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[Newbie] My First Attempt At Scraping

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Standingbear

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#1
image.jpeg Frirst I want to say hello to everyone this site has been very interesting reading thru all the good information. It has been a big help just reviewing all the old posts. I made my first attempt at scraping today and it was very addicting chasing the blue.

My first project is scraping a 4" angle plate. I did not get a pic when I started but only the corners touched. About my 3 time scraping the blue dots started covering the entire area. My questions is my dots seem to be small in comparison to some of the pics I have seen on here. I will add a pic for some feedback. Also when I rub on my granite surface plate I notice what looks like small scratches in the ink? Not sure if this is normal.
 

4GSR

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#2
The small scratches in the ink is debris. Right before you take the impression, take the palm of your hand and wipe the surface clean on the angle plate and gently do the same on the bluing applied to the surface plate. Doing this should stop the scratching you are seeing. The scraping is looking fine. One thing to do before you go any future. Rock the angle plate in a twisting motion about 10-15 degrees on the angle plate. doing this should establish a hinge point that is about 2/3's the way from the end, or 1/3 from the end. If you are getting this, you are about as close to flat as it comes. If it spins in the middle, you have a convex scraped into your flat surface. If it hangs on the ends, you have a convex scraped in your flat surface. Keep working at it until you get the hing action needed to tell if it is flat.
Ken
 

john.oliver35

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#3
Standingbear - that looks great! Did you start with a chi-com angle plate? What method are you using to make sure the plate stays square as well as flat?

I appreciate your input as a beginner scraper - I have done a small bit, but have projects in the future!!

John
 

Standingbear

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#4
image.jpeg Ken thanks for the help. I added a photo to see if I'm following you correctly on holding at approx 10 deg and rock. In the photo I would hold like that and rock forward? Should I just go off feeling or using the blue? Sorry for all the questions.

John I appreciate the feedback. It is just a cheap chi-com angle plate. I may have jumped the gun but I have only scraped one side and was waiting for a granite square I ordered to do the other side. I'm sure there is a way to do it without one but I am just kinda learning as I go. Sounds kind of crazy but I was anxious to get started. Big plan is once I get better at this I want to do a K&T universal mill that is is bad shape.
 

Bob Korves

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#5
The hinge test is done with the work flat on the surface plate. You push sideways on the work close to one end with a low placed finger and watch where the center of rotation is located as the part twists on the plate. If it is about 2/3 of the distance to the opposite end of the work, that is correct. It it is in the middle of the work, the work surface is convex. If it pivots at the end of the work, the part is concave. The hinge point should also be in the center of the work, side to side. A heavier side like an angle plate makes that a bit more fussy, and contamination gives false results. You can also tap the corners of the work sharply downward with your finger. If there is any bouncing noticeable in the part by feel and/or sound, the part is convex or there is contamination under the part.

For your first scraping job, that looks great!
 

Terry Worm

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#6
Here is another tip that will help with the scratches you saw: After you have done your scraping, try running a fine stone lightly over the entire surface to remove any very tiny burrs that are left over from scraping. After lightly stoning the surface, rub your hand over the entire surface to remove any foreign material from it as Ken mentioned.
 

Bob Korves

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#7
After each scraping pass, I lightly debur the surface with a fine and flat ceramic stone and generic Windex, then wipe off with paper towel followed by the palm of my hand, making sure it is dry and clean, then back on the surface plate for hinge test and marking.
 

Standingbear

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Thanks everyone for helping. Last night laying in bed thinking about blue dots I had the the moment it came to me about the hinge test. When I get off work today I will give it a try.

Emilio thanks for the PDF it is helpful.
 

Ulma Doctor

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#10
looking good!
here's something else to try , blue up your part like normal on the ink.
then go to a part of the plate that has no ink and rub the part on the bare plate.
you will see some very shiny points across the surface of the angle plate, those are your highest points
the second highest points are very dark blue to black in appearance.
you are going to spend most of your time on those 2 observations
keep up the good work!
 

Standingbear

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#12
image.jpeg image.jpeg Ok my hinge test seems to be good. Pushing on the bottem of the angle plate it pivots about 2/3 across from where I'm pushing. Next question I have is on the first pic this seem to be the most dots I can get. After 2 passes it seems to be about the same. Is this normal or am I doing something wrong. Second pic is unmarked to see if my scrapes are looking correct. Once again appreciate all the feedback.

Bob I am in the process of reading that book from Connelly. Thanks for the link!
 

Ulma Doctor

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#13
it looks like you have 2 low spots both on the left and right sides about 1/4 down from the top as pictured.
as you scrape off the tops of the peaks, the lower peaks will start to emerge.
as you get ever flatter, the blue dots will increase in size until the entire angle plate could become blue if you were to scrape it long enough.
you should be happy with 40-60% blue and 20 to 40 Points per inch dependent on use or purpose.
it's pretty flat right now as it sits.

consider this,
even if you scraped it to a tenth, had 60%, and 40 PPI...
as soon as you wrench down on it with a clamp, it will distort the work as well as the angle plate and any superfluous accuracy will be negated anyway.

trust me, you can spend hundreds of hours chasing perfection.
you'll have to be your own judge when it comes time to quit scraping on a piece, or if one more pass will do it.
 
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Bob Korves

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#14
The finish you have on the angle block is just fine for an angle block. Now you need to get the same surface quality on the other face, while at the same time holding an accurate 90 degree angle between the two faces. You will need a reference master of some sort, a granite angle block works well, and a cast iron one does, too. It needs to be a KNOWN accurate master. Your combination and framing squares are not good enough... 8^)
 

Standingbear

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image.jpeg image.jpeg appreciate the help and comments from everyone. Since I am waiting on my order for the granite angle plate before I can do the other side I practiced with 2 more cycles on this side and have another question of this new found obsession. In one of the pics I did not spread more blue between cycles and there are not many dots. In the other pic I spread more blue and it has a lot more dots. I understand the more blue will show more dots but my question is which one would be the normal way of doing it because it seem to drastically change the dots per inch. Also when I added the more blue you could feel a lot of suction to pick up the angle block I am guessing that is a good sign. I did order a carbide scraper today to try. It is a good thing we have long winters in Montana;)
 

Andre

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#16
It takes awhile to figure out how much blue to use. A general rule of thumb is to use as little as possible, and you should be able to still see your granite surface plate through the blue. There really shouldn't me much suction, I think you're using too much.

Take all the blue off the plate, wipe with a fast drying solvent, wipe surfaces clean with your palm, then slide the angle plate onto the surface plate, press down and rub gently. The idea is to burnish your high spots shiny. You can tell, from the shiny spots, your true high points if you aren't sure how much blue to use.

Take a look at the one I made quite some time ago:


http://www.hobby-machinist.com/threads/angle-plate.26230/

And how I measured squareness using a very simple tool:

http://www.hobby-machinist.com/threads/surface-plate-squareness-comparator-rig.27230/#post-240131
 

Ulma Doctor

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#17
if your ink is too thick it will give a false reading of contact.
only the very shiny points surrounded by blue halo's (on the right hand picture) are the actual points of contact.
the lower corners appear to be low still in the last picture.
corners can be challenging because there is little to reference from visually.
as a result, sometimes too much is easily taken off leaving a low.
not to despair, remove all the dots you see and blue it up again!
eventually all the dots will be in one plane.
something that may help you would be to use a different color rubbed into the work- orange, red, yellow, any contrast you'd like really.
that will take up the very low spots in your work so that you can read the high spots easier when you blue up and then scrape again.
 

Andre

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#18
Ulma reminded me of something I forgot to mention, I find red dye a lot easier to see than blue when it gets thin.
 

Standingbear

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#19
Thanks I will look for some red dye. Also the links were nice. Rubbing without dye does seem to give you a better view of what is high just hard to see without getting the light right. When you polish the high spots without dye are they really fine like the tip of a pen or are they bigger, mine seem small to me. It is really hard to tell looking at pics on the net.
 

Andre

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Thanks I will look for some red dye. Also the links were nice. Rubbing without dye does seem to give you a better view of what is high just hard to see without getting the light right. When you polish the high spots without dye are they really fine like the tip of a pen or are they bigger, mine seem small to me. It is really hard to tell looking at pics on the net.
Usually my points are about 1/16" square. Some bigger, some minuscule. However I use a flat nosed pull scraper, and you're probably using a round-nose push scraper, so your points will be of a different shape.
 

chevydyl

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#23
I use yellow ink or paint on the cast iron for a contrast when I am getting close, I use canode yellow spotting ink. Before I got that I used artist oil paint mixed with vaseline, vaseline keeps the paint from drying, wipe the paint on the angle block in an even manner, then wipe it all off until it is just a haze, until you wipe it with your hand and your hand doesn't yellow. It really helps when you are using thin blue near the end of your scrape job, when your bringing in the bearing rather than just trying to get it flat. ES Dyjack sells the blue and yellow, it's water soluble ink, and I'll never use Prussian blue again
 

Standingbear

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#24
I use yellow ink or paint on the cast iron for a contrast when I am getting close, I use canode yellow spotting ink. Before I got that I used artist oil paint mixed with vaseline, vaseline keeps the paint from drying, wipe the paint on the angle block in an even manner, then wipe it all off until it is just a haze, until you wipe it with your hand and your hand doesn't yellow. It really helps when you are using thin blue near the end of your scrape job, when your bringing in the bearing rather than just trying to get it flat. ES Dyjack sells the blue and yellow, it's water soluble ink, and I'll never use Prussian blue again
So you put the yellow on the piece your scraping and still put blue on the surface plate or no blue on the surface plate?
 

Andre

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#25
So you put the yellow on the piece your scraping and still put blue on the surface plate or no blue on the surface plate?
Yellow on the part, and blue on the plate. The two colors give a better contrast.

This video found on the 'net explains the process.
 

Standingbear

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#26
Yellow on the part, and blue on the plate. The two colors give a better contrast.

This video found on the 'net explains the process.
Perfect thanks I have watched that video before and missed that part. Amazing what you get each time you watch or read something.
 

Standingbear

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#27
image.jpeg So the Fed-ex man brought me some new scraping supplies today and all I can say is wow!!! The new carbide scraper is day and night better than the cheapie HSS. I don't know about other options but this was well worth the money.

I tried using the red canode on my part and the blue on the table and it was just to thick covered the whole part. Couldn't seem to get it thin enough now matter what I tried. Do you guys thin it with anything before you use?
 

Standingbear

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#28
image.jpeg image.jpeg image.jpeg Forgot to add my new scraping project while I'm waiting on my granite square to finishe the other side of my angle plate. It is a chi-com tail stock for my rotary table.
 

Bob Korves

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#29
For those of you who have not used the Canode ink, please try it when you get a chance. It is water based, and is dead easy to get off your hands, your tools, your surface plate, your sink, your clothes, and everything else that comes in contact with it. It spots equally as well as the oil based stuff, just a LOT easier to use and clean up. Before Canode, you could always identify a scraper hand by his blue (or red) hands and nose...
 

Bob Korves

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View attachment 126443 So the Fed-ex man brought me some new scraping supplies today and all I can say is wow!!! The new carbide scraper is day and night better than the cheapie HSS. I don't know about other options but this was well worth the money.

I tried using the red canode on my part and the blue on the table and it was just to thick covered the whole part. Couldn't seem to get it thin enough now matter what I tried. Do you guys thin it with anything before you use?
Use less and roll it out really well, so it is transparent.
 
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