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  1. #1
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    Default To resharpen endmills or not

    Hi all,

    Background:
    Just picked up about 200lbs of US made endmills for pretty much free at a shop liquidation, everything from 1/4" up to 1.5" 2,4 flute, square, radius and ball-nosed, some carbide, mostly HSS and cobalt. 1/3 of them are brand new, and the other 2/3 range from slightly dull to abused and blue. In a separate deal, I found a small surface grinder for about $400. Fully sharpened and ready to go this is a couple thousand dollars in end mills (my guess - probably 300+ endmills).

    Question:
    I always like the rational behind buying tools, so lets assume I will enjoy the process of learning how to sharpen end mills and be willing to spend the time. Will the possible extra expense and setup time of a more general purpose machine be worth it for the other things I could do with it? I understand the usefulness of a surface grinder vs. the dedicated Darex/Cuttermaster but what about the T&C machines - can they do anything besides tool grinding? If you had $1500-$2000 to spend to make this happen, which route would you go, and why?

    Possible setups:
    Darex E90
    Cuttermaster
    Air spindle and fixtures for surface grinder (and surface grinder to go with it)
    KO Lee or Cincinnati T&C grinder with fixtures
    Others that I don't know about

    TIA,
    -Niall

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    This has been hashed *many* times on this forum and there is different advice both ways.

    IMO, your best bang for the buck both all around and easiest to use, is surface grinder + airbearing + end grinding fixture, like the Eaglerock. The T & C is slightly more adaptable for cup wheels and positioning work to wheel, but surface grinder works well enough. For endwork, a PC101 Poly choke is also pretty fast on a SG especially for taps.

    Although smaller would work for endmills, i would get at least a 6-18 size grinder since your interest is versatility.

    With fixtures, a surface grinder will do most of what a T & C will, just as well and in most cases and in some cases better; plus surface grind which a T & C is very poor to non-useful for, though it can be made to happen on small parts in a bad pinch. If you need to do a lot of work between centers (reamers, e,g,) or with big face and shell mills, the T & C is probably superior.

    Many of us have the option to grind/re-sharp endmills several different ways. Have heard very few who actually like to do it. With a good tool shop nearby, it is probably cheaper to pay someone else who uses automated machines. I think there are even some who offer the service here on PM.

    smt

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    Heh, heh...all that money you saved buying those end mills is going to get spent sharpening them. Not to mention that the arsenal of fixtures available for a T&C grinder, assuming you want to use its full capabilities, is a bottomless money pit...

    Of the tools on your list, the Darex is the least versatile but probably the quickest at sharpening end mills because that's all it does. However, you'll need a diamond wheel for those carbide mills; don't try it with the wheel that comes with the machine. Then you'll need a dedicated set of 5C collets that you have tested to run true, way out from the collet face (VERY important). And a decent dryer for the air supply. Definitely get the optional hard-chromed stainless quill, otherwise it will rust. The support feather that comes with the machine is a rickety stamped POS and after a few times around the block with it you'll probably want to make a better one. It is also helpful to be able to test-run your resharpened cutters to establish just how effective your grind is. Be aware that some proprietary end mills like high-helix Ski-Cut don't have a cutting edge per se, they have a narrow land like a drill, and the drag from that land is what damps the chatter. Sharpen it like an ordinary end mill and it will scream bloody murder. You have to spin-grind it and then back it off, which you can't do on the Darex. Or at least not very well.

    I'd guess that most CNC shops today use carbide because of the spindle speeds available on the machines. HSS end mills are therefore most used on Bridgeports. So if you're thinking of selling those cutters after you grind them, keep in mind what your market is going to be...

    Good luck in any case. Oh, and get a good Shop-Vac.

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    Put the sharp ones away to use, send the moderately dull ones out to be resharpened, scrap the rest. My 0.02.

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    Quote Originally Posted by kuraki556 View Post
    Put the sharp ones away to use, send the moderately dull ones out to be resharpened, scrap the rest. My 0.02.
    Or sell the rest on E-bay

    It is a good experience to learn to sharpen but sharpening does not pay as well as machining so it is not often wise to sacrifice machining time to sharpen cutters if a good sharpening source is nearby.

    Still it is good to know and having the capability allows one to sharpen a needed tool ASAP and make specials.

    A sizable sharpening machine like a KO-lee, Cincinnati#2 or the like can be use as a first or second operation machine for cut-off and grinding jobs and so can be sometimes more valuable then a single use sharpening machine with using little more space. Simply adding a v-block it can become a square end grinder.

    Mentioned a small land to stabilize was a method my friend Ray used for conventional HS end mills for conventional mill work with back spin grinding OD then back off to primary to a small land. Back grinding is climb grinding (heal into the wheel) for final finish of OD sizing. He said they out lasted sharp-grind almost double. Climb grind spinning causes a minuet radial relief to the OD when grinding an interrupted grind such as an end mill OD.

    To be a functional T&C grinder accessories are needed so figure what operations you want to do and add up the numbers. Unless you get some super deals I think you should expect 3 to $5K for a conventional cutter grinder with some fixtures. Decide what you wish to do such as grind ends, sharpen OD, sharpen small ODs, sharpen reamer ends, mill saws, spin OD size with back-off ends and OD of step tools and specials. Then add a vise and v-block to make it do job work also.

    Buck

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    I have to agree with stephen thomas. Given a choice between a T&C grinder and a surface grinder, take the latter. I started with a well-tooled Cincinnati #2 T&C grinder but recently picked up a surface grinder because the T&C grinder is so useless as a surface grinder. Elevation control on most T&C grinders is hideous compared to a surface grinder.

    T&C grinder, with proper tooling, is not a bad small cylindrical grinder (ID or OD), and I've finished many tapers on mine. So it's not strictly limited to tool grinding.

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    I bought my first cnc mill in 1989. That was the last time I bought a HSS or COBALT end mill. If you are a manual shop then the steel tools are great, but if cnc then don't waste your time . . . invest in carbide. The speed (= money!!) is just so much faster, and the carbide is not all that much more expensive.

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    Quote Originally Posted by Goober68 View Post
    If you had $1500-$2000 to spend to make this happen
    For about 10x that much money you could be in the game. Don't forget that you will need a comparator, microscopes, lots of diamond/cbn wheels and years of experience to go along with your grinders.

    Your best bet is to find someone in your neighborhood who specializes in cutting tool grinding. He will be able to recommend grinds that you haven't thought about yet.

    Even then resharps may not be cheaper than new. But they are purpose ground.

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    Ok, I'll weigh in on this too...... because I'm one of those guys who bought every grinding widget that fit Cinci 1's 2's and Monosets....... not to mention Ace and Gorton, Taft Pierce........ back in the 80's for my home shop. Caveat is that I grew up with these machines. And a money pit......... you bet! And you'll be wanting an OD grinder too, it's a slippery slope

    Standard end mills much below 1"........ we buy those new. The tool grinders see enough work, converting old end mills, shell mills and slabs to any manner of specials. And if all you run is CNC, then the need for specials goes way down.

    If you want to tool grind for your own amusement or if you have a need for specials....... great. But for the cost of really setting up to grind..... you could likely replace much of what you just bought with brand new OSG, Sossner or etc.

    Having said that, I'd likely have bought the 200 pounds of cutters too.

    Cyclotronguy

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    Well, I have never had to resharpen any tooling yet (I got my mill a few weeks ago) If I had to resharpen it, I would use a India oilstone about 600 grit and lightly stone the cutting edges.
    Keep in mind, NEVER SHARPEN REAMERS!

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    Quote Originally Posted by Spyderedge View Post
    Well, I have never had to resharpen any tooling yet (I got my mill a few weeks ago) If I had to resharpen it, I would use a India oilstone about 600 grit and lightly stone the cutting edges.
    Keep in mind, NEVER SHARPEN REAMERS!
    Why? I''ve had many reamers sharpened. Usually just the ends redone, but sometimes resized to a couple thou. smaller. Generally cheaper to buy new, but in a pinch....

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    Quote Originally Posted by Spyderedge View Post
    Well, I have never had to resharpen any tooling yet (I got my mill a few weeks ago) If I had to resharpen it, I would use a India oilstone about 600 grit and lightly stone the cutting edges.

    Keep in mind, NEVER SHARPEN REAMERS!
    I'm eagerly awaiting for a demo of end mill sharpening using oilstone.

    P.S. You can relatively easily sharpen a reamer on a surface grinder if you know the standard procedure. Moreover, it's easier for me to imagine doing a reamer with an oilstone than thinking about manual stoning of an endmill for sidecutting. No I wouldn't sharpen my reamers by hand either unless I have no choice.
    Last edited by MichaelP; 09-06-2013 at 07:13 PM.

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    Default reamer

    And if you're really good with a carbide burnisher you can within limits turn a burr on the lands of a hss reamer, do a very light circle grind and regain a couple tenths.

    Cyclotronguy

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    We re-sharp endmills that are used for plunge operations (specialty sized counterbores). Otherwise endmills get tossed in tool scraps. Everything is designed around a certain diameter endmill. If you're dinking around in a tooling type shop it makes sense, but not in a production environment.

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    Good that it was mentioned the down feed is not highly accurate on many T/C grinders so a T/C grinder does not make a surface grinder. Also on many T/C grinders the in-feed is less accurate as well. Tenths work can be done but often it is bump and feel rather than dial in to the mark. Some grinders like the Brown & Sharpe-13 do have fine in- feed and the 13 has a precision down feed but even with that it does not work well as a surface grinder. We always used the BS 13 as an OD grinder for that it is excellent.

    I have sharpened end mills and cutters on surface grinders but I do not think a surface grinder is very good for cutter sharpening.

    But almost every shop needs a surface grinder, and a T/C is a nice option that most shops can do without.

    For most shops sending out is best with in house good if specials need to be made (and someone knows how to make them) and/or there is enough cutter work to have the T/C working more than just once in a while.

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    Just throwing out there that in the shop I work at we use carbide endmills exclusively. The majority of them get tossed after we use them. Anything over 3/8" we will look at and decide if it is worth a resharp.....maybe half of them are. We do our best to use dull finishers as roughing tools. With the specialty grinds and coating found on many of todays high end cutters, I have yet to find one that will perform nearly as well as factory sharp. A lot of the dull stuff ends up getting used on manual mills to add holes or cbores to hardened parts.

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    I can see a shop not wanting to OD grind end mills because much may be relevant to diameter but those that can be end sharpened .030/.050 or cut off and end sharpened it is a huge waste of money to toss them.

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    What toolsteel said raised a comment for me -

    At the shop I work at, we have manual and CNC equipment. The manual equipment is primarily in support of the CNC equipment, and for us fabrication guys to use to get things done. Whenever I try to work on a project and need an endmill or drill other than what I have squirreled away somewhere, invariably I'm directed to some dull, blown out piece of crap that the boss or CNC machinists have sitting on their bench, or have put in the drawer near one of the manual machines. I can't understand why people think that a dull/broken cutter is going to work any better on a manual machine than on a CNC machine. People struggle with frustration to make a tool, or repair some part, and I'll see that the cutter they are using is some gad-awful thing that has 2 of 4 flutes utterly destroyed. I'm always baffled by this thought pattern.

    In my personal shop, I have manual, automatic, and CNC equipment. I've never once found a dull tool to work well in either type of machine. It seems the laws of physics operate equally between machine types, at least whenever I am around.

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    Quote Originally Posted by michiganbuck View Post
    I can see a shop not wanting to OD grind end mills because much may be relevant to diameter but those that can be end sharpened .030/.050 or cut off and end sharpened it is a huge waste of money to toss them.
    To be sure. Spin grind the good ones back to a clean, sharp flute if need be & skip the bulk of effort (ODs) with just an end grind on the T&C. Mic the ODs to see how much/whether to lop off. Use a cupped CBN and some air to keep things cool, esp when gashing. Your collets have to run true & a whole degree of dish in the face should be enough.

    btw: Isn't a (std or stepped) reamer where you start out on the T&C, where you learn to true up in the collet & compound the work head to get reliefs at angles on pri & sec?

    Anyway, IMO it's really about sorting which of those mills are worth your time/trouble. (I'd have a field day diggin' for gold in that pile of 'ore'. )

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    Working as a die maker for Jim Robbins (seat belt dies) we had a rule, If it won’t shave you finger nail it goes out for sharpening. Fortunately we had a good sharpening source. No ,we did not shave a finger nail every time we took an end mill out of the box or we would not have any finger nails left. We developed a feel for sharp and not sharp. Also we did not pile end mills on top of each other. The sharp edges should never be bumping anything hard like another cutter.

    That work was much done on manual vertical mills so OD could be sharpened and was.

    What a pleasure it was to not have to use junk cutters.

    (Yes I have worked in shops where junk cutters was the norm.)

    When I worked as a cutter grinder hand at Chrysler a re-sharpened cutter had to work as good as new or you would end up on the dirtiest job in the shop.

    Buck


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