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Surface plate mounted on five points?

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  • Surface plate mounted on five points?

    Has anyone seen this before? I thought that maybe it's resting on three points, and the other two are just shy of the surface to stop it from tipping over if someone leans on it. It's 60 X 60 X 10 cm, about 2' X 2' X 4".


  • #2
    Probably backed off on 2 as you said, guys used to map the plates in work, autocolimeter job, even actually especially brand new ones, they used to do an optical bench too, that thing was full of holes.
    Mine is 3/4 plywood so it's guaranteed to be as flat as it is!
    The supports look more like machists jacks I used to own, same thing I suppose
    Mark

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    • #3
      Yes, I've seen support installations like that. It's essentially a three point support at the Airy point with two outboard of the single support end to prevent tipping if a heavy workpiece were placed on the corner. They're usually just snugged up or left slightly slack to catch if there were any tendency to tilt.
      .
      "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
        I'd not be happy with that setup, one hard knock and you could have half a mountain falling on you.

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        • #5
          I'm not sure what you mean. What's wrong with the setup?

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          • #6
            Originally posted by old mart View Post
            I'd not be happy with that setup, one hard knock and you could have half a mountain falling on you.
            I don't think someone bumping into it with their hip would move it. But something with more momentum could result in it moving off the intended support points. Not to mention the edges are exposed to being chipped by mishandled heavy items being moved around or onto the plate. A somewhat protective frame around it attached down to the stand would not be a bad idea at all.

            I also assume that the jacks are secured to that frame. If not a hard enough nudge would indeed see the plate go tumbling if the jacks were bumped off the frame.
            Chilliwack BC, Canada

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            • #7
              I have to agree with BC. Some kind of protective frame (angle iron) around the plate is definitely an advantage for both the plate and the people working around it. And it would probably eliminate the need for the extra two "supports".
              Paul A.
              SE Texas

              Make it fit.
              You can't win and there IS a penalty for trying!

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              • #8
                Ok, got it. Probably not going to be an issue for me. It will be in a corner with a cabinet beside it, so it will be boxed in from three sides. The only way you could make it fall off would be to pull it towards you.

                This is a MeasureMax surface plate, probably not the best quality. Couldn't find much info about the company, but I think it comes from either China or India. Would prefer something better, but hard to find around here.

                Thanks for all your replies.

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                • #9
                  I wasn't thinking of an angle iron frame as Paul suggests but such a frame would kill two birds with one stone. The lower flats of the "L would perform the safety function given by the added jack screws. All that is needed is for the three jacks to lift the plate slightly clear of the lower inside of the frame.

                  Pinstripe, you don't even really need jack screws for the plate. Three old hockey pucks or three small pads of plywood at the right spots works just fine. Seems to me the only upside of using jacks like this is that you can level the plate at the same time you support it on the three points. If you have a good machinist's level then it's something that would be nice because it gives you the option of using the level during any work. But otherwise any old three pads to lift the plate a touch off the bench top is all you really need.
                  Chilliwack BC, Canada

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                  • #10
                    A brainwave occurred to me just after hitting "post".

                    If I had a suitable machinist's level I think the way I'd go is put the single point at the rear where it's hard to reach. And for giggles stick the slightly shorter "safety posts" out to the sides as well. The single rear support does not need to be adjustable. The other two would be jack screws that are able to adjust to a little shorter to a little longer than the fixed rear support. With the two on the front able to be reached you can adjust for level in both axes easily.

                    They COULD be just two independent jacks with three pads of something like 1.5" round bar for the rear pad and safety pillars. But in the end I think I'd use a sheet of plywood and fit it with some 1/2" UNF inserts that stick out the bottom slightly to rest on washers as pads on the benchtop. Then I'd use short 1/2" UNF screws with the top of the heads skimmed in the lathe to remove the markings to support the plate. I'd likely use a pad of something like 1/8 masonite so the hard contact points of the bolts are padded slighty against the stone. A mounting and leveling plate of this style would aid in preventing the plate slipping around or tipping over the jacks.
                    Chilliwack BC, Canada

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                    • #11
                      Thanks BCRider. I'm having a bit of trouble understanding the benefit of your setup though. The Masonite being more grippy than steel on stone I get, but not the rest of it. This won't be sitting on a bench, it comes with a stand and I think the jacks are attached to the stand. There is also an adjustable levelling foot on one leg of the stand. It looks like this.

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                      • #12
                        This is a completely normal way of mounting a surface table. Both my 36"x48" and my 24"x36" Crown Windley tables are mounted this way... With one minor difference, the metal support on the 36"x48" has five legs as well to avoid sagging with the centre support of the granite. All of the ones at work are the same. The 'jacks' are bolted to the metal frame. The feet should be adjustable as well on a good design for leveling equalization of load.

                        The outer two supports on the three-support side are snugged up so that there is no gap at all. That way the plate won't tip when you put a heavy item on one of the corners at that end. The heaviest single item I've worked on with my 36"x48" table was about 400lb. That's about 40% of the weight of the granite. That weight on an unsupported corner might have been marginal.
                        Last edited by Mark Rand; 11-11-2016, 04:37 PM.
                        Location- Rugby, Warwickshire. UK

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                        • #13
                          OH! That's a bit different. I'd assumed you ran across the picture and were asking about it out of basic curiosity.

                          I see that the stand has one foot of the base that is adjustable. That's excellent since I've yet to run into any truly flat and curve free floors. The adjustable foot will allow you to more or less equalize the load of all four legs against the floor for stability. Turn the foot down so it's in contact and give it your best feel/guess at dialing in a pressure that you estimate is equal to the other three legs. Checking by lifting hard but not hard enough to lift clear on the one with the foot and the leg next to it will pretty quickly show you if the pressures are near enough to equal by how it seems to want to rock or not rock on you.

                          If the jacks are indeed secured to the stand like they SHOULD be then there's really not much else to do other than you can use them to set up the plate so it's level with the aid of a machinist's level. Once leveled just bring up the safety jacks until they touch and back off a quarter to eighth turn so they are not a supporting factor that might affect anything.

                          If you don't have a precision level I'd still level the plate as best you can with a builders level even if it's only the one commonly found in the handle of an adjustable square. It'll aid in slowing down stuff that wants to try to roll off the plate. And if using it for surfacing with wet sanding it'll aid in keeping the pool of lubricating water or oil on the paper.

                          For whatever reason I don't like the idea of a hard point like a metal screw jack sitting against something as hard as the granite. So I might still be inclined to use that piece of masonite to soften the pressure and spread the contact load out a little. The added friction should also aid a little in keeping the plate from skidding around at all and in keeping the screws from rotating with any vibrations from use of the plate itself or from any vibration up through the floor from other machines. But I may be worrying about nothing and it's my OCD kicking in again.

                          EDIT- I see from Mark's reply that the instructions for his plates call for the tipping support jacks to be in contact but with, I assume, no real pressure. Sounds like a good time to go with the option that is directly from the manual for a change.... Might be worth checking them at some point a week or two afterwards to ensure nothing settled at all in the stand and ends up putting too much load on either of the tip supports.

                          Very nice score on the plate and stand too. It might be an import but if it's more accurate than you require by a factor of 10 then it's accurate enough for anything you might need it for. Anything more becomes a matter of bragging rights and feeling posh.
                          Last edited by BCRider; 11-11-2016, 04:50 PM.
                          Chilliwack BC, Canada

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                          • #14
                            Thanks Mark and BCRider. No gap definitely sounds like the way to go. I've got a 6-inch machinist's level, so I will use that to level it.

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                            • #15
                              When you align motors to pumps the very first step is to identify the "soft foot" which is the one making full contact. You then shim that one before proceeding with the alignment.

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