[Newbie] My First Attempt At Scraping

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