Grinding Stainless Steel vs 'standard' Steel - Page 2
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  1. #21
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    Quote Originally Posted by swarfless View Post
    Hi Skround, If I were doing what you are I'd arrange the workpiece to move on a pivot rather than the 'tool'. For the 'tool' I'd use a fixed vertical linisher .. the rationale is lots of 'tool' as in belt, to last the distance. No worry about 'self feeding' linishing across the feed direction. With the flat vertical bed the linisher only has 'line contact' so less heating of the stainless.. allowing more aggressive feed, but keeping that heating in mind all the same. I dare say you don't want to de-bond the stainless. Anyway I reckon a 'cross grind' on 'line contact' is the way to go, being 'feed neutral', you simply feed as the belt is able to cut. I'm sure there would be belts specific to stainless just as are cut-off wheels/discs. Consult with an abrasive company .. perhaps Pferd? If desired you could modify the 'lay' of the grind manually with a sanding block after 'machining'.
    Thanks - the more I think about that the more I think that what I've set up had the assumption to deal with less than 0.1mm or run-out. I need mechanical precision to a certain extent whereas the finish is less important

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    Aint got no Bridgeport!
    Or to be more exhaustive I need to come up with a DIY way to do this. The process to build this object has to be attainable and replicable anyway in the world where you can find a generic ironmongery - so no "big" machinery.

    I have some expectation from the precision of the sandwich - having a ground surface will also give me the chance to check how the run out evolves with time

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    Quote Originally Posted by michiganbuck View Post
    What tolerance do you need?
    ...
    Likely I would mount a grinder and then turn/rotate the part. white aluminum oxide wheels usually grind SS better than most others.
    ...
    The current grinder/router motor could have a bearing mounted above and below the part as any run-out will deter good grinding.. Stalling so to reduce the speed of surface feet per minute is a deterrent to any grinding action.. and stalling likely will lose some accuracy needed for decent spark-out.
    .
    Can't say much bout the tolerance target....without embarrassing myself! But I have a feeling that IF this contraption works then few hundredths of mm are achievable.

    I think what I'm going to do is to order some d.50/75mm Alox wheels and do "rough" grinding with the tool being ca. 1/3 of the total height - that'll help with the cutting power/stalling/speed issue.

    Only when everything is under control I might create a full-height tool -again with grinding wheels, dressed appropriately- as fine grinding passages.

    I've almost convinced myself that it's gonna work while writing this down!

    You paid attention to the details in the vid -can you elaborate on the last quote about bearings?

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    On second thoughts .. I would not attempt it.

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    Way too wide of a wheel.
    Way too much tool pressure.
    Very weak machine tool.

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    Quote Originally Posted by digger doug View Post
    Way too wide of a wheel.
    Way too much tool pressure.
    Very weak machine tool.
    I can't believe this thread is still going...you guys are sick if this is entertaining

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    Hi skround:
    Are you trying to take off all the surplus material in a single pass?
    If you are you will never get there.
    Go to Youtube and look at how a surface grinder operates.
    You need to find a way to do the same.
    So at a minimum:
    A mechanism to control the infeed...you want to be able to make it infeed in increments of less than 0.0005"
    Second, a mechanism, to control the crossfeed...ideally you can traverse the width of your 1" strip in 0.010" increments, just like a surface grinder traverses across a surface in small increments
    Third, the right abrasive wheel, properly dressed...I've had better success with silicon carbide wheels than aluminum oxide on austenitic stainless steels...at a guess your strip is probably 304 SS
    Fourth coolant or compressed air directed at the wheel right where it touches the workpiece.
    Fifth lots of patience.

    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining

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    How much can one take in single pass in stanless on a grinder and hold +/- .0005?
    So many variables but I'll go with 0.100 deep single pass if you have the power and normal machine.
    That depth in one cut seems very weird to most SG people, I'll do 0.500 deep in carbide all day long and hold a tighter tolerance.
    Do the drill flute people make lots of passes or is it one cut and done?
    Bob

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    Quote Originally Posted by implmex View Post
    Hi skround:
    Are you trying to take off all the surplus material in a single pass?
    If you are you will never get there.
    Go to Youtube and look at how a surface grinder operates.
    You need to find a way to do the same.
    So at a minimum:
    A mechanism to control the infeed...you want to be able to make it infeed in increments of less than 0.0005"
    Second, a mechanism, to control the crossfeed...ideally you can traverse the width of your 1" strip in 0.010" increments, just like a surface grinder traverses across a surface in small increments
    Third, the right abrasive wheel, properly dressed...I've had better success with silicon carbide wheels than aluminum oxide on austenitic stainless steels...at a guess your strip is probably 304 SS
    Fourth coolant or compressed air directed at the wheel right where it touches the workpiece.
    Fifth lots of patience.

    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining
    Hi Marcus thnks the advices - I'm familiar with the stock removal rate and sure never thought it can go in one pass. Little increments like on a lapping machine and a lot of patience is what it takes here. I need to build a better controllable feeding adjustment -I'll probably make it 'tangent' and trigonometry will help out with small increments.
    The material is pretty mundane - it's either a 304 as you say or a 316

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    Quote Originally Posted by CarbideBob View Post
    How much can one take in single pass in stanless on a grinder and hold +/- .0005?
    So many variables but I'll go with 0.100 deep single pass if you have the power and normal machine.
    That depth in one cut seems very weird to most SG people, I'll do 0.500 deep in carbide all day long and hold a tighter tolerance.
    Do the drill flute people make lots of passes or is it one cut and done?
    Bob
    Hi Bob, not sure it I get you right but since power is not on my side (with a 1Kw machine) I'll try a tow-fold approach - small increments, say 0.01" and using the an abrasive wheel that is 40mm high. Wheels (several, different grit size, material and geometry but all with a 20mm hole so that I can shove the ground bar in them) have been posted -just waiting to show up

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    Hi skround:
    You said:
    "small increments, say 0.01" and using the an abrasive wheel that is 40mm high."

    .010" radial DOC is milling territory, not surface grinding territory.
    Yes, it is possible to take a large DOC with a grinder, as CarbideBob points out.
    Creep feed grinders do it all the time.

    But notice what CarbideBob also says:
    "So many variables but I'll go with 0.100 deep single pass if you have the power..."

    A router attached to a swing arm is no way comparable to a nice stout surface grinder, and if you ever look at the construction of a creep feed grinder, you'll see it's MASSIVE, dumps tens of gallons per minute of coolant into the grind zone and feeds at a very slow rate under full control.
    Even a normal surface grinder would be extraordinarily hard pressed to take a 0.100" deep cut in stainless steel and survive...these machines are built to take small fast cuts, not large slow ones.

    If you try this with your lash-up, you will never be able to control it; the stainless steel will overheat, expand into the wheel and stall the grinder.
    I also predict you will instantly load up the wheel and break it.

    If you really want to try to take these kinds of cuts, you need to go at it with a carbide burr and even then I have serious doubts you can get away with it
    You want lots of teeth in the cut at once, but not so many as are provided by a grinding wheel.
    It will be a helluva a job to hang onto the router, and it'll buck like a crazy bronco.

    Just to convince yourself, take a carbide burr in a die grinder and plow it into a chunk of 304 stainless.
    Report back to us how much force it took and how well you were able to control it.

    Give us your feedback on how successfully you think you could do this taking a one inch wide pass 0.010" deep all in one go using a router on a swing arm that's only attached on one side.

    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining
    Last edited by implmex; 06-11-2021 at 01:03 PM.

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    I have run a part on a surface grinder (not SS) with such high stock removal that the part turned cherry red...Not recommend anyone doing that because it could overheat and blow a wheel, plus the material can stress build or stress relive to change size or hardness...or throw the part right off the chuck.

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    I like the project.

    Also agree that making the part move against a rigid, fixed tool seems more practical

    Per stock removal rate: I imagine the cut depth/volume is limited by your ability to keep it cool, or the parts are likely to separate/de-bond???

    If this is truly to be one of those "accessible to anyone even without machine tools" the best approach might be a rigid fixture in which the work is swung to an adjustable indicating surface which is square to the face. use a marking medium, and scrape. Or with small grinders, selectively grind the indicated marks until the geometry is correct. Use the die grinder as a stabbing tool to eliminate spots, not areas, as when precision scraping hard surfaces. This mostly eliminates material heating issues and is controllable to fine limits with somewhat less rigid/massive machine elements, than grinding is.

    Given the vagaries, i sort of doubt any other method yet mentioned will get you within .5 mm overall, maybe not even within 1 mm, if you have an accurate method to measure (indicate) your results.

    Good luck!

    smt

    PS, if, with suitably accurate bearings and fixturing you can reliably control the position of the rim while moving the part, say flat to a relatively flat steel plate, it could be possible to contrive a small machine slide vertically to take an HSS lathe bit, and swing the part around against it with a suitably long bar. The mass of the part is an advantage. step the lathe bit down (or up) as you progress. After the roughing pass, hone the bit and bump it out a couple/few .001's and go again for a finish pass. People have made large precise bores with similarly contrived armstrong powered bars.

  14. #34
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    Quote Originally Posted by implmex View Post
    Hi skround:
    You said:
    "small increments, say 0.01" and using the an abrasive wheel that is 40mm high."

    .010" radial DOC is milling territory, not surface grinding territory.
    Yes, it is possible to take a large DOC with a grinder, as CarbideBob points out.
    Creep feed grinders do it all the time.

    But notice what CarbideBob also says:
    "So many variables but I'll go with 0.100 deep single pass if you have the power..."[COLOR=#333333]

    ...

    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining
    Sorry to have created confusion - it's my unfamiliarity with the imperial. I'm thinking about 0.05mm (or less) which is 0.002" territory.
    This is going to be a work of patience rather than brute force

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    is the lower end of the shaft supported?

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    Quote Originally Posted by dian View Post
    is the lower end of the shaft supported?
    Without a lower bearing the whole thing would be totally hopeless.

    I've uploaded another video with the run-out check. The digital gauge might not be super accurate but the resolution is 1 micron. This is the check before starting any grinding attempt. The run-out on the effective surface is around 0.7mm.

    https://www.youtube.com/watch?v=YFBpQbSzjn8


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