pipe/rod hinge advice needed

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I'm not sure if this is the right section to post this but hopefully it is.  I'm trying to make a hinge for an arm to swing out of a peice of pipe and solid rod.  I have looked at a few charts and also searched mcmaster carr to try and find what size combo fo pipe and solid rod to use to get a decent hinge.  Here is a small pic of what I'm trying to accomplish. The arm needs to be half way strong so I was thinking around a 3/4" solid rod for the pin and 3 sections of pipe to make the hinge.  The upper and lower sections of pipe get welded to the frame and the middle piece of pipe gets welded to the arm that will swing on the pin.  Hopefully this makes sense.After lots of searching I'm still having a hard time finding a combo of pipe/pin so the pin will slide inside the pipe and the piece of pipe will rotate on the pin.  It doesn't have to be 3/4" pin but something close.  I've looked at precision rods/pins at mcmaster and can't seem to find the right size to fit in a pipe.  Can anyone tell me a size pipe and rod that I can use to make a hinge?  I need 4 of these hinges and in total the pin needs to be around 8" long.  Is there a place that makes precision rods/pipes?  I know mcmaster sells precision rods but couldn't find precision pipes.  I would like this to not have alot of "slop" between the pin and pipe but some is ok.This is for a spring compressor I'm trying to make to duplicate one I saw online that is really expensive.  Thanks for any suggestions with this, Scott
Reply:Get 1/2 in  pipe and drill it out to 3/4 ? Mickey mouse way of doing it. I have allways run in to this problem and I could never find the right tube stock with out cutting the rod down or the tube down
Reply:Ya I've thought about getting a pipe slightly smaller and either drilling it out or using a flap wheel to hone it out but worried about getting everything straight.  Someone found this chart for me of different pipe sizes. http://www.wiremasters.com/SubFolder...re%20chart.htm  The 3/4" pipe sch. 40 would work with a 3/4" pin but be kinda sloppy at .824.  The 3/4" sch. 80 pipe has an inside diameter of .742 so that is pretty close but I would have to bore it out .003+ to get the pin in and probably a little more so it swivels nice.  Maybe I'll just try and get a few feet of each and see how sloppy the sch 40 is and see how it comes out trying to drill the sch 80?  I'll have to see what I can get locally.
Reply:I dont know where you are geographically, but if there are any oilfield supply stores around they will have several thicknesses of pipe and nipples. We get the 3/4" XX pipe or nipples when using 3/4" rod for hinges. You may have to ream the seam out of the pipe but that can be done by running the rod in and out of the pipe..............................."Look Good Doing It"!!!!!!!!!!!!!!!
Reply:1/2 rod and 1/2 schd. 80 pipe make a good hinge.
Reply:Thanks for the repleys guys.  I'm in wisconsin so no oil field supplies here!  That sch. 80 1/2" pipe and 1/2" rod are a good fit that I didn't see.  Only .046 over.  I was looking for something a little thicker but think 1/2" should be good.  Plus won't have to  do any work to make it work.  Thanks guys.  Do most metal supply places carry all the scheduals of pipe or is sch. 80  pipe going to be a special hard to find or maybe a plumbing store?  Thanks.
Reply:Use 1 inch dom tube with .125 wall, has .760 id.dom=drawn over mandrel.Peter
Reply:Originally Posted by 7A749Got a lathe?If you did, you can turn down the pins to get the undersize fit you want. Just a thought. You most likely do not, or you would be showing us pics of the cool hinges you already made. That, or better yet, drill/bore out solid stock for the pin. I've made dozens of them that way with a lathe. You can even do it in a drill press if you center it & take your time. Works out well with lots of coolant & an S&D drill bit.Make sure you include some spacing & offset when you install them, or you'll get binding like you won't believe.
Reply:Castweld's suggestion of DOM tubing sounds easiest to me, provided you can find some locally or order the amount you need. A small machine shop in the area might be able to do the boring cheaply if you supply the material to save them the time and especially have anything, like welding, to trade for their work. Otherwise, you might try advertising in the Wanted section of Craigslist for a hobby metalworker with a lathe to do the job.
Reply:Spring compressors..... Can't picture what this is. Oh well.Last edited by STwelder; 08-25-2009 at 03:22 AM.Miller Thunderbolt 225Millermatic 130 XPLincoln HD 100 Forney C-5bt Arc welderPlasma Cutter Gianteach Cut40ACent Machinery Bandsaw Cent Machinery 16Speed Drill PressChicago Electric 130amp tig/90 ArcHobart 190 Mig spoolgun ready
Reply:Originally Posted by castweldUse 1 inch dom tube with .125 wall, has .760 id.dom=drawn over mandrel.Peter
Reply:Why not just buy a hinge that will work? That would be a lot easier and probably much cheaper. I know, I know, doing the work is the fun part, but sometimes it does not make the best sense.Burt _____________________Miller Syncrowave 250Millermatic 211Miller 375 Plasma Cutter Hobart Handler 12010FtDrillBit.com
Reply:Originally Posted by 7A749The offset will be making sure the hinge has room to move fully after it is attached to the item you are putting it on. Since you are using a center swivel design, make sure you relieve where it actuates so it does not bind when it moves.Hitting it with an endmill is the easiest way, but you can easily do it with a grinder or belt sander before you weld the tab to the two barrels that will support the pin. Hope this helps.
Reply:Welding to this tubing is likely to cause some swelling on the inside (bumps/ridges). If an extremely flush fit is required either some reaming may required post welding or wait till after welding for the initial drilling.
Reply:Alfred's favorite hinge and joint elixir:DOM tube over TGP shafting Attachment 38061Shown is 1-1/8 DOM tube over 1-1/8TGP.The fit is tight enough that it won't slip past one thin dollar.One weld, or heat and cool, will shrink it even tighter.With grease, the combination will also hold up for many medium duty pin/bushing applications.Good LuckLast edited by denrep; 10-19-2010 at 11:42 PM.
Reply:Originally Posted by lincweld1/2 rod and 1/2 schd. 80 pipe make a good hinge.
Reply:Originally Posted by weldbeadsch 80 pipe is smaller on the inside. you'll need to grind the rod down .
Reply:Originally Posted by denrepAlfred's favorite hinge and joint elixir:DOM tube over TGP shafting Attachment 38061Shown is 1-1/8 DOM tube over 1-1/8TGP.The fit is tight enough that it won't slip past one thin dollar.One weld, or heat and cool, will shrink it even tighter.With grease, the combination will also hold up for many medium duty pin/bushing applications.Good Luck
Reply:TGP = Turned, ground, polished.or just calledG&P,  Ground and Polished.Last edited by denrep; 08-25-2009 at 01:36 PM.
Reply:Originally Posted by ponch37300According to the chart I have sch. 80 1/2" pipe is .546 ID which would mean that it is .046" bigger than 1/2" rod.  http://www.wiremasters.com/SubFolder...re%20chart.htm
Reply:Ya I learn alot from others on here everyday!  It's amazing how much you can learn by reading the forums!