# Scraping Help



## Richard King (Jun 13, 2013)

Hi everyone,

I am scraping the ways of a Nippon Center-less Grinder this week.  It looks a lot like a Cincinnati.  Yesterday I took some photos.  My students who have attended my scraping seminars know what I am doing here as I teach them this trick in the class.  When you first look at a way, look for an unworn surface to judge or measure how much the part is worn and then scrape it off first.  In you work booklet I say remove all ridges as it wil change the geometry of the way as in this case it is a dove tail.  The factory cut the bottom of the dovetail low on purpose as you will see in a photo.  But when doing this the mating surface will end up with a narrow ridge on it as it does not wear.  

I blued the part and on the top of the dovetail is a 1/6" narrow strip of bluing, that is the ridge.  I scrape it off if I didn't do this and scraped the bottom of the dovetail and the ridge I would change the angle and when I go to blue up the mating surface the angles will be different and make for more work.  This machine is a fine example of another thing I teach.  The machine uses grease as a lubricant and the principal of using grease on a grinder is the grease acts as a seal and not allow the coolant with the grit to penetrate under the ways. The problem is the owner never cleans the grease off the end when it is pumped out or purged and the grease on the ends get full of grit and acts like lapping compound and the ends wear faster and the ways get high in the middle.  So this is why we hing the master straight edge we use to blue up the part.   

The way that is worn on the ends gets high in the middle and looks like the bottom of a rocking chair.  We lay the master flat straight-edge on the dovetail, rub it, then pull it out of the bottom about a 1/8" and pivot by alternating pull and pushing you hands to check the shake or some call them airy points.  It should be between 25 to 30% from the ends when it is flat.  I will also relieve the middle 40% of the shorter way when I am finished so when the machine runs again the ways will become flatter and the .0005" to .001" lower area will act as a oil reservoir or lake for the oil.   This something I teach a lot in my classes!  If any of my students can comment please help me explain this to the readers..  Bill from the GA class wrote about this in another thread.
Got to get to work.  Rich


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## turbotadd (Jun 14, 2013)

Richard,
Great info! Your photos do indeed illustrate the principles you taught in class. Is there anything different that needs to be done to ways that use grease instead of way-lube (like different flaking scheme or anything)?

Tadd


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## Richard King (Jun 15, 2013)

Update, 

I am still scraping the ways of a Centerless Grinder and I took some more pictures yesterday.  I am showing the procedure of stoning the ways after scraping them.   As you scrape using a Biax Scraper using cross scrapes 
a small burr is left at the top of the scrape. 

 I ground a med grit Indian lapping stone at a 45 deg angle to fit under the 50 deg dovetail.   I also show how important it is to use the yellow high lighter as when the shinny iron reflects the light it is hard to see the high spots.  I use the yellow color ink diluted with glass cleaner.   In this case I am using a paint brush to apply it and then wipe it off so 99% of it is gone and it's dry to the touch, I just want to leave a dull color so I can see the blue better.    You can see I am in a rough / finish mode as some of my scrapes are touching in some areas and in others I am finish scraping as the scrapes are separated.  I am also showing you how I set the bottom slide on a granite surface plate setting on 4 ground blocks and using a surface gage / .0005" Best Test indicator to make all sides parallel to 0005".   I already scraped the machine base where this part sets flat and parallel.  It is a static fit under there so I only scraped it to 2 to 5 PPI.  The top I am scraping it to 15 to 20 PPI.    Will add more later.   Rich


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## komatias (Jun 15, 2013)

Hi Richard,

in second foto, is it chatter that can be seen in the trough of each stroke?

Regards


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## Richard King (Jun 15, 2013)

Yes.....I am still getting it close I call it a combo of roughing and semi finish, so a little chatter is acceptable.  It's hard not to get it no matter what you do.  When I shorten my stroke and slow down the motor the chatter will be hard to notice.


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## komatias (Jun 16, 2013)

Ok, that is what I getting before I slowed down my biax, thanks


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## Richard King (Jun 16, 2013)

Yeah when you are roughing you get it.  Have to be sure to change directions or if you don't it gets really bad.  On the dovetail I roughed with the Biax and finished it by hand to avoid it.  The  Biax will increase productivity by 50 to 75% but you get chatter.  Most people will never see it or even know what it is. It won't affect the way the way system works.  what is important is the depth .0002" to .0005" deep scrapes and 40 to 60% high spots.  Once you get the hang of it, you will consistently get 20 PPI (points per inch) by accident.


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