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Tool Post Grinder

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  • Tool Post Grinder

    I think I need a tool post grinder, but I can't justify $1200 for new one. The class 7 bearings even for a quarter or half inch shaft are over $100 apiece. I'm thinking of building one. Why couldn't I use $10 class five bearings. I'm thinking of using a sewing machine motor with a foot switch. Flat belt. Can I achieve a decent finish with a high-quality grinding wheel with this type of the setup. What are your thoughts pro or con and your experiences.

  • #2
    High speed and cheap bearings may give you a poor finish. I recently sold a small Toolpost grinder on ebay for $189.00 (Bought it locally in a used tool store for $115.00) so you can still get bargains if you're willing to wait.

    There's alot to be said for building one yourself. Someone recently posted a method of using a chinese drill press spindle to make one. Try searching the site for it.
    Have fun.
    Ed Pacenka


    • #3
      Lesser grade are used in small TP grinders from Dumore. I replaced my unobtainable Dumore bearings with ones from the bearing store. With the original spring preload, they do just fine.

      Don't sweat it that much. Get he best grade that you A) can afford, and B) that you can convince the bearing store are available (they seem to always say there is no such thing).

      Keep eye on ball.
      Hashim Khan


      • #4
        FWIW, the plans for the Quorn tool and cutter grinder include an excellent design for a grinding spindle. It uses magneto bearings that certainly aren't ultra-precision, but they seem to work okay.

        The finish you get most likely won't be up to what a Dumore would give you, but it ought to be good enough.

        Oh -- don't use a universal motor. Top speed of a universal motor is regulated only by the load, which with a grinding wheel could be highly dangerous. Use an induction motor.

        [This message has been edited by SGW (edited 03-22-2005).]
        Try to make a living, not a killing. -- Utah Phillips
        Don't believe everything you know. -- Bumper sticker
        Everybody is ignorant, only on different subjects. -- Will Rogers
        There are lots of people who mistake their imagination for their memory. - Josh Billings
        Law of Logical Argument - Anything is possible if you don't know what you are talking about.
        Don't own anything you have to feed or paint. - Hood River Blackie


        • #5
          If you are talking about a universal motor used on a sewing machine I think you will find that it doesn't have the power you need to turn the wheel and do a good job. The speed will decrease as the load goes up. You can stop the low amp, 1 amp,sewing machine motors without much effort. Don't know what kind of grinding you are going to do but you will probably need 1/4 to 1/2 hp to do a good job for external grinding.


          Hope this helps.


          • #6
            How 'bout a teenie-weenie toolpost grinder built on Class 7 and 9 rollerskate bearings?

            [This message has been edited by lklb (edited 03-22-2005).]


            • #7
              For what it is worth, the Dumore I have uses a 1/14 HP universal motor. It does not explode wheels, but they do need to be rated for the speed.

              Using the OD grinding pulleys, that is about 10,200 RPM at the wheel. For the ID setup it is 18,000 RPM.

              Motor is bigger than a sewing machine motor, but it does slow down if I try to do too deep a cut.

              Rudy K made and used a TP grinder that did use a sewing machine motor.

              For most larger purposes, a small induction motor would give known speeds that would be adjustable by pulley ratio to anything you wanted. Probably a better idea, if your machine can fit them.

              When you design it, be sure to consider clearance for the spindle body and pulley guard. You need it to pass the tailstock and get the wheel to the end of a part that you are holding between centers.

              I use mine as little as possible, because of the cleanup issues. it is nice to have, and I am glad I didn't pay full pop nor the going used rate for it.

              Keep eye on ball.
              Hashim Khan


              • #8
                Pssst...hey JimA


                Now don't tell anyone else.


                • #9
                  Also, Dumore used to sell a bracket that allowed this type of hand grinder to be mounted to a lathe tool post for light, occassional grinding.


                  I think I have a copy of the print for the bracket somewhere.


                  • #10
                    3 or 4 yrs ago in HSM there was a 3 part article by Deene Johnson on a neat TP grinder he built, powered by a Ryobi laminate trimmer/router. I'm confident that would provide a lot more Oomph than a sewing machine motor. And, since the pulley is just chucked into the motor unit, the Ryobi is easily converted back to its intended purpose. That was one of my favorite HSM/MW projects. I've accumulated all the ingredients to build it, but haven't gotten the proverbial rountoit yet.

                    The article is reprinted in the "ShopWisdom of D.E. Johnson" book from Village Press.

                    [This message has been edited by lynnl (edited 03-22-2005).]
                    Lynn (Huntsville, AL)


                    • #11
                      Thanks everyone. What I have is 4 pins that are a half inch in diameter and the short end past a shoulder for about 5/8 inch need to be polished to about a 32 RMS. I thought about doing it by hand with consecutive grade emery cloth. This might work for these pins but I have six others that require the whole length of the pin to be polished. I'm not sure how patient I could be in holding the diameter tolerance and do it by hand when these are three or 4 inches long. I left an extra 10 thousands on the part of the pins that need to be polished. Tool post grinder would be used for this and I find it would be nice to have one because you never know what future projects you're going to attempt. In this type of grinding application you're really not grinding very hard, more like brushing the part to take out the machine markings are you not?


                      • #12
                        I mounted my Makita electric die grinder to a flat plate that goes on my lathe compound.

                        It did the job for my at a fraction of the cost of a purpose build grinder. A lot depends what your tolerances (and wallet) are.



                        • #13
                          Check Little Machine Shop. He has two imports that look usable, and supposedly work well that are affordable. I decided that this was simpler than going from scratch, and if necessary, one could upgrade the bearings.


                          • #14
                            There are LOTS of Dumore's on eBay. Their most popular model is the 57, but they also sell the 12, 25, 44 & there are lots of older models too. Friend bought a complete 57 external with box, manual, good condition for $250.

                            Barry Milton
                            Barry Milton


                            • #15
                              Bob I have looked at those tool post grinders at little machine shop. If I built one the only cost I will have is in the bearings. I know those are imports and then not real sure of the quality. I have all the material I need for the housing and the shaft and lynnl reminded me that I have a Makita trim router back on the shelf somewhere that I haven't used for a long time. I like the Dumore concept and will build a tube that contains the bearings and shaft. I'll splice another tube that this will slide into and clampdown that's fastened to a housing that goes to my tool post. If a sewing machine or small fan motor will not do what I need it to then I'll use the laminate trimmer for the motor. I am really leery of buying stuff off of eBay, yet if I can't score one of those tool post renders for less than a hundred bucks I would be very tempted.