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  • Machining newb, grinder rec'd?

    Howdy everyone,

    I am trying to start getting a home shop set up for my projects, after several years of job changes and relocations. I just retired from the power company, in distribution where I rarely used my mechanical engineering education, or my basic gear head instincts and nature. Now this is my chance to do some things I have wanted to do for a long time.

    I have a second-hand Atlas 6" bench lathe that I got many years ago, but it has been stored up to now. I got it out and started cleaning it up the other day, mainly because of a project I was working on where I needed it. That's when I realized that all of the quarter-inch tool steel I have is either new in the box, or dull from prior use - and I don't have a grinder!

    So, I am soliciting recommendations for a tool and cutter grinder. I searched the forum, and it seems there are some with the Deckers, Gortons, etc. But I know nothing about those. I have seen a Tormek in a woodworking shop. Can I get good results with an 8" variable speed bench grinder? Or should I try to get a higher-quality one specific to tool sharpening?

    BTW, I am into experimental aircraft and engines and such, and that involves some alloys like 4130 chromoly and stainless, so tool accuracy seems to be a bit more critical, right?

    Thanks
    Brad

  • #2
    Actually you can do just fine with an ordinary bench grinder, good eyesight and some care. Tool accuracy has no bearing on what you are cutting , only tool hardness has to be harder than what you are cutting (or wear out faster). Remember, most of WW2 production was done with HSS including aircraft.

    If you want to spend the money on a specific tool grinder, I recommend the Baldor 500 tool and cutter grinder (google it) but be forewarned that it is not cheap. I wish I had one.
    Last edited by nickel-city-fab; 03-12-2020, 12:03 PM.

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    • #3
      Sharpening lathe toolbits can be quite a learning curve.
      Learning the geometry is one thing, but learning to use a grinder is quite another.
      You do not just walk up to a bench grinder and get good results. Seriously.
      You need to know if the wheel type is right for what you are grinding, or at least
      recognize if it is not giving you the results that you desire.
      Recognize if the grinder itself is working for your best results.
      Do the wheels run true? Are the flanges even adequate enough to locate the wheel?
      Many are not. Is the grinder bolted down properly? Is it balanced? Are the rests
      even capable of being steady enough to use? Are they safe enough to not move in use?

      Lots of variables when using a bench grinder to control in order to get good results.
      Don't buy a $40 grinder and expect good results, unless you know a lot about all the
      aforementioned variables.

      --Doozer
      DZER

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      • #4
        I think what Doozer is alluding to is, it takes a bit of practice and certainly some thought. I am fortunate that I had some formal training as well as practice, so I can sharpen my bits on most anything. Failing that, I can recommend some reading all about tool sharpening:

        Atlas lathes had their own manual of general lathe operation, quite good IMHO:
        https://coffeeshopmath.files.wordpre...ts-tables1.pdf

        As well as the industry classic "How to Run a Lathe" by South Bend (1966 edition):
        https://www.pdf-archive.com/2017/02/...lathe-1966.pdf

        Both of those can be downloaded, highly recommended.

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        • #5
          Brad, first off WELCOME ABOARD to the forum!

          For grinding the HSS blanks you can get by nicely enough with a basic two wheel bench grinder. But you'll want to include a couple of extra things on the shopping list to go with it. You'll want to get a single point diamond dresser and you'll want to get a softer bond aluminium oxide wheel to replace one of the generic wheels that come with the grinder.

          The hard HSS steel tends to glide over the grit of the standard wheels with too little grab to correctly break away. As a result the regular wheels go smooth and don't cut well. A softer bond Al-O wheel cuts cleanly and with a nicer "lathe ready" finish for longer. Yet still lasts a long time as long as you ONLY use the wheel for harder tool steels.

          The wheels do need to be dressed initially and occasionally as needed as they are used. And for that the best tool seems to be a single point diamond dresser with a travel stop used with the rest to pass over the edge and both true the wheel and open up the face for better grinding.

          I would not suggest you buy one of the simple $40 grinders either. But you don't need to jump in the deep end on a $500 Baldor either. There's some pretty reasonable brand name stuff you can get for around $80 to $100. At that price point we seem to see decent machines that come with decent wheel flanges and properly faced off retention nuts. The same certainly can't be said of the bargain options.

          You WILL use a rest a lot for grinding lathe tools. A lot of the rests that come with grinders are not that great. Making your own rest that has a nice amount of platform area and can tilt and lean into and away from the wheel to establish the proper face angle can be a good shop project.

          If you're like a lot of us you won't end up with only one grinder. I've got three that I use regularly. One is a cup wheel grinder I got from my father when he closed up his shop and two are regular wheel types. One has the stock wheels for grinding mild steel and the other has a blue Al-O wheel for HSS and other tool steel roughing before using it on the cup wheel. And an open end which gets a wire wheel when needed. The wire wheel only goes on when needed because none of them are all that well balanced it seems. I also use it with a felt buffing wheel now and then.

          For a shop based around a 6" Atlas I'd say you could easily get by with a 6" grinder. The last couple of wheels I've gotten for grinding HSS and other tool steels came from Lee Valley since I'm addicted to their wood working tools and was already in the store.
          Chilliwack BC, Canada

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          • #6
            X2 on the grinding rest, it is crucial to have a decent one. I've seen people use stationary belt sanders for that reason. Most guys end up making a decent grinder rest or table for the regular type of bench grinders.

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            • #7
              If you are willing to spend the money, or build one your self you can’t beat a 2x72 belt grinder. I use mine for everything never use rock anymore.
              be sure to get one with a VFD so you can control the speed.
              you can use it for heavy fab work or sharpening small drill bits.

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              • #8



                Here's a couple of pictures to help with the tool grinding. I mostly stick to the simple method shown in the first one, using ~8 degrees for all angles. It does most everything at least passably well. Sometimes I leave out the side rake altogether, giving a neural rake. Especially on threading tools. See pics (stolen from the South Bend forum at PM)



                Click image for larger version  Name:	toolbit-generic.jpg Views:	0 Size:	67.9 KB ID:	1861167



                Click image for larger version  Name:	SinglePoint_TurnTools.jpg Views:	0 Size:	86.4 KB ID:	1861168

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                • #9
                  Yes, I actually like the belt sander idea.
                  More forgiving and you never have to true a wheel.
                  Good call.

                  -D
                  DZER

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                  • #10
                    Originally posted by Brad.Wilkinson View Post

                    BTW, I am into experimental aircraft and engines and such, and that involves some alloys like 4130 chromoly and stainless, so tool accuracy seems to be a bit more critical, right?

                    No, not really, free hand on a bench grinder followed up with a few licks on an oil stone and you're good to go. The angles are far from being an exact thing, lots and lots of latitude before things don't work.

                    The geometry is also pretty simple once you understand the basics - essentially there is one surface the chip slides over. the angle that it is presented to to the work is the "rake" angle. It matters and changes with materials (but still with lots of latitude). Everything else is clearance so things don't rub.

                    Grind a tool is like tying your shoe .....it to once seemed daunting.....then almost instantly that became wonder at what all the fuss was about

                    Reading through some basic machining texts, many available online, will really help you come up the curve more quickly


                    Welcome to this fascinating craft.
                    Last edited by Mcgyver; 03-12-2020, 05:39 PM.
                    .

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                    • #11
                      I have used an angle grinder to sharpen drill bits in a pinch. Seriously. Grinder fixed in a bench vise so I have two hands to manipulate the bit.

                      Second the comments above. Give it some practice.

                      I would like to have a nice Baldor someday but in the meantime I have a cheapo 6 inch bench grinder that does what I need. Green wheel on one side to sort of sharpen brazed carbide and gray wheel on the other side for steel. You don't need to spend much to get started.

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                      • #12
                        Welcome Brad,
                        I can't really say anything bad about my Metabo 6" bench grinder, although the rests are not very useful. It runs smooth and the motor is a smaller diameter than most models so you have more clearance toward the middle. I use a carborundum stick to dress the wheels - easier to use than a diamond point and bench grinder wheels don't have to be perfect anyway.
                        Location: Northern WI

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                        • #13
                          Originally posted by Mcgyver View Post
                          Grind a tool is like tying your shoe .....it to once seemed daunting.....then almost instantly that became wonder at what all the fuss was about
                          .
                          +1 on this. Too often people make it seem complex and put beginners off, push them towards expensive tool rests or ready made inserts. Like Nickel said just make every angle vaguely 8 ish degrees or 10 ish doesn't matter. There is a way of getting this on a simple grinder wheel - blocks of wood for a rest at centre height of the wheel then the curve of the wheel gives you an angle. Add a thin bit more wood and the angle gets sharper. Just make sure the rest is firm to prevent the tool tilting into the wheel especially when doing the sides. Glue a steel sheet 1/16in or hard laminate on top of the wood to give a hard slidey surface to move the tool on.
                          Next job - challenge yourself to something difficult like falling off a log.

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                          • #14
                            Screw grinding! Buy carbide inserts and get to making parts for your project. The only time I grind a HSS tool is to make a special contour. Or to sharpen a drill bit.
                            Location: The Black Forest in Germany

                            How to become a millionaire: Start out with 10 million and take up machining as a hobby!

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                            • #15
                              Originally posted by true temper View Post
                              If you are willing to spend the money, or build one your self you can’t beat a 2x72 belt grinder. I use mine for everything never use rock anymore.
                              be sure to get one with a VFD so you can control the speed.
                              you can use it for heavy fab work or sharpening small drill bits.
                              Yes on this! I made my own 2x72 for about $300 and it has almost completely replaced my old bench grinders.

                              Dan
                              Salem, Oregon

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