Re: [CAD_CAM_EDM_DRO] Re:Lapping and scraping

turbulatordude wrote:

>--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Ted Gregorius" <ted@t...>
>wrote:
>
>
>>Hey Guys. I'm completely ignorant about this lapping and scrapping
>>
>>
>stuff. Although I believe I understand the methods and pitfalls of
>lapping (did a few telescope mirrors many years ago) could someone
>explain what hand scraping is.
>
>
>>I have heard the term many times and it's obviously a good thing to
>>
>>
>have hand scrapped ways on your machine. How is it done?
>
>
>>Thanks
>>
>>Ted
>>
>>
>>
>
>Hi Ted,
>
>I have never scraped a way so cannot make comments, but I too would
>be happy to hear the answer to the way the real pro's would do it.
>
>

A sharp tool with a slightly convex arc to the blade is applied to the
material,
and tiny shavings are scraped off the surface. because the tool
presents only
the slightest curve when the blade is laying nearly flat on the surface,
it automatically
scrapes off the local high spots. But, you use it with dye and a known flat
surface (surface plate or master straightedge, etc.) so you only scrape
in the areas
that have general high spots for the whole surface.

Cast iron can be scraped into fine alignment with this method in a
fairly short
time. I've made a master straightedge and some other small tools to
generate
the correct shape on dovetails and similar machine slides.

Michael Morgan has written a book and made a video on hand scraping.
I saw him at the NAMES show a couple years ago, and it was a treat to watch
a pro do it so effortlessly!

Jon