Couple of scraping questions (Part 1 of ???)

[macardoso]

A newbie just barely getting his feet wet here...

Picked up a copy of Machine Tool Reconditioning, watched about every scraping video I could find on Youtube, bought some spotting dyes (canode and hi-spot), bought a 20mm Sandvik hand scraper, and I am currently building a slow speed diamond lapper to sharpen the blade.

Couple of random questions that have come up already:

1) My Sandvik scraper has a seemingly wide radius which has been giving me some trouble. My accuracy for where the cutting occurs across the width of the blade is very poor and I seem to shoot left and right of my high points with no discernable roll of the scraper. I read online that the factory provides 150mm radius as the default as they don't know what radius people will want to use. Is my frustration normal? I need to finish building the slow speed grinder and then I should be able to put a new radius on the blade.

2) What blade radius is appropriate for general work on small machines by a beginner? I have read 60 or 75mm, but don't know what is appropriate.

3) I don't yet have a piece of cast iron to work with so I have been practicing on a rusty V block. Pretty sure it is steel but soft enough to get a good bite even with a dull file. When I try to scrape it, I find the blade likes to bite, but not let me scrape forward. It just catches in the material and leaves a little flat line. If I push harder it will scrape, but taking off a wider swath of material than I want. Is this a function of the wide scraper blade, the material, or both? Is there a different grind for scraping steel?

4) I have read about the depth of the zones between high points is important for oil retention and too shallow is undesirable. I feel like the entirety of my scraped surface has very little texture. It is very flat, not necessarily in the sense of the "trueness" of the surface, but rather the scraping texture. I have nothing to compare against, but I feel like I am unable to develop the depth of texture required. Again, is this a function of the overly wide scraper blade?

5) I've used hi-spot blue for quite a while and have a good feel for how to develop a thin film on my surface plate. I can get decent spotting this way. The canode blue seems much tackier and I am having trouble getting anything but the thickest film. Any tips? I ordered a rubber brayer, but it has not yet arrived.

6) Are there good substitutes for red lead as a contrast medium? I don't really like the idea of anything lead in the shop, especially with pets and it being my house. Dapra was sold out of canode yellow when I ordered, but I did get some red. Is there another source for the canode inks besides Dapra?

7) I am having a much harder time seeing my spotting on this steel practice part than I was when I was scraping in some bearing blocks on my steam engine a few weeks ago. Those were cast iron. Something with the extra reflectivity of steel is making it hard to see. Any tips?

8) I might have a source of a 12x18 cast iron surface plate and an 18" cast iron parallel. Would these be good projects to start practicing on?

9) After those, I'd like to do a straightedge. my needs are to do a small mill and a 12" lathe cross slide. A 12" straight edge would be plenty long enough to do everything on both machines except the mill column and table. The column is roughly 18" of dovetails and the table is roughly 24". What would be right size straightedge casting to buy? I'd like to keep it as small as possible, both to help with cost and the difficulty of rough machining it (I only have small machines not capable of roughing the castings, so I'd need to make a friend).

10) Is there any good material on the technique for flaking? I have found nothing more than perhaps a 15 second clip of Abom79 doing a draw stroke with a dead blow mallet at one of Rich's scraping classes, but with zero explanation. I have no immediate need to figure this out, but I am curious.

11) I watched Robin Renzetti's video on Moore pattern scraping. Is there any particular benefit to doing it this way? Should I be developing the muscle memory for that? I'm finding it nearly impossible to form the crescents without digging the corners, but I suspect that is also a function of the overly large radius on the scraper blade.

12) Is there an appropriate corner treatment for the scraper blade? Out of the box, the Sandvik insert is sharp all the way to the corner. Should this be blunted?

13) I do not own precision ground flat stones. I do have a cheap fine india stone that I have sanded flat relative to my surface plate (abuse I know...). Is this acceptable for the time being, or are the PFG's a requirement? They aren't cheap and I feel like scraping has turned into $100 here, $100 there, $100 everywhere.

14) I have not found a source for the little lapped steel scrapers block used to bridge high points during measuring. Anyone know where to find one? I don't have a shop full of nice flat ground stuff, so I'm coming up short with anything to substitute.

That ended up being a few more than a couple questions, but I want to say thinks in advance for any answers.

Mike

 

[Janderso]

You can't do anything without a surface plate.

Grade A 12" x 18" Black Granite Surface Plate

www.shars.com

 

[macardoso]

You can't do anything without a surface plate.

https://www.shars.com/gradxe-a-12-x-18-black-granite-surface-plate

Whoops, forgot to mention that. I have an 18x24x3 black granite plate, grade 00 (B) with a cal cert showing max deviation of 2um, low in the middle, high in the corners.

It is an import plate, so I only trust the calibration so much, but it is what I have.

Edit, I'm doing research now. I bought the plate new for $120 advertised as a grade B. The cal cert states Grade 00, which upon further research is metrology lab grade. I'm calling BS on that cal cert and now have no clue how flat my plate is. Ugh.

 

[benmychree]

The Canode inks can be thinned out on the surface plate with a spritz of Windex glass cleaner, yes, the corners of the insert should be rounded to avoid digging in, and the radius should be smaller as you suggest, that can be done on a diamond grinding wheel if it is fine enough; I have scraped for many years without a slow speed lapper. I have always used a India stone for deburring. Texture is achieved by using more downward angle with the scraper.

 

[Cadillac]

Use a gauge block to span the points. Can be bought separately through places like McMaster Carr or so. You want to get familiar with your technique so that you can control your depth of stroke. Lots of practice and practice.

 

[Cadillac]

I bought my canode at artco.

 

[Richard King 2]

Go to You Tube and watch my friend and student Stefan Gottswinter

Robin R does not show the Moore scraping. It's his take on it. If you want to see it done the correct way. check this out

I have been experimenting with Arcryic paint I found in the arts and crafts dept at Walmart. It's the tubes hanging on hooks and cost around $2.00 for a 8oz. tube. Squirt out a quarter size amount and dilute it with 4 or 5 squirt of Windex. There is Yellow, red, white and blue. I have also had good luck with Canode for years and if you want to see it better mix some Charbonel water based Prussian blue in it. Spread it with a soft foam roller first and then a hard rubber brayer. It needs to be transparent on the plate. You should be able to find some scrap cast iron at a scrapyard or surplus steel yard. Many of my students have you tube shows on there. Just search "Richard King Scraping" . I'll write more later... its past my bedtime...lol Pic's showing inks, plates, control gage we use to count points and grind blade radius. I say 60 mm rad for beginners, home made lappers, yours truely working inside BIAX show booth. PS: You know if you come to one of my classes I will teach you how to do it all. I also sell a DVD and HSB Stick showing you how. Check out my forum at the top of the forum lists

 

[macardoso]

Go to You Tube and watch my friend and student Stefan Gottswinter

Robin R does not show the Moore scraping. It's his take on it. If you want to see it done the correct way. check this out

I have been experimenting with Arcryic paint I found in the arts and crafts dept at Walmart. It's the tubes hanging on hooks and cost around $2.00 for a 8oz. tube. Squirt out a quarter size amount and dilute it with 4 or 5 squirt of Windex. There is Yellow, red, white and blue. I have also had good luck with Canode for years and if you want to see it better mix some Charbonel water based Prussian blue in it. Spread it with a soft foam roller first and then a hard rubber brayer. It needs to be transparent on the plate. You should be able to find some scrap cast iron at a scrapyard or surplus steel yard. Many of my students have you tube shows on there. Just search "Richard King Scraping" . I'll write more later... its past my bedtime...lol Pic's showing inks, plates, control gage we use to count points and grind blade radius. I say 60 mm rad for beginners, home made lappers, yours truely working inside BIAX show booth. PS: You know if you come to one of my classes I will teach you how to do it all. I also sell a DVD and HSB Stick showing you how. Check out my forum at the top of the forum lists

Hi Richard, thanks for the response!

I've been through Stefan's videos and many others. They really make up the limited foundation of my scraping knowledge, supplemented by some books, and information given by others here who have taken your class.

My very first try working with Canode blue was that it did not mark as vividly as an equivalent film thickness of prussian blue, but the clean up was very easy. I should revisit it and try again. I will probably give your Charbonel blue a try as well.

Having a buddy 3D print me a control gage. I still need to adjust the factory grind on my Sandvik scraper, and them I'm going to jump into some practice pieces.

BTW, I hit the section in MTR where he describes the water bed leveling method. Just curious why this gets so much flak? It seems impractical to set up, but it does sound like it would provide a good absolute reference surface to level to.

 

[Richard King 2]

How do you measure the height? From a raw casting to the water top, no thanks. I used to use that method when I was a Boy Scout and was setting up a fire pit grill Water in a fry pan...not to precision. I can call John Saunders (Nyccnc) and see if he would host one again in Zanesville, OH next fall....

 

[Richard King 2]