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Questions about scrapers

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macardoso

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I am completely new to scraping. I have never really scraped a surface but I understand the high level concepts. I am not trying to fully invest myself into learning all the tiny details, nor do I expect to have many projects that require scraping. With that being said, I'd like to have the ability to do a small amount of scraping to improve the fit and function of the machine tools that I own. They are all imports and not worth the effort to fully scrape in the machine, but I think a few passes on the various surfaces would make a dramatic difference in how the parts fit together.

My questions are:
  1. I've seen Sandvik, Biax, and Anderson scrapers for sale but they are large and fairly expensive. Are there any smaller sub-$100 scrapers for things like gibs and touchups that you could recommend. Maybe one day I'll take the leap and get all the scraping essentials, but for now having something to do some touchup would be great. I'm using a file right now, but I think it is a far cry from working as well as a real scraper.
  2. Can anyone provide a reference for how a blade should be ground? I have been using the end of a file to do some trial scraping but I find that it wants to skim and burnish the surface much more than it wants to cut. This is especially true of a positive rake. I can seem to get the negative rake tool to bite very slightly into the cast iron.
 

Bob Korves

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Below is a design and plans for a generic scraper by Keith Rucker. The drawing below is page 1 of 6. It can hold Biax tooling or Sandvik inserts, or other tools of the same thickness. It can be modified to meet your needs. I made two of them. It works every bit as well as a store bought one, and is relatively easy to make. Add a file handle or other push device of your choice. At some point I will be milling some relief into the shank to make it a bit less stiff.
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macardoso

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Wow. Thanks! That's perfect. I'm sure I have enough material on hand to make this.

What about the inserts? Are they all a standard size and grade or do they vary as much as lathe inserts? Any special grinding requirements?
 

Bob Korves

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Many of us find that learning scraping by ourselves does not really give good results. I can vouch for that. It seems that most of us need some amount of mentoring to get the concepts and techniques down well enough to do decent work. I highly recommend that you find a mentor and/or take a Richard King class if you are interested in scraping machines, surface plates, and other tooling. If not, you may very well do more harm than good. My scraping sucked, even after I had a couple sessions of mentor support from a H-M member who understood scraping well. On about day 3 of Richard King's class, something clicked and I started getting quite acceptable results. Part of that was immersion with a group and a master instructor, and part of it was working hard at it all day for multiple days. I now consider myself barely competent to work on stuff that really matters.
 

Bob Korves

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Wow. Thanks! That's perfect. I'm sure I have enough material on hand to make this.

What about the inserts? Are they all a standard size and grade or do they vary as much as lathe inserts? Any special grinding requirements?
Sandvik inserts work perfectly with that tool. They are available from eBay, but the prices keep going up and up. They are very high quality carbide, but need reshaping for scraping before using them. The 25x25mm (1x1") ones work well for ordinary work on larger surfaces. It takes a carbide grinder of some sort to shape them, and a lapping setup to finish them for use. It takes some knowledge to purchase, shape, lap, and use generic carbide blanks.
 

macardoso

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I'd love the opportunity to learn formally, but I can't justify the expense of the Richard King scraping class as much as I'd love to go. Hopefully I might be able find someone willing to mentor. To start off, I am hoping that I could (for a small expense) get enough of a tool and skill set to simply clean up the substantially crappy ways of my machines. I don't expect to generate perfect alignment or bearing surfaces, but at least going from 2 or 3 points of contact up to maybe 30-40% would be a wonderful improvement. I won't venture any further than that as like you said, I don't want to do more harm than good.
 

Bob Korves

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One more thing. YouTube videos on how to scrape are often put up by people with no clue what they are doing. Well more than half of them. As a novice, you will be totally unable to discern what is good technique and advice, and what is not.
 

macardoso

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One more thing. YouTube videos on how to scrape are often put up by people with no clue what they are doing. Well more than half of them. As a novice, you will be totally unable to discern what is good technique and advice, and what is not.

Good advice. I've watched many of them and haven't seen a difference...
 

kev74

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I made a crude scraping tool by brazing a broken carbide insert onto a piece of thin (1/8 - 3/32") 1/2" wide scrap with a file handle on the end. I roughed out the shape of the cutting edge on the grinder and honed it with diamond hone. Its not the most ergonomic, but it works.
 

benmychree

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My first scraping tools were made from mill files that I ground the teeth off of, then heated and forged down to a thin edge and re hardened and ground to a working edge, they worked fine, but dulled much sooner than carbide, but were easily re sharpened with an oil stone. when I apprenticed, the shop had Sandvik scrapers, and I made one of them my own, that was nearly 50 years ago --- and it still works just fine, but I was lucky to be given a Biax scraper and a flaker after their owner passed away. If you are just touching things up a hand scraper like the Sandvik is just fine, even the one made from a file is good enough, it just needs more sharpening. A tool of that sort is sharpened straight across with no rake, actually a slight negative rake, as the end of the tool is forged down on a taper, on the other hand, a carbide insert such as the Sandvik is parallel in cross section, the working end of the insert is ground/lapped to a negative rake on both sides so that there is a ridge in the center of the end. I like to round over the corners at each side of the insert to avoid scratching the work if the corner should catch, and also chamfer the corners of an insert for working into dovetails.
 

Bob Korves

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If you cannot afford Richard's class, find a mentor who has learned from Richard or another journeyman scraper hand. Richard tells us to spread the knowledge. Vet the mentor as carefully as possible. Again, it is very easy to damage a machine further by clueless scraping. Reconditioning machines is first about getting the geometry and flatness of the surfaces correct, and only near the end getting more points and a beautiful finish. Lots of 'so called' scraping is only done to make it look pretty.
 

macardoso

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Benmychree, I am working with the file type for now, but will be looking for a low cost way to get a better scraper.

Bob, would you know of anyone willing to help me out? It would be great to just have someone to bounce conversation off of to start.

The things I am doing right now are purely to slightly flatten out a few parts that should be flat. I have a large surface plate to reference so that shouldn't be too bad. I don't have any way of working on the ways so forget that.
 

Bob Korves

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I would come over and help you, but it is quite a drive...

Perhaps someone reading this thread who lives in your area will offer to help you get started with scraping...

Flat things are the easiest to scrape, blue them up on the surface plate and then scrape wherever there is blue showing. But the devil is in the details. It is easy to make the plate concave or convex, and convex is more difficult to notice and deal with. Also, scraping using techniques you make up will only make it more difficult to learn how to do it correctly later. I have mentors, helpers, experts, and master machinists I can call on for help, simply by being willing to ask for it, and return the favor by being willing to help others as best as I can as well. Quite simply, ask for help. That is what I did with scraping about 5 years ago. I contacted Ulma Doctor and asked for help learning to scrape. And he helped me. We have been friends since then.

Being a hobby machinist does not mean you also need to be a self declared hermit! This forum is a great source of help, and getting knowledgable help in person is even better. Ask!
 

Cadillac

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Here are some pics of the scrapers I've made and acquired in the couple yrs I've been trying to learn the skills of scraping
287669287667287668
The one in the center is one I made to hold the sandvik style blades. The one on the right I got from a flea market find its a Anderson style has a brazed carbide piece. The one on the left I just made for getting in dovetails and such. You can find the sandvik blades on eBay. Problem is they can be expensive gotta look. I've read of people putting a different radius on each side giving you four options. And grinding both sides like the picture gives you two cutting edges just flip it over. These are at a neg. 5 degrees which if read is about the go to. Different materials different angles. You'll need some diamond files, laps or green wheel for sharpening the carbide. Some spotting dyes I use Canode dye which is easy to clean up another is Dykem which is a oil base and is a bear to clean. You'll look like a smurf for days. It's alittle challenging you need to just do it and try and under stand what's going on with each pass of the scraper. It's easy to see the difference in you tubers the skilled ones show the results through measurements. Check out Stephan G I'd butcher his last name but he's a German fella with a wealth of knowledge about scraping. He's done richard kings class and is outstanding at what he does. Another is nick maybe mueller on utube he has some about scraping a compound quite thorough with some good tips.
 

benmychree

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The inserts from Sandvik come sharpened on both sides, but a person may want to change the radius, usually to something of a smaller radius for finer spotting, also I keep a insert that is ground nearly flat for scraping rust off way surfaces. The best thing for sharpening is the Glendo lapping machine, next in line a carbide grinder with a diamond wheel, then the green wheel. When I started scraping, about 56 years ago, I started out using Dykem (Prussian) blue, then after doing some reading in the Machine Tool Reconditioning book, started using red lead in oil, kept in a paper snuff box; you mix it well with a minimum amount of oil, press it into the box, and the box wicks the excess oil, for use put in a few drops of oil and rub it in with the fingers and transfer it to the marking tool and rub it into the surface, and piece of grit or forigen matter can be felt and rubbed off. I have the Canode that Rich K. gave me and it sure is a lot easier to clean off than any other medium, and I like using the yellow for background on the article being scraped; it is applied very thinly and mostly rubbed off, it makes the blue medium stand out much more clearly when rubbed off the marking tool.
 

Dabbler

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Bob is right in general, but I'll 'scrape' my archives to find the really good ones. I really believe that you can get the basics from a good video or 2, and then you can better utilize formal training if that time comes.

If I can fit it in soon, I'll post my 'best of' in this thread...

My scraping mentor missed some of the great advice from some oif the videos I've viewed on the 'tube!
 
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