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Aluminum for disk grinder disk

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  • Aluminum for disk grinder disk

    I have been thinking of building a 20" disk grinder and was going to use 3/4 aluminum plate for the disk. I have looked at discountsteel.com for the plate and they have a few options but I am not sure what to go with.


    here is what they have available cut to 21"x21"
    b209-10 6061-t651 is $110
    b209 2024-t3 is $233
    b209-10 7075 t651 is $220
    c250 cast tooling plate (mic-6) $173

  • #2
    C250 is more stable
    Mark

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    • #3
      If you could go a little smaller in diameter this place has has 1 1/4" tooling plate for a good price:

      http://www.sandsmachine.com/alumweb.htm#Specifications

      Leo

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      • #4
        I have built several disc sanders over the years. One of them with an aluminum disc and the other with a steel disc. I actually preferred the steel disc as the momentum from the heavy disc helped the speed remain constant under a heavy pressure...plus, you could have someone plasma or A/O cut the disc much cheaper than buying a aluminum chunk...I think.

        Stuart

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        • #5
          How do large disc sanders like this compare to belt sanders in terms of usefulness, purpose, cost, etc?

          Is keeping the paper stuck to the disc a challenge?

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          • #6
            Originally posted by Glug View Post
            How do large disc sanders like this compare to belt sanders in terms of usefulness, purpose, cost, etc?

            Is keeping the paper stuck to the disc a challenge?
            In this case say 20" disk he's thinking bigger; so then a 6" wide belt sander would
            be far more usefull. Discs load up easilly. Discs have the same problem draft-cutters do.
            'SFM' too low near the center and too high out at the edge.

            You can change your belts as needed like on a bandsaw.
            A disc goes on gets used up. End of story.
            Last edited by Old Hat; 04-04-2014, 07:06 PM.

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            • #7
              I have a 12 inch sander with an aluminum disk and I like it and I use it a lot.

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              • #8
                I too think you would be happier in the long run with a good belt sander--more versatile and you'll get better life from your abrasives. IF you go with a disc make it of steel; it will run a lot better...
                Keith
                __________________________
                Just one project too many--that's what finally got him...

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                • #9
                  Never liked the disc, for all the reasoned mentioned. My 12 inch wide belt sander makes the 6 inch one look like crap, and the disc look like a cruel joke perpetrated on the unsuspecting. I like the 4 inch wide, 12 inch diameter drum sander. It has a soft backing under the sandpaper, which is a standard 4x36 belt. Can't wait for the zirconia belts to come in for it-
                  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
                    Disc does a better job with accuracy because the disc is flat and abrasive stuck to it. Belt is less accurate due to platen wear and the abrasive is not held firmly.

                    Belt, however, seems to remove more material than disc in my experience.

                    You could have both. For example, a rough sawn piece of steel box tubing. Hit it first with the belt to get it close then finish with the disc, flipping to all four sides will get you a nice square end. Just an example.

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                    • #11
                      I had access to a small shop at work where we had a decent Delta belt - disc combo machine. The guy who ran the shop said they could never keep the paper stuck to the discs. I'd always remembered that and wondered. It is very possible the problem was more the users of the shop - untrained interns and scientists. Seeing them used in big shops, I knew that had to be a solved problem.

                      Originally posted by strokersix View Post
                      Disc does a better job with accuracy because the disc is flat and abrasive stuck to it. Belt is less accurate due to platen wear and the abrasive is not held firmly.
                      That's a good point. The belt tends to bunch up ahead of the cut, at least in some cases. A disc is obviously far easier to build. A disc also has the advantage of variable removal rate - the SFM being slower as you near the center. Of course a VFD on the belt gives you that too.

                      The ease of building a big disc has to be a big factor. I wonder how much aluminum helps pull the heat away?

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                      • #12
                        I agree the disc would allow a bit more accuracy, provided you stay away from the center portion. Using the outer 1/3 or so of the diameter should give decent results. But the paper wears and often needs to be removed by using solvents so a fresh piece can be applied. Takes time, and the discs are relatively expensive from what I've seen.

                        I guess I'll be finding out over time how bad the platen wear problem can be with my belt sander. I can just replace the platen in my case, without doing anything structural. So far the granite tile seems to like the job I've put it to. Can be replaced in about five seconds if need be.

                        Back to the disc- yes I think the aluminum would dissipate heat more quickly than steel. Strength vs weight- I don't really know which material would be safer as a large (20 inch diameter) disc rotating at likely 3450 rpm, or which would have less tendency to warp. Personally, I think I'd opt for the cast aluminum tooling plate.

                        You may have the option to use a thinner piece of material and back it up with several ribs- these ribs would terminate at the hub and make for a stiffer design than might otherwise result. I suppose going fairly thick with the disc would make it stiff, but you still have the possible flex where the hub mounts- having a rib structure bonded to the hub and the disc would lessen the stresses at the hub/disc junction, regardless of the thickness of the disc. Even for a 20 inch disc, I think 3/4 inch thickness is overkill- 3/8 tooling plate would be lots, IMHO.
                        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
                          I actually already have access to a delta 12" disk sander with a 6" belt sander and use the disk all the time but it alost never has a belt on it. I also have just built a KMG style 2x72 belt grinder.

                          The reason I want to build a 20" disk is because the 12" is in the carpenter shop and if we keep useing it it will eventually start a fire. I aready have both a 3 hp and 5 hp motor on hand that I can use with it. All the material except the disk is scrap or leftover from other jobs.

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