Learning to scrape - with help from Richard King

[p3bhambama]

Besides that I expect it will sag into flatness on it's own weight.

Perhaps so. Mine has a foot in the middle maybe to prevent just that though it’s only 12x18 so no idea

 

[Richard King]

Besides that I expect it will sag into flatness on it's own weight.

No if it's a 3 point surface plate 18 x 18 with ribsike a Bush or Challenge it won't sag, just that's where it's used the most. If it's a bench plate used to emery cloth something. It might sag. I was looking for the used more in the middle answer.

 

[p3bhambama]

I’ve seen Richard say a thousand times to be a detective. Along those lines I did some measuring and as he suspected it was high in the middle - and the low areas were as low as .0007 - so I did a sort of modified step scrape. Though I don’t have as much coverage the middle came down a bit. I think a couple more regular passes will get the (now around .00035) low areas in line with the rest.

I’ve been hinging the part the whole time. But what I didn’t know was to hinge from each corner - and the amazing information that provides when looking straight down while doing it. You can see exactly where the high areas are doing this. Thanks again Richard - another great tip.

 

[Richard King]

I think about a target practice target when scraping square plates high in the middle. Outside to inner circle. Center 3 times. Then 2 times and then 1 on 3rd ring.

 

[p3bhambama]

I think about a target practice target when scraping square plates high in the middle. Outside to inner circle. Center 3 times. Then 2 times and then 1 on 3rd ring.

That's a good visualization - basically what I did. I also find that it's really important to sort of "get my mind right" about a pass before I make it - and not to just start scraping and decide on the fly what to scrape and what not to. Taking a few minutes to wipe off the grey blue and really have a plan as to which areas I'm hitting on the pass results in a better pass. Each cycle I get better at recognizing what is needed. Also being able to recognize what is a false print has been important - I've generally been ignoring any marks that are a little bit smeary as I find that often indicates a false blue.

 

[Richard King]

We call a smear a "false reading". After you learn a bit more knowing where to scrape and how much to take off will become 2nd nature. Lol. People are amazed how I can look at a picture and know it high in the middle. But I've been hand scraping since the 1960's. One of my best students calls me the professor on his YouTube shows. He has probably over a 100 on rebuilding. Jan Sverre Haugjord over in Norway. He has both English and Norwegian versions. He's taken 5 or 6 in person classes.

 

[p3bhambama]

We call a smear a "false reading". After you learn a bit more knowing where to scrape and how much to take off will become 2nd nature. Lol. People are amazed how I can look at a picture and know it high in the middle. But I've been hand scraping since the 1960's. One of my best students calls me the professor on his YouTube shows. He has probably over a 100 on rebuilding. Jan Sverre Haugjord over in Norway. He has both English and Norwegian versions. He's taken 5 or 6 in person classes.

Yes I've watched several of his videos. Very good content and obviously was taught well...

 

[p3bhambama]

On another thread Richard was discussing highlighter colors. I chimed in and also mentioned I wanted to try a 50/50 mix of canode red and Charbonnel Aqua Wash Sanguine. I did tonight and it really works well. One spritz of windex on the plate and spread around. I’m certain if I use a roller it will be even better but didn’t want to waste one in case the mix didn’t work.

 

[p3bhambama]

My self administered reset is coming back into focus. Messed it up doing too many passes now bringing it back.

What I mean is I think I took too many passes on my modified step scraping and I ended up with holes - at one point the whole middle went to very pale blue/no blue and the edges had dark blue. Been working it back. Another learning experience.

 

[p3bhambama]

Four more passes and the method paid off. Now pretty good everywhere. Going to take a closer look and maybe one or two more passes on the heavier areas before going to spotting.

 

[avivz]

You will have to stop scraping that plate at some point, just saying…

 

[p3bhambama]

Never! Lifetime achievement award

 

[p3bhambama]

Two more passes. Officially moving to spotting. Going to use some Charbonnel black I dried out as a highlighter then polish on a clean granite plate to shine the high spots and see if that helps them stand out more.

 

[p3bhambama]

That works. I squeezed two tubes of Charbonnel Aqua Wash Black Luxe into a lidded container and put it in a small dehydrator for a week. It’s been sitting in the cabinet for probably six months since and is very firm - almost wax like. It’s what I use for roughing and for spotting highliter. For spreading it I put a hockey puck in my crappy mini lathe and turned about half of it down, pulled some natural shammy over it then secured that with a wire/hot glue. With a spritz of windex it’s easy to get a nice coat on the workpiece.

 

[p3bhambama]

Some spotting work. Used a method I saw Keith do to mark the polished high spots with marker to make them easier to see. Not a bad technique but I’ll save it for when I’m at a much higher ppi. For now I’ll go with just hitting the darkest blue ones. And a clean plate pic - scraped surfaces are beautiful.

 

[Richard King]

I'd say, start a new project like a straightedge. Buy one from Denise or Martin Models. Or buy some cut Dura a Bar . I have some longer prime I could say sa a 12" piece off. I could give you a deal...you will learn more now on something else, the go back to the plate after you refine you skill. As far as Kieth using the magic marker. That's a lousy way. I never mark high spots by dabbing them. I lay out lines to get the checkerboard or mark area not to or where to, depending on the circumstances.

 

[p3bhambama]

I'd say, start a new project like a straightedge. Buy one from Denise or Martin Models. Or buy some cut Dura a Bar . I have some longer prime I could say sa a 12" piece off. I could give you a deal...you will learn more now on something else, the go back to the plate after you refine you skill. As far as Kieth using the magic marker. That's a lousy way. I never mark high spots by dabbing them. I lay out lines to get the checkerboard or mark area not to or where to, depending on the circumstances.

Sounds good. I’ve actually been thinking the same thing in as far as a different project.

I didn’t end up liking the magic marker method. It takes too long to lay out and it doesn’t differentiate between the darker and lighter blue spots - because it seems to me even within the realm of “shiny” spots there are some that are higher/shinier than others.

Thanks for the offer on the durabar I’ll send you a message about it.

 

[avivz]

Sorry for my ignorance, what durabar means?

 

[Mark Rand]

Sorry for my ignorance, what durabar means?

Continuously cast cast-iron bar. (Durabar is one manufacturer)

 

[Richard King]

Look up Dura Bar in Woodstock IL . They have a good website. I'd recommend grey iron. They sell it in rectangular or square 72" lengths. Or they will flat saw or prism parts out of plate. It needs to be machined. Or ground.