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Pinging Forrest: Harbor Freight Tool Grinder Question

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  • Pinging Forrest: Harbor Freight Tool Grinder Question

    I've been using my Harbor Freight 46727 tool grinder (the Baldor 500 clone) with plate-mounted aluminum oxide wheels (the 46 grit J&L special), but I'd like to mount a diamond wheel on it.



    The problem I'm running into is that the wheel plates have 8mm x 1.25mm screws (roughly 5/16" in size), but Western diamond wheels have countersunk holes for 1/4" screws.

    What is everyone doing to mount a diamond wheel on the HF grinder? I don't want to modify the diamond wheel, but I can't re-tap the 8mm holes for 1/4" flat head socket screws with (82° countersink).

    The only two options I seem to have is to re-tap the smaller holes on the mounting plate for 1/4" cap screws, or make a new mounting plate?

    Forrest, I know you use the HF grinder to mount your diamond laps -- how do you do this?

    Thanks!

    Robert
    Last edited by lazlo; 08-20-2007, 01:30 PM.
    "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

  • #2
    I am not Forrest, but I have one of the HF grinders that you are speaking of. On mine I remade the backing plates as they had large voids from the casting.

    If your backing plates are fine just figure out what the bolt PC is on the grinding wheel. Find center of the backing plate and drill four new holes for the PC of the wheel you are using. Split the distance between the present metric holes.
    Don\'t ask me to do a dam thing, I\'m retired.
    http://home.earthlink.net/~kcprecision/

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    • #3
      Charlie,

      Where are the voids in the castings, the backing plates on mine are solid, and the replacement backing plates, I bought fron HF parts were also solid. Maybe HF is using different vendors for the parts, they are not great quality, I've had to redrill them numerous times as the 8mm x 1.25mm threads keep stripping out. The replacement backing plates were far better quality than the originals.

      Jack
      jack

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      • #4
        I scounged up socket flathead screws that worked for the back plate and ran them in. Problem ignored; expedient used by reflex. The aluminum is soft and the engagement is short so don't over torque the screws or you'll pull the threads right out.

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        • #5
          drill four new holes for the size you need.
          It's only ink and paper

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          • #6
            Originally posted by platypus2020
            Where are the voids in the castings
            The mounting plates are cast, and the back sides are unmachined, and several people have found large casting voids on the backside.
            I actually have what was probably a casting void on the front side -- there's an aluminum plug press-fit into a hole that's not on the bolt hole circle.

            the backing plates on mine are solid, and the replacement backing plates, I bought fron HF parts were also solid.
            ...
            The replacement backing plates were far better quality than the originals.
            How much were the replacement plates?

            I've had to redrill them numerous times as the 8mm x 1.25mm threads keep stripping out.
            My aluminum shoulder bolts were way undersize for an 8mm thread, I'm assuming to make tolerance, so it doesn't surprise me that you had problems with them stripping out.
            "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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            • #7
              Originally posted by Forrest Addy
              I scounged up socket flathead screws that worked for the back plate and ran them in.
              There are two sets of threaded holes in the mounting plates: 8mm x 1.25mm thread, and what look like M6 holes.
              I'm guessing you drove 1/4 x 20 socket flatheads into the smaller, M6 holes?

              Thanks Forrest!
              Last edited by lazlo; 08-20-2007, 01:29 AM. Reason: Fixed word-wrap
              "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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              • #8
                Thanks for the Info!

                I have one of those grinders I have not used yet and was planning on replacing the wheels and this will help me avoid some problems I hope!

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                • #9
                  Originally posted by lazlo
                  There are two sets of threaded holes in the mounting plates: 8mm x 1.25mm thread, and what look like M6 holes.
                  I'm guessing you drove 1/4 x 20 socket flatheads into the smaller, M6 holes?
                  As an update on this, you're supposed to use the smaller set of holes for the diamond wheels:

                  M6 x 20mm (length) flat-head socket screws fit the smaller set of holes perfectly.
                  I just spun-up a 3M diamond wheel with the new screws and it works perfectly, with no unusual runout.

                  Just as a reminder, flat-head screws are measured from the top, so the shoulder screws for the big holes are M8 x 16mm (length).
                  "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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                  • #10
                    I assume you're talking about this grinder -

                    http://www.harborfreight.com/cpi/cta...emnumber=46727

                    and this aluminum oxide wheel -

                    http://www.jlindustrial.com/catalog/...?id=CPW-14210H

                    and perhaps this diamond wheel -

                    http://www.use-enco.com/CGI/INSRIT?P...PMPXNO=8204881

                    or this diamond wheel -

                    http://www.use-enco.com/CGI/INSRIT?P...&PMPXNO=952556

                    This diamond wheel is much too expensive for my wallet -

                    http://www.jlindustrial.com/NOD-9166...D/product.html

                    I already have the tool grinder but just wanted to see if these wheels are the closest fitting wheels available before I purchase them?

                    I didn't see a 3M diamond wheel on enco's site. Can you provide a link to the one you're talking about?

                    Thanks,
                    Dan
                    Last edited by pgmrdan; 08-20-2007, 01:28 PM.

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                    • #11
                      Originally posted by pgmrdan
                      I assume you're talking about this grinder -
                      http://www.harborfreight.com/cpi/cta...emnumber=46727
                      Yep, that's the one. I'll add that to the thread title...

                      Right, although the particular wheel doesn't matter. The aluminum oxide or silicon carbide (green) plate-mounted wheels take a 3/8" socket shoulder screw, which the HF 46727 translates to 8mm x 1.25mm thread x 16mm length. These are the hand-made aluminum shoulder bolts that come with the grinder. Those bolts work fine with the J&L, KBC Tools, or Norton plate-mounted (Type 35) aluminum oxide wheels.

                      The problem that I ran into is that all the diamond wheels (at least, all the western ones) come with 82° countersunk, 1/4" holes. So if you want to mount a diamond wheel on the HF grinder, you need to use the smaller set of holes on the aluminum wheel plate, with 6mm x 16mm (length) screws.

                      I've tried 3 different diamond wheels that I've gotten off Ebay, and they all have the same hole pattern.
                      "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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                      • #12
                        Originally posted by pgmrdan
                        I already have the tool grinder but just wanted to see if these wheels are the closest fitting wheels available before I purchase them?
                        Any 6" plate-mounted Type 35 wheel will fit the HF grinder. I like the one from J&L Industrial, because it's a Norton wheel.

                        Originally posted by pgmrdan
                        This diamond wheel is much too expensive for my wallet -
                        http://www.jlindustrial.com/NOD-9166...D/product.html
                        I've gotten all my diamond wheels from Ebay. The standard wheel designation is D6A2. I usually pay around $75 for a new Norton/Elgin/3M diamond wheel.

                        By the way, the "Mesh" ratings on diamond wheels are somewhat higher than the "Grit" rating on an aluminum oxide wheel. I sharpen my scraper
                        blades with a 220 Mesh diamond wheel, which is about equivalent to 180 grit.
                        "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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                        • #13
                          backing plates

                          Lazlo,

                          IIRC, I paid about $25.00 with shipping for the replacement backing plates, shipping was the same or slightly more than the parts.

                          Jack
                          jack

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                          • #14
                            Why not make a new plate from 6160 or steel? When I bought a US made oxide wheel I had to grind a small amount of clearance in the cast iron guard that the wheel didn't quite clear.

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                            • #15
                              Now I'm confused.

                              Some old posts on this forum said this grinder takes 6A2C wheels but you're saying it takes D6A2. I'm not sure what these signify.

                              Are they both correct?

                              I also went to the J&L website and found some D6A2C wheels. Are D6A2 and 6A2C both part of D6A2C so they really are both right?

                              Where does (6" plate-mounted) type 35 fit into this?

                              Thanks.
                              Last edited by pgmrdan; 08-20-2007, 04:00 PM.

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