How Good is Good when rebuilding and scraping
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  1. #1
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    Default How Good is Good when rebuilding and scraping

    Many new to scraping start to evaluate the project and over do what they need. I was telling my group about a Psychiatrist who emailed me with photo's showing how he was indicating a Rung-Fo Mill table using an Inter-rapid .0001" indicator and how bad it was. If my memory serves me right it was off .008" When he bought it he thought it would be less then .001" He held a class inside his 3 car garage and the first thing we did was to scrape the 4 feet so they were all touching at the same time. It also bolted to a metal stand and the stand was bad.

    We drilled and tapped the cabinet legs to add leveling screws then we took the machine base and set it on the cabinet and shimmed so it set solid on the stand. I told him he could not expect better then .0005" per foot after we were done as the machine wasn't designed to hold .0001". In good German, American, European conventional machines were built correctly and the spec's were .0002" per 12" on machines like a lathe, mill. If I was scraping a surface plate or jig bore you would expect a new machine to be .00005" in 12".

    So the Doctor wanted tenths and settled for .001" Now think about the work envelope. Most of those cheap machines only had a travel of 12" and if he put a vise on the table, his work envelope was the width of the vise. Most vises are 6" wide, so his spec then was .0005" in 6". If he had a lathe he was scraping the bed and it was 10' long then it could be out .002" as you have to think of the multiplication of error is .0002" x 10' = .002" Also when scraping a conventional machine you only need to have is 20 PPI (Points per inch) and 50% contact. I

    I taught a class 40 years ago at Gallmeyer and Livingston Surface Grinder Company in Grand Rapids, Michigan and before the class they only used hand-scrapers and on there surface grinder builds to 12 PPI. Using a BIAX power scraper one can get 20 PPI by accident. Another thought is the more PPI and POP (Percentage of Points) of 40 to 60% contact, the longer it will last. This is why we scraped straight-edges to 40 PPI. You can use it longer.
    dsc00534.jpgimag0613-1-.jpg20140903_160708.jpgppi-booklet-chart.-3.jpgppi-booklet-chart.jpg
    Last edited by Richard King; 06-03-2021 at 12:57 PM.

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  3. #2
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    Quote Originally Posted by Richard King View Post
    I taught a class 40 years ago at Giddings and Lewis Surface Grinder Company in Grand Rapids,
    Sure it wasn't Gallmeyer & Livingston in Grand Rapids Michigan?

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    A lathe with a 10ft bed with .002 error would be pretty nice!, I believe Monarch says their much shorter ee bed, has not more then .0005"
    The American machine tool industry standards for a toolroom lathe, were published in the blue ee brochure 1983, I could copy and post that if there is an interest.

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    Quote Originally Posted by donie View Post
    The American machine tool industry standards for a toolroom lathe, were published in the blue ee brochure 1983, I could copy and post that if there is an interest.
    Sure, I'd like to see it.

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    I will dig out that brochure.
    Last edited by CBlair; 06-04-2021 at 01:21 PM. Reason: off topic discussion

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    Quote Originally Posted by donie View Post
    This forum is not a safe place in my opinion, to enjoy machinery.
    Donie, I wanted to send you a note but your Inbox is full. Could you please clear it out, or add your email address to the PM configuration so that we can also reach you that way? Cheers, Bruce

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    Not a chance of that, moving in a positive direction. The Blue Lathe brochure!
    Ha Ha! many tried to nail the color, but failed miserably, ended up poopy blue. That paint job cost $4000+.
    I remember it well! It was October 1983, I walk into Royal machine tools, the Monarch dealer in Seattle, with my boss, that just purchase a factory reconditioned machine for just under $30000.
    I was handed this brochure showing the new 1984 ee with solid state drive $60000 to $70000.
    I then went to the Boeing surplus, and found a Wilton SJ450 vice for $50!
    ooooh the blue lathe!

    Hopefully, this mother fucker is readable! I can say as an operator, the rotational accuracy is more important then spindle nose run out.
    and, another thing that may interest the scraper, is concave on a faced part can be specified at extra cost, that factory adjustment is by scraping the crosslide. I have the specs for the extras, on one of my machines. I now return you to regular programing.

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    One has to be realistic to use.
    People get a 50 millionths indicator and go nuts over the needle not moving.
    Yet none test the machine under load or in the cut. Free state checks but how many of us are machining air all day?
    Close to a million dollar grinder and checks well under a micron with a lot of work at install. Lean on the enclosure or if big truck drives by kiss that number goodbye by a factor of 10 or 100.
    Everything moves under load and that includes the block walls and floor of your shop.
    Where you stand in front a a machine can do this unless one has put in a isolated base. How many think about that?
    Better free state is better in most all cases but this number is never true in real use.
    Many get just too crazy wanting lots of zeros.

    Big fan here of higher PPI for longer life.
    Bob

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    What is ‘cam action’ on a leadscrew?

    L7

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    I will tell you this, if you can make good parts on an Atlas lathe, you can squeeze the precision out of a monarch, because things can move around with the machine when working in tenths or better, not unlike the Atlas going out a few thou...

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    Quote Originally Posted by lucky7 View Post
    What is ‘cam action’ on a leadscrew?

    L7
    Drunkeness.
    Variation over one turn to true. Lead/Lag in a turn and all screws ball or hard have this wandering.
    Bob

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    Can someone explain why you would prefer the Headstock Alignment to be "Back of center at end of bar" instead of "Forward of center at end of bar"?

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    There is also camming in error.
    it is easy to do, and can be pretty much avoided by engaging the half nuts slightly early, following the leadscrews left flank on right hand threads on down to the bottom.
    If engaging late, the tool will trail slightly giving inconstant results. Also, the mechanical parts in the half nut engagement mechanism can take a while to settle in.
    These problems were solved with leadscrew reverse mechanisms, where as the half nuts are left engaged full time. the parts settle in and a more accurate thread can be made.

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    When I discuss levels during my classes I do a experiment where I have the lightest student stand still and watch the bubble of a Starrett 199 Level sitting on a granite plate. Then I have the rest of the class stand behind the light guy. Have him watch the bubble and then we all move 180 degrees and stand on the other side of the plate and the light guy, 9 out of 10 times see's the bubble move. I mentioned my Make a Wish class. Hunter the student told me he had a choice to take the class or get a rebuilt Monarch EE from Monarch and he picked the class. That was a heck of a compliment. I think he said the lathe was worth over aa 100 grand. Garwood, have Hunter come back as he used to be a member. Hunter met a Moore Scraping Tech and he taught Hunter how to scrape the Moore method. Hunter also makes high end Jack knifes. I just found his name on here. It's been a while since he wrote anything here though. Iridium77

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    Quote Originally Posted by Chris Lesiak View Post
    Can someone explain why you would prefer the Headstock Alignment to be "Back of center at end of bar" instead of "Forward of center at end of bar"?
    I don’t understand that either. We always set the headstock test bar 0.001” in 12 inches nearer to the operators station at the free end.

    Regards Tyrone.

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    Ha! the machines rebuilder may not understand what the operator is doing, and the stresses she or he are putting the machine through.
    As an operator of a Monarch ee, I am the one that in reality is paying for the high dollar machine, and making the owner money. Its hubba hubba, get moving, wear a neck tie, knuck, knuck. just joking on the neck tie, get a texas string tie!
    One may not believe how much a Monarch ee can twist or distort when pushed at reasonable capacity, but that is something I can deal with.
    By the way, there is no one that comes close to Monarch itself rebuilding their own machines. I know that as an operator.
    this one was made in 1983, the last vacuum tube fired ee made before the "Blue Lathe" of 1984, each one hand built only on special order. The later machines are not the hobby grade antique machines, these later ones are serious machines, and investment.


    well, you dont run it! oh, you drive it.

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    Quote Originally Posted by donie View Post
    Ha! the machines rebuilder may not understand what the operator is doing, and the stresses she or he are putting the machine through.
    As an operator of a Monarch ee, I am the one that in reality is paying for the high dollar machine, and making the owner money. Its hubba hubba, get moving, wear a neck tie, knuck, knuck. just joking on the neck tie, get a texas string tie!
    One may not believe how much a Monarch ee can twist or distort when pushed at reasonable capacity, but that is something I can deal with.
    By the way, there is no one that comes close to Monarch itself rebuilding their own machines. I know that as an operator.
    this one was made in 1983, the last vacuum tube fired ee made before the "Blue Lathe" of 1984, each one hand built only on special order. The later machines are not the hobby grade antique machines, these later ones are serious machines, and investment.


    well, you dont run it! oh, you drive it.
    Looks like you eat your lunch off of it to me.

    Regards Tyrone.

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    Disagree a little. You want to use the full X axis length for an operation. That can be accomplished in several ways, be it with more than a vice, be it by clamping the part directly onto the table or whatnot.

    Milling is a middle process between sawing or any other brute cutting and finer processes such as grinding, lapping, even straight cutting. To give parts a very good finish at milling takes expensive tools. Lapping compounds cost little compared to millers but take you to millionths easily.

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    Quote Originally Posted by Mechanola View Post
    Disagree a little. You want to use the full X axis length for an operation. That can be accomplished in several ways, be it with more than a vice, be it by clamping the part directly onto the table or whatnot.

    Milling is a middle process between sawing or any other brute cutting and finer processes such as grinding, lapping, even straight cutting. To give parts a very good finish at milling takes expensive tools. Lapping compounds cost little compared to millers but take you to millionths easily.
    I'm a little confused by your post: did you intend to reply to a different thread?

    Paolo

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    Quote Originally Posted by Paolo_MD View Post
    did you intend to reply to a different thread
    No, it’s for Richard King and the perfectionistic psychiatrist. Typical amateur error to overdo. Milling machines and lathes need only to be accurate to a healthy extent. Like the ancient Egyptians who didn’t shape multi-ton stone blocks more precisely than necessary. The underground was carved out of the grown rock, crudely here and there. About half of the building time of the Giseh pyramid went into the underground. There Nile water could rush in and start to give pressure. Once the water ram supplied pressure the ground plane could be levelled. Then the stones.

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