Announcement

Collapse
No announcement yet.

buying a surface plate... how big to go

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • buying a surface plate... how big to go

    I am learning to scrape and might be reconditioning bridgeport a few years from now(as a HOBBY). I am getting ready to buy a surface plate. My question is, do I need a 24 by 36 or can I get by with one a bit smaller like a 24 by 18. What do you guys use? I know it is preferable to have a reference the same size as longest way, however, can it be done with a reference shorter. I would hate to buy a smaller and a couple years later realize that I should have bought the large one. I talked to a local supply and they quoted me 210 for a 24by36 and 350 for shipping. Yikes!

    I see grizzly has one for 300 with shipping. So much for supporting local economy.

    As always, thanks for any advise.

  • #2
    I'd go with the bigger one. BTW, since you do not need it ASAP take some time and keep an eye out on Craig's List for something fairly local. that way you could pick it up and avoid the outrageous cost of shipping.

    You could also look at Enco and take advantage of one of their free shipping offers when available.

    On edit:

    "Enco free shipping on order of $25 or more, till May 31 2012 is NCCAPR"
    Last edited by Dr Stan; 04-11-2012, 12:32 PM.

    Comment


    • #3
      In the Seattle area, surface plates often show up at auctions and it seems like they go dirt cheap. Usually the only bidders are headstone makers. I tried for months to sell a mint 18x24" Starrett pink plate with zero luck, not even a lowball. Basically most guys that want one already have a black import surface plate.

      So my advice to you is to be patient and go to local auctions ready to bid. No way in h*ll would I buy one new, you'd just be throwing your money away.

      Comment


      • #4
        metalmagpie, you don't happen to live in Jax fl. I saw an add for same plate a few months ago.

        Comment


        • #5
          +1 on local auctions... At a auction a year back, they has dozens - all in use and "pristine". My friend bought a 30x48x6 on a stunning custom table/drawer set for $100. The big unit (48x72x8 ) went for close to nothing... I was tempted to buy one for a garden step, but I'd have had to flame the surface to break it up for safety in the wet

          At the machine shop estate sale where I bought my lathe they has a 24x36x6 pink Starrett. He'd heaped tooling on the surface so it was filthy and had minor scratches. Wanted $200, I offered $100... then I decided I really didn't want a pretty tombstone just yet.
          Last edited by lakeside53; 04-11-2012, 12:50 PM.

          Comment


          • #6
            Size for a surface plate?

            As a scraping reference about 2/3 the length of the longest surface. You can with care overlap the reference without sacrificing the accuracy imparted to the work. For precision layout and metrology ideally you want to place the work near the center of the plate and have access all around it for height gages, transfer gages, indexing head, toolmaker knees, jo block stacks, and other surface plate toys. Figure 8" to 14" margin all around.. So if you want the optimium, minimum width would be part size plus a couple feet. If I had my 'druthers'd, I'd have a 3 ft x 4 ft plate 10" thick . It's big enough to do anything automotive and for smaller work you can have several things going at once.

            This is the real world. Most home shop types are pressed for space or budget and have to get by with less. For these I suggest a surface plate that's bench sized but muscleable if it needs to be moved. 18" x 24" for example. A strong man can carry one across a shop and a clever man will slide it on a castered cart whose top is bench height. 12" x 18" is usable but the working space is restricted. You spend a lot of time shuffling work and apparatus around to access all part features.

            24" x 36" really is a better choice but at nearly 400 lb it's difficult to move. If it's on a cart the damn thing will be in the way when not needed in a crowded shop.

            Good choices in affordable imports are available for either size.

            Remember frieght. It usually cost more to ship them than to buy them.

            Somewhere in the archives is a reccommended tool list for a turret mil re-scrape.
            Last edited by Forrest Addy; 04-11-2012, 10:25 PM.

            Comment


            • #7
              Originally posted by lakeside53
              +1 on local auctions... At a auction a year back, they has dozens - all in use and "pristine". My friend bought a 30x48x6 on a stunning custom table/drawer set for $100. The big unit (48x72x8 ) went for close to nothing... I was tempted to buy one for a garden step, but I'd have had to flame the surface to break it up for safety in the wet
              Blah, if you can't walk on a surface thats flat to within a thou without falling over, you deserve it! :P
              Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

              Comment


              • #8
                lowcountrycamo - As big as you can afford, have space for, and can muscle around. Used is fine if you can have some confidence in the surface flatness. Since you are or will become a scraper hand, you will be familiar with ways to check this. On the shipping cost, it is worthwhile to consider getting in your car and driving to a supplier for pickup. There must be one or two of the Grizzley type places within striking distance of Savannah. Buying a tankful of gas beats paying 300 bucks for the same thing.

                Comment


                • #9
                  Yep..... as big as you can deal with.

                  BUT

                  ALSO get a smaller one that is within your "lift and manipulate" range..... you will want it when the plate is lighter than the item you want to check.... combining straightedge with smaller plate is perfect for many things.
                  1601

                  Keep eye on ball.
                  Hashim Khan

                  Comment


                  • #10
                    Originally posted by lakeside53
                    +1 on local auctions... At a auction a year back, they has dozens - all in use and "pristine". My friend bought a 30x48x6 on a stunning custom table/drawer set for $100. The big unit (48x72x8 ) went for close to nothing...
                    Those big ones don't seem to bring much because, at 166 lbs/cu ft, they are seriously heavy. That 48x72x8 would be about 2700 lbs.

                    lowcountrycamo - If you buy a used one realize that they do wear and, if not cared for properly, may not be what you want for a scraping master. I've got a 12" x 18" cast iron that looks like it was pounded on with a hammer for some bizarre reason.

                    Steve

                    Comment


                    • #11
                      Every body is talking about size - which is a sensible thing to do.

                      But the important thing about surface plates is the Class/Grade of flatness of the plate which may be determined by the size and class of flatness you want or need on the job that is to be scraped.

                      It is usually best to have the plate one Class/Grade higher than the work you want to do.

                      All plates of the same Class/Grade of the same size will be the same flatness but the same Class/Grade but diffrent sizes will not be as flat.

                      It is best to have a plate that had been calibrated and a printed "map" of the high and low points where it was calibrated.

                      http://www.starrett.com/metrology/me...surface-plates

                      http://www.tru-stone.com/pdf/FedSpec...ndment%201.pdf

                      See pages 4, 6 and 7 for tolerance of different sizes and grades.

                      Note The flatness tolerance for metric grade AA plates listed in Table (III) (metric) are obtained from the following formula:

                      Total flatness in micrometers (um) is = 1 + 1.6D^2 x 10^-6

                      where D = diagonal or diameter of the plate in millimtres (mm)

                      The tolerances on the A and B grade plates are 2 and 4 times respectively those for Grade AA
                      Note that in 1 + 1.6D^2 x 10^-6 that D is the only variable and that all other terms are constants.

                      If D = 300 then D^2 = 300 ^2 = 90,000

                      but if D = 600 then D^2 = 600^2 = 360,000

                      which is why flatness for the same grade varies with distance "D"

                      It is also the reason that Grade must be increased if the sane flatness isw required for the same grade but different distances "D".

                      A Grade AA plate is 2 x flat as a Grade A plate and 4 x flat as a Grade B.

                      If the calibration "map" is available, the best path for best flatness is easily obtained.

                      Here are my "maps" for my Chinese Grade AA (their Grade 00) 630 x 630 mm and 400 x 300 mm plates:





                      My granite square (Grade 00):


                      And just some of the stuff that goes on or with them here - all of the squares and angle plates have been accurately re-machined:


                      Note: 1 micrometer (um) ~ 40 micro-inches (ie 40 millionths of an inch) ~ 0.0004: (say 0.4 "tenths" of an inch).

                      So prepare and be wary and be warned when assessing or buying a surface plate.
                      Last edited by oldtiffie; 04-11-2012, 10:47 PM.

                      Comment


                      • #12
                        I was lucky enough to purchase a used one from work. We had about 10 that were 48" x 96" x 10"thick and they even included the steel stand for free. Final bonus was they delivered it to my barn. Had to buy the guy across the street donuts and beer so he would bring over his fork lift and unload it. Move it on a set of machine skates to its new home in the shop and it hasn't move in 8 years. It probably have seen more woodworking stuff on it but it is a great foundation for that.

                        Oh yes, price was $180 total (silent auction) and after the bidding was over the guy with the highest price was only $75.00 so I over paid a little.

                        Comment


                        • #13
                          An indication in $US prices regarding grade, accuracy and price is at the Shars web site at:
                          http://www.shars.com/files/products/...11/page138.pdf

                          Comment


                          • #14
                            Originally posted by lowcountrycamo
                            I am learning to scrape and might be reconditioning bridgeport a few years from now(as a HOBBY). I am getting ready to buy a surface plate. My question is, do I need a 24 by 36 or can I get by with one a bit smaller like a 24 by 18.

                            You don't need a big one now so save your money and use it to by the add-ons you're going to need later. Examples:
                            http://www.gaging.com/trustone.htm

                            And get a good brayer and place to store it so it doesn't get flat spots.

                            You will need these accessories later and they're not cheap. Later on you can buy an appropriately sized surface place and your accessories will be right at home with it, and you will have been able to use all your accessories on the smaller plate to learn the ropes in the mean time.

                            Comment


                            • #15
                              I bought a dozen plates a few months ago for a group buy down here. Larger plates are hard to find, and the prices are stupid. i ended up getting plates labelled as Grade A from Enco, with very reasonable shipping to my forwarder in Indy.

                              We got 24" X 36" plates which were the best value on the size/cost curve, and a great aize for both survey work and mastering 3' straightedges etc.

                              BTW, I checked three of the plates at random with my Taylor Hobson Talyvel and they did indeed meet the grade A specifications. Who knew?

                              Greg...previous owner of an 18 X 24, very happy with the extra real estate. Oh- I made a stand that also houses a roller cabinet full of metrology tools and shelves for all the plate accessories. With a plywood cover for the granite it is my best little work table when the granite is not in use.
                              Last edited by Greg Q; 04-12-2012, 11:00 AM.

                              Comment

                              Working...
                              X