# Metal Scraping, Why and How-To



## Andre

[h=1]Andre[/h][h=4]Metal Scraping, Why and How-To[/h][h=6]Rate this Entry[/h]1 Comment 
by Andre
, 05-25-14 at 12:52 PM (11 Views)*Metal Scraping, Why and How-To.*




*What is Metal Scraping?*
Metal scraping is the process of removing high spots from the work, making it flatter or to conform it to a certain shape (Ie, tapered bearing, V block) in a very precise manner that even a lot of machine tools can not match.



*Why?*
Scraping does not just create flat surfaces, when properly done, bearing surfaces, oil pockets, and specific wear patterns can be scraped in.



*What Tools Do I Need?*

The things you will need are a scraper, surface plate or other reference edge like a straightedge, surface plate cleaner, marking medium, a rubber wheeled roller to roll the dye, workholding device, bench stone (or a lapping machine if you use carbide) smaller hand stone to remove burrs after a pass, very good lighting, light solvent for cleaning swarf out of your stones, rags, metrology instruments (indicators, or other tools depending on the job.)





*The Scraper.*


A good scraper is required for a good scrape job, and it has to work for you. 
There are many types of hand and power scrapers to be made or purchased, including Anderson tube scrapers, the Biax power scraper, pull scrapers, etc. In both HSS and carbide.
If you are scraping a lot, or scraping hard materials, carbide is by far your best option. Does not require frequent sharpening, and saves a lot of time. If you are scraping soft steel, aluminum, or gib shim stock (ie, Turcite) HSS is a better option. It can be sharpened to a keener edge, and does not require a lapping machine or diamond stones, but requires frequent sharpenings.



*What This Article is About.*

This article is for the beginner, to teach the basic principle of hand scraping using common tools to achieve the simple task of flattening the top of a plate. I will not go into moving planes, shifting surfaces, etc. in this article.


Before we begin the article, I have to crush your hopes and dreams. Scraping is not a pretty activity. It's backbreaking, tiring, hard work, laborious, and messy. You will have transfer dye all over the walls, on everything you touch, black hands for awhile from touching a lot of metal and endless frustration. It's not fun, but the final product is more than worth it, trust me! 




*Lets Begin*

First, prepare your scraper. Make sure it's sharp, and that it's comfortable. If it's not sharp, you will be scratching not scraping, never getting anywhere. 



*Preparing your work*

Prepare your work by feeling for and stoning dings, and slightly stoning the edges to keep them from cutting yourself. If there is rust on the work, scrape a few passes without marking for high spots over the entire surface to remove it. 
Make sure to sharpen your scraper often, as iron oxide is highly abrasive (grinding wheels are made from it). This process for rust removal also gives you a feel for your scraper.
After scraping to remove rust, stone the surface to remove dings created when the scraper stops, this has to be done after every scraping pass throughout the job. Then clean the surface with paint thinner or other thin solvent.



*Surface Plate Preperation *

Next, prepare your surface plate. There are different types, the most common are cast iron, and granite. Cast iron plates can be cleaned with household glass cleaner (dry thoroughly to prevent rust!) but since granite has a texture, it needs a deeper clean. I like Comet detergent, lightly abrasive so it cleans the plate's texture well. But since it is abrasive it can wear the plate over time if you are not careful. Never use abrasive cleaners on metal plates! It will wear them quickly.
When you clean your surface plate, clean it lightly and wait for it to normalize. When cleaners evaporate from the plate's surface, it chills it (Thats why fast drying solvents feel cold) and can warp the plate. My advice is to clean it, cover it with a very clean sheet or towel to normalize then wipe it with clean hands to make sure there is no lint on the surface.




*Inking the Plate*

Now that your part and plate are clean, we need to ink the plate with a transfer medium. This will mark all the high spots on your work, showing what needs to be scraped away. 
Get an idea of the space on your surface plate you need, and put a few very small touches of dye on the plate inside the area you need. You will soon get a feel for how much marking medium you need. (For my fairly large piece, it took less than a pea sized blob)
Then take your rubber roller and spread the dye. Spread it as thin as possible, but don't go too crazy. Make sure you have an even spread all over the area of the plate you need. You can always take it off if you put too much on.


(Notice the even, thin layer. The dark spot is a stain.)



*The Rub*


Now one of the most important things about scraping, the rub. This is crucial to a good job, not too hard, not too soft. Not too long, not too short. You'll get a feel for it.
Clean the work well with solvent, dry it then gently put it on the plate. Rub it in a circular or figure-8 pattern to transfer the dye to our work's high spots that will then be scraped away. 



*Scraping*


Now that you have the ink transferred from the plate to the work, you need to scrape. Hold your work down to the bench, put your scraper on the work, and with light to moderate pressure push (or pull) the scraper and watch as a little chip comes off. Since this is a roughing pass, remove all the blue from the work by scraping them off. These are your high spots, and they need to be removed.

After several passes, you will notice the blue start to spread from a few points to cover our entire surface. This is a good sign, it means your getting flatter and flatter. This is when we have to be careful, if we take a pass too deep we can create a lot more work for ourselves. 



*Spotting*


When the blue starts covering the surface in spots, we will start a process called "spotting." 


This is not a quick stock removal process, it's only very light scraping to remove the peaks and valleys from the part. The scraping strokes should be smaller and shorter to only remove the blue, with very little removed around the blue to none at all if possible.


Keep doing this untill you have reached your desired level of flatness. This can be done with an indicator, usually a tenths (0.0001) indicator. As a thousandths (0.001) is not precise enough for scraping. I will not go into metrology, as I do not know enough on the subject and do not want to make a fool out of myself.


Once you have reached your desired level of flatness, you are done. You have just completed your first scraping project. 



*Recap*:


1. Work Prep: Remove all rust, dings, nicks, sharp edges, etc.
2. Surface Plate: Prep cleanliness cleanliness cleanliness!
3. Inking the Plate: Spread a thin layer of blue on the plate, in an even and uniform spread.


4. The rub: the most important part in scraping, marking high spots on the work. Make sure everything is very clean! A piece of lint can ruin the work.


5. Scraping: The process of removing high spots, and stock removal in a precise, but coarse manner.


6. Spotting: A more precise version of scraping, removing only the tips of the peaks. 


7. Pinpointing: (Not discussed in this article) A form of marking the work by using a material harder than the work to burnish the high spots. This can bring a much flatter surface than high spot blue, but is not needed in most cases.


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## tertiaryjim

Andre
I've been jumping from trying to get a good bearing surface with about 20 spots/inch to seeing how flat a surface I can scrape.
All good practice if I remember which effect I'm after!
Am still building and testing different scrapers to see what works best for me and what works with differing techniques.
Got a long way to go but am seeing progress.
I welcome all information that you want to share and I love pictures.

Can anyone tell me where to find the hard rubber rollers for spreading the blue?
Not adverse to making one if they're too expensive.


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## chuckorlando

Good write up man.


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## Andre

tertiaryjim said:


> Andre
> I've been jumping from trying to get a good bearing surface with about 20 spots/inch to seeing how flat a surface I can scrape.
> All good practice if I remember which effect I'm after!
> Am still building and testing different scrapers to see what works best for me and what works with differing techniques.
> Got a long way to go but am seeing progress.
> I welcome all information that you want to share and I love pictures.
> 
> Can anyone tell me where to find the hard rubber rollers for spreading the blue?
> Not adverse to making one if they're too expensive.



I like pull scrapers for fast metal removal and a small push "conventional" scraper for the small spots.

This is not the roller I use (and I have no idea what their actual use is) but here's one that looks good: http://www.dickblick.com/products/s...qs33g4rnTfIdKE8SBzJ-h15ys7f_EuaAAoQ4yNJ_D_BwE

- - - Updated - - -



chuckorlando said:


> Good write up man.



Thanks, Chuck!


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## chuckorlando

You would not happen to have a pic of your pull scrapper would you?  Do they just remove more per pass? This is an amazing skill IMO. I would love for Richard or the like to do a class down my way.


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## tertiaryjim

Thanks for the roller info. I googeled a bunch of stuff without finding them.
I made and tried one version of pull scraper but my design was seriously flawed. 
Will work on gen 2.
It was good for fast removal and if a flat surface is desired it will do it well.


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## Chandos

tertiaryjim said:


> Andre
> I've been jumping from trying to get a good bearing surface with about 20 spots/inch to seeing how flat a surface I can scrape.
> All good practice if I remember which effect I'm after!
> Am still building and testing different scrapers to see what works best for me and what works with differing techniques.
> Got a long way to go but am seeing progress.
> I welcome all information that you want to share and I love pictures.
> 
> Can anyone tell me where to find the hard rubber rollers for spreading the blue?
> Not adverse to making one if they're too expensive.



Do a Google search for "brayer."  They're used in printmaking.


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## Andre

chuckorlando said:


> You would not happen to have a pic of your pull scrapper would you?  Do they just remove more per pass? This is an amazing skill IMO. I would love for Richard or the like to do a class down my way.



I'll take one. They don't remove more material unless you do some special grind or really bear down. I like it to remove material because it's more comfortable. But because since the blade is squared off, (not rounded) it leaves square marks on the work. Meaning it can't take only blue off for spotting so I switch to a smaller push scraper for spotting. Plus I like the looks of smaller scrape marks. 

Depending on your scraping style, scraping marks are beautiful. Some better than others, and no two peoples patterns are the same. An art with function.

I'd love to see some of your scraping work if you do any. A lot of work to not show anything off )

- - - Updated - - -



tertiaryjim said:


> Thanks for the roller info. I googeled a bunch of stuff without finding them.
> I made and tried one version of pull scraper but my design was seriously flawed.
> Will work on gen 2.
> It was good for fast removal and if a flat surface is desired it will do it well.



I'll show a pic of my pull scraper sometime. The angle is crucial to your shoulder/work height.


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## Don B

Andre said:


> *Metal Scraping, Why and How-To*




Andre, this is a great thread, very well done.:allgood:


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## Andre

Don B said:


> Andre, this is a great thread, very well done.:allgood:



Thank you, Don!


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## chuckorlando

Oh I'm no scraper. But it is a skill I fully intend to learn in the next year. At least to the extent where I can practice and know what to do and what order to do it all in. I agree with the art aspect. When a man can take a machined surface and make it better, with the power of his own arms, and make it look so pretty, brother thats special and to be respected. We got brand new mills in school and the scrapping are by far the nicest looking part.


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## Andre

chuckorlando said:


> Oh I'm no scraper. But it is a skill I fully intend to learn in the next year. At least to the extent where I can practice and know what to do and what order to do it all in. I agree with the art aspect. When a man can take a machined surface and make it better, with the power of his own arms, and make it look so pretty, brother thats special and to be respected. We got brand new mills in school and the scrapping are by far the nicest looking part.



What mills did you get? Most mills (including Bridgeports) aren't scraped. Their flaked, creating oil pockets. 

After your done using them, you HAVE to clean the ways and re-oil them if they have flaking. Flaking keeps oil....but it also holds in grit and dirt. Increasing the wear in the ways....


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## chuckorlando

Yea you could be right there. They are sharps. The table and all are flaked. They look really good. I have a bridgeport that I intend to scrap some day.


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## Andre

chuckorlando said:


> Yea you could be right there. They are sharps. The table and all are flaked. They look really good. I have a bridgeport that I intend to scrap some day.



Scraping a Bport would be a good project. I'd like to do it, but I'm lost on how to keep the X and Y axis perfectly perpendicular. And how I do I know the column is perfectly vertical? Or should I not worry about that and just worry about keeping the dovetails straight with a dovetail-o-meter?


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## toolman_ar

Andre,

Good post, I just signed up for Richards class in KC.
I have all the tools, but little knowledge of what to do with them.

I have a small project that I am about to start once I get Richards DVD.

Something I don't think I can mess up, if I don't get it write the first time.

Chuck,
I know that Orlando would be a long drive, but you should join us for the KC class. I plan on driving up and over. So I can bring all the tools and get Richards advice on a plan of attack.


toolman_ar


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## chuckorlando

Best I can tell you would lay the column down on it's back and level the non bearing flats between the ways. Then scrap the way's level to that. But I really dont know for sure. These are things I need to learn. I intend to cut my teeth on straight edge and the like, then my 9x20 lathe, then to the BP. Cost to much to ruin a BP column trying to learn.

If this class was in winter it would be a possibility. But I run a landscape company and it simply wont happen. Way to much grass to cut this time of year to take a week off


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## toolman_ar

Chuck,

I understand, but just incase the dates are October 24, 25, & 26th.

We need a few more hands to make it work.

My plans are to start out on a 2" square bar.

I look forward to learning how to properly make a flat bearing surface.


toolman_ar


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## The Liberal Arts Garage

toolman_ar said:


> Chuck,
> 
> I understand, but just incase the dates are October 24, 25, & 26th.
> 
> We need a few more hands to make it work.
> 
> My plans are to start out on a 2" square bar.
> 
> I look forward to learning how to properly make a flat bearing surface.
> 
> 
> toolman_ar


.                   Brayers- rubber ink spreaders for artists-  try art or hobby supply stores. Note; must be flat and "just right" soft. Examine old or used ones carefully. ....BLJHB


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## iron man

I have scraped a few machines to get where it was not practical to grind or machine and have had very good results but if machined right I have not seen where scrapping is needed. I have a hard time with flaking part of it because all it does is limit surface contact which glides easy but also can chatter more and wear quicker like a golf ball surface. I dont know I am up in the air about it I read this and thought I would share he has some good points to keep in mind ideas and opinions can go either way there is good and bad to everything I guess.

The scraping process is incredibly crude, and totally incapable of producing anything like a smooth surface or precision flatness. It is simply impossible for that process alone to produce the result desired.

The scraper gouges a swath of material away.  The scraper is not flat on the end, so the gouge it produces is rounded. The resulting surface is therefore a series of gouges, in a random pattern and of random depth.

You cannot simply scrape a surface flat. End of story.

Because of that, scraping is inevitably associated with various other items besides the scraper. These are necessary to correct the horrible distortions of the surface which the scraping process produces if uncorrected.

That is the secret of how the scraping process ends up with a flat surface....  The extra equipment tells you where to apply the incredibly crude process, and where NOT to.  By correctly following the directions given by the comparison straightedge etc, as shown by the blue (or red, etc) spotting material, you can remove the high spots, and bring the surface down to where the "surface" is a series of flat spots with the "residual gouges" between them. 

The net result is a surface defined by those flat spots, which is as flat and planar as your comparison device is.  If the straightedge is curved, you can scrape a very accurate curve to match, but never a flat surface.

Luckily, geometry allows the creation of a flat surface of any desired flatness by the principle that if  A=B, and B=C, and C=A, then A=B=C.  A may have a curve "up" , and B may have a matching curve down, but C cannot then match both. Only when all are flat can C match  A and A match B AND B match C. 

A side note:
The existence of scraping marks on a machine may either mean that scraping was used to bring the machine into alignment, OR that someone made marks all over the surfaces in order to make you assume that a proper re-alignment was done.  

This is usually obvious when a surface with visible linear wear marks also has "Nike swoop" marks on it that cut across the wear marks......  Most of the tricksters don't put a full surface of scraping marks on... that would be too much like work. They are satisfied with crude "flaking" to fool the unwary.


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## The Liberal Arts Garage

If you have or borrow an old- old beginning machinist's instruction book. Further on in it you wil be
instructed in the making of a surface plate, or we should say, three- because there is no other way 
except to make three cast iron plates, planed flat, one blued, rubbed, and one of the other two scraped. The third one is rubbed and scraped and the process in irregular order until there are three perfect. Have fun!           BLJHB


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## Koi

Andre said:


> [h=1]Andre[/h][h=4]Metal Scraping, Why and How-To[/h][h=6]Rate this Entry[/h]1 Comment
> by Andre
> , 05-25-14 at 12:52 PM (11 Views)*Metal Scraping, Why and How-To.
> 
> 
> 
> 
> What is Metal Scraping?*
> Metal scraping is the process of removing high spots from the work, making it flatter or to conform it to a certain shape (Ie, tapered bearing, V block) in a very precise manner that even a lot of machine tools can not match.
> 
> 
> 
> *Why?*
> Scraping does not just create flat surfaces, when properly done, bearing surfaces, oil pockets, and specific wear patterns can be scraped in.
> 
> 
> 
> *What Tools Do I Need?*
> 
> The things you will need are a scraper, surface plate or other reference edge like a straightedge, surface plate cleaner, marking medium, a rubber wheeled roller to roll the dye, workholding device, bench stone (or a lapping machine if you use carbide) smaller hand stone to remove burrs after a pass, very good lighting, light solvent for cleaning swarf out of your stones, rags, metrology instruments (indicators, or other tools depending on the job.)
> 
> 
> 
> 
> 
> *The Scraper.*
> 
> 
> A good scraper is required for a good scrape job, and it has to work for you.
> There are many types of hand and power scrapers to be made or purchased, including Anderson tube scrapers, the Biax power scraper, pull scrapers, etc. In both HSS and carbide.
> If you are scraping a lot, or scraping hard materials, carbide is by far your best option. Does not require frequent sharpening, and saves a lot of time. If you are scraping soft steel, aluminum, or gib shim stock (ie, Turcite) HSS is a better option. It can be sharpened to a keener edge, and does not require a lapping machine or diamond stones, but requires frequent sharpenings.
> 
> 
> 
> *What This Article is About.*
> 
> This article is for the beginner, to teach the basic principle of hand scraping using common tools to achieve the simple task of flattening the top of a plate. I will not go into moving planes, shifting surfaces, etc. in this article.
> 
> 
> Before we begin the article, I have to crush your hopes and dreams. Scraping is not a pretty activity. It's backbreaking, tiring, hard work, laborious, and messy. You will have transfer dye all over the walls, on everything you touch, black hands for awhile from touching a lot of metal and endless frustration. It's not fun, but the final product is more than worth it, trust me!
> 
> 
> 
> 
> *Lets Begin*
> 
> First, prepare your scraper. Make sure it's sharp, and that it's comfortable. If it's not sharp, you will be scratching not scraping, never getting anywhere.
> 
> 
> 
> *Preparing your work*
> 
> Prepare your work by feeling for and stoning dings, and slightly stoning the edges to keep them from cutting yourself. If there is rust on the work, scrape a few passes without marking for high spots over the entire surface to remove it.
> Make sure to sharpen your scraper often, as iron oxide is highly abrasive (grinding wheels are made from it). This process for rust removal also gives you a feel for your scraper.
> After scraping to remove rust, stone the surface to remove dings created when the scraper stops, this has to be done after every scraping pass throughout the job. Then clean the surface with paint thinner or other thin solvent.
> 
> 
> 
> *Surface Plate Preperation *
> 
> Next, prepare your surface plate. There are different types, the most common are cast iron, and granite. Cast iron plates can be cleaned with household glass cleaner (dry thoroughly to prevent rust!) but since granite has a texture, it needs a deeper clean. I like Comet detergent, lightly abrasive so it cleans the plate's texture well. But since it is abrasive it can wear the plate over time if you are not careful. Never use abrasive cleaners on metal plates! It will wear them quickly.
> When you clean your surface plate, clean it lightly and wait for it to normalize. When cleaners evaporate from the plate's surface, it chills it (Thats why fast drying solvents feel cold) and can warp the plate. My advice is to clean it, cover it with a very clean sheet or towel to normalize then wipe it with clean hands to make sure there is no lint on the surface.
> 
> 
> 
> 
> *Inking the Plate*
> 
> Now that your part and plate are clean, we need to ink the plate with a transfer medium. This will mark all the high spots on your work, showing what needs to be scraped away.
> Get an idea of the space on your surface plate you need, and put a few very small touches of dye on the plate inside the area you need. You will soon get a feel for how much marking medium you need. (For my fairly large piece, it took less than a pea sized blob)
> Then take your rubber roller and spread the dye. Spread it as thin as possible, but don't go too crazy. Make sure you have an even spread all over the area of the plate you need. You can always take it off if you put too much on.
> View attachment 167683
> 
> (Notice the even, thin layer. The dark spot is a stain.)
> 
> 
> 
> *The Rub*
> 
> 
> Now one of the most important things about scraping, the rub. This is crucial to a good job, not too hard, not too soft. Not too long, not too short. You'll get a feel for it.
> Clean the work well with solvent, dry it then gently put it on the plate. Rub it in a circular or figure-8 pattern to transfer the dye to our work's high spots that will then be scraped away.
> 
> 
> 
> *Scraping*
> 
> 
> Now that you have the ink transferred from the plate to the work, you need to scrape. Hold your work down to the bench, put your scraper on the work, and with light to moderate pressure push (or pull) the scraper and watch as a little chip comes off. Since this is a roughing pass, remove all the blue from the work by scraping them off. These are your high spots, and they need to be removed.
> 
> After several passes, you will notice the blue start to spread from a few points to cover our entire surface. This is a good sign, it means your getting flatter and flatter. This is when we have to be careful, if we take a pass too deep we can create a lot more work for ourselves.
> 
> 
> 
> *Spotting*
> 
> 
> When the blue starts covering the surface in spots, we will start a process called "spotting."
> 
> 
> This is not a quick stock removal process, it's only very light scraping to remove the peaks and valleys from the part. The scraping strokes should be smaller and shorter to only remove the blue, with very little removed around the blue to none at all if possible.
> 
> 
> Keep doing this untill you have reached your desired level of flatness. This can be done with an indicator, usually a tenths (0.0001) indicator. As a thousandths (0.001) is not precise enough for scraping. I will not go into metrology, as I do not know enough on the subject and do not want to make a fool out of myself.
> 
> 
> Once you have reached your desired level of flatness, you are done. You have just completed your first scraping project.
> 
> 
> 
> *Recap*:
> 
> 
> 1. Work Prep: Remove all rust, dings, nicks, sharp edges, etc.
> 2. Surface Plate: Prep cleanliness cleanliness cleanliness!
> 3. Inking the Plate: Spread a thin layer of blue on the plate, in an even and uniform spread.
> 
> 
> 4. The rub: the most important part in scraping, marking high spots on the work. Make sure everything is very clean! A piece of lint can ruin the work.
> 
> 
> 5. Scraping: The process of removing high spots, and stock removal in a precise, but coarse manner.
> 
> 
> 6. Spotting: A more precise version of scraping, removing only the tips of the peaks.
> 
> 
> 7. Pinpointing: (Not discussed in this article) A form of marking the work by using a material harder than the work to burnish the high spots. This can bring a much flatter surface than high spot blue, but is not needed in most cases.


So umm  can scraping bring one side of the workpiece down to dimension like filing cuz when i see people scraping they would scrape and leave some space between each scrape and they would then scrape again crossong the previous direction.


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## Janderso

Hi Koi,
You have awakened a six year old thread.
Hopefully someone will be along to help you.


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## Richard King 2

Janderso said:


> Hi Koi,
> You have awakened a six year old thread.
> Hopefully someone will be along to help you.


Jeff you know the answer don't you?   It is to get a checkerboard pattern or a basket weave appearance of over lapping high and low spots.  the more high spots the longer the ways will last and the low spots hold or lets the oil adhere to the ways providing you keep them clean and lubricated.


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## Janderso

Richard King 2 said:


> Jeff you know the answer don't you?   It is to get a checkerboard pattern or a basket weave appearance of over lapping high and low spots.  the more high spots the longer the ways will last and the low spots hold or lets the oil adhere to the ways proving you keep them clean and lubricated.


Richard,
Yes, I know the basics, you taught us.
However, I would not feel comfortable answering a scraping question in this public forum.
Maybe between me and the guys.
I hope you are well!
Jeff


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