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  1. #21
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    Quote Originally Posted by cyanidekid View Post

    aluminum oxide "sandpaper" is NOT my first choice, for the simple reason that one of the constituents of some mill scale IS aluminum oxide. (ever wonder why some scale is nearly impervious to a regular sanding disk?)
    How can you form aluminum oxide hot rolling steel? The aluminum has to come from somewhere.

    Bill

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    It's like all things, there are pros and cons, I use one to mill on, I have a round one on the lathe, 8" ish, you can hold some thin stuff, even thin brass sandwiched, downside it will pull the work flat to the chuck, when released it will spring back, mag chucks are great for thin washers etc, no heavy cutting
    It will slip, very frowned on by the old machinists in work!, I was skimming washers on the lathe, one of the fitters walked past and said "bloody heathan, hope it hits you in the head and knocks some sense in"
    However neither happened, the job was done on super quick time as I covered the chuck with washers, one cut done.
    It has a place but only to be used with caution!
    Mark

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  5. #23
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    Quote Originally Posted by 9100 View Post
    How can you form aluminum oxide hot rolling steel? The aluminum has to come from somewhere.

    Bill
    It does in deed come from somewhere, most steels are AK, aluminium killed, excess oxygen is scavenged by adding Ali, in fact no one can cast steel by con casting without Ali killing (OK Ti, Ca also do the job but rare)
    The bulk of shite in steel is Al2O3, it's also in the mould powder and refractories, several tons of Ali get added to each ladle of steel, usually killing but reheating in cas-ob and vacuum degassers.
    Dirty steel is normally due to it, when rolled it forms long strings that can cause lamination and cracks too.
    Mark

  6. #24
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    Quote Originally Posted by Edster View Post
    I use Schunk Magnos magnetic chucks. They work great for larger parts that cover most of the surface of the chuck. Each chuck has 20,000 pounds of holding force if the entire chuck is covered. The magnets are permanent, electricity is used to flip the poles, which causes magnetic flux to come out of the top of the chuck. Once clamped the power is disconnected and machining starts. Pole extensions are used to lift the part off the surface of the chuck. 3 fixed extensions are used to support the part. The rest of the extensions are floating to conform to the workpiece. The floating extensions lock when the chuck is clamped. These magnets are best at clamping larger workpieces that are thick enough that most of the flux stays within the workpiece.

    Magnos - Shunk - YouTube
    Does the chuck also have a demagnetizing cycle like the typical electric chuck? Does it magnetize by a large pulse? I do a lot of magnetizing, motor and generator fields and magnetos. The magnetizer puts a pulse through the "coil", which can be a single turn, that as close as I can estimate is over 100,000 amps. The magnets are driven to saturation, the maximum flux they can carry. Magnetizing a horseshoe magnet, the keeper you put across the poles to complete the magnetic circuit will be stuck on so tight it takes an act of God to remove it. I think a lot of the reason is that the flux pulls them together tighter than would be possible by most other means because the pressure comes between each bit of surface area and the mating part, like putting a C clamp on every square millimeter of the surfaces, mashing down any irregularities. Besides, most steel will hold some residual magnetism and will be magnetized just as the chuck poles are.

    I have no trouble believing that the Schunk chuck holds that well.

    Bill

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    not my bailiwick but seems like a good solution would be plate that laid over/secured to the periphery of the mag chuck, and pockets cut into(clear through) the plate for the parts??

    Merry Chrismas fellas!

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    Per Walker when I looked into this many years ago. Mag chucks can achieve 70 psi hold max, reduce this as you add scale, uneven surface, etc. You will need a demagnatizing cycle when "unclamping" the parts. Your parts are not optimal for this method of holding as they are tall for the footprint. If you can set them against a rail to take the side cutting loads then I would feel it has a good chance of working. If you are only doing a few hunderd parts you would probably be better off just using vises and getting it done. The mag chuck will have much more setup time, learning curve, and risk of a block comming loose under a face mill, ouch and a change of underwear.

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    Many think of magnetic chuck's holding power at to what it takes to tip over a held part. The real holding power is what it takes to lift a part straight up.. That is why I recommend the high bump stop as that most uses the straight up power.. It would not surprise me that a 5x10" brown and Sharp permanent chuck would lift a few hundred pounds straight up....yes I have a lose one (a B&S 5x10) and will try that one of these days.

    I use the 5x10 as a squaring device to hold a part up from my horizontal (attached) chuck.so getting one side square to a right angle.

    Agree nothing like the holding power of a screw thread..a good 1/4 screw might be near 2000lbs on a good day. On a good day because I would not wish to be standing under such.

    It is surprising how little holding a vise has when often you can soft hammer down jaw knock and move a part..

    OPs 2"3" down siding should have a high bump at near 5" and that bump bolted to the table.. just standing with a rail block would not be that safe even for grinding.

    Trickey is filling a Blanchard chuck with a few hundred parts setting on wires or set on angle parallels to get a bottom angle...

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    Quote Originally Posted by 9100 View Post
    How can you form aluminum oxide hot rolling steel? The aluminum has to come from somewhere.

    Bill
    aside from the excellent description by boslab, another source is Al mixed in with the scrap charge in the furnace. just think, how many bev cans wind up mixed in, stuck in recesses, and how many mixed metal items mag separate as "ferrous". because it is a de-ox, it is allowed in the scrap charge in a certain percentage as a common practice, I believe.

    the lower the quality of the steel, the less care is taken to ensure a high quality, consistent scrap addition as well.

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    Quote Originally Posted by adama View Post
    I agree, im just a hack running out of a single car garage, but customers absolutely love my surface ground parts, totally unneeded, just shiny sells!!!
    hey, not disputing that a quality finish is absolutely indispensable.

    just saying' it should make sense in my book and look "right".

    if "areo-overdone" is your look, go for it, but if you are producing a premium product in a professional manner, hot rolled with scale doesn't sound like the right starting point to me.

    mag chuck, milling machine, mill scale, just sounds all wrong, but if it works for you, knock yer self out! (oh, wait, actually, no DON'T do that!)

    merry merry all!!

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    Used an electro mag chuck chuck many times roughing shims for the grinder. Once under an 1/8 thickness things got a little sketchy but doable with proper "fencing".

    Maybe you could make a fixture that has rails down the middle with set screws angled in from the top of the rails that force the part down and against a fence.

    Not only do you have the magnet holding down but set screws to hold part still against a fence.

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    [QUOTE=cyanidekid;3094727]aside from the excellent description by boslab, another source is Al mixed in with the scrap charge in the furnace. just think, how many bev cans wind up mixed in, stuck in recesses, and how many mixed metal items mag separate as "ferrous". because it is a de-ox, it is allowed in the scrap charge in a certain percentage as a common practice, I believe.

    the lower the quality of the steel, the less care is taken to ensure a high quality, consistent scrap addition as well.[/QUOTE

    I have some experience with steel making too. Think about it. The aluminum oxide will float on the bath. It does not combine with the steel. I have never seen continuous cast that was not bottom poured. The aluminum oxide is in the slag on top.Aluminum is not even considered a contaminant.
    The OP needs to job this out to a blanchard. They would probably spend more time loading and unloading than grinding.

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    Quote Originally Posted by DMF_TomB View Post
    .
    magnetic vise used to hold parts that get blanchard coarse ground. usually removes .001 to .005 in less than a minute and removing .20" can take many minutes but often used on difficult to hold parts.
    .
    thinner metal has less holding power, sometimes parallels are stuck to magnetic to give extra so parts dont slide along vise.
    .
    vacuum vise is used sometimes instead

    Come back when you get some Blanchard experience.

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    yes td, once it is oxidized, it "will float on the bath", given a static, gravity segregated melt, (if that were even possible), but in an actual steel making operation, there are a lot of dynamic forces going on that mix the constituents, and we aren't even talking about oxides that form in the melt.

    regarding the hardness of the mill scale on hot rolled, we are talking about the oxides that form in the scale as it is being rolled. the aluminum oxide in the scale is the result of any metallic Al remaining in the steel, (not the oxides in the slag from the melt) as well as silicon, titanium, niobium (way less likely to be a factor), and manganese and vanadium, perhaps?

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    Re the mill scale,

    Why not just soak the stock in a weak mix of hydrochloric acid? the scale falls of in about 15 mins.

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    Quote Originally Posted by itsallkuhlmann View Post
    Re the mill scale,

    Why not just soak the stock in a weak mix of hydrochloric acid? the scale falls of in about 15 mins.
    that sounds like a blacksmith /knife maker hack. and from my understanding it works. other thn tht i agree with others start with better stock

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    I have been trying to refrain from telling the OP to use equipment he doesn't have, but one of my customers has a similar situation with flame hardened pieces and warp along with it. They have a Camut grinder with a two foot wide table and a wheel like a Blanchard with stone segments that covers the whole two feet. The table has longitudinal travel, no cross travel. With 60 HP driving the wheel, anything that gets in its way gets ground. They fill the table with parts and do serious production.

    Bill
    Last edited by 9100; 12-26-2017 at 07:42 AM.

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    Quote Originally Posted by 9100 View Post
    I have been trying to refrain from telling the OP to use equipment he doesn't have, but one of my customers has a similar situation with flame hardened pieces and warp along with it. They have a Camut grinder with a two foot wide table and a wheel like a Blanchard with stone segments that covers the whole two feet. The table has longitudinal travel, no cross travel. With 60 HP driving the wheel, anything that gets in its way gets ground. They fill the table with parts ans do serious production.
    I had a Norton, much smaller than that, same principle. Vertical spindle surface grinder ... but seems like the force on tiny parts would not be good. Why not a normal rotary surface grinder ? Not the Blanchard type, the reciprocating horizontal spindle type. Put a rail around the chuck for safety and set it to a small downfeed, come back in a half hour.

    If the other type would work, of course that would be faster. You still see them occasionally, usually cheap because they aren't very versatile.

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    A local tool steel company has one of those grinders. You can order one little piece of steel with enough stock to finish to a certain size, decarb free, etc. Of course they will charge for the service, but you will get it with all surfaces ground to a medium finish, just the way you want it. The grinder has been running every time I went there.

    Bill

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    I'll have to agree that a Blanchard would be the way to go here. The local steel supplier would charge $32 ea. for a Blanchard ground piece. 2"x3" bar stock cut to 5" is just under $7 ea. That makes it worthwhile to mill the pieces, a $2500 difference per 100, but it would be nice to get almost finished parts with no fuss by going the pricier route.

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    Quote Originally Posted by 9100 View Post
    Does the chuck also have a demagnetizing cycle like the typical electric chuck? Does it magnetize by a large pulse? I do a lot of magnetizing, motor and generator fields and magnetos. The magnetizer puts a pulse through the "coil", which can be a single turn, that as close as I can estimate is over 100,000 amps. The magnets are driven to saturation, the maximum flux they can carry. Magnetizing a horseshoe magnet, the keeper you put across the poles to complete the magnetic circuit will be stuck on so tight it takes an act of God to remove it. I think a lot of the reason is that the flux pulls them together tighter than would be possible by most other means because the pressure comes between each bit of surface area and the mating part, like putting a C clamp on every square millimeter of the surfaces, mashing down any irregularities. Besides, most steel will hold some residual magnetism and will be magnetized just as the chuck poles are.

    I have no trouble believing that the Schunk chuck holds that well.

    Bill
    No demagnetize cycle for the parts. They don't become magnetic, at least that I noticed so far. There is an unclamp cycle that reverses the polarity of the permanent magnets. The flux flows through a different path in the bottom of the chuck instead of coming out of the top of the chuck.

    The box that plugs into the magnet runs off 480v single phase. Kind of a strange service, and it took a little bit for our electrician to find the correct plug and outlet.

    Here are a few pics on my instagram page.

    Instagram

    Instagram

    The chuck held the kurt vise fine, but the stop would slip a little if I tried to move it. I think it would be fine if it covered 4 poles.

    On that plate, I installed the 3 fixed pole extensions then milled a few thou off all of them. I left .010 on the plate for grind and the grind shop had no problem cleaning up both sides. The plate was real flat right off the mill.


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