# scraping in a surface gauge feedback needed.



## Braeden P (Dec 3, 2020)

So I made a scraper for 1/8 by 1 hot rolled and used a hss parting blade and I bought a 9 by 12 wood river surface plate from wood craft it says it is accurate to the tenth but not what distance so I smell something fishy but now back to the scraper. I am scraping in a starrett surface gauge and I did a cross-hatch on it then covered it with a sharpie and put some water on the plate and a piece of USA made 2000 grit sandpaper which is not accurate I need some Prussian blue but I will get some soon. The bright spots are glare and that piece of granite is not the surface plate and co staring lemu emu chip brush brought to you by liberty mutual flyer.


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## pontiac428 (Dec 3, 2020)

Smart design, that jack bolt setup for fixing the blade was a good move.  You're off to a flying start!


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## Braeden P (Dec 3, 2020)

pontiac428 said:


> Smart design, that jack bolt setup for fixing the blade was a good move.  You're off to a flying start!


Last one had a different way and was horrible this one is much better


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## Braeden P (Dec 3, 2020)

I just went out and bought some Prussian blue and a rubber roller for inspection and I could use the Prussian blue for putting on the cranks of lathes and mills


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## benmychree (Dec 3, 2020)

Braeden P said:


> I just went out and bought some Prussian blue and a rubber roller for inspection and I could use the Prussian blue for putting on the cranks of lathes and mills


There are SO MANY places to put prussian blue!


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## vtcnc (Dec 3, 2020)

Hey Braeden, pull the ledge pins out of your surface gage. There is no need to flatten or scrape the ends of them.


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## Braeden P (Dec 3, 2020)

vtcnc said:


> Hey Braeden, pull the ledge pins out of your surface gage. There is no need to flatten or scrape the ends of them.


I did that already because I knew that they would be a pain.


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## Braeden P (Dec 3, 2020)

I did some more with inspecting it with some Prussian blue and that stuff does get every where.


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## Ulma Doctor (Dec 4, 2020)

you can always tell a sraper, by the blue upper lip


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## Braeden P (Dec 4, 2020)

Ulma Doctor said:


> you can always tell a sraper, by the blue upper lip


i had to use mineral spirits to clean off my hands.


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## Braeden P (Dec 6, 2020)

Did a bit more and I have to get the feel still


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## Braeden P (Dec 7, 2020)

Am I using to little blue? I just hinged it and it hinges about the middle of the other side I push on


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## Braeden P (Dec 8, 2020)

I now have about 35-40 points of contact per square inch I think that is when you start finish scraping but I may be wrong dang glare strikes again.


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## Braeden P (Dec 14, 2020)

would this be a bad first time project because of the 2 sides and if I scrape one side but not the other the blue will show up in different on the non scraped side but I thing it will work.


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## vtcnc (Dec 15, 2020)

I think you should be marking and scraping both sides for every marking. One side may require less scraping than the other and vice versa as you progress.

Otherwise you could introduce some tilt to the surface gage.


Sent from my iPhone using Tapatalk


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## Braeden P (Dec 15, 2020)

vtcnc said:


> I think you should be marking and scraping both sides for every marking. One side may require less scraping than the other and vice versa as you progress.
> 
> Otherwise you could introduce some tilt to the surface gage.
> 
> ...


yea that is what i was thinking but the part is held too high for me so a lower work bench and I have to hold the scraper at a 30 degree anger because the blade is short and i dont have a way to mill down the body of it so that the blade is lower but christmas is just around the corner and i like sandvik scrapers so....


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## Janderso (Dec 15, 2020)

Have you hinged the part on your surface plate?
That helps to verify if your part is flat. It should hinge 1/3 in on each side (pivot point)
Looking good.


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## Braeden P (Dec 15, 2020)

I have and it hinges as it should but i only have about 15 percent contact I am using prussian blue oil paint is that bad because i roll it out to a thin layer i do it until it slides freely and if i dont roll it much it sticks and do you know where to get a highliting color like red?


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## Janderso (Dec 15, 2020)




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## Braeden P (Dec 20, 2020)

This is all that I will do I have 34-40 high spots per inch and about 30 to 40% contact I’m have I got trouble with the pictures they won’t load after ten minutes and I have good WiFi I will try again soon.


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## Braeden P (Dec 22, 2020)

it looks horrible in the picture and the blue wont show up need leds and a highlighter color to make it show up


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## Braeden P (Dec 23, 2020)

Maybe this will work


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## Braeden P (Dec 23, 2020)

I can only put one picture per reply because the other ones won’t load


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## graham-xrf (Dec 30, 2020)

Braeden P said:


> it looks horrible in the picture and the blue wont show up need leds and a highlighter color to make it show up


One of my pet little endeavours is to make up my own version of the contrast yellow against blue, or red ochre, or black, and to have it water washable. When I mess with oil-based Prussian Blue, it gets everywhere, and won't easily come off clothes, and I end up looking like a Smurf!

However - that said, if you are careful, keep handy a squeeze-bottle of denatured alcohol, or IPA + a supply of paper towels, almost any pigment fine enough, in a grease that can be wiped away, will work. Simple tubes of artist's oil paint does the trick.

Adding some yellow to the part so thin, it is barely there, transparent, and putting the blue (or other) on the reference surface does indeed show up the contrast. I found spreading the red ochre art paint down to a thin near transparent stain on the part, also will show up the blue high spots well.

I got some "Sun Wellow" powder pigment for only a few bucks from eBay. I plan to mix it with the sulfonated caster oil, + a few drops of detergent, but the yellow oil paint does work all by itself, straight out of the tube.


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## Braeden P (Dec 30, 2020)

I got some dykem  hi spot blue that I will use now instead.


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## graham-xrf (Dec 30, 2020)

Braeden P said:


> I got some dykem  hi spot blue that I will use now instead.


For excellent contrasting, and easy too, there is the "evaporative" method, dabbing on the red pigment with a home-made chamois leather pad. There is the tip that you have to use _real_ chamois leather. Many car-cleaning "chamois" are plastic faux substitutes. You dab up with a little mineral spirits as a caking "drying" paste, then as it evaporates, you get to wipe out and thin the colour at will, and you don't need to smear up your hand.

Robin Renzetti (ROBRENZ) is of course the famous YouTube contributor for the very highest standards in precision engineering. He fully explains the red pigment method in his video about Moore Pattern oil retention pattern scraping. The bit about the evaporative method, starts at around *18:18*, but if you haven't already seen the rest of the video, I can almost guarantee you will get hooked.




I think he used hi spot blue on the granite. I never before thought of crayola as a source of pigment , but it is mentioned in the video.


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## Janderso (Dec 30, 2020)

Do you see the spots that have a polished center?
Those are your high spots.
I remember when we got to the point in our project where we had 20+ spots per inch we would rub the piece on a plate, it was obvious how the high spots came out as mirror finish spots with a dark blue around the perimiter.
I know you said you were done and all. It's easy for me to sit here and tell you what I think 
Have you hinged it? Does it pivot 1/3 on the opposite side you are touching?



			https://www.hobby-machinist.com/attachments/image-jpg.348397/


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## Braeden P (Dec 30, 2020)

I have those shiny spots pretty even around it I’ve hinged it it hinges at the right spot but with two separate flats it is a pain.


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## Janderso (Dec 30, 2020)

Braeden P said:


> but with two separate flats it is a pain.


I bet it would be. Didn't think of that. no rocking?


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## Braeden P (Dec 30, 2020)

To cold to go out tonight I will have to test tomorrow.


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## Janderso (Dec 30, 2020)

Braeden P said:


> To cold to go out tonight I will have to test tomorrow.


I remember we would place an indicator on one side and push each corner while working around with the indicator.
If it moves, you know what to do.


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## Optic Eyes (Apr 12, 2021)

Braeden P said:


> i had to use mineral spirits to clean off my hands.


WD 40 works good,


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## Braeden P (Apr 12, 2021)

now I use eastwood chassis clean it eats anything really fast just don't let it on for to long it is insane how fast it works


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## macardoso (Apr 12, 2021)

Braedon,

I'll offer some thoughts are someone who is just a neophyte in the subject (just hit my 50 hours mark).

1) You have some deep scoring from what I would guess is you rolling the blade until the corner digs in. Take a moment to round the corners of your blade so they won't scratch or cut, even if you try on a scrap piece.

2) You have no contact within 1/8" from any edge. I'm guessing you are rolling off your corners (I do!). It is hard, but try to approach the edges at 45 degrees and be careful to not allow your blade to roll sideways as you exit the cut and take a chunk off the edge.

3) It looks like you are using a piece of polished granite countertop as a surface plate. 2 comments. First, it might not be as flat as you want. Not bad to start but I'd keep an eye out for a small (maybe 9x12") surface plate. Second, the gloss finish on the granite likely poorly transfers blue in comparison to the matte finish of granite surface plates or the scraped surface of a cast iron plate or straight edge. Sort of how blue does not transfer to a ground surface very well. This could be complicating the clarity of your printing.

4) Your latest pictures show pretty good distribution of spots (even if they are a bit sparse).

5) Be very careful of making the bottom convex, probably easy to do on such a short part. You can tell by if the part hinges in the middle (as one of your comments implied). If it is convex, you will be rolling the part when bluing and getting a false reading of coverage. When working on my vise, I had a feeling I was getting convex but couldn't get the high points to prove it. Ended up taking a scraping pass only on the middle third and still kept getting contact on the ends. Two more passes in the middle only were taken until the middle stopped showing many high points. Only then was it no longer convex.

Good luck and keep practicing!

Mike


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## Braeden P (Apr 12, 2021)

well i lost the surface gauge and I got a sandvik blade pre ground (Thanks Paola) that works well now currently working on a comparator base


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