How to hold a finish reamer after roughing reamer?
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    Default How to hold a finish reamer after roughing reamer?

    It doesn’t seem to me that a floating reamer holding a finish reamer after running a roughing reamer or pre drill would be as true as running the finish reamer from the beginning. What am I missing?

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    Yeah I'd run the finish reamer first, don't worry about drilling and stuff...

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    A roughing reamer is used to take out the majority of the chamber material quickly (fewer flutes, wider spaces) and limit wear on the finish reamer. It is used in high volume production situations. I have never used one for any of the barrels I have chambered but I am never in need of speed.

    Driiling is a low budget way of approximating a roughing reamer, but with less accuracy. Depends on your needs.

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    Reamers can not true holes.
    Get how they are made and work.
    They do not and can not cut past the very tip as the are cylindrical ground (hence no cutting ability) and with a back taper.
    The ability to straighten bad holes is the result of the cyl grind following which will not cut and forces the tip but this is hard to control, needs many experiments and depends on grind and process parameters.
    Easy-peasy if you make 2,000 a day, not so much if you need one.
    Which is why Gunsmiths are artists and not machinists.
    Bob

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    I've never used a rougher but do pre-drill and bore .020" under the finish body diameter of the chamber, .050" short of the shoulder (on short action, my boring bar won't reach the shoulder on most long action cartridges. I feel this gives good alignment and location of where the finished chamber will be. I do hold the finish reamer rigidly, but a floating holder would follow that roughed out hole, too. With a floating holder, you may want to stop your pre-boring short enough so the reamer pilot can still make purchase in the bore.

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    Thx guys. Still not seeing how a finish reamer could work correctly after a pre drill since the pilot won’t be following the bore in the beginning. Seems it would have to be very rigid or it would wobble

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    Quote Originally Posted by Mram10 View Post
    Thx guys. Still not seeing how a finish reamer could work correctly after a pre drill since the pilot won’t be following the bore in the beginning. Seems it would have to be very rigid or it would wobble
    With a floating holder, it’s probably best to pre-bore short enough so the pilot just makes purchase in the bore.

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    They do not and can not cut past the very tip as the are cylindrical ground ...

    I assume you are talking about ordinary reamers (like chucking reamers, hand reamers, et cetera) here, not chamber reamers. Virtually all chamber reamers have some degree of taper in the body and do cut for the whole length, although most of the material is removed by the edge at the shoulder in bottleneck cartridges.

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    Quote Originally Posted by GGaskill View Post
    They do not and can not cut past the very tip as the are cylindrical ground ...

    I assume you are talking about ordinary reamers (like chucking reamers, hand reamers, et cetera) here, not chamber reamers. Virtually all chamber reamers have some degree of taper in the body and do cut for the whole length, although most of the material is removed by the edge at the shoulder in bottleneck cartridges.
    That's because they are properly called "form cutters", not reamers. Not much different at all from port tools or for that matter a countersink.

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    Quote Originally Posted by tdmidget View Post
    That's because they are properly called "form cutters", not reamers. Not much different at all from port tools or for that matter a countersink.
    That would not be the "proper term" in barrel chambering discussions among practitioners.

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    Quote Originally Posted by CalG View Post
    That would not be the "proper term" in barrel chambering discussions among practitioners.
    They don't use proper terms. Proper terms are too mundane. They have to make up new Buck Rogers sounding names and buy every trendy gemcrack. We use to have a guy here who cut thru the BS, Speerchucker. He could chamber a barrel while most were selecting what black magic playtoys to use. Unfortunately he got sick of the BS.

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    Quote Originally Posted by tdmidget View Post
    They don't use proper terms. Proper terms are too mundane. They have to make up new Buck Rogers sounding names and buy every trendy gemcrack. We use to have a guy here who cut thru the BS, Speerchucker. He could chamber a barrel while most were selecting what black magic playtoys to use. Unfortunately he got sick of the BS.
    Make up a term? I’m curios as to the year “chamber reamer” was first referenced. Wonder iif any of us were alive yet. Yes, I agree that it is technically a form tool, but I’d also agree chamber reamer is also correct.

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    Quote Originally Posted by tdmidget View Post
    ...We use to have a guy here who cut thru the BS, Speerchucker. He could chamber a barrel while most were selecting what black magic playtoys to use. Unfortunately he got sick of the BS.
    Yeah, too bad about that. He always cut to the chase. Even though I'm not really into guns I still enjoyed his posts...

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    Call them what ever you want but when you go to buy one "chamber reamer" is what you'll need to be asking for.

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    The floating reamer holder will allow a reamer to align itself with a bore that might be a little eccentric. Ideally they allow only side to side movement, not angular. I have a pretty low opinion of some of the so called floating holders sold to gunsmiths. Some are likely to cause a reamer to break if it catches a bit during reaming. I suggest looking on the Bay for a Galenzer or Scully Jones floating holder. Some have a female Morse taper. A 7/16 drill driver for taper length drills or a tap driver works well to hold the reamer. Yu can get some control over how hard the driver grabs the reamer by varying the force used to seat it in the Morse taper.

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    Ill, I still don’t see how a floating reamer holder can center the reamer without the pilot being engaged. It just don’t make no sense

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    As 300 sniper said, you must let the pilot engage. Then the chamber will be right behind the pilot. If you try to rough bore it and are off then when/if the pilot engages you will be cutting heavy on one side and in bad cases , could break the pilot off. Don't try to outsmart the tool. Let the pilot do it's job.

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    That’s the point though, you can’t have the pilot engaged for the first part of the chamber if you predrill. It has nothing keeping it centered

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    Quote Originally Posted by Mram10 View Post
    That’s the point though, you can’t have the pilot engaged for the first part of the chamber if you predrill. It has nothing keeping it centered
    Well, duh. Don't do any of that crap. Let the tool do it's job. It is entirely possible to remove at least 75% of the material without interfering with the pilot. But , if this is a rented tool then have at it. You are paying to resharpen anyway.

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    Quote Originally Posted by Mram10 View Post
    That’s the point though, you can’t have the pilot engaged for the first part of the chamber if you predrill. It has nothing keeping it centered
    If you're using carbide reamers with the long pilot, you can damn near bore out the entire short action body of the chamber and the pilot will still be in the bore when you start. If you're using a HSS reamer with the half inch long pilot, you can usually bore 1.1" to 1.2" of the body and the pilot will still be in the bore when you start. The pilot keeps the tip pointed the right direction, the bore and pre-bore keep the cutting tool centered.

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