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  • Parallels

    All,

    Has anyone bought a set of 1/2 or 1/8" x 6" flat parallels lately that they measured to check their accuracy ?
    Will you share the vendor/part numer ?

    I am needing accuracy down to .0005".....thickness, length etc. The ones i have are not cutting it....

    Thanks
    Lenord

  • #2
    At risk of showing my ignorance what are parallel bars used for. I got a set w/ the lathe but I've never used them. They are cheap ones so not to be used in precision lathe work. Didn't mean to hijack the thread.

    Krems

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    • #3
      parllels are use in a mill.

      we made our own as part of our trining and we ground them closer then .0005

      Comment


      • #4
        Krems - i'm new to this game too, but my understanding is that they are used in a milling machine vise to keep work off of the bottom of the vise. For example, today i cut some .515" slots in some 1/4" thick strap (2.25" by 1.25") for mounting a bike wheel on an HMV car. To hold the pieces in the vise and still cut the slot through the metal without also cutting a groove in the bottom of the vise or table, i used some very inaccurate parallels (read some pieces of 1/4" thick 1" wide strap ) to keep the work above the bottom of the table but still parallel to it.

        Lenord - check Travers and JL industrial and, even, Enco. Most of them give specs for accuracy.

        1/8" Thin style 10 pair Parallel Set carried through Enco
        .0002 parallelism
        Paired +/- .0004 in height
        52-58 HRC

        Brands: Enco Model Number
        USA $112.27 505-1864
        Fowler $184.37 422-184.37
        Brown and Sharpe $ 199.83 637-7529


        Brown and Sharpe 1/4" 9 Pair Pallel Set
        .0002 parallelism
        Nominal Abosolute heights, plastic case

        Brown and Sharpe $211.95 - enco model number 601-1150


        Enco 1/2" 8 pair parallel set
        .0003" parallelism
        paired +/- .0003 in height
        Length +/- .006
        Width .4921 +/- .0008
        Woodcase - HRC 52-58

        $159.80 Model Number 240-03262

        Enco 1/2" Steel Parallels - 4 piece set
        .0003 parallelism
        $28.04 Model number 637-7536



        Among many others
        Go to use-enco.com and plug in one of those item numbers or just browse around for what you need...they'll probably have free shipping in january but then are you outside the US? This might not help you at all :P
        Last edited by Fasttrack; 12-27-2006, 11:15 PM.

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        • #5
          Ok, I was curious, so I checked mine.

          Ho-made set (I'm not a ho but you get the point ). Checked with standard Starrett 0.0001" mic's.
          1" parallels - 0.0002" from end to end, bar to bar max change (ete, btb).

          1/2" - Checked with Mit digital mic's 0.00005" resolution.
          Brand x from IDG (McMaster Carr like dealer) - 0.0004" ete, btb.
          Brown & Sharp thin parallels - 0.0002" ete, btb.
          Brown & Sharp thin wavy parallels - 0.0003" ete, btb.

          So, I was curoius about the brand x and checked the 5/8".
          Try 0.0014" - sucks. Now I'm wondering what the rest are.
          So I might cehck them....... after Mythbusters.
          Civil engineers build targets, Mechanical engineers build weapons.

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          • #6
            Now I understand what the parallel bars are used for. I checked mine...not even close to being straight or consistant thickness..ie..JUNK

            Thanks...Krems

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            • #7
              Parallels-mine suck

              You can also put parallels on a rotary table to keep the work off the table.

              I required a good accuracy, put the parallels on there, bolted down the Al. slab, put on the DI, flatness off by .003", after retorquing the nuts...
              Took the slab of Al. off, checked the slab and table, perfect. (good Al. slabs)
              Mic'd the parallels, .007" off on one, .007 on another...These are cheap parallels from J&L. I got them when I started machining a few years ago. Suppose to be better accuracy than this !
              Mic is a Starrett. Checked it too. It's fine.

              I want some "known to be decent" parallels for a reasonable price. I don't want the hassle of reshipping and fussing about with returns from J&L or Enco.

              I can buy bar stock that has a better thickness tolerance than these things. For the RT, I may just make a ring of the right size and use that. The Mic6 I am using is awesome.

              Thanks for the replies so far !

              Lenord

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              • #8
                Not junk at all. I true mine on a surface grinder. It is important to grind each pair together and perpendicular to the table. It is not important that they be exactly 1/2", 5/8", etc. unless you have to space the part an exact distance off the table or vise. I have never had to have them an exact width. I use tool steel bar stock or cold roll to make my own. I do have a store bought set.
                It's only ink and paper

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                • #9
                  Not everyone has a surface grinder though...

                  Lenord

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                  • #10
                    Originally posted by lenord
                    Not everyone has a surface grinder though...

                    Lenord
                    For the cost of a really good set of parallels, you could probably almost BUY a surface grinder these days!

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                    • #11
                      Being new at this machining business, I have asked questions all over-- One guy showed me some rings he cut in varying thicknesses from a 1 1/2 " dia. heavy walled SS pipe to use in the place of parallel bars, and he says they work well-- He is now cutting rings from a 1" piece of SS pipe-- He cuts these on a lathe, and has offered to make me some if I pay for material-- Have any of you heard of this before?? Practical?? Comments?? Thanks--
                      Best regards, Ron

                      " I just had it a minute ago"

                      Comment


                      • #12
                        .007 off in 6 inches? Huh? Might as well start with some threaded rod and hammer the threads flat on four sides- probably get you just as close.

                        You could cut some strips of maple on a table saw and get closer than that. You could stack 167 strips of paper to get the 1/2 inch thickness and be better than that.
                        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
                          Parallels & ring parallels....

                          OK, parting off pieces of pipe or tubing would work, but best if they are ground flat after parting. Better yet, why not use races from ball bearings. Dead bearings are available at most motor rewind shops for free. Great when you need clearance for a boring bar or reamer, for faceplate work etc. Also useful for packing up around a hold-down. (My dad used to use them. Also read the idea in Sparey's book "The Amatures Lathe".)
                          Yes, grind parallels in pairs. Mark them if you need to know dim'n. Usually it's the parallelism you need....
                          Helps to have a saurface grinder though.
                          Rick

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                          • #14
                            Cheap parallels,

                            Bearing races. They're ground within a gnat's nut.
                            Just got my head together
                            now my body's falling apart

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                            • #15
                              Of course if the surface the parallels are sitting on is out of flat. The point being you are always at the mercy of the compounding errors. Murphy's Law says they always make things worse. They never cancel each other out.

                              As an aside magnetic parallels are always flat if used properly (the secret is to grind them every single time you use them).
                              Forty plus years and I still have ten toes, ten fingers and both eyes. I must be doing something right.

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