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  1. #61
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    I have always had good luck with floating reamers. They run true and don't act like a whiping borebar. I make my floating reameres no need to buy anything special. Just pin the reamer's shank to another shank that is held in the collet and make sure the fit is loose between the reamer and the shank in the collet. It will slightly whip untill contact with the hole then run true. If you have a good chamfer on the end of your reamer and don't have to do blind holes to the bottom it works great.
    Good luck.

    We all live in Tents! Some live in content others live in discontent.


  2. #62
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    Hi all, one of the misconceptions of reaming is that if you have a floating reamer everything is OK.

    Quite the opposite.

    A number of factors are in force.

    The reamer if it is rigidly held will BORE the hole like a boring bar, and can deflect as it gets deeper under the influence of the offset forces.

    If the reamer is off centre in the horizontal plane it will pull to the side as it gets deeper.

    The same happens if it is off centre in the vertical plane, that is too high or too low.

    The floating reamer holder will resist the deflection to a degree, but with a sharp reamer the hole can get shaved at the entry or exit point.

    Even a rubber or resilient bushed holder will get harder on the deflection and cause uneven parallelity.

    One trick we used to use in the 60's, when I was on a horizontal borer, and when holes of smaller size were reamed instead of boring them , was to just rub the cutting edge along the reamer with a HSS tool bit to take the side cutting ability of the reamer away, not much, just a couple of rubs to dull it.

    This made the reamer cut on the front angle and the sides just acted as a guide, keeping the tool straight into the cut hole, very much like the cutting action of a D bit.

    There were some occasions when the reamer wouldn't cut to size, and that is when we rubbed a small burr on the side of the flutes for about a 1/4" at the end, and it cut "oversize", or to size.

    I never used a floating reamer holder, because the spindle of the borer was maintained in good order, and also due to the fact that it was a live tool, that is, it rotated about it's axis as opposed to a lathe that had the tool usually held stationary in a socket that was "supposedly" in line wth the chuck.

    In a drill press, (live tooling), the hole that is drilled is also in line with the hole that is reamed, it cannot be otherwise, which cannot be said for a tailstock or tool post in a lathe setup.

    Rotating a tool is far more accurate than rotating the job.

    You can bore a hole on a lathe and nine times out of ten the hole will be tapered, either due to misallignment or tool wear, but in a mill if the hole is bored from the spindle with a boring head and boring bar the hole is inherently accurate and can only be parallel, tool wear taken out of the equation.

    I would make a test bar, and fit it into the holder that the reamer fits in, and run a dial indicator along it on top and on the side.

    I wouldn't mind betting that if you are using a carbide reamer, the reamer is just too sharp on the flutes and is shaving the hole on it's sides.

    Reamers should only cut on their ends and get guided by the side of the flutes.
    Ian.



  3. #63
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    I had no idea reaming was so hard?

    To the original poster. A .001 press fit for a 3/16 dowel pin going to require a big ass arbor press or a big ass hammer. .0005 should work a lot better.



  4. #64
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    We always used a rule of thumb of .001" per inch of diam for press fits, same for running clearances.

    The biggest press fit I ever had to do was a loco wheel tyre, 36" diam, with .036" press.

    The tyre was heated to expand it and then dropped on the wheel in one move, no stopping.
    Ian.



  5. #65
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    Quote Originally Posted by handlewanker View Post
    We always used a rule of thumb of .001" per inch of diam for press fits, same for running clearances.

    The biggest press fit I ever had to do was a loco wheel tyre, 36" diam, with .036" press.

    The tyre was heated to expand it and then dropped on the wheel in one move, no stopping.
    Ian.
    I'd use .0005 press on a 1" pin. Your rule of thumb sounds like it's more practical for big parts.



  6. #66
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    Take the reamer and put it in a Lathe (Collet if available)....Run the Lathe in Reverse and lightly stone the reamer over the Flutes with a Fine India stone.....Takes the Sharp edge off and forces the reamer to do what it was intended to do...........By the way... .0002 P.F. is about right for Dowel Pins, anything more is un-necessary

    Ken



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    Quote Originally Posted by John Welden View Post
    I had no idea reaming was so hard?
    .
    No kidding!

    worrying about getting a reamer straight is a bunch of BS. In fact the specifications for making reamers call for the shaft lengths to be what they are so it IS flexible enough to follow the hole. Its not going to act like a boring bar, more important that pilot is aligned with the spindle axis. If location is out, your original was out, or you didn't have/allow the work to find itself under the spindle axis....all of course in context of what is reasonable accuracy to expect with the machinery/task at hand; ie the don't ream the holes they make on jig borers

    if the size is out, well its crappy reamer. shouldn't be with the good ones

    for best results, feed slowly with flood coolant and retract equally slowly. very smooth and accurate holes result...bore and lap when round holes are desired.

    .....Oh yeah, don't start the hole with a centre drill, they're for drilling centre drilled holes for turning, start the hole with a spot drill. Its the right tool for the job and I've never busted a centre drills pip off when using a spot drill



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I hate reamers!

I hate reamers!