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Thread: Cetme L build planning

  1. #71
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    I see the designs are very similar....good to know I'm not way out there.
    I only freeze in the grinding room. I have to use the grinder at a friends machineshop and they do a lot of precision stuff...68 deg all the time. My shop is a pleasant 77 deg.

    Frank

  2. #72
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    Last night when I was typing the response it was 66.2 and I was wearing a sweatshirt. It's supposed to stay 68-70 but the humidity control goes nuts for a couple hours every night.

    Frank, I'm glad you posted the pic, I was imagining something completely different from your description. In fact, if I was going to make another style of fixture I might try one like I was imagining!

    As an amateur CAD guy I've found it useful to do a layout of a new locking piece angle in place with the shoulder angles contacting the rollers in the trunnion and a .016" bolt gap between the bolt head and carrier. Knowing the length on paper doesn't usually work out the same as measuring in place because of stack up tolerances, but gives me a target for machining.

  3. #73
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    Quote Originally Posted by holescreek View Post
    Frank, I'm glad you posted the pic, I was imagining something completely different from your description. In fact, if I was going to make another style of fixture I might try one like I was imagining!
    Ha ha! Yep.....this is why I work with machinery. Not a people person who can transmit info verbally very well....not so hip with computer info transfer either but I try. Pics make up for a whole lot of that.
    I am still using autocad 2000 but I try to set up drawings to understand what's going on too. The L is a bit of an oddball though and doesn't follow all the logic of the HK and Cetme C roller lockers. We're coming to understand it a lot better now though.

    Frank

  4. #74
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    The idea I was thinking about was buying one of the cheap adjustable angle blocks like the pic below and mounting a fixture on top of it to hold the LP. Even if you didn't trust the scale on the side you could verify the angle with a sine bar before grinding.

    HTB1jbC9OpXXXXafXXXXq6xXFXXXq.jpg

  5. #75
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    That is an excellent idea. I don't do a lot of surface grinding so I'm always thinking it has to be something that the magnetic chuck will hold....keep forgetting you can put a tool makers vise or other stuff on the thing too. Adjustable angles are better than cutting a new jig for every angle....

    Frank

  6. #76
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    Mike those little angle blocks are pretty accurate to the scale, in minutes of angle anyway. I've had one for years and used it for grinding angles. Go to seconds of angle, then a sine plate/bar is necessary.

  7. #77
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    We learned in the LP study that the original LP's weren't all that close sometimes, even +/- a degree would be close enough for most shooters. Once you got the fixture made for mounting it'd be easy to grind it in to the zero setting on the protractor. I wish Frank would have put the idea in my head a few years ago.

  8. #78
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    Hopefully Monday I'll have some time on the cylindrical grinder to do the shanks, I pretty well have one of the old manual surface grinders to my self anymore-no one wants to use it because it doesn't have coolant fitted.

    Drew the LP blanks back to 50RC, when I tested the rollers in my kit they were 56RC so I want to maintain a difference of about 5RC in hardness-this prevents galling and erosion pretty well. Next on the list of stuff to make is the 40 and 45 degree grinding jigs.

    On these LP's, the angle is measured from the side of the LP, angling in toward the firing pin clearance hole, correct?

  9. #79
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    From my measurements its the included angle between to two ground portions in contact with the rollers. I set my jig up with half that angle or 23.5 deg to grind the locking parts for my 47 deg unit. The sides on many of the locking pieces are not necessarily very precise as they don't really do a lot. Many of the locking pieces have wear on one side and not the other because they aren't concentric to the centerline. I've also seen a few where the sides are not even parallel to the centerline. They don't have any real function other than to keep the bolt head from flopping around too much. The ground angles need to be concentric to the centerline of the locking piece for which I use the shank as a reference.
    Does that make sense?

    Frank

  10. #80
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    Yes, that clarifies quite nicely. May get the chance this afternoon to put the part on the cylindrical grinder and get the shank ground, but the heat treat schedule I am running today (CAD, inspection, assembly, reverse engineer, and now hear treat....) is pretty tight.

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