Grinding an edge on a stainless part- what wheel?
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  1. #1
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    Default Grinding an edge on a stainless part- what wheel?

    I am making some little stainless cutters- like a round cookie cutter but only 15mm id. I have them blanked out and need to grind a bevel on the end. I have the blank turned with a 15 degree bevel. My plan is to put a secondary bevel on it at about 30 degrees. I need to experiment with this some by testing a bevel on the outside and the inside. Materials are 316 and 17-4ph h1150 for the moment.

    I have a tool and cutter grinder with a motorized head. No real id grinding capability. I am going to try to rig something using a router or a hand grinder just for testing the id. This is my first outing with this grinder so I only know what I have read, watched on youtube, and read here.

    My question is what kind of wheel would be best for grinding the o.d. secondary bevel? And what kind of point would be best for grinding an id bevel?

    I am inclined to use some sort of type 11 wheel for the od and a cbn point for the id. And where to get these? Norton seems like this huge big company now that does not even know what it is selling anymore. I called a few what appeared to be smaller vendors but no help yet here either.

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    How sharp do you really need them to be? I have done a lot of die cutting like tooling for clicker press usage, in harder materials a duller edge can hold up a lot longer than a sharper one. Know that sounds odd, its kinda like a honed edge on a turning insert. A sharp delicate edge is easily damaged, a couple of thou wide flat edge holds up a lot longer for my customer in there material and the resulting hole finish is not any worse surprisingly. A sharp edge was just chipping out or if i increased the anneal would just bend and deform.

    I caution you on the ID bevel too, it makes for a slug that bigger than the punch id, hence they can end up splitting the punch as the pressure builds up if the materials your cutting is hard enough not to readily deform. If it will deform though you can get a lot cleaner punched surface left by using internal angles

    Grinding 316 is something i have always failed at though, it just loves to load the wheel up in my experience. CBN points are avalible pretty cheaply on the bay if plated points are all your after, i use a wide assortment of thoes in a large electric die grinder to shape up custom form tools and they hold up really well, again my concern with them would be gumming up with the 316.

    Angle wise for most stuff i have had best luck in the 20-25 degree range, but im using carbon steel at about circa low 50HRC. For the softer 316 30 degrees might be wise.

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    Think more information needed. what are you going to cut? what part thickness? SS is a bugger to grind and it likes to load the wheel/Going to hammer whack the punch or other/11 type wheel likely need run at 3400 to 3600 at what it is labeled/46K White AO may be a first try wheel / to bevel the punch OD edge or the ID edge? spinning cutter or a punch?
    Have you considered a 5/8 drill or reamer bushing, they are hard and easy to grind, I have made hole punched and spinning cutters out of them /
    What TC grinder do you have.,,,,,

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    It is a cutter for human skin. Used by hand like a cookie cutter, maybe give it a twist to affect the cut with a UHMW backer (cutting board). Not on a person but for a lab application. The material (316 stainless) is not ideal but the customer requested it so I am trying to get the best I can with it. I have been turning the blank so that the edge is left a few thousandths thick then filing the last little bit at a steeper angle for the last operation- trying for 30deg. The trouble is that the edge eventually rolls in a little after 40-50 cuts but it is still pretty sharp. They are testing on teflon. So my thinking is that by grinding it I can have a little better control over the angle and extend of the secondary bevel.

    The cutter grinder is an Elliott number 5 which is a Cincinnati No 2 clone and pretty nice. It has has a motorized work head with a 5c collet nose and drawbar. I bought the thing 10 years ago and never got it going but I about have it all setup now. I have a 38A60-JVBE cup wheel that looks like, based on my reading, might be worth a try. Just exactly how sharp is yet to be determined it does not need to be scalpel sharp. I ordered a Kool Mister today thinking that might be helpful. I also just bought a lot of 5sg cup wheels on ebay, not for just this but could try that too.

    Like you say Adama the CBN points are cheap so I will probably get a few to evaluate.

    Michiganbuck the thing has a grip of a design that I have worked out with the customer machined onto the back so a drill bushing would not work.

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    How many are you making? If one or two then you can make do with almost any wheel. If a production job then austenitic stainless is usually ground with a silicon carbide wheel. Will the quantity support the investment?

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    For now it is only 5-10. If it all works out it will be lots of 50 or so.

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    What you are making already exists as easily obtainable items in a variety of diameters. You need to get from a medical supplier some biopsy punches. I know in the UK at least they are available in sizes up to 20mm.

    I'm pretty sure there is no internal bevel, only on the outside. If you really have to make one also consider the traditional "Wad punch " style turned from solid and again only beveled on the outside.

    In explanation my "day job" is as a Veterinary Surgeon although I also have a small engineering firm in theory concentrating on specialised surgical instruments.

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    Nice grinder and that wheel ok. Good to diamond skim dress the flare cup wheel OD to make wheel run better. I like to dress the ID wheel bevel with a Cracker Jack Minie. A norbide stick might be used for th wheel ID bevel.

    Your work head can be set in the place where swing from 15* to 30* will be made with least travel in the cross direction to save time and a set diamond dresser can be made with least travel..to save time.

    Some materials are best cut with a small radius perhaps .002 at the cutting edge.

    Grinding the part bevel on the OD you can use a straight wheel (surface grinder wheel). Straight wheel will have much more area so not load up as quickly.

    You can dress the part ID edge with a ceramic round stick while you are still grinding outer edge to relive the burr and sharpen that edge.

    A true India stick will also work for this.

    Sorry! Something went wrong!

    Sorry! Something went wrong!
    Yes, the mini is for a seasoned grinder hand or an alert person who can follow instruction to the T.

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    I had a plastic surgeon friend tell me the same thing about biopsy punches but the diameters he knew of were not that big. I will pass the info along. I don't think the internal bevel would be preferable either. The thing is that a cutting edge is made when two surfaces come together. The bore is turned, nice finish but maybe not quite good enough for a cutting edge. I think I will need to to something with the id at least at the edge. Maybe not a noticeable bevel but I don't want to hone the whole bore.

    Thank you all for the input- Very helpful!

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    I like white AO wheels for SS they are contaminant free and still a low cost. Actually they seem sharper in many uses..I have use ceramic wheels but find not much if any improvement.
    Once you get set-up and have a reasonable process call Radiac to explain what you are doing, what problems and what wheel they would recommend.
    No sense to call Radiac now because you are cold turkey green on this.

    You can private message me and perhaps email photos of your set-up and the part...I may be able top aid process.

    No I don't need a photo of the machine. (spindle speed 2950/4100)

    Buck

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    There called dermal punches in medical circles, there oftern used by the more extreme piercing people too, but nothing like your dia, that said, there not going to last hundreds of holes, there very much more a razor like edged item. No idea on best cutting angles, but 316 is really too soft, will be damaged by what ever there cutting on more so than the fleshy stuff, as im assuming this is not dried and tanned like the cow skin some of mine get used on.

    One solution may be to fit them in a simple toggle press, like this you can limit the stroke and not cut too hard into the cutting surface bellow, also keep it stable in the cut and then you can use a harder surface you just kinda kiss upto. Sounds nuts, but you can easily use a surface nearly as hard as the punch with good guidance and get great tool life. Carbon steel punches against a stainless anvil and tens - hundreds of thousands of hits through paper and bord are commonly achived.


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    Yes I talked with him about using a simple press, didn't want, I emailed him also this afternoon about the possibility of off the shelf cutters.

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    Quote Originally Posted by michiganbuck View Post
    Nice grinder and that wheel ok. Good to diamond skim dress the flare cup wheel OD to make wheel run better. I like to dress the ID wheel bevel with a Cracker Jack Minie. A norbide stick might be used for th wheel ID bevel.

    Your work head can be set in the place where swing from 15* to 30* will be made with least travel in the cross direction to save time and a set diamond dresser can be made with least travel..to save time.

    Some materials are best cut with a small radius perhaps .002 at the cutting edge.

    Grinding the part bevel on the OD you can use a straight wheel (surface grinder wheel). Straight wheel will have much more area so not load up as quickly.

    You can dress the part ID edge with a ceramic round stick while you are still grinding outer edge to relive the burr and sharpen that edge.

    A true India stick will also work for this.

    Sorry! Something went wrong!

    Sorry! Something went wrong!
    Yes, the mini is for a seasoned grinder hand or an alert person who can follow instruction to the T.
    What is a "true India stick"?
    W

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    Quote Originally Posted by tdmidget View Post
    What is a "true India stick"?
    W
    My guess would be a India stone not a synthetic alternative.

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    Quote Originally Posted by Hazzert View Post
    My guess would be a India stone not a synthetic alternative.
    You realize that there is no such thing? "India" is a trademark owned by Norton for aluminum oxide hand stones.
    India Abrasive Files

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    Guess one can’t get hard black natural stones from India anymore. Perhaps the hard-black Arkansas and the Belgium blue are the last natural hard stones.

    So scratch that and use a ceramic stick perhaps 3/8"diameter for a 5/8 ID hole and a black Arkansas for the OD.

    I do like Norton stones and use them for my grinder chucks, tables and my iron plate..

    It would make sense for someone to need a special design hole cutter if thinking about a production process.

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    My apologies if this has already been mentioned and I overlooked it.

    For this knife-like application, it would be better if the grinding wheel contacted the cutting edge more perpendicular than parallel. You can't arrange that for ID grinding, but on the OD you can position a cup wheel or side-relieved flat wheel so the grinding face is substantially perpendicular to the edge. You can also use the periphery of a flat wheel. Grind on to, not off of, the edge. I believe this will make a noticeable improvement in the useful lifetime of the edge, compared to conventional cylindrical grinding.

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    Quote Originally Posted by tdmidget View Post
    You realize that there is no such thing? "India" is a trademark owned by Norton for aluminum oxide hand stones.
    India Abrasive Files
    Nope. I didn't. Learn something new every day.

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    I messed with this some today. It really did not work well at all. The result was a very coarse edge.

    Sfriedberg: I tried this a few ways. See if I can describe this- I angled the work head at 30 degrees. Cup wheel face was parallel to the travel of the table. I then brought the work piece by the bottom of the face of the wheel. My goal was to have the abrasive cut marks perpendicular to the edge. With the wheel turning toward the edge. The problem seems to be that this stuff just is too gummy and at the edge it is very jagged. I also tried it with so the scratch pattern was parallel to the edge and no good there either.

    Michiganbuck: How come the inside of a cup wheel needs to be trued? Is this for balance? I did not do this because I don't yet have the tools to true the inside but I will get them. I also tinkered some just cutting a 60deg point on a dowel pin. Generally it worked pretty well but I noticed that the the surface was sort-of faceted. Could this be because of wheel balance? I trued the outside with a diamond point but not the inside.

    I have some cbn points on order I'd will try them next.

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    Cup wheels..and other wheels usually grind in a direction away from the desire sharp edge taking the generated bur away from that edge. Grinding towards the desired edge The burr is dragged/pushed to the edge and builds there... Hard materials like HSS have a very fine burr that often can be swiped away with a hone, swiped away with a finger nail or just left to break away with a cutters first use. Gummy materials drag that burr to leave it on the edge.

    Gummy material like SS can load up a wheel and that load being small chunks of material stuck to the whee can act like little hammers bumping the part and chattering the wheel.
    cbn points likely to also load up.

    Small cup wheel only has perhaps 9" circle to load up.
    A 7" straight wheel has perhaps 21" to load up so likely to last longer. If having a tilt work head you might tilt a tad upwards so a shear angle grinds pulling material away from your edge. a slippery coolant might help to avoid loading up so fast.

    be sure you are on the right RPM for a 7" or 8" wheel if you try a straight wheel.

    Best to not direct questions to me because there are many other guy who might help with this part.

    QT:[ How come the inside of a cup wheel needs to be trued?] SS does not break down a wheel to expose new sharp grits but tends to load the wheel..a very smooth wheel might do more grinding before the wheel loads up.


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