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Building a Contact wheel for belt grinder?

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  • Building a Contact wheel for belt grinder?

    I didn't want to Hi-jack Challengers thread on casting PU so I will start a new one. I need to build three or four 200mm contact wheels for belt grinders I am building. The wheel itself will be aluminum. I wanted to try casting the outside PU or whatever compound you all think is best. Any suggestions on material and where to buy it in the civilized world meaning the EU?
    Location: The Black Forest in Germany

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

  • #2
    I bought some alumilite PU resin last year to cast my own contact wheel, but haven't got around to it yet. Off memory I think it was 60d? but It might be 80, can't remember. https://www.alumilite.com/resins/flex-urethane-60/

    The resin itself is almost as much as a complete import contact wheel, so don't screw it up . Off memory again, but I think when I did the volume calculations for a serrated wheel I could get both a 10" and 6" wheel from a 32 oz bottle. I plan on 3d printing the mold form in segments.

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    • #3
      Thank you Dan. The contact wheels I have seen from China are crap. They vibrate like crazy and I think they use left over noodles from a restaurant for the rubber! I had one and tried to true it up but never got it right. A good contact wheel costs 300-400 Euros so it might be worth to try to cast one myself. And it is something I have never done so I would like to try it.
      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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      • #4
        That was my train of though too. I view everything from china as a "kit" that needs work before being put to work. I wanted to do things a bit different with my belt grinder design, so didn't want to go down the import wheel path either. Good luck with it, and post up when you're done. Maybe it will spur me on to get back to my belt grinder project lol.

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        • #5
          I want to do this too. It will be a bit harder because I come from an uncivilized world. Meaning Africa. I have dabbled a bit in urethanes but they are very expensive in my neck of the woods. I have a need to make a contact wheel of the same size but could not wrap my head around how to do the serrations.

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          • #6
            yes, a contact wheel without serrations is no good. they are pretty soft too.
            Last edited by dian; 01-15-2021, 01:02 AM.

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            • #7
              Originally posted by plunger View Post
              I want to do this too. It will be a bit harder because I come from an uncivilized world. Meaning Africa. I have dabbled a bit in urethanes but they are very expensive in my neck of the woods. I have a need to make a contact wheel of the same size but could not wrap my head around how to do the serrations.
              I'm going to 3d print the segmented negative in sections to form a mold. Cutting them after the fact is a waste of expensive resin. I might need to skim the od to make it run true and balance it, but the space between the Chevrons isn't critical and a 3d printed mold will work fine. I might get on it this weekend now that it's back on my radar as I've got a new printer coming tomorrow, and with the new lockdown rules here, nowhere to go (was planning on going fishing )

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              • #8
                Originally posted by plunger View Post
                I have a need to make a contact wheel of the same size but could not wrap my head around how to do the serrations.
                Mill them, dividing head or spacer as you choose.


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                • #9
                  Seems to me you could set up in the lathe to cut the pattern into a surface like cutting a thread. It's going to be a very coarse thread, and both left hand and right hand. If you can cut the pattern into the OD of the wheel, you could then paint the wheel with PlastiDip. Several layers would give you enough to surface grind for accuracy. You'd be using a lot less material than casting PU

                  The trick is how to do the cutting. With an 8 inch diameter wheel you would probably be cutting the grooves with a router, and turning the spindle by hand. You'll be figuring out inches per turn rather than turns per inch.

                  How wide are these wheels going to be?

                  I think you would be using the carriage to rotate the spindle through a linkage, not the spindle to move the carriage through the threading gears.
                  I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                  • #10
                    My brain is not wired to see stuff in 3d. If I were to take a flat piece of delrin long enough to cover the circumference of a 200mm contact wheel. If it were 50mm wide (width of contact wheel) and if I machined slots in the plastic at 30 degrees or just a nice angle . Then if one would place this around the aluminum contact wheel as true as possible. If one glued it to the glass or granite base plate so you are making a mould around the alu contact wheel . Now if you mixed some urethane and poured it in the gap and let it set I would hope it would leave its thread in the wheel and hopefully can be used many times.

                    Would that work.? I would hope to do it this way because from my experience urethane is not an easy thing to machine on a lathe so one would like to keep all machining to a minimum if possible.

                    Then hopefully it just needs a minimum of dressing on the circumference to get it true and better balanced.

                    Ive tried to google this and came up with very little..

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                    • #11
                      How accurate do the slots need to be? Cutting helixes by hand is quite easy to do.

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                      • #12
                        Plunger, your idea will work if the PU is runny enough. Make sure it won't stick to delrin

                        What you might also do is make your delrin hoop slightly larger than the wheel, and mount it within a hole in a plywood jig. The jig would hold it perfectly round, and under some compression so the gap closes up nicely. With the wheel placed inside it, shim to center the wheel. When you pour, there's lots of room for air to flow out, and the resin will bond to the whole outside surface of the wheel. You'll be sealing the edges so the resin doesn't leak out, so that will hold the wheel centered and you can pull the shims out before pouring.

                        I'm also wondering about the resin- PU is great stuff, but do you really need the rubber surface here? I'm not saying you don't, but you could also use just epoxy, like the two part coffee table resin. That would be a lot cheaper. I wonder if it has a durometer rating- it's hard, but not like granite or even the bare aluminum. It might be fine.

                        Either your idea or mine will work, and like you say it will save on the amount of resin you need, plus there would be little to no final prep needed after the delrin comes off. You still could true it up on the lathe if need be, but you won't need to take much off.
                        I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                        • #13
                          Originally posted by darryl View Post
                          Plunger, your idea will work if the PU is runny enough. Make sure it won't stick to delrin

                          What you might also do is make your delrin hoop slightly larger than the wheel, and mount it within a hole in a plywood jig. The jig would hold it perfectly round, and under some compression so the gap closes up nicely. With the wheel placed inside it, shim to center the wheel. When you pour, there's lots of room for air to flow out, and the resin will bond to the whole outside surface of the wheel. You'll be sealing the edges so the resin doesn't leak out, so that will hold the wheel centered and you can pull the shims out before pouring.

                          I'm also wondering about the resin- PU is great stuff, but do you really need the rubber surface here? I'm not saying you don't, but you could also use just epoxy, like the two part coffee table resin. That would be a lot cheaper. I wonder if it has a durometer rating- it's hard, but not like granite or even the bare aluminum. It might be fine.

                          Either your idea or mine will work, and like you say it will save on the amount of resin you need, plus there would be little to no final prep needed after the delrin comes off. You still could true it up on the lathe if need be, but you won't need to take much off.
                          I like this idea. Maybe one could make the entire thing out of mdf and glue the serrations to some pliable mdf. Then take two sheets and mill a groove at 200mm in the two sheets and a center pin hole. Then the alu wheel could be dowelled to the center of the sheet and the groove would hold outer mold piece exactly true to the wheel and the top could be put on so it doesnt lean out at an angle.
                          Then it can be poured in through the top sheet of mdf untill its full. I think your idea is great.

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                          • #14
                            https://www.pinnacletechnologies.com/new-page-5, as an alternative or comparison. Jim

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                            • #15
                              If you use two 25mm strips you could flip one to get a herringbone pattern on the wheel.
                              Last edited by Hawkeye; 01-17-2021, 12:57 AM.
                              When I get Time... I'll...

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