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  1. #1
    Member Homer03's Avatar
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    Op Rod Bending?

    I know the right thing is to send it off to someone with the gauges but was wondering if anyone knows any tricks for fixing an op rod that binds. Anyone ever had success correcting a rod by eyeballing its contours against a good one and doing some judicous bending? It is off just enough to bind at the rearward end of travel and I was thinking that some slight tweeking might be worth a try and I can always send it out if it doesnt work. TIA H


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    Senior Member cary m2a's Avatar
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    Dont tweek on it, send it in and have it fixed and every thing checked out.
    M1icon's like to be in spec. not tweeked

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    Member Larry McLarty's Avatar
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    I've heard that it is best done in the fork of a tree

    Cylinders tend to kink when bent. You need to put bending forces over an AREA as opposed to a POINT. So that soft fork in a tree trunk would spread out the bending force over an area.

    Electricians use a tube bender when being conduit. You get a stretch on one side and a compression on the inside of the bend.

    I would send ir to Jim Swartz. I'll bet he is experienced enough to do it on a vice, a jeep bumper, or a fork in a tree. But chances are that you can't.

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    Really Senior Member Jim K's Avatar
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    I have straightened out a couple but I have never used a tree fork or a jeep bumper - those must be specialized tools for experts. I don't think some careful bending after careful analysis is beyond a DIY job. Just note that the rod is supposed to be bent at certain places, so don't try to really make it straight! Also note that some slight rubbing on the barrel is pretty normal, and if that is all, I wouldn't do anything.

    Jim

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    Member mousegun's Avatar
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    Quote Originally Posted by Homer03 View Post
    I know the right thing is to send it off to someone with the gauges but was wondering if anyone knows any tricks for fixing an op rod that binds. Anyone ever had success correcting a rod by eyeballing its contours against a good one and doing some judicous bending? It is off just enough to bind at the rearward end of travel and I was thinking that some slight tweeking might be worth a try and I can always send it out if it doesnt work. TIA H

    Does it bind hard enough to cause a stoppage?
    Does it fail the tilt test with the stock off?

    I have an HRA SG that won't return the bolt to forward during the tilt test. It only takes a light bump to start it, but it won't go forward at over 45 degrees. All my other oprods work in this receiver, and this oprod works on all three of the other M1s. Hmmm.

    This receiver/barrel/oprod combination appear uncycled/unfired; it shows very little wear. The oprod shows minor differences in the curvature compared to the others, as the others do among themselves, but nothing really stands out. What's a fella to do?

    Measure the tab, that's what.

    The tab on the culprit oprod measures .324" height (should be .320" max). It displays no up and down slop in the tab race at all. The other oprods "wiggle" very slightly. This one does not. Also, inside the race there are two machining marks on the bottom showing a polish. None of the other receivers show this. The top of the offending tab has a highly polished spot on top. The other oprods do not.

    Think we're getting close here?

    I think Gus called this "tolerance stacking."

    Upshot: don't bend that oprod! Check for tolerances, scuff marks and crud.

    Then, if all else fails, Jim Swartz is still your friend.
    (o)(-)
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    Member Homer03's Avatar
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    Hmmm Offending op rod looks like .322 on the tab.(I get .320 on the rod that works) It cranks over and hits the sight base with the inside of the hump. Fails the tilt test on two rifles. Im thinking about trying paper tracings to locate the angles and compare this with a known good rod. Id gladly pay Mr Swartz for his services --and will before i get too radical with this tube--but i really hate packing and shipping things. Thanks for all the brain power Gentlemen.

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    Member RogerFoxDog's Avatar
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    I once watched a Garandicon Guru try to straighten out an op rod that I had that wouldn't pass the tilt test. He spent quite a considerable amount of time and effort but he just couldn't get it to cooperate. This gentleman has a vast amount of experience and I have a profound amount of respect for him and his gunsmithing abilities but, he even admitted that with out the proper gages and equipment it is a hit or miss task. You don't know how many people have "tried their hand" at correcting that particular rod. Jim
    swartz was able to correct mine without a problem. No more binding and it stays in the track now. JMHO

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    Member roland beaver's Avatar
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    We fitted op rods by hand bending in RTE Shop, but---

    When building match grade M1icon's in the Marine Corps RTE (Rifle Team Equipment) Shop we fitted op rods by hand bending as a last resort. We had a good supply of new op rods and would first try fitting several op rods if the first one didn't give quite the desired fit. We preferred to find one that was satisfactory without bending, but often wound up selecting one that was close and tweaking it a bit.

    No gauges were used and I ruined a number of op rods before I really got the hang of it. Everybody learned that way--just bounce it off the concrete floor, then chase it down and toss it in the scrap bin in disgust.

    The part of the tube that forms an extension of the handle and the part of the tube that enters the gas cylinder must both lie in a plane that is parallel to the bore and on the centerline of the barrel. The two complimentary bends must be formed to accomplish this condition. Alignment can be checked in both these planes most easily by just engaging the op rod to receiver and bolt and running it forward with the front handguard and gas cylinder removed to allow a clear view of the alignment. If either of those planes is at angle to the bore that must be corrected before any real fitting can be begun.

    Tuning op rods is an art and is very much complicated by variations in the temper of the tube. Some tubes have a good spring temper and are difficult to bend. They must be bent further than the desired alignment to allow for springback. Other tubes have only a little springback and others are near soft to dead soft. The tubes that are most difficult to bend will retain their configuration in long use much better than softer tubes.

    The typical M1 enthusiast will probably never get enough experience in this art to approach hand tuning with confidence (or consistent results). Have fun, and evaluate your progress--but be prepared to have Jim salvage it for you.

  11. #9
    Really Senior Member TDH's Avatar
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    Jim Swartz made an op rod for one of my Tankers and I can't say enough good things about him. He had it done in a couple of hours and it works like a charm and his price was very very reasonable. Thank You Jim.

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