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Is it worth having 40 yr old carbide endmills re-sharpened?

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  • #16
    I send cutters out for regrind a few times a year and we regrind everything 3/8" and up (sometimes smaller, but rarely), usually about 3-4 times before it's not worthwhile. We use https://www.rmepvd.com/ and I've always been satisfied with their work. I went back through my emails and found the quote from the last batch we sent them and here's the cost. They've done corner rads, and even some re coating for us a few times over the years too.



    I checked your profile for location and I'm sure there's a regrind shop near Rochester NY that would provide the same service, and even a bit cheaper (my prices are in CDN $$). IMO it's tough to beat a like new 3/4" solid carbide for $25. If you can, then buy it.

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    • #17
      Forty years ago, huh? Think about it, high positive carbide inserts weren't available then. Not because there was no way to grind them, but because the older carbide wouldn't hold up with a razor sharp edge that's common with newer carbide, especially aluminum cutting tools.

      If the older cutters are professionally re-sharpened on a CNC grinder like a lot are they may re-flute them to give a high positive cutting edge. But that high positive edge on older carbide won't hold up, so what's the point? If they don't re-flute to high positive you've got a cutter that's not so good on low power machines. If the cutters are re-sharpened only on the OD that further reduces any positive cutting rake they may have had.

      It's still common to run into older machinists that learned about carbide back in the day and talk about not being able to have high positive grinds on carbide. They're wrong of course.

      BTW: to the OP, 3/4" is a pretty large cutter to be held in a draw in collet like on a B'port. I try to only use ER collets on up to 1/2" shank cutters. Beyond that I use a holder with a set screw to lock the cutter.

      I guess the bottom line on sharpening is how much does it cost and are you satisfied with the results?

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      • #18
        Another thing is I think you can specify, flat bottom end cutting ...... handy to have sometimes..,
        I hat it when I want to counterbore a hole for Allen screw, and have to search thru 6 end mills to find the flat cutting one..

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        • #19
          Originally posted by DR View Post

          It's still common to run into older machinists that learned about carbide back in the day and talk about not being able to have high positive grinds on carbide. They're wrong of course.

          I agree with you. \\

          I will buy new, neg rake inserts for a penny on the dime just because they are so large and Neg rake.

          Haa, I regrind them to a very nice Positive rake. They work for me.../ JR
          My old yahoo group. Bridgeport Mill Group

          https://groups.yahoo.com/neo/groups/...port_mill/info

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          • #20
            the question is what to do with endmills that are not on size. facing? thats what face mills are for. side milling? maybe, but rarely. pockets? you mostly use smaller sizes.
            Last edited by dian; 03-20-2021, 06:28 AM.

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            • #21
              40 years ago, seems like a long time but at my age 1981 seems like yesterday. I must agree with those who are worried about the formula of the carbide matrix, that may be the main reason for not proceeding with sharpening. Perhaps just keep them for rough jobs like removing millscale before committing the best tooling.

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              • #22
                Originally posted by dian View Post
                the question is what to do with emdmills that are not on size. facing? thats what face mills are for. side milling? maybe, but rarely. pockets? you mostly use smaller sizes.
                Resharps are like gold, (particularly for CNC work where you can "lie" to the machine about cutter size), for slotting or cutting steps or pockets in few passes and still ending up just a touch under final size to allow for one finish pass.

                And inventory management is easier. Fewer small sizes needed. I prefer resharps over new endmills.
                If you think you understand what is going on, you haven't been paying attention.

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                • #23
                  Seems to me that an undersized end mill can be used for anything that an "on size" one can. And then some.

                  Why not for side cutting as long as the flutes are sharp? You just need to use an adjusted figure for the diameter/radius.

                  Pocket? Why not? Again, just adjust for the actual diameter/radius.

                  And if you want an accurate slot, then an end mill that is 0.002" under makes it easy. Once down the center. Move over one way 0.001" and go back. Then move over 0.002" the other way and make one more trip. Should be dead nuts.

                  You do need to know the actual diameter. But then, you need to know that anyway.



                  Originally posted by dian View Post
                  the question is what to do with emdmills that are not on size. facing? thats what face mills are for. side milling? maybe, but rarely. pockets? you mostly use smaller sizes.
                  Paul A.
                  SE Texas

                  And if you look REAL close at an analog signal,
                  You will find that it has discrete steps.

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                  • #24
                    If you can't find uses for regrind under size endmills.. you are thinking inside the box...

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                    • #25
                      im just talking out of personal experience. if i grab a carbide endmill its to produce a precise slot. side milling? couldnt even say when i did it last time. why?* stand it up and face it. cheating on the cnc with undersized end mills? really? move the table by 0.001"? i want to see that done. and how did you check the size of the slot to 0.001 reliably? on a good fit for a 8 mm key you have +/- 1ยต to play with. i have a box of hss regrounds and never touch them. if they were carbide i would maybe use them more, but pay for them? no.

                      * the only good reason for sidemilling i can think of right now would be if you want to square up a piece fast: clamp it shallow, sidemill around and machine off the base.

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                      • #26
                        I would say slotting is less than 10 percent of my milling jobs.
                        on my 2300 lb mill, if I do 8 niches of key way with an endmill in one go its never straight.
                        so ltd of profiling or just removing metals I don't care about size,
                        but a big use of 're grinds for me.... counterbores for Allen heads..... std Counterborss way to sloppy a hole for horrid or bike use..

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                        • #27
                          Nope, no good. If you mail them to me, I will dispose of them for you.
                          -paul

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                          • #28
                            This article explains some situations where regrinds and side milling are just fine. Mostly CNC. However, the one old machinist at my old job had no problem at all with using regrinds on a manual Cincinnatti mill. He made whatever the company needed.
                            Article here: https://makeitfrommetal.com/trochoid...-peel-milling/

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                            • #29
                              I don't mind what diameter an endmill is We have metric, imperial and regrinds. The size which looks likely to do the job is the method I use. I have even been lucky buying used carbide endmills very cheaply, they might not cut the mustard on a CNC, but they are cheap enough to not worry if they get broken. I would not touch used HSS, though.
                              The only important factor is matching the shank to the collet.

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                              • #30
                                Originally posted by old mart View Post
                                I don't mind what diameter an endmill is We have metric, imperial and regrinds. The size which looks likely to do the job is the method I use. I would not touch used HSS, though.
                                The only important factor is matching the shank to the collet.
                                Believe it or not, I actually save and collect used HSS of all kinds -- I make them into lathe bits for odd jobs. Even if you braze them onto an odd shank and quench in oil, they have all kinds of uses. I save dead carbide end mills for "poor man's gauge pins".

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