Conventional versus Blanchard type grinders
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  1. #1
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    Default Conventional versus Blanchard type grinders

    Hey people, here is a question for you; what type of machine would ultimately give you a flatter, more precision surface, a conventional style surface grinder, or a vertical, Blanchard style machine? I can see the argument for either; for the conventional style machine, there is potential for deflection of the spindle/column (come on, we are talking in theory ), but there is less contact area of the wheel on the work. In the case of the Blanchard machine, the load is inline, with less (potentially) deflection, but the wheel has more contact area on the work, meaning more pressure....If anyone has any insight to this, please feel free to chime in...
    Thank you,
    Mark

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    Compare spindle horsepower. The metal removal capability is directly related to horsepower, and precision (in this instance) roughly inversely related to spindle horsepower.

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    I think it is more to the type of work each is best to do. Both can do precision work for size and flatness.
    Stock removal rate often can be better served by the Blanchard or other rotary grinders because of horsepower, rigidity, and weight to allow more wheel contact and pressure on the part.

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    The question wasn't about efficiency or the ability to remove material, but which machine would provide the flattest possible part given optimal conditions...Thanks for the input tho...

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    I have run .0001/.0002 on rotary grinders like Blanchard's, Healds, and Arters, and I have run a few millionths to right-on with surface grinders but that's just me. likely some guys have run near zero on Blanchard's.

    Yes, nothing is dead on, so no error found is considered right on.

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    Either machine can produce very accurate results, or not. Depends on several factors, including the skill of the operator and the condition of the machine.

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    Is this a real question? So sorry but giggle a bit.

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    Blanchard Grinders are excellent tools, but they where designed for heavy grinding applications where flatness and parallelism requirements are not extreme. Conventional surface grinders tasks' are far more demanding.

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    Here is an article that compares Blanchard to other types of machines but actual skilled users will argue that rotary grinders are capable to run .0002 flatness on a large surface or a full chuck load of parts.
    The surface grinder might have difficulty achieving .0002 flatness and size on the flat sides of apart 36" or larger diameter part because of wheel breakdown in such a long travel.
    Blanchard Grinding vs. Precision Grinding | Summit Steel & Manufacturing, Inc.
    From this article:
    It’s less precise: Grinding of any type is for precision work, and Blanchard grinding is no exception. The fact remains, however, that out of all the different grinding methods, the Blanchard system is among the least precise. Because of this lack of accuracy, machine shops will only use this process for projects that have a tolerance of over 0.001 inch.
    It leaves a grinding mark: Most people think the unique cross-hatching pattern left behind by Blanchard grinding is very visually appealing. If the metal in question needs to be blank and free from any markings, however, this will be an undeniable drawback.

    Mine- but .0002 size can be achieved on a rotary type grinder, and a mirror finish on a chuck full of carbide inserts can be made with talent and the right wheel.

    So this question is like "What is better to go from New York to California a box truck or a sports car?"
    Last edited by michiganbuck; 06-03-2021 at 11:02 AM.

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    Thank you for the article...that kind of sums it up!

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    I once had to repair a big ( 21” stroke ) slotter, the back faces of the ram were badly scored. I made the mistake of allowing the customer to send it to his favourite grinding shop. Instead of it being surface ground it was put on a “ Lumsden “, which is a British “ Blanchard “ type machine. The ram came back with a 0.002” dish in the ways which I had to scrape flat again !

    Horses for courses.

    Regards Tyrone.

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    So much depends on part size, material and thickness.

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    Blanchards are fast. In the right setting will make a VMC look like it is standing still when peeling off steel.
    Dish is a problem.
    Big SG's also tend to dip off a tad at the ends, and also very much slower so cost is higher.
    A good grind shop like Cash here has both and can provide input and feedback on what needs to be done and the tradeoffs.
    I love both Blanchard style and conventional SG.
    Bob

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    Quote Originally Posted by cash View Post
    So much depends on part size, material and thickness.
    And the machine design:
    Large vertical single disc grinders for optimum stock removal - Fives Group

    The page shows a 3 foot diameter ball bearing being ground with a position resolution of one micron.

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    Quote Originally Posted by Robert R View Post
    And the machine design:
    Large vertical single disc grinders for optimum stock removal - Fives Group

    The page shows a 3 foot diameter ball bearing being ground with a position resolution of one micron.
    Interesting machine, I did not know Fives was into "blanchard" style grinders for bearings. This machine looks pretty specific for the operation to grind bearing faces, I would assume this is low stock removal, very tight tolerance. The clue to me here is the machine spindle horsepower for a 125" table is pretty low, only 125 HP. A blanchard of this size would be 250 HP minimum.

    There is another member here, Motion Guru, he is doing some crazy tight tolerance parts on a blanchard style grinder. It took him quite a bit of work to get down to where is is, but it shows it can be done. Off hand I believe he is grinding tenths over a 24" magnetic chuck.

    Surface grinders, when I say this it can be a rotary table machine like a blanchard, but it has to be a horizontal spindle with a type 1 grinding wheel, tenths or better are standard on these kind of machines.

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    Quote Originally Posted by Tyrone Shoelaces View Post
    I once had to repair a big ( 21” stroke ) slotter, the back faces of the ram were badly scored. I made the mistake of allowing the customer to send it to his favourite grinding shop. Instead of it being surface ground it was put on a “ Lumsden “, which is a British “ Blanchard “ type machine. The ram came back with a 0.002” dish in the ways which I had to scrape flat again !

    Horses for courses.

    Regards Tyrone.
    If operators done use caution, this is pretty common on long narrow parts grinding blanchard style.

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    Rumor had it that a Lumsden went down on the Titanic. I ran a Lumsden tool grinder back in the 60s and thought it a decent but crude machine. One 0ff .oo2 may have been trammed that way for dishing large face mill cutter.. or just wore out.

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    The Fives Group uses a 26" diameter wheel driven by a 125 HP spindle motor on their 120 inch diameter table machine.

    Bourn and Koch uses a 72" diameter wheel driven by a 200 HP spindle motor on their 120 inch diameter table machine.

    The smaller wheel requires less power input at full wheel loading.

    The weakest links in the Blanchard design are the wheel adapter and the spindle. according to one machine design reference. The smaller wheel is one of the reasons why the Fives Group (Giustina Grinding Division) machine is capable of higher accuracy. The design may limit it to machining rings or smaller parts mounted on the wheel perimeter. They could use the servo drive on the table feed axis to gain access to parts mounted in the center of the chuck.

    The smaller diameter wheel may also permit higher wheel pressures and the use of seeded gel grinding segments. It may be that the lower power spindle combined with a SG wheel can achieve material removal rates approaching the removal rates of a higher power spindle operating with conventional aluminum oxide abrasives.
    Last edited by Robert R; 06-14-2021 at 02:44 PM.

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    the question is interesting, but has not really been answered. lets disregard the size (there are small vertical grinders too). the surface grinder is only as good as the ways. it seems that a rotating table has a better chance of being true. but, how do you dress the segments on the vertical?

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    I have run segmented rotary verticle spindle grinders and most had a swing arm dresser to dress the wheel. One did not have a swingarm and I used a diamond with not rotating the table, just going in and out under the wheel. Mostly the Blanchard type self dresses the wheel with the wheel bond letting loose the grits when the grits get loaded up or get dull. A Blanchard wheel loading up with material and acting dull often gets a swing arm dressing. The swing-arm is most often a stack of disks that roll on the wheel.
    Blanchard types have much wheel area contact so need high horsepower to keep RPM up to grinding wheel surface per minute, with not that SFPM it would be honing not grinding. flooding with coolant takes away the high heat that would be generated.
    The surface grinder's amount of wheel contact is very small in comparison so stock removal is much less and horsepower needed much less.

    I have set the wheel segmented and cylinder (type-2) that were set in place and then molten sulfur was poured into the wheel cavity, the sulfur turned into a glass-like hardness and made solid the wheel assemblage. Yes, it was a bugger to hammer and chisel out the wore out wheel.

    Both types of grinders, rotary and surface (along with all grinders) need precise ways in good condition to run precise parts.


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