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  • Tool post grinder

    Better title might have been tool post multi-tool- whatever. On a whim I went into the shop and found a trim router that I purchased a couple years ago. This is a Ridgid brand, not that it matters for this. Setting it on the cross slide, I found that it would have to clear the cross slide by 1-1/2 inches to put the spindle on center height with the lathe spindle. This makes me think you could fit it to a much smaller lathe than my 8x18. This router has a speed control- slowest speed is 10,000 rpm. Doesn't give much hope of spinning wheels or discs rated for slower speeds. However-

    This is where my idea comes in. You would obviously need a mount of some kind to hold the router in position above the cross slide. What if you added a second spindle on the same mount parallel to the router and drove it with a belt with about 3 to 1 reduction from the router spindle. Now you have a 3 to 10k slow spindle, plus the 10 to 30k router spindle. A tool post tool with two spindles. Use whichever one suits.

    My lathe has the cross slide with two parallel T slots in it. This makes it very easy to position an accessory fore and aft to suit. The body of this router is just the right length to span the width of the cross slide- a pair of identical saddles to hold both the router and the second spindle would be fairly easy to make. You could bore both saddles on the lathe using a tool mounted in the chuck- this would put the center axis of both spindles at a perfect height.

    Just throwing a few ideas around.

    Something else about this router- it's a permanent magnet motor. This probably makes it more efficient than the typical series wound motors used in routers. This could mean less heat build-up if you're running such an accessory for say tens of minutes at a time. I think it's a great start for a tool post machine.
    Last edited by darryl; 05-24-2020, 06:08 PM.
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

  • #2
    That would make for a nice conversion. And if your trimmer has an easy way to mount it accurately and in a stable manner then double bonus. I've got a Dewalt wall trimmer but it does not have anywhere on the body where I could mount it into any sort of holder in a stable manner. Mind you I could always make something a touch large and "bed" it in some epoxy to make such a holder... Hmmmmm........ Oh GREAT! Another tool making idea.....

    Don't fret over the high RPM. Something that size should not be turning anything large anyway. I would not really want to see things like angle grinder wheels running on the max 1/4 shaft size that trim routers will hold. I'd say that you would really not want anything bigger than maybe 2 inch diameter give or take a little.
    Chilliwack BC, Canada

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    • #3
      There was a good article in the Jan/Feb and Mar/Apr 1999 HSM magazine - the author built a toolpost grinder around a trim router. I built it and it worked nicely.

      Click image for larger version

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      Here are some notes I wrote up about the project: https://www.strappe.com/grinder_notes.html

      -js
      There are no stupid questions. But there are lots of stupid answers. This is the internet.

      Location: SF Bay Area

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      • #4
        One possible flaw in that plan, trim routers are usually open-frame. Doesnt matter much with woodworking, but if you use it to run a grinder and it starts sucking up that iron dust thats floating around, well, it doesnt agree with the magnets much. If you try it, make sure you do some sort of shielding on the air inlet

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        • #5
          My Dumore has a motor rpm of 9500 or so, and several pulleys which can be arranged to cover the general range you mention.

          It seems like perfectly good idea. The only issue I can see is getting the router spindle balanced well, if it is not now.
          CNC machines only go through the motions.

          Ideas expressed may be mine, or from anyone else in the universe.
          Not responsible for clerical errors. Or those made by lay people either.
          Number formats and units may be chosen at random depending on what day it is.
          I reserve the right to use a number system with any integer base without prior notice.
          Generalizations are understood to be "often" true, but not true in every case.

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          • #6
            Spindle balance- looking at die grinders one day at Princess Auto, I test ran a few of them and picked the smoothest one. There was a difference for sure. The Ridgid router I have is pretty smooth- I actually have two of those and they are both good. I did not have to rout through more than those two to make sure they were smooth.

            I bought a second Power Fist die grinder, and again I went through three boxes to get the best of the bunch. And it turned out to not be as good as the first one I bought. So much nicer to use one that's balanced.
            I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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            • #7
              It'd be lots of belt flying around, but I've thought about taking the TPG motor off the tool post and mounting it on a bench to get its vibration off the lathe.
              Last edited by Mcgyver; 05-26-2020, 07:04 AM.
              in Toronto Ontario - where are you?

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              • #8
                Well, that's a fundamental alternative- putting the motor off the lathe entirely. That's what I've done with the lathe motor. Belt drive to a jackshaft, second belt to the spindle pulley. It's the smoothest this lathe has ever been. No reason why it can't work for a TPG. Two of mine have the motor on the mount, but belt drive to the separate spindle. I had at one point my Dremel handle mounted on the cross slide, and the flex shaft gently flexing upwards to the motor, which was hanging by a wire. That worked ok, but it's still a pretty small spindle. I really like being able to use 1/4 inch shank cutters.
                I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                • #9
                  Originally posted by Mcgyver View Post
                  It'd be lots of belt flying around, but I've thought about taking the TPG motor off the tool post and mounting it on a bench to get its vibration off the lathe.
                  Don't any of your smaller bench lathes have the "drum" pulley up above so the belt on a TPG can move the length of the bed? Quite a few older jeweler's clockmaker's and modelmaker's lathes were set up like that. I think early Rivett 608 were.
                  CNC machines only go through the motions.

                  Ideas expressed may be mine, or from anyone else in the universe.
                  Not responsible for clerical errors. Or those made by lay people either.
                  Number formats and units may be chosen at random depending on what day it is.
                  I reserve the right to use a number system with any integer base without prior notice.
                  Generalizations are understood to be "often" true, but not true in every case.

                  Comment


                  • #10
                    Or one of these nice little units from Schaublin

                    Click image for larger version

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                    Cayuga, Ontario, Canada

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                    • #11
                      Originally posted by J Tiers View Post

                      Don't any of your smaller bench lathes have the "drum" pulley up above so the belt on a TPG can move the length of the bed? Quite a few older jeweler's clockmaker's and modelmaker's lathes were set up like that. I think early Rivett 608 were.
                      I've got a few including the Schaublin Tom posted and Levin. problem is 1) the lathes are too small for a lot of work, and 2) neither have a saddle moving on bed ways.

                      It wouldn't be hard to try, taking the motor off the lathe, but before that I'm trying to improve the balance of the motor/pulley assembly
                      in Toronto Ontario - where are you?

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                      • #12
                        I have a little 12V angle grinder that uses 75mm X 1mm X 10mm bore discs. They are rated for 20100 rpm. The discs I have are metal cutting fibre reinforced and metal discs with brazed on carbide grit for multi use. The equivalent in the USA would be 3" X 1/24" X 3/8" bore. I recon an adaptor made of decent steel with a 1/4" shank would be ok to hold them in a router.

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                        • #13
                          Originally posted by Mcgyver View Post

                          I've got a few including the Schaublin Tom posted and Levin. problem is 1) the lathes are too small for a lot of work, and 2) neither have a saddle moving on bed ways.

                          It wouldn't be hard to try, taking the motor off the lathe, but before that I'm trying to improve the balance of the motor/pulley assembly
                          I think they were not really to actually move the TPG much under power, but to allow it to easily be at any point along the bed. They might have worked to move it while working also, don't know.
                          CNC machines only go through the motions.

                          Ideas expressed may be mine, or from anyone else in the universe.
                          Not responsible for clerical errors. Or those made by lay people either.
                          Number formats and units may be chosen at random depending on what day it is.
                          I reserve the right to use a number system with any integer base without prior notice.
                          Generalizations are understood to be "often" true, but not true in every case.

                          Comment


                          • #14
                            You mention the T-slots on the cross slide. I'd suggest you mount your TPG on the compound. You're usually grinding just the last few thou to a tight tolerance. By setting the compound to slightly less than 6° from the main spindle axis you get a 10X fine infeed. E.g. advancing the compound .005" gives you .0005" radial infeed, or .001" diametral. You can work in tenths that way. I can hit a target of .0002 or .0003, and a really nice lathe might do better.

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                            • #15
                              Originally posted by J Tiers View Post

                              I think they were not really to actually move the TPG much under power, but to allow it to easily be at any point along the bed. They might have worked to move it while working also, don't know.
                              what would you do with the grinder if you couldn't move it?

                              The reason those lathes (ones with slide rests vs a saddle on bed ways) are a lot less than idea for grinding is the traverse is painfully slow - you are cranking on a little feed screw instead a handwheel and rack. Schaublin has a super cool grinding attachment that is lever operated, but its still too small a lathe for the projects I have in the que. I've also got an air spindle off a jig borer I haven't tried yet....maybe I should rig that up, not sure of the air consumption though
                              Last edited by Mcgyver; 05-27-2020, 05:23 PM.
                              in Toronto Ontario - where are you?

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