Re: [CAD_CAM_EDM_DRO] How to scrape lathe ways

I have watched real scraper hands do their jobs and own a flaker which is
used after scraping to allow lubricnts to do their job. If you do a
perfect job of scraping, the two surfaces will ring together like a couple
of jo blocks and you will have too much friction. To Scrape a way you need
a flat surface long eouugh to go all or most of the way along the way. You
can do it with overlapping the flat surface, but it is harder.

The flat surfaces that a scraper hand uses are normally granite bars, but
it is possible to do the same thing with ground mehanite bars (cast iron),
They should be stable enough if they are thick enough.

Just cover the flat surface with diechem or some other easily renewed
die/paint and carefully lower it onto the surface to be scraped. Then
scrape away the dots of dye on the worn surface. Replenish the die on the
flat bar and do it again until you have enough tiny points over the whole
surface to give you the accuracy you want.

A jig borer will have about 200 points per square inch, while a large mill
may have only about 20 such dye points per square inch. If your bar
dowsn't bridge the warn areas of the way, you risk getting a flat, but not
aligned surface. In the beginning you will have large splotches of dye,
but as you continue, the points will get smaller and evener.

Be aware of the cautions of doing this on a machine where a center is fixed
and cannot be adjusted to the new hight of the ways. Moglice is used more
and more to avoid the extreme efforts involved in scraping.

A scraper is a flat file shaped steel bar with comfortably round corners
and a carbide edge clamped to the tip. If you want to flake or scrape a
small area, you can take an old file and carefully grind away the tip to
get a convenient flat end with a curve to allow you to avoid gauging the
way. Files have ductile innards, so don't grind away much or you will
lose the case hardened outer surface. You can flake with the same tool.


At 11:45 PM 10/21/00 -0500, you wrote:

>
>
>Wally K wrote:
>
>> I have a 10K South Bend lathe that needs to have its ways ground,
>> scraped, or both. I can feel a lip of 1/32 or so on the V way of the
>> lathe. My local machinery dealer told me it would cost to much to
>> have it sent out and ground.
>>
>> I have never used a scraper before or saw anyone using one. I have a
>> feeling that scraping is a learned skill and do not know if i should
>> attempt it.
>
>It would be good to practice on some scrap of similar material to the
>bed.
>
>> One person told me i should start with a belt sander and finish with
>> a scraper.
>
>I can't imagine how you could do an inverted V way lathe bed with a belt
>sander.
>I CAN imagine how you could ruin the entire bed in less than a minute!
>
>You need to make a 'gauge' which is an accurate reproduction of the
>bottom of the carriage to spot the high spots and know where to scrape
>metal off. After reading the William Connelley book, it seems the real
>trick is knowing WHERE to scrape some metal off, that's the real art!
>The actual scraping of the metal is something learned in an afternoon,
>or thereabouts.
>
>> Does anyone have any advice on what i could do with these ways. Or
>> have any links describing the process to bring the ways up to spec.
>
>The book "Machine Tool Reconditioning" is great, but the author,
>the William Connelley mentioned above, is selling it for a rather high
>price.
>That is $92.95! You can get it from Dan at Machine Tool Publications,
>651 458-1540.
>
>There is a guy who sells a book and video :
> http://www.machinerepair.com/scrapingbook.html
>
>My other scraping links have gone dead!
>
>Jon
>
>
>
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