Scraping - What Can You tell Rookies to improve Their Scraping?

It has been long enough for me to ask my many students who have taken my class on Machine Rebuilding
"What can you share to the new rookie scrapers who come here for answers."

I have been teaching my Richard Kings 4 Rules of scraping and writing about it on here for years. In recent threads I see the readers who have never met me are following those rules in the photo's they share. I know the Techniques I teach are long known Rules in the professional rebuilding world, so I can't take credit for inventing them. I just wanted to "change and spread the correct info" before I head up to the scraping world in the sky...lol (hopefully for not at least 20+ years)

I have so many members of Practical Machinist who have now taken my class who already share on here. I ask my students in the classes to pledge to me they will pass on my knowledge I taught them in the future.

I am so proud of what I have seen in the past year when I see the young and old who used to be shy and never spoke out to the old groups who used to fool rookies giving bad advice on here and on other area's of the net. I again want to thank the management of this forum for giving me and others some leeway on what we teach to the future generations who will read the archives in the future.

Please limit your answers to things you have learned from a professional scraper. Recently I know I have upset a couple of folks who tried to share their experiences who I challenged with what they wrote about. I didn't do this to Hyjack your info, But I challenged your info as I found it to be not the professional or common sense way.

I want the once rookies to teach here. I want to observe and will add a few comments from time to time.
One thing the students will learn is sometimes you will upset a few folks, but worth it to see something once called "a lost art" to be now called a "once a Lost Art" .

The major thing I have always taught was to scrape the checkerboard pattern,."

What say You on what you learned to make your scraping improve?

Practice! Scrape as often as you can.

Getting my scraper truly Sharp buy lapping with diamond paste and a proper rest
switching from Permatex Prussian Blue to dykem High spot
following 4 rules

Hmm. Talk about a minefield...

I'll tell you my experience. When I started scraping, I didn't really understand the difference between roughing and finishing. There is a lot of great information about how to finish scrape and endless discussions about points per inch and spotting techniques and how to blue. There is very little info available on how to rough. And, IMO, roughing correctly is where you can really save time.

I think the other trap guys fall into is thinking that they can fix any clapped out machine with a minimal investment in hand scraping gear. The reality is that if the ways on even a modest sized machine (say a Bridgeport or 40" center lathe) are worn more and .005 or so, you might be scraping for a month. I think a lot of people view scraping as an alternative to machining a worn surface, and it can be, but there are practical limits.

Scraping is kind of like any other repair work. There is endless debate about the "right way" and people like to throw around absolutes (never, always, can't, won't, must, etc). The reality is much more blurry.

If you put 10 mechanics in front of identical engines and asked them to rebuild them, you would see 10 different techniques, 10 different sets of tools, 10 different selections of parts, etc. And, there could well be some tension between the guys. But, in the end, I would bet all of those engines would run fine and live a long life. The trained observer would see that while the specifics are slightly different, the methods were pretty similar, and the outcomes were generally the same.

One big thing that I understand now and I make a point of when someone starts talking scraping is all the alignment that goes along with it. Seems like too many think you can just scrape a saddle and its ways to fit and you're golden. That would be great if a machine had only one axis of alignment. Reality is you start moving one piece and the whole rest of the machine may have to come along with it.

up to the scraping world in the sky...lol

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I'm sure all the ways are perfect in heaven and God scoffs at an accuracy of a mere 50 millionths.

Sandvik carbide blades come from the factory sharp enough to scrape with, but they are the wrong radius for you.
You are very likely to dig in an edge leaving a big scratch. It will be hard to control the scraper, especially if using a Biax.

Grind the radius down to a 60mm radius, and learn how to scrape. You can later increase the radius for roughing if you want- but wait until you have good control.

Sharpen the blade more often than you think you need to at first. They dull slowly, and you get used to the feel, but have less and less control. You need to learn the "feel" of a sharp blade as being "normal" so you will recognize a dull blade as what it is (and is not).

In addition to the Four Rules. I learned not to confuse flat with smooth, hinge the part and do not go for bearing until you are in fact flat. Also with the part on the surface plate, Tap around the edges with a rubber mallet, listening for a solid thud. If it is not a solid thud and hollow sounding the part is not flat in that area or in full contact with the plate.

However the lid is not nailed down quite yet, so I am not done learning, there is more to come.

Thanks Rich for your help & support.

Individual Scrape Marks

Individual Scrap Lines

From the class last year at B&K this was the biggest thing for me.

Rule No. 5. Don't park on wife's carpet grass! Sorry Richard, couldn't resist. Ken

cash said:

Individual Scrape Marks

Individual Scrap Lines

From the class last year at B&K this was the biggest thing for me.

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That was an epiphany for me too: before the class at Tuckahoe all my attention was to remove any possible speckle of blue. Doing individual scrape marks and individual lines was counterintuitive at first, since there was too much blue left for my taste. But I compare scraping this way, developing the checkerboard pattern to developing a black and white print in the darkroom a few decades ago: nothing, nothing, and then the image starts appearing rather quickly.

Paolo

Pick your projects visely

starting out start with something rewarding, recondition and old Stanley plane, 20 bucks for a beat up one and it is made out of good CI. Get the sole flat, scrape the frog and the frog seat, and enjoy a truly well tuned wood plane. Learn the four rules, do not be afraid to put force into the scrape, you need it for depth.

The hardest thing to develop is control, you need to be able to to feel where the blade will cut, Put a mark on the top of the blade and use it judge how you need to tilt the blade to move the cut to the right spot. Will not need it for roughing, but you will not be able to finish without getting the control.

Remove as much rust as possible before you start scraping, rust kills the edge. If you can, machine the surface before scraping. Do not try to scrape off more than 3 to 4 thousands. A pass of roughing removes 2 to 3 tenths. To remove 3 to 4 thou you will have to rough 20 to 30 passes. Have a plan to step scrape for alignment. Mark the areas with a sharpie, so you know where to scrape how many times. I learned that step scraping more than 5 steps can create uneven surfaces. I try to limit my steps to five or less. remember step scraping tilts the surface. Need to take that into account when scraping a machine surface that one needs to keep in alignment.

When you are done roughing you want a checkerboard pattern already established. I do not like paint scraping, after i am done with the first surface removal i switch to individual marks and rows, i just use long marks. keep your marks evenly spaced and even length, with spaces about as wide as the marks. Kinda hard at first, but you get used to it. Do not start finishing until you have even coverage. A surface ready for finishing should have evenly spaced highs maybe 10 PPI. The bearing percent is not that important, but if you have a very low bearing then once you start finishing you will have peaks moving all over the place and you will not know where your lows will develop. The more even the roughed surface the easier your finishing will be.

Learn to spread ink thin. Keep chips off the surface plate. Always wipe everything off with your hand. Sounds like an oxymoron when you are blue as a smurf, but cleanliness is supreme, anything in the ink, on the part can totally throw you off. Learn to spot right. The closer you get to finishing the more you have to rub the part on the surface plate. learn to read the spots. Colors and edges indicate the height of the spot. When roughing you can ignore spot color, concentrate on areas. areas with many spots are high and few sots are generally low. You need to bring down the high areas, not just the high spots.

Sharpen sharpen sharpen, and use the right angle for your material. Not all CI created equal, softer material need more negative angle. Watch for chatter. You can play with the attack angle, but remember if too low the cut is shallow. you need good depth. You want the surface look hand scraped but not helter-skelter, keep you rows even length for each pass. You can't sharpen too often, when you feel that the tool is no longer biting into the surface with quite low pressure, it is time to sharpen. it takes only a few seconds.


I will think of there things that I either learned from others or just stumbled onto it.

dee
;-D

Paolo_MD said:

That was an epiphany for me too: before the class at Tuckahoe all my attention was to remove any possible speckle of blue. Doing individual scrape marks and individual lines was counterintuitive at first, since there was too much blue left for my taste. But I compare scraping this way, developing the checkerboard pattern to developing a black and white print in the darkroom a few decades ago: nothing, nothing, and then the image starts appearing rather quickly.

Paolo

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Third that! That was the biggest thing for me too. You read places that it is all about removing the high spots, but in reality it is to develop even bearing across the whole surface, when you have lows that are 1 or 2 thou below the high areas, you just go at it and "waffle" the high area down to where it is level with the rest. And you need not to worry about hitting only the blue spots since you will take 5 to 20 passes to get it down to the level of the hole, it will average out. Also it is important during the roughing to stone well after each pass. The reason i do not like to step scrape more than 5 steps, because the surface scraped 5 times becomes quite gnarly without being stoned between passes. The stoning knocks the top of the peeks off and provides bearing flats that are better than some narrow ridges.

But yeah, it is very much nothing, nothing, nothing and puff all starts showing up. Sometimes putting fresh ink on the stone provides a bit "encouragement" during roughing. BTW this is independent of wheter you hand scrape or biax it.

dee
;-D

I've made mistakes with consistency in ink thickness. Each cycle I was just going over the plate with with the roller, but not applying new ink. After a few cycles the ink gets thin and the readings change. I get more consistent readings if I apply a little ink each cycle, instead of just spreading out what is already there.

This goes along with Rich's method of not applying the ink to the mark-up area directly. Instead, spread the ink in a small area for re-inking the roller and then applying it to the markup area. I also find it useful to apply a little sideways force to the roller as I'm going over the markup area. This smearing action helps me redistribute the ink more evenly. Often times one part of the roller will be more heavily inked, resulting in stripes in the markup area. A little smearing action with the roller helps even it out, as does rolling from several different directions.

I also fail to re-sharpen soon enough. I don't notice how dull the blade is until I start scraping with a sharp blade. Then its obvious the blade was very dull. I thought my hand methods of sharpening were good until I used Rich's Glendo. Now I have a Glendo

Blade stiffness makes a difference. I made a hand scraper that was too stiff. It was much closer to a chisel than a paint scraper. Thinning out a section of it on the mill made it much more pleasant to use.

Make sure your stone is flat. I rolled edges of my part because the stone was concave. I've used a diamond knife sharpening 'stone' to flatten them.

Bevel the thin edge of the stone to reach into dovetails.

The same goes for scraping. Bevel one side of a scraper (insert) to get into dovetails.

Using a small vacuum on the part before markup keeps chips off the surface plate.


Andy

Likewise, lift the roller at the end of the stroke to keep it spinning after it's off the plate. Especially on small blue-up areas it helps randomize the roller/plate contact areas for a more even blue up. I smear the roller sideways as well.

Sent from my XT1053 using Tapatalk

Spyderedge said:

Likewise, lift the roller at the end of the stroke to keep it spinning after it's off the plate. Especially on small blue-up areas it helps randomize the roller/plate contact areas for a more even blue up. I smear the roller sideways as well.

Sent from my XT1053 using Tapatalk

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on the surface plate I roll in both orthogonal directions, it helps to even out the ink. On a straight edge i do two passes of one short diagonal strokes and then even out with long strokes along the whole length. The ink can never be too even .

How about Hand scraper styles?

I find it amazing how I have been telling everyone for years how I do not like Andersons and people continue to buy them. In the last class at Steve Watkins I think someone did bring an Anderson wide and stiff one and it worked pretty good. But the smaller smashed tube ones are not so hot. Lets hear what you all like. You all know which one I like. I'm trying to let you students and non students show your favorite scrapers. Please include a few pictures.

Student in B&K class with his homemade Biax Type, Boston student bump scraping using a drafting magnifying light. Germany scraper using a Sanvik type, Yours truly scraping a slide off a Swiss Screw machine and a home made Biax Type and a real Biax type with rubber pad on the end.

I was one of the guys that preferred hand scraping to using a Biax power scraper. Every time I tried a power scraper it felt out of control. Since taking the class at Bourne and Kotch there hasn't been a week that I haven't scraped on something. Within the last two weeks I have scraped a set of angle plates, four dovetail straightedges, three levels, and a surface plate. I probably don't go two days without scraping on something.

My point is like the others have already mentioned, practice, practice, practice. What practice will do for you after learning the basics is how thick the spotting ink should be, when to sharpen the blade, how long the stroke should be, how fast the variable speed should be, and how to read the piece after spotting.

What Rich teaches is the basics but it's up to you to put in the time. I don't know how I got along without a power scraper! Oh yeah, very slow...

Other Brother said:

I was one of the guys that preferred hand scraping to using a Biax power scraper. Every time I tried a power scraper it felt out of control.

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Darryl.

Good to see you back in here. You were M.I.A for a while? I was worried about you. Glad to see you are back.

I'm still inspired by that Quill / Moglice / Devitt thread from a year or two back. We need the top end blokes here.

Of which, you are one. Some of the stuff I read here is very suspicious.

Regards Phil.

You know I was an Anderson guy, smashed tube and filled with babbitt.

But now I prefer the Dapra/Biax hand scraper. Springy.

machtool said:

Darryl.

Good to see you back in here. You were M.I.A for a while? I was worried about you. Glad to see you are back.

I'm still inspired by that Quill / Moglice / Devitt thread from a year or two back. We need the top end blokes here.

Of which, you are one. Some of the stuff I read here is very suspicious.

Regards Phil.

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Put a link to that would you. Did he tell you who told him about Moglice ?? lol

Daryl is an amazing guy with tons of checking squares and devices.