Re-grinding the bed on my South Bend 13 - Page 3
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  1. #41
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    Quote Originally Posted by Richard King View Post
    If the bed is soft and not hardened the SB beds were planned, stoned and then the were square cut or scraped to break up the flat iron. If the ways are not scraped the will begin to gall up. We match fit the saddle to the bed ways. The scraping is .0002" deep and way wipers can clean out dirt as long as you replace them periodically and clean. I do not recommend you 1/2 moon flake the soft bed as normal 1/2 moon flaking the flake is .002" deep and wipers no matter how good they are will hold small chips and work under the saddle.

    I will 1/2 moon under the saddle as Tom mentioned. If the bed is ground and flame hardened or induction heat treated the bed is smooth and flat. The bottom of saddle is scraped and in some cases 1/2 moon flaked.

    Some 1/2 moon flake the bed when they are soft more for cosmetics and oil pockets. I have always been the believer that you scrape the bed and not 1/2 moon flake it. I base that on many years of scraping Bridgeport mills and finding scratched and galling because the wipers were never replaced and chips worked under there. Rich
    Our 10" SB is as you describe. There's a bit of wear but in the unworn areas, you can see ground ways with long scrap marks 1/4"-3/8" apart. I've never had the saddle off but I imagine the flaking is long gone.
    sb1-6.jpg

    On my basket case Hendey, you can kind-of see a similar approach in the un-worn areas. The V-ways down on the tailstock end have shadows of long and wide scraper marks, 1/2" or so apart. The "untouched" ways around the headstock look like they were finely planed, but no scraping.

  2. #42
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    Sorry for the late answer but I was at IMTS show and never turned on the computer. I just my cell phone and it's a pain to type on it. I wrote in another thread and it was full of typo's, lol. When they grind the bed most grinding companies indicate the ways to be sure the grinding wheel is dressed so it matches the OEM angle. Then the rebuilder / scraper depending on amount of wear will machine or grind the bottom of the saddle to that same angle. They can't grind or machine to the exact perfect 100 contact "match" fit. They have yet to find a way to make an exact fit metal to metal contact yet that's why scraping is used. If you want an exact fit you can use Moglice which is a German product the is similar to epoxy glue and you inject or apply and it will dry making an exact fit.

    I say Moglice, Rulon 142, Turcite B and there are other brands of materials, that you either inject, apply. that have revolutionized the machine tool building / rebuilding.


    As I said before a soft bed machine wears faster if it is left alone. Think about when an inspector rubs 2 gage blocks together and they stick together. Or laying 2 plates of glass with a thin layer of water or oil on it and trying to separate them, they stick. On a soft bed machine the exact 100% contact will not allow oil to stay under the saddle. It will force out all the oil and act more like a seal and stick and then as the iron fatigues it starts pull the metal out and scratch and eventually gall.


    That's why they scrape the bed so they have a "flat way bearing" that the oil can circulate around. Think about the old days when they used bronze bushings instead of ball bearings. The scrape mark is like the ball of a ball bearing. That's a ball "bearing" the high spot next to a scraped mark is a "flat bearing" .


    Many times the machine rebuilder or builder just ground the bed accurately enough so all they did or do is break up the super ground flat surface. Like SB did. They use a hand or power scraper to "break" up the surface so the high spot holds the weight and low scraped spot is an oil reservoir. The bottom of the saddle is match fit 50% contact and 50% low spots. I'll attach a sheet "Sip, the famous Swiss machine builder" made and gave BIAX and I permission to copy and use. It shows the difference of bad scraping to good or contact.

    The other 2 are out of my work booklet I give to my students that I wrote and have copyrighted. They show why we like to scrape 20 PPI to carry the weight of the "matched fit" "riding" surfaces.

    There are all sorts of techniques used in breaking up the surfaces. 1/2 moon flaking, long scraping as NB shows, square cutting as I have described. :-) Rich
    Attached Thumbnails Attached Thumbnails 20170201_141959_008.jpg   20170201_142101.jpg   20170201_142115.jpg  

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  4. #43
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    Good information Rich.
    If a guy went through the work of grinding and scraping a South Bend could it then be flame hardened?
    Or is the casting the wrong mix of iron?

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    Quote Originally Posted by Richard King View Post
    On a soft bed machine the exact 100% contact will not allow oil to stay under the saddle. It will force out all the oil and act more like a seal and stick and then as the iron fatigues it starts pull the metal out and scratch and eventually gall. That's why they scrape the bed so they have a "flat way bearing" that the oil can circulate around.
    Richard, to clarify for anyone reading this thread who might not fully appreciate the difference between "scraping" and "flaking": Scrape marks are very shallow (in the neighborhood of 0.0002" once you're beyond the roughing stage). I think you're saying it's OK to scrape all sliding surfaces, including the exposed bed ways and the underside of the saddle (although I'm pretty sure you would recommend hollowing out the middle 50% of the saddle bearing surfaces several thousandths deeper so that as the saddle wears and drops it does not begin to "rock" on the high center). If I understood you correctly, your target for scraped sliding surfaces is a pattern of roughly 50% bearing surface (high spots) at a minimum of 20 points per square inch (ppi).

    Flaking is much deeper (more like 0.002") to hold oil. It's most commonly seen as a "half moon" shape on top of the underlying scraped pattern. Other flaking patterns may be seen depending on who taught the rebuilder his/her trade and how much is being invested in the machine. Flaking should generally be found only on the underside of sliding ways to avoid catching and holding abrasive particles that will get in between mating parts. Way wipers help, but they're always fighting gravity which wants to concentrate the ugly bits in these deeper troughs.

    Does that jive with what you tried to teach us in class, Richard?

    And BTW, what's up with posting your copyrighted stuff? Next thing you'll be posting all your dirty jokes, too! Ha.

    Best regards,

    Tom

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    Great discussion points.
    As one of those who owns a 1941 13" South Bend, this subject is close to home.
    I may buy a new lathe someday but meanwhile, I am learning and improving my skills on my worn SB.
    OP, only you will know what is right for you. I agree, it's not always just the money.

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    Quote Originally Posted by thomasutley View Post
    And BTW, what's up with posting your copyrighted stuff?
    So long as the Copyright notice is still ON it, it doesn't matter HOW he distributes it, or if he charges for it.

    The rights are still protected. All-else bases off the IP "rights".

    In any case, its a compendium of thousands of years of learning since mankind first began "incremental corrections" to alter wood and stone, even before metals.

    It's the arrangement, commentary, explanation, and guidance that adds the value.

    Scraping itself is REALLY OLD!

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    Quote Originally Posted by thermite View Post
    It's the arrangement, commentary, explanation, and guidance that adds the value.
    Precisely why I tell anyone who will listen to sign up for one of Richard's classes. There's nothing like seeing it in person.

    Also I'm secretly trying to open the market wider for Biax power scrapers and flakers so their cost comes down out of the stratosphere.

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  12. #48
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    Quote Originally Posted by thomasutley View Post
    Precisely why I tell anyone who will listen to sign up for one of Richard's classes. There's nothing like seeing it in person.

    Also I'm secretly trying to open the market wider for Biax power scrapers and flakers so their cost comes down out of the stratosphere.
    Ahead of you. I think.

    I bought ONE Biax blade from Rich. Figure to plant it in the back garden, fertilize and oil it, try raising the rest of the Biax from the blade.

    Same DNA, right? Works for mighty Oak trees.

    What have I got wrong, here?

    ??

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    Quote Originally Posted by thermite View Post
    Ahead of you. I think.

    I bought ONE Biax blade from Rich. Figure to plant it in the back garden, fertilize and oil it, try raising the rest of the Biax from the blade.

    Same DNA, right? Works for mighty Oak trees.

    What have I got wrong, here?

    ??
    Ironically, cast iron swarf is an ideal fertilizer for iron-loving plants like rose bushes. Might work well for growing Biaxes, too...never know.

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    Here's a picture of my advertising agent in training...lol
    Attached Thumbnails Attached Thumbnails 20170121_160721.jpg  

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    Quote Originally Posted by Richard King View Post
    Here's a picture of my advertising agent in training...lol
    Now THAT is one fine looking...piece of Durabar!

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