMO knives don't need to be that flat, but arguably I'm just sloppy
 
The sen is a scraper tool used traditionally in Japan for fast stock removal of unhardened steel. Different shapes have been used for different effects (for example the hi [fuller] on katana, or urasuki [hollow back] on single bevel knives). You can see one being used here, about 4 minutes into the video:

I've made one, but never could get the hang of using it. It removes metal fast for sure, but it requires a lot of practice to not leave the surface badly gouged. I suspect that if you were skilled in using one it could be a big time saver for some things, and it's more pleasant to produce metal shavings than grinding dust.
 
Back in the early '80s I spent two years of my apprenticeship doing scraping in the machine rebuild shop at Dana Axle. Spending several months on a single machine frame was the norm. It was slow work, but rewarding once the machine was reassembled and running.
 
Thanks for the dropped knowledge above. What an awesome process.... This may be one of those things I never do myself, but that I get great pleasure out of seeing the fished products other skilled people produce. Extremely cool.
 
Frosting (which is done similarly to scraping, but as opposed to scraping is done to gouge the surface) might have a place in tangs, but it's the same concept as filing and a whole lot more work. That's how they scrape prismatic ways to create pockets of lubricant. Filing would be better for a tang, but if you wanted it to just be decorative (and I've thought about that) frosting could look pretty interesting.

Scraping (as it's used for industrial purposes) would be unsuited to knife making. Firstly, a knife never needs that level of precision. It's just absurd to aim for millionths of an inch flatness on a knife that will ever be used for anything. Scraped surfaces are created as such to improve the mate between other scraped surfaces (which is why ways are scraped with their mating parts together, and once done, they will not be interchangeable with another pair unless they are re-scraped. Scraping allows you to count points per square inch of flatness to create maximum surface area contact at any time between two surfaces. This kind of finish would serve no purpose in a knife, and would be ruined quickly. A mirror or smooth satin polish would be better in every instance.

Scrapers are almost always carbide ground around 90* (I can't remember if theyre a little over or a little under). On some of the higher wear resistance steels, you might not even be able to scrape them at high hardness. I've tried it once on a 1095 beater, and cosmetically you can get scratches, but it is more trouble than it's worth. I ended up just polishing out the scratches with a dmt plate.
 
WhitleyStu said:
Back in the early '80s I spent two years of my apprenticeship doing scraping in the machine rebuild shop at Dana Axle. Spending several months on a single machine frame was the norm. It was slow work, but rewarding once the machine was reassembled and running.
Click to expand...

By hand, or did you have a power scraper ?
 
I've wondered about flaked surfaces in two applications: kitchen knives, and folder pivots. I'm really curious how it would compare to tsuchime - if it achieved a similar result, it would be nice for this kitchen knives. However, I'm inclined to think that the conforming nature of food might prevent any benefit.
 
12345678910 said:
By hand, or did you have a power scraper ?
Click to expand...
We scraped everything by hand, but flaked with a power unit. Several times a year we would check our reference plates with the granite block and correct any spots on the reference plate. A guy from Starrett came in every six months and hand rubbed the granite block to make sure it was near perfect. I don't remember the granite block's tolerance, but it was crazy flat.
 
Here they show inspection and lapping of the surface plate, interesting



These two tour the manufacturing granite surface plate facility- Standridge
It's in California so it's interesting to see all the dirty machines working outside in the open whereas here it would all be indoors



 
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