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  • CRS bar stock run out.......

    I need a 60" piece of 1.25 bar stock for an alignment jig I am putting together....does anyone have a general idea of what to expect for runout of this as it comes from a supplier.....I want less than a 1/16 overall. Im I going to have to have one machined to get this tolerance.....its for welding alignment on rear axles using a collet system with the bar as the reference

  • #2
    In my limited experience, you'd have almost zero chance of getting a 60" long piece that's straight to less than 1/16". You're also going to have errors in diameter and out-of-round to deal with, too.

    I think a taught wire would make a much better reference. You'll just need to figure out a way to support it and get it located with respect to some reference points on the axle.

    The round bar isn't going to keep the axle housing straight while you're welding it.
    Any products mentioned in my posts have been endorsed by their manufacturer.

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    • #3
      Hmmmm......using the bar as the reference has been used for many years. Collets are placed in the bearing race areas to support the bar and then the two housing ends are located per the inner bearing alignment, then welded.....maybe I am expecting to much accuracy here. I can go through the trouble of having a bar machined, but it may be too long to hold a low tolerance...Im preparing to make the collets now but need help on the bar part......

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      • #4
        If you really need one, ask for TGP rod, it is Turned, Ground and Polished. Certainly will be in your specs.

        ith luck some cold drawn stuff could be within that straightness, but it comes to down what the supplier or steel maker promises for it. They do publish those specs, usually found on their website or by calling.
        Amount of experience is in direct proportion to the value of broken equipment.

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        • #5
          you would have a better chance with a better quality piece of steel. DOM heavy wall tubing might be that straight and concentric.

          Hot rolled/cold rolled is just not going to be a precision piece of steel.

          doug

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          • #6
            Oh and forgot: If you only need the ends to be certain diameter and straight with respect to each other, then have it machined from a slightly large diameter rod and the center portion can be relieved in diameter, so that only the ends are the same diameter. This is easily done in a lathe between centers, guarantees to get you a straight reference.
            Amount of experience is in direct proportion to the value of broken equipment.

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            • #7
              60 inches sounds long for a single axle tube so I'm assuming that the 60 inch piece will pass thru one axle tube, thru the center section and then thru the other axle tube to the outer bearing. This would mean that the shaft will have to be accurate in 4 places (2 inner bearing & 2 outer bearings). If so, the shaft would have to be accurate all the way or you wouldn't be able to pass it thru the center bearings. This leaves you with two choices. Buy a bar like drillrod that has the tolerances you require or buy a lesser grade steel and have it machined locally. Price will probably work out close either way. With drill rod you risk it being knocked out of alignment in shipping and with the second option you have to rely on the machinist to do accurate work. You may be able to save some $$$ by buying a piece of stock from a local scrap yard and having it machined. Either way, the welder is going to have to tack each tube 360 degrees before finish welding or it will warp and that 1.25 inch rod will not stop it. Good luck.
              Ed P

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              • #8
                Make two plugs that fit the outer ends of the axle where the bearings go. In the center of each plug drill a hole for the wire. Make discs with a similar hole in the center, and make their OD to fit the place where the inner bearings go with just a little clearance. Be certain that the holes are dead center in the plugs and discs.

                Install the four pieces and the wire, draw the wire very tight, and clamp it. The wire defines the center line of the axles.

                As you weld, you'll be able to see how the discs in the center is moving with respect to the inner bearing seats. Use that as a guide to select which part of the joint(s) to weld next. Weld opposite the place where the disc touches a bearing bore.

                Keep in mind that I have no details of what you're actually working with, and I've never done anything remotely like this, but it seems like a workable plan.
                Any products mentioned in my posts have been endorsed by their manufacturer.

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                • #9
                  I appreciate all the input, I actually never thought about DOM, but it has to hold tolerance pretty close......and it is a rear axle for a race car that will go from one axle bearing housing, through the carrier bearings, and back out to the opposite axle bearing housing......I can buy the set up for $400 to $500, but having a basic machine shop, I can make most of it, just dont have a large enough lathe to pass a bar through, my Southbend only takes a 1" through the head, and I want a large enough bar to make good alignment

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                  • #10
                    Oh, proof read that......I meant.....the the DOM usually has to hold good tolerances.....

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                    • #11
                      Stress proof is usually pretty good on tolerances. It comes a few thou undersized which drives me nuts.

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                      • #12
                        good to know............lookin into all possibilites.....hell I cuda bought the whole rig by now, but something about using my machinery to make my stuff just trumps that, hehehe

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                        • #13
                          I just recieved a 1 inch dia bar x 4 feet long for a simular application. The bar has .010 bow in the center and the diameter is within .001. Thays pretty dam straight for a four foot bar.

                          I purchased it here: this was the cheapest price I found on the internet.
                          http://www.midweststeelsupply.com/st...hp?product=132

                          As for specs, mcmastercarr.com lists their tolerances for referance.

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                          • #14
                            I made this setup 15 or so years ago to narrow 8 3/4 Mopar and 9" Ford r/ends.
                            The turned, ground and polished, or TPG bar stock is what I used.
                            It worked great!!!

                            THANX RICH
                            People say I'm getting crankier as I get older. That's not it. I just find I enjoy annoying people a lot more now. Especially younger people!!!

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                            • #15
                              Originally posted by mohead1 View Post
                              I appreciate all the input, I actually never thought about DOM, but it has to hold tolerance pretty close......and it is a rear axle for a race car that will go from one axle bearing housing, through the carrier bearings, and back out to the opposite axle bearing housing......I can buy the set up for $400 to $500, but having a basic machine shop, I can make most of it, just dont have a large enough lathe to pass a bar through, my Southbend only takes a 1" through the head, and I want a large enough bar to make good alignment
                              This is just a whim, pie in the sky, but I'll toss it out there....
                              Since you only need the centers to be aligned at 4 places (if i understand correctly) why not use a 1" bar that will pass through your headstock, turned slightly undersize except for where the alignment points are at which place you could press collars the correct diameter for the bearings?

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