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Protractor Base for Grinder mounted on cross-slide

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  • Protractor Base for Grinder mounted on cross-slide

    I have ordered a toolpost grinder from Little Machine Shop that doesn't really mount to the toolpost. It mounts to the cross-slide. Somewhere in all of my searching for toolpost grinders I seen where someone had mounted a protractor base which sets between the cross-slide and the grinder so the grinder could be set at any desired angle. Of course now I can't find it. Does anybody have a link to that?---Brian
    Brian Rupnow
    Design engineer
    Barrie, Ontario, Canada

  • #2
    Chris on another forum found it for me. Thank you Chris!!

    https://www.micro-machine-shop.com/t...st_grinder.htm
    Brian Rupnow
    Design engineer
    Barrie, Ontario, Canada

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    • #3
      Won't any grinding be done with the traverse of the carriage (straight cylindrical) or compound slide (tapers) so the actual angle of the grinder is only semi relevant? For ID grinding you'd probably set the grinder a little like a boring bar to cut with the leading edge of the small wheel. That way you don't build up heat with full-width wheel grinding. For the OD, you'd likely want to dress the wheel using the carriage traverse to start with so it brings the wheel edge in line with the ways more-or-less automatically.
      .
      "People will occasionally stumble over the truth, but most of the time they will pick themselves up and carry on" : Winston Churchill

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      • #4
        TGTool---there are far more things that I don't know about this than things that I do. I just went in and looked at my lathe, and it appears that you are right. I can't see why You would want a protractor base when you can only feed parallel or 90 degrees to the lathe bed.---actually though, if you scroll down in the link I posted, you can see him setting the entire grinder on an angle and approaching a tapered point with the full face of the grinding wheel.
        Last edited by brian Rupnow; 04-30-2021, 03:38 PM.
        Brian Rupnow
        Design engineer
        Barrie, Ontario, Canada

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        • #5
          A small grinder could fit in the toolpost like the type I bought, and it would be possible to rotate the compound to an angle for limited taper grinding. I have only ever used mine for truing chuck jaws, so tapers were never considered.

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          • #6
            Just spit balling here, but ...

            Why does a "TOOL POST" grinder have to be mounted to an actual tool post?

            Why not mount it directly to the compound, in place of a tool post? Then you can easily grind at any given angle.

            And, in some cases at least, the mount could be designed to connect to either the compound or to the cross slide in place of the compound.

            Please be kind if I am missing something obvious.
            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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            • #7
              Paul---The biggest drawback to mounting a grinder in place of the toolpost, is that the backing dimension from the mounting base of the grinder to the center of the grinder spindle is 2". The distance from the center of my lathe chuck to the top of the compound is only 7/8". As I understand things, the centerline of the grinder spindle must be on the centerline of the chuck spindle, horizontally. The vertical backing on my lathe is 3 3/8" down to the top of the topslide. It may be possible to design a much slimmer compound to fit in that 1 3/8" gap, but I haven't looked at it closely. I won't really do much design wise until I have the grinder here.-----Brian.
              Brian Rupnow
              Design engineer
              Barrie, Ontario, Canada

              Comment


              • #8
                All TPG I've had or seen mount on the compound, afaik thats the norm. Probably called TPG because they sit where the tool post would be. Have a look at the photo, the spindle height is barely above the bottom of the grinder. You can see the frame dips down for the spindle mount - so you need very little height. In my case I pull the compound unless its needed have have a scraped T slot plate there instead - needs quite a bit of packing that's machined to bring to the exact height.

                in Toronto Ontario - where are you?

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                • #9
                  My lathe does have T slots in the compound rest where the top-slide mounts on. I could possibly make a very shallow topslide, but there is no point in designing anything until the new grinder is here. I just got notified by email that it won't be here until Monday.-----Brian
                  Last edited by brian Rupnow; 04-30-2021, 08:32 PM.
                  Brian Rupnow
                  Design engineer
                  Barrie, Ontario, Canada

                  Comment


                  • #10
                    I built this grinder 21 years ago from the article in HSM in early 1999. It's worked nicely, although I don't use it much.
                    As you can see, the grinder axis is near the top of the compound.

                    Click image for larger version  Name:	grinder1[1].jpg Views:	0 Size:	31.9 KB ID:	1940905 Click image for larger version  Name:	grinder1[1].jpg Views:	0 Size:	31.9 KB ID:	1940906

                    Some details:
                    https://www.strappe.com/grinder_notes.html

                    -js
                    Last edited by Jim Stewart; 04-30-2021, 09:03 PM.
                    There are no stupid questions. But there are lots of stupid answers. This is the internet.

                    Location: SF Bay Area

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                    • #11
                      EDIT: I have no idea how that pic got inserted twice.
                      There are no stupid questions. But there are lots of stupid answers. This is the internet.

                      Location: SF Bay Area

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                      • #12
                        Looks good, Jim.---Brian
                        Brian Rupnow
                        Design engineer
                        Barrie, Ontario, Canada

                        Comment


                        • #13
                          Both the Dumore grinders I have had have their OWN toolpost stud and t-nut, with a regular nut at the top to tighten it in place. The post mounts to the compound, and the grinder is adjusted for height as it clamps onto the post. After one adjustment, you take it off without disturbing the clamping, you just loosen the nut that holds the post, and slide the post, nut, stud, and t-nut out.

                          As for how you can move it:

                          First, you can obviously move it any old way with the compound, which has degree marks to set it's movement vs the carriage.

                          Second, if you wish to grind a conical surface that is not as wide as the wheel, you can set that angle and then just bring the wheel into contact with the surface. Having the grinder angle settable to any arbitrary angle allows you to plunge grind in that way without needing to set the wheel truing to that angle, as you might with a cylindrical grinder. Since the TP grinder is often used for one-off items, that saves fouling up wheels with odd angles.

                          The TP grinder definitely is NOT limited to feed using the carriage alone, UNLESS it is so sized that it cannot be set on the compound and have proper contact. That seems to be the case with the LMS grinder, which has a fixed height and not any means to adjust vertically, unlike Dumore or Themac.
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                          • #14
                            Originally posted by brian Rupnow View Post
                            I have ordered a toolpost grinder from Little Machine Shop that doesn't really mount to the toolpost. It mounts to the cross-slide. Somewhere in all of my searching for toolpost grinders I seen where someone had mounted a protractor base which sets between the cross-slide and the grinder so the grinder could be set at any desired angle. Of course now I can't find it. Does anybody have a link to that?---Brian
                            I picked up a toolpost grinder (probably the same one) for the 7x16 bench lathe. Noticed the same thing when I set it up, which led to much cursing as the job I had set up in the lathe was a long awl-like taper that I had intended to grind to a point. Can't really do that without the grinder being mounted on the compound. Ended up doing it in stages.

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                            • #15
                              I am rapidly losing faith about getting a small heat treat oven, however my toolpost grinder (which doesn't actually fit on a toolpost, but instead bolts to the cross slide) just arrived as I was posting this. I have created a 3D model of my lathe, and will also create a model of the grinder, and then see what is involved with making a new, very shallow topslide that can fit between the grinder and the cross-slide so that the grinder can also be "set over" to grind a taper.

                              Brian Rupnow
                              Design engineer
                              Barrie, Ontario, Canada

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